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• Standard term for a thread I/O reorder buffer?

  - by Crashworks

  I have a case where many threads all concurrently generate data that is ultimately written to one long, serial file. I need to somehow serialize these writes so that the file gets written in the right order. ie, I have an input queue of 2048 jobs j0..jn, each of which produces a chunk of data oi. The jobs run in parallel on, say, eight threads, but the output blocks have to appear in the file in the same order as the corresponding input blocks — the output file has to be in the order o0o1o2... The solution to this is pretty self evident: I need some kind of buffer that accumulates and writes the output blocks in the correct order, similar to a CPU reorder buffer in Tomasulo's algorithm, or to the way that TCP reassembles out-of-order packets before passing them to the application layer. Before I go code it, I'd like to do a quick literature search to see if there are any papers that have solved this problem in a particularly clever or efficient way, since I have severe realtime and memory constraints. I can't seem to find any papers describing this though; a Scholar search on every permutation of [threads, concurrent, reorder buffer, reassembly, io, serialize] hasn't yielded anything useful. I feel like I must just not be searching the right terms. Is there a common academic name or keyword for this kind of pattern that I can search on?

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• MySQL: Limit rows linked to each joined row

  - by SolidSnakeGTI

  Hello, Specifications: MySQL 4.1+ I've certain situation that requires certain result set from MySQL query, let's see the current query first & then ask my question: SELECT thread.dateline AS tdateline, post.dateline AS pdateline, MIN(post.dateline) FROM thread AS thread LEFT JOIN post AS post ON(thread.threadid = post.threadid) LEFT JOIN forum AS forum ON(thread.forumid = forum.forumid) WHERE post.postid != thread.firstpostid AND thread.open = 1 AND thread.visible = 1 AND thread.replycount >= 1 AND post.visible = 1 AND (forum.options & 1) AND (forum.options & 2) AND (forum.options & 4) AND forum.forumid IN(1,2,3) GROUP BY post.threadid ORDER BY tdateline DESC, pdateline ASC As you can see, mainly I need to select dateline of threads from 'thread' table, in addition to dateline of the second post of each thread, that's all under the conditions you see in the WHERE CLAUSE. Since each thread has many posts, and I need only one result per thread, I've used GROUP BY CLAUSE for that purpose. This query will return only one post's dateline with it's related unique thread. My questions are: How to limit returned threads per each forum!? Suppose I need only 5 threads -as a maximum- to be returned for each forum declared in the WHERE CLAUSE 'forum.forumid IN(1,2,3)', how can this be achieved. Is there any recommendations for optimizing this query (of course after solving the first point)? Notes: I prefer not to use sub-queries, but if it's the only solution available I'll accept it. Double queries not recommended. I'm sure there's a smart solution for this situation. Appreciated advice in advance :)

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• Parallel doseq for Clojure

  - by andrew cooke

  I haven't used multithreading in Clojure at all so am unsure where to start. I have a doseq whose body can run in parallel. What I'd like is for there always to be 3 threads running (leaving 1 core free) that evaluate the body in parallel until the range is exhausted. There's no shared state, nothing complicated - the equivalent of Python's multiprocessing would be just fine. So something like: (dopar 3 [i (range 100)] ; repeated 100 times in 3 parallel threads... ...) Where should I start looking? Is there a command for this? A standard package? A good reference? So far I have found pmap, and could use that (how do I restrict to 3 at a time? looks like it uses 32 at a time - no, source says 2 + number of processors), but it seems like this is a basic primitive that should already exist somewhere. clarification: I really would like to control the number of threads. I have processes that are long-running and use a fair amount of memory, so creating a large number and hoping things work out OK isn't a good approach (example which uses a significant chunk available mem). update: Starting to write a macro that does this, and I need a semaphore (or a mutex, or an atom i can wait on). Do semaphores exist in Clojure? Or should I use a ThreadPoolExecutor? It seems odd to have to pull so much in from Java - I thought parallel programming in Clojure was supposed to be easy... Maybe I am thinking about this completely the wrong way? Hmmm. Agents?

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• Please tell me what is wrong with my threading!!!

  - by kiddo

  I have a function where I will compress a bunch of files into a single compressed file..it is taking a long time(to compress),so I tried implementing threading in my application..Say if I have 20 files for compression,I separated that as 5*4=20,inorder to do that I have separate variables(which are used for compression) for all 4 threads in order to avoid locks and I will wait until the 4 thread finishes..Now..the threads are working but i see no improvement in their performance..normally it will take 1 min for 20 files(for example) after implementing threading ...there is only 5 or 3 sec difference., sometimes the same. here i will show the code for 1 thread(so it is for other3 threads) //main thread myClassObject->thread1 = AfxBeginThread((AFX_THREADPROC)MyThreadFunction1,myClassObject); .... HANDLE threadHandles[4]; threadHandles[0] = myClassObject->thread1->m_hThread; .... WaitForSingleObject(myClassObject->thread1->m_hThread,INFINITE); UINT MyThreadFunction(LPARAM lparam) { CMerger* myClassObject = (CMerger*)lparam; CString outputPath = myClassObject->compressedFilePath.GetAt(0);//contains the o/p path wchar_t* compressInputData[] = {myClassObject->thread1outPath, COMPRESS,(wchar_t*)(LPCTSTR)(outputPath)}; HINSTANCE loadmyDll; loadmydll = LoadLibrary(myClassObject->thread1outPath); fp_Decompress callCompressAction = NULL; int getCompressResult=0; myClassObject->MyCompressFunction(compressInputData,loadClient7zdll,callCompressAction,myClassObject->thread1outPath, getCompressResult,minIndex,myClassObject->firstThread,myClassObject); return 0; }

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• SQL: Limit rows linked to each joined row

  - by SolidSnakeGTI

  Hello, I've certain situation that requires certain result set from MySQL query, let's see the current query first & then ask my question: SELECT thread.dateline AS tdateline, post.dateline AS pdateline, MIN(post.dateline) FROM thread AS thread LEFT JOIN post AS post ON(thread.threadid = post.threadid) LEFT JOIN forum AS forum ON(thread.forumid = forum.forumid) WHERE post.postid != thread.firstpostid AND thread.open = 1 AND thread.visible = 1 AND thread.replycount >= 1 AND post.visible = 1 AND (forum.options & 1) AND (forum.options & 2) AND (forum.options & 4) AND forum.forumid IN(1,2,3) GROUP BY post.threadid ORDER BY tdateline DESC, pdateline ASC As you can see, mainly I need to select dateline of threads from 'thread' table, in addition to dateline of the second post of each thread, that's all under the conditions you see in the WHERE CLAUSE. Since each thread has many posts, and I need only one result per thread, I've used GROUP BY CLAUSE for that purpose. This query will return only one post's dateline with it's related unique thread. My questions are: How to limit returned threads per each forum!? Suppose I need only 5 threads -as a maximum- to be returned for each forum declared in the WHERE CLAUSE 'forum.forumid IN(1,2,3)', how can this be achieved. Is there any recommendations for optimizing this query (of course after solving the first point)? Notes: I prefer not to use sub-queries, but if it's the only solution available I'll accept it. Double queries not recommended. I'm sure there's a smart solution for this situation. I'm using MySQL 4.1+, but if you know the answer for another engine, just share. Appreciated advice in advance :)

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• Multiple locking task (threading)

  - by Archeg

  I need to implement the class that should perform locking mechanism in our framework. We have several threads and they are numbered 0,1,2,3.... We have a static class called ResourceHandler, that should lock these threads on given objects. The requirement is that n Lock() invokes should be realeased by m Release() invokes, where n = [0..] and m = [0..]. So no matter how many locks was performed on single object, only one Release call is enough to unlock all. Even further if o object is not locked, Release call should perform nothing. Also we need to know what objects are locked on what threads. I have this implementation: public class ResourceHandler { private readonly Dictionary<int, List<object>> _locks = new Dictionary<int, List<object>>(); public static ResourceHandler Instance {/* Singleton */} public virtual void Lock(int threadNumber, object obj) { Monitor.Enter(obj); if (!_locks.ContainsKey(threadNumber)) {_locks.Add(new List<object>());} _locks[threadNumber].Add(obj); } public virtual void Release(int threadNumber, object obj) { // Check whether we have threadN in _lock and skip if not var count = _locks[threadNumber].Count(x => x == obj); _locks[threadNumber].RemoveAll(x => x == obj); for (int i=0; i<count; i++) { Monitor.Exit(obj); } } // ..... } Actually what I am worried here about is thread-safety. I'm actually not sure, is it thread-safe or not, and it's a real pain to fix that. Am I doing the task correctly and how can I ensure that this is thread-safe?

