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  • Problem using python QPID and gevent together [closed]

    - by William Payne
    I have a python script that pulls messages from an Apache QPID queue, and then uses gevent to perform (IO-bound) tasks on those messages in parallel. The queue that this script pulls from was recently changed: I suspect the version of the C++ QPID broker changed, although I cannot verify this at the present time. Now, my process deadlocks and hangs upon QPID queue creation. I strongly suspect that this is a result of an incompatibility with gevent, although I have not done the work yet to produce a minimal example to demonstrate the problem. (Next on my list). Does anybody else have experience of getting gevent and QPID to work together? or Has anybody else seen the same issues?

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  • Even distribution through a chain of resources

    - by ClosetGeek
    I'm working on an algorithm which routes tasks through a chain of distributed resources based on a hash (or random number). For example, say you have 10 gateways into a service which distribute tasks to 1000 handlers through 100 queues. 10,000 connected clients are expected to be connected to gateways at any given time (numbers are very general to keep it simple). Thats 10,000 clients 10 gateways (producers) 100 queues 1000 workers/handlers (consumers) The flow of each task is client-gateway-queue-worker Each client will have it's own hash/number which is used to route each task from the client to the same worker each time, with each task going through the same gateway and queue each time. Yet the algorithm handles distribution evenly, meaning each gateway, queue, and worker will have an even workload. My question is what exactly would this be called? Does such a thing already exist? This started off as a DHT, but I realized that DHTs can't do exactly what I need, so I started from scratch.

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  • AWS elastic load balancer basic issues

    - by Jones
    I have an array of EC2 t1.micro instances behind a load balancer and each node can manage ~100 concurrent users before it starts to get wonky. i would THINK if i have 2 such instances it would allow my network to manage 200 concurrent users... apparently not. When i really slam the server (blitz.io) with a full 275 concurrents, it behaves the same as if there is just one node. it goes from 400ms response time to 1.6 seconds (which for a single t1.micro is expected, but not 6). So the question is, am i simply not doing something right or is ELB effectively worthless? Anyone have some wisdom on this? AB logs: Loadbalancer (3x m1.medium) Document Path: /ping/index.html Document Length: 185 bytes Concurrency Level: 100 Time taken for tests: 11.668 seconds Complete requests: 50000 Failed requests: 0 Write errors: 0 Non-2xx responses: 50001 Total transferred: 19850397 bytes HTML transferred: 9250185 bytes Requests per second: 4285.10 [#/sec] (mean) Time per request: 23.337 [ms] (mean) Time per request: 0.233 [ms] (mean, across all concurrent requests) Transfer rate: 1661.35 [Kbytes/sec] received Connection Times (ms) min mean[+/-sd] median max Connect: 1 2 4.3 2 63 Processing: 2 21 15.1 19 302 Waiting: 2 21 15.0 19 261 Total: 3 23 15.7 21 304 Single instance (1x m1.medium direct connection) Document Path: /ping/index.html Document Length: 185 bytes Concurrency Level: 100 Time taken for tests: 9.597 seconds Complete requests: 50000 Failed requests: 0 Write errors: 0 Non-2xx responses: 50001 Total transferred: 19850397 bytes HTML transferred: 9250185 bytes Requests per second: 5210.19 [#/sec] (mean) Time per request: 19.193 [ms] (mean) Time per request: 0.192 [ms] (mean, across all concurrent requests) Transfer rate: 2020.01 [Kbytes/sec] received Connection Times (ms) min mean[+/-sd] median max Connect: 1 9 128.9 3 3010 Processing: 1 10 8.7 9 141 Waiting: 1 9 8.7 8 140 Total: 2 19 129.0 12 3020

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  • pdns-recursor allocates resources to non-existing queries

    - by azzid
    I've got a lab-server running pdns-recursor. I set it up to experiment with rate limiting, so it has been resolving requests openly from the whole internet for weeks. My idea was that sooner or later it would get abused, giving me a real user case to experiment with. To keep track of the usage I set up nagios to monitor the number of concurrent-queries to the server. Today I got notice from nagios that my specified limit had been reached. I logged in to start trimming away the malicious questions I was expecting, however, when I started looking at it I couldn't see the expected traffic. What I found is that even though I have over 20 concurrent-queries registered by the server I see no requests in the logs. The following command describes the situation well: $ sudo rec_control get concurrent-queries; sudo rec_control top-remotes 22 Over last 0 queries: How can there be 22 concurrent-queries when the server has 0 queries registered? EDIT: Figured it out! To get top-remotes working I needed to set ################################# # remotes-ringbuffer-entries maximum number of packets to store statistics for # remotes-ringbuffer-entries=100000 It defaults to 0 storing no information to base top-remotes statistics on.