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• PTLQueue : a scalable bounded-capacity MPMC queue

  - by Dave

  Title: Fast concurrent MPMC queue -- I've used the following concurrent queue algorithm enough that it warrants a blog entry. I'll sketch out the design of a fast and scalable multiple-producer multiple-consumer (MPSC) concurrent queue called PTLQueue. The queue has bounded capacity and is implemented via a circular array. Bounded capacity can be a useful property if there's a mismatch between producer rates and consumer rates where an unbounded queue might otherwise result in excessive memory consumption by virtue of the container nodes that -- in some queue implementations -- are used to hold values. A bounded-capacity queue can provide flow control between components. Beware, however, that bounded collections can also result in resource deadlock if abused. The put() and take() operators are partial and wait for the collection to become non-full or non-empty, respectively. Put() and take() do not allocate memory, and are not vulnerable to the ABA pathologies. The PTLQueue algorithm can be implemented equally well in C/C++ and Java. Partial operators are often more convenient than total methods. In many use cases if the preconditions aren't met, there's nothing else useful the thread can do, so it may as well wait via a partial method. An exception is in the case of work-stealing queues where a thief might scan a set of queues from which it could potentially steal. Total methods return ASAP with a success-failure indication. (It's tempting to describe a queue or API as blocking or non-blocking instead of partial or total, but non-blocking is already an overloaded concurrency term. Perhaps waiting/non-waiting or patient/impatient might be better terms). It's also trivial to construct partial operators by busy-waiting via total operators, but such constructs may be less efficient than an operator explicitly and intentionally designed to wait. A PTLQueue instance contains an array of slots, where each slot has volatile Turn and MailBox fields. The array has power-of-two length allowing mod/div operations to be replaced by masking. We assume sensible padding and alignment to reduce the impact of false sharing. (On x86 I recommend 128-byte alignment and padding because of the adjacent-sector prefetch facility). Each queue also has PutCursor and TakeCursor cursor variables, each of which should be sequestered as the sole occupant of a cache line or sector. You can opt to use 64-bit integers if concerned about wrap-around aliasing in the cursor variables. Put(null) is considered illegal, but the caller or implementation can easily check for and convert null to a distinguished non-null proxy value if null happens to be a value you'd like to pass. Take() will accordingly convert the proxy value back to null. An advantage of PTLQueue is that you can use atomic fetch-and-increment for the partial methods. We initialize each slot at index I with (Turn=I, MailBox=null). Both cursors are initially 0. All shared variables are considered "volatile" and atomics such as CAS and AtomicFetchAndIncrement are presumed to have bidirectional fence semantics. Finally T is the templated type. I've sketched out a total tryTake() method below that allows the caller to poll the queue. tryPut() has an analogous construction. Zebra stripping : alternating row colors for nice-looking code listings. See also google code "prettify" : https://code.google.com/p/google-code-prettify/ Prettify is a javascript module that yields the HTML/CSS/JS equivalent of pretty-print. -- pre:nth-child(odd) { background-color:#ff0000; } pre:nth-child(even) { background-color:#0000ff; } border-left: 11px solid #ccc; margin: 1.7em 0 1.7em 0.3em; background-color:#BFB; font-size:12px; line-height:65%; " // PTLQueue : Put(v) : // producer : partial method - waits as necessary assert v != null assert Mask = 1 && (Mask & (Mask+1)) == 0 // Document invariants // doorway step // Obtain a sequence number -- ticket // As a practical concern the ticket value is temporally unique // The ticket also identifies and selects a slot auto tkt = AtomicFetchIncrement (&PutCursor, 1) slot * s = &Slots[tkt & Mask] // waiting phase : // wait for slot's generation to match the tkt value assigned to this put() invocation. // The "generation" is implicitly encoded as the upper bits in the cursor // above those used to specify the index : tkt div (Mask+1) // The generation serves as an epoch number to identify a cohort of threads // accessing disjoint slots while s-Turn != tkt : Pause assert s-MailBox == null s-MailBox = v // deposit and pass message Take() : // consumer : partial method - waits as necessary auto tkt = AtomicFetchIncrement (&TakeCursor,1) slot * s = &Slots[tkt & Mask] // 2-stage waiting : // First wait for turn for our generation // Acquire exclusive "take" access to slot's MailBox field // Then wait for the slot to become occupied while s-Turn != tkt : Pause // Concurrency in this section of code is now reduced to just 1 producer thread // vs 1 consumer thread. // For a given queue and slot, there will be most one Take() operation running // in this section. // Consumer waits for producer to arrive and make slot non-empty // Extract message; clear mailbox; advance Turn indicator // We have an obvious happens-before relation : // Put(m) happens-before corresponding Take() that returns that same "m" for T v = s-MailBox if v != null : s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 // unlock slot to admit next producer and consumer return v Pause tryTake() : // total method - returns ASAP with failure indication for auto tkt = TakeCursor slot * s = &Slots[tkt & Mask] if s-Turn != tkt : return null T v = s-MailBox // presumptive return value if v == null : return null // ratify tkt and v values and commit by advancing cursor if CAS (&TakeCursor, tkt, tkt+1) != tkt : continue s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 return v The basic idea derives from the Partitioned Ticket Lock "PTL" (US20120240126-A1) and the MultiLane Concurrent Bag (US8689237). The latter is essentially a circular ring-buffer where the elements themselves are queues or concurrent collections. You can think of the PTLQueue as a partitioned ticket lock "PTL" augmented to pass values from lock to unlock via the slots. Alternatively, you could conceptualize of PTLQueue as a degenerate MultiLane bag where each slot or "lane" consists of a simple single-word MailBox instead of a general queue. Each lane in PTLQueue also has a private Turn field which acts like the Turn (Grant) variables found in PTL. Turn enforces strict FIFO ordering and restricts concurrency on the slot mailbox field to at most one simultaneous put() and take() operation. PTL uses a single "ticket" variable and per-slot Turn (grant) fields while MultiLane has distinct PutCursor and TakeCursor cursors and abstract per-slot sub-queues. Both PTL and MultiLane advance their cursor and ticket variables with atomic fetch-and-increment. PTLQueue borrows from both PTL and MultiLane and has distinct put and take cursors and per-slot Turn fields. Instead of a per-slot queues, PTLQueue uses a simple single-word MailBox field. PutCursor and TakeCursor act like a pair of ticket locks, conferring "put" and "take" access to a given slot. PutCursor, for instance, assigns an incoming put() request to a slot and serves as a PTL "Ticket" to acquire "put" permission to that slot's MailBox field. To better explain the operation of PTLQueue we deconstruct the operation of put() and take() as follows. Put() first increments PutCursor obtaining a new unique ticket. That ticket value also identifies a slot. Put() next waits for that slot's Turn field to match that ticket value. This is tantamount to using a PTL to acquire "put" permission on the slot's MailBox field. Finally, having obtained exclusive "put" permission on the slot, put() stores the message value into the slot's MailBox. Take() similarly advances TakeCursor, identifying a slot, and then acquires and secures "take" permission on a slot by waiting for Turn. Take() then waits for the slot's MailBox to become non-empty, extracts the message, and clears MailBox. Finally, take() advances the slot's Turn field, which releases both "put" and "take" access to the slot's MailBox. Note the asymmetry : put() acquires "put" access to the slot, but take() releases that lock. At any given time, for a given slot in a PTLQueue, at most one thread has "put" access and at most one thread has "take" access. This restricts concurrency from general MPMC to 1-vs-1. We have 2 ticket locks -- one for put() and one for take() -- each with its own "ticket" variable in the form of the corresponding cursor, but they share a single "Grant" egress variable in the form of the slot's Turn variable. Advancing the PutCursor, for instance, serves two purposes. First, we obtain a unique ticket which identifies a slot. Second, incrementing the cursor is the doorway protocol step to acquire the per-slot mutual exclusion "put" lock. The cursors and operations to increment those cursors serve double-duty : slot-selection and ticket assignment for locking the slot's MailBox field. At any given time a slot MailBox field can be in one of the following states: empty with no pending operations -- neutral state; empty with one or more waiting take() operations pending -- deficit; occupied with no pending operations; occupied with one or more waiting put() operations -- surplus; empty with a pending put() or pending put() and take() operations -- transitional; or occupied with a pending take() or pending put() and take() operations -- transitional. The partial put() and take() operators can be implemented with an atomic fetch-and-increment operation, which may confer a performance advantage over a CAS-based loop. In addition we have independent PutCursor and TakeCursor cursors. Critically, a put() operation modifies PutCursor but does not access the TakeCursor and a take() operation modifies the TakeCursor cursor but does not access the PutCursor. This acts to reduce coherence traffic relative to some other queue designs. It's worth noting that slow threads or obstruction in one slot (or "lane") does not impede or obstruct operations in other slots -- this gives us some degree of obstruction isolation. PTLQueue is not lock-free, however. The implementation above is expressed with polite busy-waiting (Pause) but it's trivial to implement per-slot parking and unparking to deschedule waiting threads. It's also easy to convert the queue to a more general deque by replacing the PutCursor and TakeCursor cursors with Left/Front and Right/Back cursors that can move either direction. Specifically, to push and pop from the "left" side of the deque we would decrement and increment the Left cursor, respectively, and to push and pop from the "right" side of the deque we would increment and decrement the Right cursor, respectively. We used a variation of PTLQueue for message passing in our recent OPODIS 2013 paper. ul { list-style:none; padding-left:0; padding:0; margin:0; margin-left:0; } ul#myTagID { padding: 0px; margin: 0px; list-style:none; margin-left:0;} -- -- There's quite a bit of related literature in this area. I'll call out a few relevant references: Wilson's NYU Courant Institute UltraComputer dissertation from 1988 is classic and the canonical starting point : Operating System Data Structures for Shared-Memory MIMD Machines with Fetch-and-Add. Regarding provenance and priority, I think PTLQueue or queues effectively equivalent to PTLQueue have been independently rediscovered a number of times. See CB-Queue and BNPBV, below, for instance. But Wilson's dissertation anticipates the basic idea and seems to predate all the others. Gottlieb et al : Basic Techniques for the Efficient Coordination of Very Large Numbers of Cooperating Sequential Processors Orozco et al : CB-Queue in Toward high-throughput algorithms on many-core architectures which appeared in TACO 2012. Meneghin et al : BNPVB family in Performance evaluation of inter-thread communication mechanisms on multicore/multithreaded architecture Dmitry Vyukov : bounded MPMC queue (highly recommended) Alex Otenko : US8607249 (highly related). John Mellor-Crummey : Concurrent queues: Practical fetch-and-phi algorithms. Technical Report 229, Department of Computer Science, University of Rochester Thomasson : FIFO Distributed Bakery Algorithm (very similar to PTLQueue). Scott and Scherer : Dual Data Structures I'll propose an optimization left as an exercise for the reader. Say we wanted to reduce memory usage by eliminating inter-slot padding. Such padding is usually "dark" memory and otherwise unused and wasted. But eliminating the padding leaves us at risk of increased false sharing. Furthermore lets say it was usually the case that the PutCursor and TakeCursor were numerically close to each other. (That's true in some use cases). We might still reduce false sharing by incrementing the cursors by some value other than 1 that is not trivially small and is coprime with the number of slots. Alternatively, we might increment the cursor by one and mask as usual, resulting in a logical index. We then use that logical index value to index into a permutation table, yielding an effective index for use in the slot array. The permutation table would be constructed so that nearby logical indices would map to more distant effective indices. (Open question: what should that permutation look like? Possibly some perversion of a Gray code or De Bruijn sequence might be suitable). As an aside, say we need to busy-wait for some condition as follows : "while C == 0 : Pause". Lets say that C is usually non-zero, so we typically don't wait. But when C happens to be 0 we'll have to spin for some period, possibly brief. We can arrange for the code to be more machine-friendly with respect to the branch predictors by transforming the loop into : "if C == 0 : for { Pause; if C != 0 : break; }". Critically, we want to restructure the loop so there's one branch that controls entry and another that controls loop exit. A concern is that your compiler or JIT might be clever enough to transform this back to "while C == 0 : Pause". You can sometimes avoid this by inserting a call to a some type of very cheap "opaque" method that the compiler can't elide or reorder. On Solaris, for instance, you could use :"if C == 0 : { gethrtime(); for { Pause; if C != 0 : break; }}". It's worth noting the obvious duality between locks and queues. If you have strict FIFO lock implementation with local spinning and succession by direct handoff such as MCS or CLH,then you can usually transform that lock into a queue. Hidden commentary and annotations - invisible : * And of course there's a well-known duality between queues and locks, but I'll leave that topic for another blog post. * Compare and contrast : PTLQ vs PTL and MultiLane * Equivalent : Turn; seq; sequence; pos; position; ticket * Put = Lock; Deposit Take = identify and reserve slot; wait; extract & clear; unlock * conceptualize : Distinct PutLock and TakeLock implemented as ticket lock or PTL Distinct arrival cursors but share per-slot "Turn" variable provides exclusive role-based access to slot's mailbox field put() acquires exclusive access to a slot for purposes of "deposit" assigns slot round-robin and then acquires deposit access rights/perms to that slot take() acquires exclusive access to slot for purposes of "withdrawal" assigns slot round-robin and then acquires withdrawal access rights/perms to that slot At any given time, only one thread can have withdrawal access to a slot at any given time, only one thread can have deposit access to a slot Permissible for T1 to have deposit access and T2 to simultaneously have withdrawal access * round-robin for the purposes of; role-based; access mode; access role mailslot; mailbox; allocate/assign/identify slot rights; permission; license; access permission; * PTL/Ticket hybrid Asymmetric usage ; owner oblivious lock-unlock pairing K-exclusion add Grant cursor pass message m from lock to unlock via Slots[] array Cursor performs 2 functions : + PTL ticket + Assigns request to slot in round-robin fashion Deconstruct protocol : explication put() : allocate slot in round-robin fashion acquire PTL for "put" access store message into slot associated with PTL index take() : Acquire PTL for "take" access // doorway step seq = fetchAdd (&Grant, 1) s = &Slots[seq & Mask] // waiting phase while s-Turn != seq : pause Extract : wait for s-mailbox to be full v = s-mailbox s-mailbox = null Release PTL for both "put" and "take" access s-Turn = seq + Mask + 1 * Slot round-robin assignment and lock "doorway" protocol leverage the same cursor and FetchAdd operation on that cursor FetchAdd (&Cursor,1) + round-robin slot assignment and dispersal + PTL/ticket lock "doorway" step waiting phase is via "Turn" field in slot * PTLQueue uses 2 cursors -- put and take. Acquire "put" access to slot via PTL-like lock Acquire "take" access to slot via PTL-like lock 2 locks : put and take -- at most one thread can access slot's mailbox Both locks use same "turn" field Like multilane : 2 cursors : put and take slot is simple 1-capacity mailbox instead of queue Borrow per-slot turn/grant from PTL Provides strict FIFO Lock slot : put-vs-put take-vs-take at most one put accesses slot at any one time at most one put accesses take at any one time reduction to 1-vs-1 instead of N-vs-M concurrency Per slot locks for put/take Release put/take by advancing turn * is instrumental in ... * P-V Semaphore vs lock vs K-exclusion * See also : FastQueues-excerpt.java dice-etc/queue-mpmc-bounded-blocking-circular-xadd/ * PTLQueue is the same as PTLQB - identical * Expedient return; ASAP; prompt; immediately * Lamport's Bakery algorithm : doorway step then waiting phase Threads arriving at doorway obtain a unique ticket number Threads enter in ticket order * In the terminology of Reed and Kanodia a ticket lock corresponds to the busy-wait implementation of a semaphore using an eventcount and a sequencer It can also be thought of as an optimization of Lamport's bakery lock was designed for fault-tolerance rather than performance Instead of spinning on the release counter, processors using a bakery lock repeatedly examine the tickets of their peers --

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• Cacti: "An internal Net-Snmp error condition detected in Cacti snmp_count"

  - by Recc

  There's the odd forum topic about an error similarly obscure as this, but I haven't seen any for snmp_count in particular. Also I don't see graphing problems, though I can't simply go and eyeball all graphs. However the poller does time out and has to be stopped by its internal process preventing overruns. If I filter out the flood of this error in the log I dont get anything else except the poller timeout: 06/12/2014 12:48:00 PM - POLLER: Poller[0] Maximum runtime of 58 seconds exceeded. Exiting. 06/12/2014 12:48:00 PM - SYSTEM STATS: Time:58.8566 Method:spine Processes:1 Threads:40 Hosts:1923 HostsPerProcess:1923 DataSources:61584 RRDsProcessed:0 06/12/2014 12:48:00 PM - SPINE: Poller[0] ERROR: Spine Timed Out While Processing Hosts Internal I saw in the running processes /usr/local/spine/spine 0 2053 that's always left behind. When I kill it the flooding of the error stops. Of course it's the same on the next poll run as it goes through the devices. 2053 is apparently the DB ID for a device. I deleted it completely to see if that stops it. It doesn't, instead 2052 is seen there. I suspect It'll be the same if I keep deleting devices which I will not do. This started happening midday when I wasn't doing anything to the cacti server. I have tried reducing Maximum Threads per Process to 1 and Number of PHP Script Servers to 1. I've been running it at 10 script servers / 40 threads for months with poll cycle time of about 20 sec. I just found out Running snmpwalk on any host would begin returning the values but then timeout halfway through. This doesn't happen from different servers on the network this Cacti is suggesting still that it's a problem with it locally. Any suggestions? For one polling cycle I changed to use cmd.php instead. then I started getting errors like CMDPHP: Poller[0] Host[45] DS[541] WARNING: Result from SNMP not valid. Partial Result: U Perhaps as expected. Looking closely I see that every snmpwalk I do is interrupted at the same place as if some byte limit is hit and the connection torn down.

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• Android AsyncTask testing problem with Android Test Framework

  - by Vlad

  I have a very simple AsyncTask implementation example and have problem to test it using Android JUnit framework. It works just fine when I instantiate and execute it in normal application. However when it's executed from any of Android Testing framework classes (i.e. AndroidTestCase, ActivityUnitTestCase, ActivityInstrumentationTestCase2 etc) it behaves sarngely: - It executes doInBackground() method correctly - However it doesn't invokes any of its notification methods (onPostExecute(), onProgressUpdate(), etc) -- just silently ignores them whitout showing any errors. This is very simple AsyncTask example package kroz.andcookbook.threads.asynctask; import android.os.AsyncTask; import android.util.Log; import android.widget.ProgressBar; import android.widget.Toast; public class AsyncTaskDemo extends AsyncTask<Integer, Integer, String> { AsyncTaskDemoActivity _parentActivity; int _counter; int _maxCount; public AsyncTaskDemo(AsyncTaskDemoActivity asyncTaskDemoActivity) { _parentActivity = asyncTaskDemoActivity; } @Override protected void onPreExecute() { super.onPreExecute(); _parentActivity._progressBar.setVisibility(ProgressBar.VISIBLE); _parentActivity._progressBar.invalidate(); } @Override protected String doInBackground(Integer... params) { _maxCount = params[0]; for (_counter = 0; _counter <= _maxCount; _counter++) { try { Thread.sleep(1000); publishProgress(_counter); } catch (InterruptedException e) { // Ignore } } } @Override protected void onProgressUpdate(Integer... values) { super.onProgressUpdate(values); int progress = values[0]; String progressStr = "Counting " + progress + " out of " + _maxCount; _parentActivity._textView.setText(progressStr); _parentActivity._textView.invalidate(); } @Override protected void onPostExecute(String result) { super.onPostExecute(result); _parentActivity._progressBar.setVisibility(ProgressBar.INVISIBLE); _parentActivity._progressBar.invalidate(); } @Override protected void onCancelled() { super.onCancelled(); _parentActivity._textView.setText("Request to cancel AsyncTask"); } } This is a test case. Here AsyncTaskDemoActivity is a very simple Activity providing UI for testing AsyncTask in mode: package kroz.andcookbook.test.threads.asynctask; import java.util.concurrent.ExecutionException; import kroz.andcookbook.R; import kroz.andcookbook.threads.asynctask.AsyncTaskDemo; import kroz.andcookbook.threads.asynctask.AsyncTaskDemoActivity; import android.content.Intent; import android.test.ActivityUnitTestCase; import android.widget.Button; public class AsyncTaskDemoTest2 extends ActivityUnitTestCase<AsyncTaskDemoActivity> { AsyncTaskDemo _atask; private Intent _startIntent; public AsyncTaskDemoTest2() { super(AsyncTaskDemoActivity.class); } protected void setUp() throws Exception { super.setUp(); _startIntent = new Intent(Intent.ACTION_MAIN); } protected void tearDown() throws Exception { super.tearDown(); } public final void testExecute() { startActivity(_startIntent, null, null); Button btnStart = (Button) getActivity().findViewById(R.id.Button01); btnStart.performClick(); assertNotNull(getActivity()); } } All this code is working just fine, except the fact that AsynTask doesn't invoke it's notification methods when executed by whithin Android Testing Framework. Any ideas?

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• Why are my uWSGI processes dying immediately?

  - by orokusaki

  I'm using Supervisor and the uWSGI Emperor mode. When I set limit-as to 512 (MB), workers die instantly (respawn, die, respawn, die, every 3/4 of a second or so): [uwsgi] workers = 4 threads = 40 limit-as = 512 harakiri = 20 max-requests = 1600 ... non-performance/memory/processor-related settings ommitted But, if I change limit-as to: [uwsgi] workers = 4 threads = 40 limit-as = 1024 harakiri = 20 max-requests = 1600 ... non-performance/memory/processor-related settings ommitted and restart uwsgi, the problem is gone immediately. In order to put a sham in this, I've modified the setting back to 512, restarted again, and the problem is back immediately. Notes: My app is a simple Django app without much additional Python setup during start-up time.

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• taskmgr.exe 100% CPU Usage

  - by Burnsys

  Hi. I have 2 IBM servers Intel Xeon Dual core with 2gb RAM. the problem is that Taskmanager uses one full core when i open it. The same happens when i copy files in the explorer. OS: Windows 2003 Server Things i tried: Installed all updates They has kaspersky anti virus and they previously had Nod32. All drivers installed OK. All unused devices are disabled in the bios. Reinstalled win 2003 SP2. No conflict in drivers Tried opening via remote desktop and the problem continues. The cpu utilization is in the Kernel Times (Red in taskmanager) If i open Proces Explorer and i navigate to the threads consuming CPU the stack traces ends always in "NtkrnlPA!UnexpectedInterrupt", all threads stacks end in "UnexpectedInterrupt" ntoskrnl.exe!KiUnexpectedInterrupt+0x48 ntoskrnl.exe!KeWaitForMutexObject+0x20e ntoskrnl.exe!CcSetReadAheadGranularity+0x1ff9 ntoskrnl.exe!IoAllocateIrp+0x3fd ntoskrnl.exe!KeWaitForMutexObject+0x20e ntoskrnl.exe!NtWaitForSingleObject+0x94 ntoskrnl.exe!DbgBreakPointWithStatus+0xe05 ntdll.dll!KiFastSystemCallRet kernel32.dll!WaitForSingleObject+0x12 taskmgr.exe+0xeef6 kernel32.dll!GetModuleHandleA+0xdf Any help would be appreciated!

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• Zabbix - Some of the monitored items don't refreh

  - by Niro

  I'm experiencing a strange issue with Zabbix monitoring a MySQL server. Most of the data from the server such as MySQL queries per second and MySQL uptime , Buffers memory etc. update nicely while some data like CPU iowait time (avg1) , Host local time ,MySQL number of threads and other items which were monitored in the past has last check time of about a week ago. I can't find any logic in this, for example Mysql number of threads and Mysql queries per second are obtained in a similar way so it does not make sense one of them is monitored and one is not. Please help- how can I fix this? Update - I used zabbix_get from the zabbix server to check one of the items on the zabbix client and it works so the problem must be on the zabbix server side

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• Disable .htaccess from apache allowoverride none, still reads .htaccess files

  - by John Magnolia

  I have moved all of our .htaccess config into <Directory> blocks and set AllowOverride None in the default and default-ssl. Although after restarting apache it is still reading the .htaccess files. How can I completely turn off reading these files? Update of all files with "AllowOverride" /etc/apache2/mods-available/userdir.conf <IfModule mod_userdir.c> UserDir public_html UserDir disabled root <Directory /home/*/public_html> AllowOverride FileInfo AuthConfig Limit Indexes Options MultiViews Indexes SymLinksIfOwnerMatch IncludesNoExec <Limit GET POST OPTIONS> Order allow,deny Allow from all </Limit> <LimitExcept GET POST OPTIONS> Order deny,allow Deny from all </LimitExcept> </Directory> </IfModule> /etc/apache2/mods-available/alias.conf <IfModule alias_module> # # Aliases: Add here as many aliases as you need (with no limit). The format is # Alias fakename realname # # Note that if you include a trailing / on fakename then the server will # require it to be present in the URL. So "/icons" isn't aliased in this # example, only "/icons/". If the fakename is slash-terminated, then the # realname must also be slash terminated, and if the fakename omits the # trailing slash, the realname must also omit it. # # We include the /icons/ alias for FancyIndexed directory listings. If # you do not use FancyIndexing, you may comment this out. # Alias /icons/ "/usr/share/apache2/icons/" <Directory "/usr/share/apache2/icons"> Options Indexes MultiViews AllowOverride None Order allow,deny Allow from all </Directory> </IfModule> /etc/apache2/httpd.conf # # Directives to allow use of AWStats as a CGI # Alias /awstatsclasses "/usr/share/doc/awstats/examples/wwwroot/classes/" Alias /awstatscss "/usr/share/doc/awstats/examples/wwwroot/css/" Alias /awstatsicons "/usr/share/doc/awstats/examples/wwwroot/icon/" ScriptAlias /awstats/ "/usr/share/doc/awstats/examples/wwwroot/cgi-bin/" # # This is to permit URL access to scripts/files in AWStats directory. # <Directory "/usr/share/doc/awstats/examples/wwwroot"> Options None AllowOverride None Order allow,deny Allow from all </Directory> Alias /awstats-icon/ /usr/share/awstats/icon/ <Directory /usr/share/awstats/icon> Options None AllowOverride None Order allow,deny Allow from all </Directory> /etc/apache2/sites-available/default-ssl <IfModule mod_ssl.c> <VirtualHost _default_:443> ServerAdmin webmaster@localhost DocumentRoot /var/www <Directory /> Options FollowSymLinks AllowOverride None </Directory> <Directory /var/www/> Options Indexes FollowSymLinks MultiViews AllowOverride None </Directory> ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/ <Directory "/usr/lib/cgi-bin"> AllowOverride None Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch Order allow,deny Allow from all </Directory> ErrorLog ${APACHE_LOG_DIR}/error.log # Possible values include: debug, info, notice, warn, error, crit, # alert, emerg. LogLevel warn CustomLog ${APACHE_LOG_DIR}/ssl_access.log combined # SSL Engine Switch: # Enable/Disable SSL for this virtual host. SSLEngine on # A self-signed (snakeoil) certificate can be created by installing # the ssl-cert package. See # /usr/share/doc/apache2.2-common/README.Debian.gz for more info. # If both key and certificate are stored in the same file, only the # SSLCertificateFile directive is needed. SSLCertificateFile /etc/ssl/certs/ssl-cert-snakeoil.pem SSLCertificateKeyFile /etc/ssl/private/ssl-cert-snakeoil.key # Server Certificate Chain: # Point SSLCertificateChainFile at a file containing the # concatenation of PEM encoded CA certificates which form the # certificate chain for the server certificate. Alternatively # the referenced file can be the same as SSLCertificateFile # when the CA certificates are directly appended to the server # certificate for convinience. #SSLCertificateChainFile /etc/apache2/ssl.crt/server-ca.crt # Certificate Authority (CA): # Set the CA certificate verification path where to find CA # certificates for client authentication or alternatively one # huge file containing all of them (file must be PEM encoded) # Note: Inside SSLCACertificatePath you need hash symlinks # to point to the certificate files. Use the provided # Makefile to update the hash symlinks after changes. #SSLCACertificatePath /etc/ssl/certs/ #SSLCACertificateFile /etc/apache2/ssl.crt/ca-bundle.crt # Certificate Revocation Lists (CRL): # Set the CA revocation path where to find CA CRLs for client # authentication or alternatively one huge file containing all # of them (file must be PEM encoded) # Note: Inside SSLCARevocationPath you need hash symlinks # to point to the certificate files. Use the provided # Makefile to update the hash symlinks after changes. #SSLCARevocationPath /etc/apache2/ssl.crl/ #SSLCARevocationFile /etc/apache2/ssl.crl/ca-bundle.crl # Client Authentication (Type): # Client certificate verification type and depth. Types are # none, optional, require and optional_no_ca. Depth is a # number which specifies how deeply to verify the certificate # issuer chain before deciding the certificate is not valid. #SSLVerifyClient require #SSLVerifyDepth 10 # Access Control: # With SSLRequire you can do per-directory access control based # on arbitrary complex boolean expressions containing server # variable checks and other lookup directives. The syntax is a # mixture between C and Perl. See the mod_ssl documentation # for more details. #<Location /> #SSLRequire ( %{SSL_CIPHER} !~ m/^(EXP|NULL)/ \ # and %{SSL_CLIENT_S_DN_O} eq "Snake Oil, Ltd." \ # and %{SSL_CLIENT_S_DN_OU} in {"Staff", "CA", "Dev"} \ # and %{TIME_WDAY} >= 1 and %{TIME_WDAY} <= 5 \ # and %{TIME_HOUR} >= 8 and %{TIME_HOUR} <= 20 ) \ # or %{REMOTE_ADDR} =~ m/^192\.76\.162\.[0-9]+$/ #</Location> # SSL Engine Options: # Set various options for the SSL engine. # o FakeBasicAuth: # Translate the client X.509 into a Basic Authorisation. This means that # the standard Auth/DBMAuth methods can be used for access control. The # user name is the `one line' version of the client's X.509 certificate. # Note that no password is obtained from the user. Every entry in the user # file needs this password: `xxj31ZMTZzkVA'. # o ExportCertData: # This exports two additional environment variables: SSL_CLIENT_CERT and # SSL_SERVER_CERT. These contain the PEM-encoded certificates of the # server (always existing) and the client (only existing when client # authentication is used). This can be used to import the certificates # into CGI scripts. # o StdEnvVars: # This exports the standard SSL/TLS related `SSL_*' environment variables. # Per default this exportation is switched off for performance reasons, # because the extraction step is an expensive operation and is usually # useless for serving static content. So one usually enables the # exportation for CGI and SSI requests only. # o StrictRequire: # This denies access when "SSLRequireSSL" or "SSLRequire" applied even # under a "Satisfy any" situation, i.e. when it applies access is denied # and no other module can change it. # o OptRenegotiate: # This enables optimized SSL connection renegotiation handling when SSL # directives are used in per-directory context. #SSLOptions +FakeBasicAuth +ExportCertData +StrictRequire <FilesMatch "\.(cgi|shtml|phtml|php)$"> SSLOptions +StdEnvVars </FilesMatch> <Directory /usr/lib/cgi-bin> SSLOptions +StdEnvVars </Directory> # SSL Protocol Adjustments: # The safe and default but still SSL/TLS standard compliant shutdown # approach is that mod_ssl sends the close notify alert but doesn't wait for # the close notify alert from client. When you need a different shutdown # approach you can use one of the following variables: # o ssl-unclean-shutdown: # This forces an unclean shutdown when the connection is closed, i.e. no # SSL close notify alert is send or allowed to received. This violates # the SSL/TLS standard but is needed for some brain-dead browsers. Use # this when you receive I/O errors because of the standard approach where # mod_ssl sends the close notify alert. # o ssl-accurate-shutdown: # This forces an accurate shutdown when the connection is closed, i.e. a # SSL close notify alert is send and mod_ssl waits for the close notify # alert of the client. This is 100% SSL/TLS standard compliant, but in # practice often causes hanging connections with brain-dead browsers. Use # this only for browsers where you know that their SSL implementation # works correctly. # Notice: Most problems of broken clients are also related to the HTTP # keep-alive facility, so you usually additionally want to disable # keep-alive for those clients, too. Use variable "nokeepalive" for this. # Similarly, one has to force some clients to use HTTP/1.0 to workaround # their broken HTTP/1.1 implementation. Use variables "downgrade-1.0" and # "force-response-1.0" for this. BrowserMatch "MSIE [2-6]" \ nokeepalive ssl-unclean-shutdown \ downgrade-1.0 force-response-1.0 # MSIE 7 and newer should be able to use keepalive BrowserMatch "MSIE [17-9]" ssl-unclean-shutdown </VirtualHost> </IfModule> /etc/apache2/sites-available/default <VirtualHost *:80> ServerAdmin webmaster@localhost DocumentRoot /var/www <Directory /> Options FollowSymLinks AllowOverride None </Directory> <Directory /var/www/> Options -Indexes FollowSymLinks MultiViews AllowOverride None Order allow,deny allow from all </Directory> ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/ <Directory "/usr/lib/cgi-bin"> AllowOverride None Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch Order allow,deny Allow from all </Directory> Alias /delboy /usr/share/phpmyadmin <Directory /usr/share/phpmyadmin> # Restrict phpmyadmin access Order Deny,Allow Allow from all </Directory> ErrorLog ${APACHE_LOG_DIR}/error.log # Possible values include: debug, info, notice, warn, error, crit, # alert, emerg. LogLevel warn CustomLog ${APACHE_LOG_DIR}/access.log combined Alias /doc/ "/usr/share/doc/" <Directory "/usr/share/doc/"> Options Indexes MultiViews FollowSymLinks AllowOverride None Order deny,allow Deny from all Allow from 127.0.0.0/255.0.0.0 ::1/128 </Directory> </VirtualHost> /etc/apache2/conf.d/security # # Disable access to the entire file system except for the directories that # are explicitly allowed later. # # This currently breaks the configurations that come with some web application # Debian packages. # #<Directory /> # AllowOverride None # Order Deny,Allow # Deny from all #</Directory> # Changing the following options will not really affect the security of the # server, but might make attacks slightly more difficult in some cases. # # ServerTokens # This directive configures what you return as the Server HTTP response # Header. The default is 'Full' which sends information about the OS-Type # and compiled in modules. # Set to one of: Full | OS | Minimal | Minor | Major | Prod # where Full conveys the most information, and Prod the least. # #ServerTokens Minimal ServerTokens OS #ServerTokens Full # # Optionally add a line containing the server version and virtual host # name to server-generated pages (internal error documents, FTP directory # listings, mod_status and mod_info output etc., but not CGI generated # documents or custom error documents). # Set to "EMail" to also include a mailto: link to the ServerAdmin. # Set to one of: On | Off | EMail # #ServerSignature Off ServerSignature On # # Allow TRACE method # # Set to "extended" to also reflect the request body (only for testing and # diagnostic purposes). # # Set to one of: On | Off | extended # TraceEnable Off #TraceEnable On /etc/apache2/apache2.conf # # Based upon the NCSA server configuration files originally by Rob McCool. # # This is the main Apache server configuration file. It contains the # configuration directives that give the server its instructions. # See http://httpd.apache.org/docs/2.2/ for detailed information about # the directives. # # Do NOT simply read the instructions in here without understanding # what they do. They're here only as hints or reminders. If you are unsure # consult the online docs. You have been warned. # # The configuration directives are grouped into three basic sections: # 1. Directives that control the operation of the Apache server process as a # whole (the 'global environment'). # 2. Directives that define the parameters of the 'main' or 'default' server, # which responds to requests that aren't handled by a virtual host. # These directives also provide default values for the settings # of all virtual hosts. # 3. Settings for virtual hosts, which allow Web requests to be sent to # different IP addresses or hostnames and have them handled by the # same Apache server process. # # Configuration and logfile names: If the filenames you specify for many # of the server's control files begin with "/" (or "drive:/" for Win32), the # server will use that explicit path. If the filenames do *not* begin # with "/", the value of ServerRoot is prepended -- so "foo.log" # with ServerRoot set to "/etc/apache2" will be interpreted by the # server as "/etc/apache2/foo.log". # ### Section 1: Global Environment # # The directives in this section affect the overall operation of Apache, # such as the number of concurrent requests it can handle or where it # can find its configuration files. # # # ServerRoot: The top of the directory tree under which the server's # configuration, error, and log files are kept. # # NOTE! If you intend to place this on an NFS (or otherwise network) # mounted filesystem then please read the LockFile documentation (available # at <URL:http://httpd.apache.org/docs/2.2/mod/mpm_common.html#lockfile>); # you will save yourself a lot of trouble. # # Do NOT add a slash at the end of the directory path. # #ServerRoot "/etc/apache2" # # The accept serialization lock file MUST BE STORED ON A LOCAL DISK. # LockFile ${APACHE_LOCK_DIR}/accept.lock # # PidFile: The file in which the server should record its process # identification number when it starts. # This needs to be set in /etc/apache2/envvars # PidFile ${APACHE_PID_FILE} # # Timeout: The number of seconds before receives and sends time out. # Timeout 300 # # KeepAlive: Whether or not to allow persistent connections (more than # one request per connection). Set to "Off" to deactivate. # KeepAlive On # # MaxKeepAliveRequests: The maximum number of requests to allow # during a persistent connection. Set to 0 to allow an unlimited amount. # We recommend you leave this number high, for maximum performance. # MaxKeepAliveRequests 100 # # KeepAliveTimeout: Number of seconds to wait for the next request from the # same client on the same connection. # KeepAliveTimeout 4 ## ## Server-Pool Size Regulation (MPM specific) ## # prefork MPM # StartServers: number of server processes to start # MinSpareServers: minimum number of server processes which are kept spare # MaxSpareServers: maximum number of server processes which are kept spare # MaxClients: maximum number of server processes allowed to start # MaxRequestsPerChild: maximum number of requests a server process serves <IfModule mpm_prefork_module> StartServers 5 MinSpareServers 5 MaxSpareServers 10 MaxClients 150 MaxRequestsPerChild 500 </IfModule> # worker MPM # StartServers: initial number of server processes to start # MaxClients: maximum number of simultaneous client connections # MinSpareThreads: minimum number of worker threads which are kept spare # MaxSpareThreads: maximum number of worker threads which are kept spare # ThreadLimit: ThreadsPerChild can be changed to this maximum value during a # graceful restart. ThreadLimit can only be changed by stopping # and starting Apache. # ThreadsPerChild: constant number of worker threads in each server process # MaxRequestsPerChild: maximum number of requests a server process serves <IfModule mpm_worker_module> StartServers 2 MinSpareThreads 25 MaxSpareThreads 75 ThreadLimit 64 ThreadsPerChild 25 MaxClients 150 MaxRequestsPerChild 0 </IfModule> # event MPM # StartServers: initial number of server processes to start # MaxClients: maximum number of simultaneous client connections # MinSpareThreads: minimum number of worker threads which are kept spare # MaxSpareThreads: maximum number of worker threads which are kept spare # ThreadsPerChild: constant number of worker threads in each server process # MaxRequestsPerChild: maximum number of requests a server process serves <IfModule mpm_event_module> StartServers 2 MaxClients 150 MinSpareThreads 25 MaxSpareThreads 75 ThreadLimit 64 ThreadsPerChild 25 MaxRequestsPerChild 0 </IfModule> # These need to be set in /etc/apache2/envvars User ${APACHE_RUN_USER} Group ${APACHE_RUN_GROUP} # # AccessFileName: The name of the file to look for in each directory # for additional configuration directives. See also the AllowOverride # directive. # AccessFileName .htaccess # # The following lines prevent .htaccess and .htpasswd files from being # viewed by Web clients. # <Files ~ "^\.ht"> Order allow,deny Deny from all Satisfy all </Files> # # DefaultType is the default MIME type the server will use for a document # if it cannot otherwise determine one, such as from filename extensions. # If your server contains mostly text or HTML documents, "text/plain" is # a good value. If most of your content is binary, such as applications # or images, you may want to use "application/octet-stream" instead to # keep browsers from trying to display binary files as though they are # text. # DefaultType text/plain # # HostnameLookups: Log the names of clients or just their IP addresses # e.g., www.apache.org (on) or 204.62.129.132 (off). # The default is off because it'd be overall better for the net if people # had to knowingly turn this feature on, since enabling it means that # each client request will result in AT LEAST one lookup request to the # nameserver. # HostnameLookups Off # ErrorLog: The location of the error log file. # If you do not specify an ErrorLog directive within a <VirtualHost> # container, error messages relating to that virtual host will be # logged here. If you *do* define an error logfile for a <VirtualHost> # container, that host's errors will be logged there and not here. # ErrorLog ${APACHE_LOG_DIR}/error.log # # LogLevel: Control the number of messages logged to the error_log. # Possible values include: debug, info, notice, warn, error, crit, # alert, emerg. # LogLevel warn # Include module configuration: Include mods-enabled/*.load Include mods-enabled/*.conf # Include all the user configurations: Include httpd.conf # Include ports listing Include ports.conf # # The following directives define some format nicknames for use with # a CustomLog directive (see below). # If you are behind a reverse proxy, you might want to change %h into %{X-Forwarded-For}i # LogFormat "%v:%p %h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" vhost_combined LogFormat "%h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" combined LogFormat "%h %l %u %t \"%r\" %>s %O" common LogFormat "%{Referer}i -> %U" referer LogFormat "%{User-agent}i" agent # Include of directories ignores editors' and dpkg's backup files, # see README.Debian for details. # Include generic snippets of statements Include conf.d/ # Include the virtual host configurations: Include sites-enabled/

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• Shared IMAP Folders in GMail

  - by Grinn

  Our office is using Google Apps for Domains for our email. Our customer support guys use IMAP clients (such as Thunderbird and Outlook) to check both their individual email addresses and a "collective" support email address. On the support account, there are several folders for organizing email threads by client. When a user gets a support-related email (either to the support email or their individual email address) they file away the email in one of thse shared folders. Many of us greatly prefer the Gmail interface (with Folders4Gmail enabled on the Better Gmail 2 add-on for Firefox, for label-to-folder support) over Thunderbird or Outlook. However, there is no way to "share" email threads, complete with labels, between accounts. The desired end result is that a user logs into their individual account and can see both their account and the support account and can pass emails (labels and all) between the two accounts - or at least from their individual account into the support account. Any ideas?

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• Convert mkv/h264 video so it can be played on a "mid-range" Sony Ericsson phone. (using Ubuntu).

  - by Johan

  Hi As a little experiment I thinking of converting some video/movies/tv-series into a format that could be playable on my K850, but to be a little bit more generic in this question let's say "mid range Sony Ericsson" phone since they all more or less behave the same and has the same screen resolution (240 x 320). I am looking for command line based tools (for Ubuntu), since I am thinking about writing a "convert and move" script later if it is successful. A lot of the video I have is encoded in mkv/h264, but since that is not supported by the phone I guess that I need to convert it into some mp4/mpeg4 low quality video. After some googling it seems like a good candidate for the job is ffmpeg, but that seems to be a very versatile tool with a lot of magic tricks. Am I on the right track? And if so how do I use ffmpeg to do this? Thanks Johan Update: After plating a little bit with ffmeg I noticed that it only uses 1 of my 4 cores, so the transcoding takes forever. I found a arg called -threads but that did not change much, maybe I got it wrong. I also found that something like this plays in the phone. ffmpeg -i Mythbusters\ S1D1_1.mkv -threads 4 -t 180 -vcodec mpeg4 -r 15 -s 320x240 Mythbusters\ S1D1_1_mini.mp4 It was possible to use 3gp/h263, but the quality was really useless. ffmpeg -i Mythbusters\ S1D1_1.mkv -t 180 -vcodec h263 -acodec libfaac -s cif Mythbusters\ S1D1_1_cif.3gp And it seems like mp4/h264 is also possible and the result is ok, thanks to this question, this one seem to use more than one core as well so it was a little bit faster for me. ffmpeg -i Mythbusters_S1D1_1.mkv -t 180 -acodec libfaac -ab 60k -s 320x240 -vcodec libx264 -b 500k -flags +loop -cmp +chroma -partitions +parti4x4+partp8x8+partb8x8 -flags2 +mixed_refs -me_method umh -subq 6 -trellis 1 -refs 5 -coder 0 -me_range 16 -g 250 -keyint_min 25 -sc_threshold 40 -i_qfactor 0.71 -bt 500k -maxrate 768k -bufsize 2M -qcomp 0.6 -qmin 10 -qmax 51 -qdiff 4 -level 13 -threads 0 -f mp4 Mythbusters_S1D1_1_qvga.mp4 Update: I have tried to use HandBrakeCLI and it is no problem creating a new file that seem to be the same as the one created with ffmpeg with something like this. HandBrakeCLI -i Mythbusters_S1D1_1.mkv --size 100 -E faac -B 60 --maxHeight 240 -r 15 -e x264 -o Mythbusters_S1D1_1_hand.mp4 But that one did not play in the phone... I found this in the official manual: If you transfer video clips using another program than Media Go™, we recommend that you select H.264 Baseline profile video, up to QVGA at 30 fps, VBR 384 kbps (max 768 kps) with AAC+ audio at 128 kbps (max 255 kbps), 48 kHz and stereo audio in mp4 file format. So the idea to use H264 seems to be correct.

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• Why might apache2 use 100% of CPU at startup?

  - by QuantumMechanic

  This is apache 2.2.14 on SLES9. Out of nowhere (i.e. it had been working fine for ages) I am seeing apache2 suddenly start using 100% of the CPU at startup, and never completing startup. Nothing is getting written to /var/log/error_log (when it did back when things were OK). ps only shows the main httpd process and not any of the spawned threads. When things were OK, it would show the spawned threads. So it appears httpd is going into some sort of infinite loop right at startup and isn't even completing startup. It's not an issue of being overloaded by connections -- this happens even when nothing is trying to contact it. The config files haven't changed (or at least they haven't changed in a way that changed their last-modified time). I've tried added -e debug -E /var/log/apache2/startup_info to the command line, but nothing is put in the file. Any ideas what could be happening?

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• Lock-Free, Wait-Free and Wait-freedom algorithms for non-blocking multi-thread synchronization.

  - by GJ

  In multi thread programming we can find different terms for data transfer synchronization between two or more threads/tasks. When exactly we can say that some algorithem is: 1)Lock-Free 2)Wait-Free 3)Wait-Freedom I understand what means Lock-free but when we can say that some synchronization algorithm is Wait-Free or Wait-Freedom? I have made some code (ring buffer) for multi-thread synchronization and it use Lock-Free methods but: 1) Algorithm predicts maximum execution time of this routine. 2) Therad which call this routine at beginning set unique reference, what mean that is inside of this routine. 3) Other threads which are calling the same routine check this reference and if is set than count the CPU tick count (measure time) of first involved thread. If that time is to long interrupt the current work of involved thread and overrides him job. 4) Thread which not finished job because was interrupted from task scheduler (is reposed) at the end check the reference if not belongs to him repeat the job again. So this algorithm is not really Lock-free but there is no memory lock in use, and other involved threads can wait (or not) certain time before overide the job of reposed thread. Added RingBuffer.InsertLeft function: function TgjRingBuffer.InsertLeft(const link: pointer): integer; var AtStartReference: cardinal; CPUTimeStamp : int64; CurrentLeft : pointer; CurrentReference: cardinal; NewLeft : PReferencedPtr; Reference : cardinal; label TryAgain; begin Reference := GetThreadId + 1; //Reference.bit0 := 1 with rbRingBuffer^ do begin TryAgain: //Set Left.Reference with respect to all other cores :) CPUTimeStamp := GetCPUTimeStamp + LoopTicks; AtStartReference := Left.Reference OR 1; //Reference.bit0 := 1 repeat CurrentReference := Left.Reference; until (CurrentReference AND 1 = 0)or (GetCPUTimeStamp - CPUTimeStamp > 0); //No threads present in ring buffer or current thread timeout if ((CurrentReference AND 1 <> 0) and (AtStartReference <> CurrentReference)) or not CAS32(CurrentReference, Reference, Left.Reference) then goto TryAgain; //Calculate RingBuffer NewLeft address CurrentLeft := Left.Link; NewLeft := pointer(cardinal(CurrentLeft) - SizeOf(TReferencedPtr)); if cardinal(NewLeft) < cardinal(@Buffer) then NewLeft := EndBuffer; //Calcolate distance result := integer(Right.Link) - Integer(NewLeft); //Check buffer full if result = 0 then //Clear Reference if task still own reference if CAS32(Reference, 0, Left.Reference) then Exit else goto TryAgain; //Set NewLeft.Reference NewLeft^.Reference := Reference; SFence; //Try to set link and try to exchange NewLeft and clear Reference if task own reference if (Reference <> Left.Reference) or not CAS64(NewLeft^.Link, Reference, link, Reference, NewLeft^) or not CAS64(CurrentLeft, Reference, NewLeft, 0, Left) then goto TryAgain; //Calcolate result if result < 0 then result := Length - integer(cardinal(not Result) div SizeOf(TReferencedPtr)) else result := cardinal(result) div SizeOf(TReferencedPtr); end; //with end; { TgjRingBuffer.InsertLeft } RingBuffer unit you can find here: RingBuffer, CAS functions: FockFreePrimitives, and test program: RingBufferFlowTest Thanks in advance, GJ

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• Varnish, hide port number

  - by George Reith

  My set up is as follows: OS: CentOS 6.2 running on an OpenVZ virtual machine. Web server: Nginx listening on port 8080 Reverse proxy: Varnish listening on port 80 The problem is that Varnish redirects my requests to port 8080 and this appears in the address bar like so http://mysite.com:8080/directory/, causing relative links on the site to include the port number (8080) in the request and thus bypassing Varnish. The site is powered by WordPress. How do I allow Varnish to use Nginx as the backend on port 8080 without appending the port number to the address? Edit: Varnish is set up like so: I have told the Varnish daemon to listen to port 80 by default. VARNISH_VCL_CONF=/etc/varnish/default.vcl # # # Default address and port to bind to # # Blank address means all IPv4 and IPv6 interfaces, otherwise specify # # a host name, an IPv4 dotted quad, or an IPv6 address in brackets. # VARNISH_LISTEN_ADDRESS= VARNISH_LISTEN_PORT=80 # # # Telnet admin interface listen address and port VARNISH_ADMIN_LISTEN_ADDRESS=127.0.0.1 VARNISH_ADMIN_LISTEN_PORT=6082 # # # Shared secret file for admin interface VARNISH_SECRET_FILE=/etc/varnish/secret # # # The minimum number of worker threads to start VARNISH_MIN_THREADS=1 # # # The Maximum number of worker threads to start VARNISH_MAX_THREADS=1000 # # # Idle timeout for worker threads VARNISH_THREAD_TIMEOUT=120 # # # Cache file location VARNISH_STORAGE_FILE=/var/lib/varnish/varnish_storage.bin # # # Cache file size: in bytes, optionally using k / M / G / T suffix, # # or in percentage of available disk space using the % suffix. VARNISH_STORAGE_SIZE=1G # # # Backend storage specification VARNISH_STORAGE="file,${VARNISH_STORAGE_FILE},${VARNISH_STORAGE_SIZE}" # # # Default TTL used when the backend does not specify one VARNISH_TTL=120 The VCL file that Varnish calls (through an include in default.vcl) consists of: backend playwithbits { .host = "127.0.0.1"; .port = "8080"; } acl purge { "127.0.0.1"; } sub vcl_recv { if (req.http.Host ~ "^(.*\.)?playwithbits\.com$") { set req.backend = playwithbits; set req.http.Host = regsub(req.http.Host, ":[0-9]+", ""); if (req.request == "PURGE") { if (!client.ip ~ purge) { error 405 "Not allowed."; } return(lookup); } if (req.url ~ "^/$") { unset req.http.cookie; } } } sub vcl_hit { if (req.http.Host ~ "^(.*\.)?playwithbits\.com$") { if (req.request == "PURGE") { set obj.ttl = 0s; error 200 "Purged."; } } } sub vcl_miss { if (req.http.Host ~ "^(.*\.)?playwithbits\.com$") { if (req.request == "PURGE") { error 404 "Not in cache."; } if (!(req.url ~ "wp-(login|admin)")) { unset req.http.cookie; } if (req.url ~ "^/[^?]+.(jpeg|jpg|png|gif|ico|js|css|txt|gz|zip|lzma|bz2|tgz|tbz|html|htm)(\?.|)$") { unset req.http.cookie; set req.url = regsub(req.url, "\?.$", ""); } if (req.url ~ "^/$") { unset req.http.cookie; } } } sub vcl_fetch { if (req.http.Host ~ "^(.*\.)?playwithbits\.com$") { if (req.url ~ "^/$") { unset beresp.http.set-cookie; } if (!(req.url ~ "wp-(login|admin)")) { unset beresp.http.set-cookie; } } }

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• apache hangs frequently with semop

  - by PiTheNumber

  My Apache hangs frequently with multiple threads. Each thread get stucked for hours. Backtrace looks like this: (gdb) backtrace #0 0x00002af60c22b2d7 in semop () from /lib64/libc.so.6 #1 0x00002af60bbf612c in ?? () from /usr/lib64/libapr-1.so.0 #2 0x000055555559e614 in ?? () from /usr/sbin/httpd2-prefork #3 0x000055555559e9ea in ?? () from /usr/sbin/httpd2-prefork #4 0x000055555559f25d in ap_mpm_run () from /usr/sbin/httpd2-prefork #5 0x000055555557a080 in main () from /usr/sbin/httpd2-prefork With strace I see they are waiting for a pipe that is connection all Apache threads. strace -p 3069 .... read(7, 0x7fff16a04df7, 1) = -1 EAGAIN (Resource temporarily unavailable) semop(286162952, 0x2af60bd07dc0, 1 <unfinished ...> What is Apache doing here? How can I figure out what is causing this?

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• Variable mysteriously changing value

  - by Eitan

  I am making a simple tcp/ip chat program for practicing threads and tcp/ip. I was using asynchronous methods but had a problem with concurrency so I went to threads and blocking methods (not asynchronous). I have two private variables defined in the class, not static: string amessage = string.Empty; int MessageLength; and a Thread private Thread BeginRead; Ok so I call a function called Listen ONCE when the client starts: public virtual void Listen(int byteLength) { var state = new StateObject {Buffer = new byte[byteLength]}; BeginRead = new Thread(ReadThread); BeginRead.Start(state); } and finally the function to receive commands and process them, I'm going to shorten it because it is really long: private void ReadThread(object objectState) { var state = (StateObject)objectState; int byteLength = state.Buffer.Length; while (true) { var buffer = new byte[byteLength]; int len = MySocket.Receive(buffer); if (len <= 0) return; string content = Encoding.ASCII.GetString(buffer, 0, len); amessage += cleanMessage.Substring(0, MessageLength); if (OnRead != null) { var e = new CommandEventArgs(amessage); OnRead(this, e); } } } Now, as I understand it only one thread at a time will enter BeginRead, I call Receive, it blocks until I get data, and then I process it. The problem: the variable amessage will change it's value between statements that do not touch or alter the variable at all, for example at the bottom of the function at: if (OnRead != null) "amessage" will be equal to 'asdf' and at if (OnRead != null) "amessage" will be equal to qwert. As I understand it this is indicative of another thread changing the value/running asynchronously. I only spawn one thread to do the receiving and the Receive function is blocking, how could there be two threads in this function and if there is only one thread how does amessage's value change between statements that don't affect it's value. As a side note sorry for spamming the site with these questions but I'm just getting a hang of this threading story and it's making me want to sip cyanide. Thanks in advance. EDIT: Here is my code that calls the Listen Method in the client: public void ConnectClient(string ip,int port) { client.Connect(ip,port); client.Listen(5); } and in the server: private void Accept(IAsyncResult result) { var client = new AbstractClient(MySocket.EndAccept(result)); var e = new CommandEventArgs(client, null); Clients.Add(client); client.Listen(5); if (OnClientAdded != null) { var target = (Control) OnClientAdded.Target; if (target != null && target.InvokeRequired) target.Invoke(OnClientAdded, this, e); else OnClientAdded(this, e); } client.OnRead += OnRead; MySocket.BeginAccept(new AsyncCallback(Accept), null); } All this code is in a class called AbstractClient. The client inherits the Abstract client and when the server accepts a socket it create's it's own local AbstractClient, in this case both modules access the functions above however they are different instances and I couldn't imagine threads from different instances combining especially as no variable is static.

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• Change Audio title from English to Sinhalese using ffmpeg

  - by user330461

  I insert an extra Sound track in my video file and it works well. ffmpeg -i news.mov -i news.wav -map 0:0 -map 0:1 -map 1:0 -pass 1 -vcodec libx264 -preset fast -b 512k -minrate 512k -maxrate 512k -bufsize 512k -threads 0 -f mp4 -an -y /dev/null && ffmpeg -i news.mov -i news.wav -map 0:0 -map 0:1 -map 1:0 -pass 2 -acodec libfaac -ab 128k -ac 2 -vcodec libx264 -preset fast -b 512k -minrate 512k -maxrate 512k -bufsize 512k -threads 0 -f mp4 news.mp4 The default audio track come with the label "English" and I would like to give it a label "Sinhalese" The Second Audio track come up without a label as "track#1" and I would like to give that a label of "Tamil". How do I do that ?

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• Coldfusion 8 Application Crashes Under Heavy Load

  - by KM01

  Hello, We have a CF8 app that runs for 20-25 minutes before crashing under heavy load ~ 1200 users. This load is generated by our load testing tool: 1200 users ramped up in 5 mins (approx behavior of our users), running for an hour. We have this app on Solaris 10, Apache 2, JRun 4 and Oracle 10g. Java version is 1.6. During the initial load tests, the thread dumps pointed to monitor deadlocks that pointed to sessions. "jrpp-173": waiting to lock monitor 0x019fdc60 (object 0x6b893530, a java.util.Hashtable), which is held by "scheduler-1" "scheduler-1": waiting to lock monitor 0x026c3ce0 (object 0x6abe2f20, a coldfusion.monitor.memory.SessionMemoryMonitor$TopMemoryUsedSessions), which is held by "jrpp-167" "jrpp-167": waiting to lock monitor 0x019fdc60 (object 0x6b893530, a java.util.Hashtable), which is held by "scheduler-1" We increased the number of sessions relative to the number of CPUs (48 simultaneous threads against 32 CPUs), and the deadlock went away. While varying the simultaneous threads helped a little bit in terms of response time, the CF server still tanked in 20-25 minutes during all of these tests. We ran more thread dumps, and saw a thread locking a monitor, for e.g.: "jrpp-475" prio=3 tid=0x02230800 nid=0x2c5 runnable [0x4397d000] java.lang.Thread.State: RUNNABLE at java.util.HashMap.getEntry(HashMap.java:347) at java.util.HashMap.containsKey(HashMap.java:335) at java.util.HashSet.contains(HashSet.java:184) at coldfusion.monitor.memory.MemoryTracker.onAddObject(MemoryTracker.java:124) at coldfusion.monitor.memory.MemoryTrackerProxy.onReplaceValue(MemoryTrackerProxy.java:598) at coldfusion.monitor.memory.MemoryTrackerProxy.onPut(MemoryTrackerProxy.java:510) at coldfusion.util.CaseInsensitiveMap.put(CaseInsensitiveMap.java:250) at coldfusion.util.FastHashtable.put(FastHashtable.java:43) - locked <0x6f7e1a78> (a coldfusion.runtime.Struct) at coldfusion.runtime.CfJspPage._arrayset(CfJspPage.java:1027) at coldfusion.runtime.CfJspPage._arraySetAt(CfJspPage.java:2117) at cfvalidation2ecfc1052964961$funcSETUSERAUDITDATA.runFunction(/app/docs/apply/cfcs/validation.cfc:377) As you see in the last line above there were several references CFMs and CFCs, and the lines have "cflock" tags, which were scoped to the "application." We (the dev team) then changed them to be scoped to a "name". After more load tests, there is no locking going on and there no deadlocks, but now the application tanks in 7-10 minutes. We've gotten system, network and DB reports from the respective admins, and they are not being taxed; even watched the server stats with server monitor, top, prstat, ran sar reports, etc. So we believe it is an issue with the CF server or maybe the JVM. I am running out of ideas as to what else we can try. Disclaimer: I am not a CF developer or Admin. I am just running the load test, analyzing the reports, threads etc, and sharing the results with the dev and admin teams, and trying the next change, and so on. So far no dice. Has anyone run into something similar? How did you go about diagnosing and troubleshooting? All thoughts and pointers welcome. Thank you for your time! KM

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• Zabbix - Some of the monitored items dont get refreshd. how to find the reason?

  - by Niro

  I'm experiencing a strange issue with Zabbix monitoring a MySQL server. Most of the data from the server such as MySQL queries per second and MySQL uptime , Buffers memory etc. update nicely while some data like CPU iowait time (avg1) , Host local time ,MySQL number of threads and other items which were monitored in the past has last check time of about a week ago. I can't find any logic in this, for example Mysql number of threads and Mysql queries per second are obtained in a similar way so it does not make sense one of them is monitored and one is not. Please help- how can I fix this?

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• Windows 7 connect to Lion file sharing

  - by McKvack

  Trying to access my Mac from a Windows 7 computer, I fail with the infamous error 86 incorrect password. Now this appears to be a well-known problem with countless threads on the internet giving as many "solutions" as there are discussion threads about it (mostly ranging from installing third-party commercial samba servers, to switching to some other protocol, to compiling a plain-vanilla Samba installation - the latter which I will probably do when I give up this :) ) I am stubborn, and I believe there must be some problem here that can be solved or worked around, but there is surprisingly little detail about this problem. It appears to have something to do with a mismatch of authentication methods. Trying to run samba in debug mode: sudo /usr/sbin/smbd -debug -stdout gets me this output when trying to access it from Win 7 ... smb1_dispatch_one [smb_dispatch.cpp:377] dispatching SMB_COM_SESSION_SETUP_ANDX smb1_dispatch_session_setup [session_setup.cpp:261] FIXME erase existing sessions log_gss_error [gssapi_mechanism.cpp:97] gssapi: gss-code: Miscellaneous failure (see text) log_gss_error [gssapi_mechanism.cpp:113] gssapi: mech-code: unknown mech-code 22 for mech unknown What is the problem here, and how do I fix it?

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• Lightning fast forum based around metadata / tags? [closed]

  - by Dan W

  I wonder if anything like this exists. I'd like to add a forum to my site, but instead of the usual forum/subforum/sub-subforum structure, I'd like to use a metadata/tag approach where everything exists as a single directory, and where there's a search field at the top which instantly (<0.5 sec) filters the threads to a particular keyword or keywords. Also, as the admin, I would be able to add highly visible buttons at the top, which can be clicked on for the main categories I choose for the forum (nevertheless, users can also add tags to their own threads outside of these default main tags I supply if they wish). This approach, if done properly, is more powerful, efficient, maintenance free, scalable and friendly than a standard forum, so I was hoping someone had the same idea and made something out of it. It couldn't be that hard. I'd want the speed to be up to (or near) the standard of this: http://forum.dlang.org/ Other forums (e.g.: phpBB, shudder) are orders of magnitude worse than that in terms of latency (posting or browsing), and I think that is wrong, even in principle ;)

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