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  • Throttling in OSB

    - by Knut Vatsendvik
    Technorati Tags: soa,integration,osb,throttling,overload protection A common problem with integration is the risk of overloading a particular web service. When the capacity of a web service is reached and it continues to accept connections, it will most likely start to deteriorate. Fortunately there are 2 techniques, with Oracle Service Bus, that you can apply for protecting this from happening. You can either limit the concurrent number of requests for a Business Service (outbound requests) or you can limit the number of threads processing the requests for a Proxy Service (inbound requests). Limiting the Concurrent Number of Requests Limiting the concurrent requests for a Business Service cannot be set at design time so you have to use the built-in Oracle Service Bus Administration Console to do it (/sbconsole). Follow these steps to enable it: In Change Center, click Create to start a new Session Select Project Explorer, and navigate to the Business Service you want to limit Select the Operational Settings tab of the View a Business Service page In this tab, under Throttling, select the Enable check box. By enabling throttling you Specify a value for Maximum Concurrency Specify a positive integer value for Throttling Queue to backlog messages that has exceeded the message concurrency limit Specify the maximum time in milliseconds for Message Expiration a message can spend in Throttling Queue Click Update Click Active in Change Center to active the new settings If you re-publish the service, it will not overwrite the settings. Only if the resource is renamed or moved, it will. Please note that a throttling queue is an in-memory queue. Messages that are placed in this queue are not recoverable when a server fails or when you restart a server. Limiting the Number of Threads A better approach, in my opinion, is to limit the number of threads that can work with request. Follow these steps to do it: Open the WebLogic Server Console (/console) In Change Center, click Create to start a new Session In the left pane expand Environment and select Work Managers In the Global Work Managers page, click New    Click the Work Manager radio button, then click Next Enter a Name for the new Work Manager, and click Next In the Available Targets list, select server instances or clusters on which you will deploy applications that reference the Work Manager Click Finish. The new Work Manager now appears in the Global Work Managers page. Select the new Work Manager Right next to the Maximum Threads Constraint drop-down box, click New   Click the Maximum Threads Constraint radio button, then click Next Enter a Name and a thread Count to be the maximum size to allocate for requests. Click Next  In the Available Targets list, select server instances or clusters on which you will deploy applications that reference the Work Manager Click Finish Click Save Click Active in Change Center to active your changes.  A restart may be necessary.   Puh! Almost there. Start a new session. Go to the Service Bus Console (/sbconsole) and find your consuming Proxy Service. Click the Edit button of the Transport Configuration tab. Click Next Set the Dispatch Policy to the new Work Manager Click Last Click Save Click Active in Change Center to active your changes. 

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  • NServiceBus Generic Host and mqsvc.exe high CPU

    - by Michael Stephenson
    We have been doing some work with NServiceBus recently and observed some unusual behaviour which was caused by our mistake and seemed worthy of a small post.   The Scenario In our solution we were doing some standard NServiceBus stuff by pushing a message to a queue using NServiceBus.  We had a direct send/receive scenario rather than a publish/subscribe one.   The background process which was meant to collect the message and then process it was a normal NServiceBus message handler.  We would run the NServiceBus.Host.exe which would find the handler and then do the usual NServiceBus magic.   The Problem In this solution we were creating some automated tests around this module of the integration process to ensure that it would work well.  We had two tests.   Test 1 This test would start NServiceBus.Host.exe using the Process object, then seed a message to the queue via our web service façade sitting above the queue which wrapped NServiceBus.  The background process would then process the message and the test would check the message had been processed fine.   If all was well then the NServiceBus.Host.exe process was stopped.   Test 2 In test 2 we would do a very similar thing except that instead of starting the process the test would install NServiceBus.Host.exe as a windows service and then start the service before the test and once the test was executed it would stop the test.   The Results of the Tests Test 1 worked really well, however in test 2 we found that it didn’t really work at all, instead of doing the background process we were finding that between mqsvc.exe and NServiceBus.Host.exe the CPU on the machine was maxed and nothing was really happening.   The Solution After trying a few things we found it was the permissions on the queue were not set correctly.  Once this was resolved it all worked fine and CPU was not excessive and ran just like the console application.   I think the couple of take aways from this are:   Make sure you set the windows service for NserviceBus Generic Host to the right credentials When you install the generic host as a windows service then by default it will use the default windows credentials.  For any production like scenario you should be using a domain account to run the process as via the windows service. Make sure you have the queue set with the right permissions For the credentials you have used to configure the generic host as a windows service you should ensure that this user has the appropriate permissions for any queues it will interact with. Make sure you turn on the right logging configuration in NServiceBus When this wasnt working correctly we didnt know there was an issue, we were just experiencing the high CPU condition.  I am a little surprised that there wasnt something logged and that the process didnt crash.  I guess this could be by design bearing in mind that the process could be monitoring many queues.  In this point Im just saying that originally we didnt have all of the log4net logging which is available from NServiceBus turned on.  Its probably a good idea to have this turned on and configured until you are happy your solution is working fine.   Thanks to Ahmed Hashmi on my team who got this working in the end.

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  • The new Auto Scaling Service in Windows Azure

    - by shiju
    One of the key features of the Cloud is the on-demand scalability, which lets the cloud application developers to scale up or scale down the number of compute resources hosted on the Cloud. Auto Scaling provides the capability to dynamically scale up and scale down your compute resources based on user-defined policies, Key Performance Indicators (KPI), health status checks, and schedules, without any manual intervention. Auto Scaling is an important feature to consider when designing and architecting cloud based solutions, which can unleash the real power of Cloud to the apps for providing truly on-demand scalability and can also guard the organizational budget for cloud based application deployment. In the past, you have had to leverage the the Microsoft Enterprise Library Autoscaling Application Block (WASABi) or a services like  MetricsHub for implementing Automatic Scaling for your cloud apps hosted on the Windows Azure. The WASABi required to host your auto scaling block in a Windows Azure Worker Role for effectively implementing the auto scaling behaviour to your Windows Azure apps. The newly announced Auto Scaling service in Windows Azure lets you add automatic scaling capability to your Windows Azure Compute Services such as Cloud Services, Web Sites and Virtual Machine. Unlike WASABi hosted on a Worker Role, you don’t need to host any monitoring service for using the new Auto Scaling service and the Auto Scaling service will be available to individual Windows Azure Compute Services as part of the Scaling. Configure Auto Scaling for a Windows Azure Cloud Service Currently the Auto Scaling service supports Cloud Services, Web Sites and Virtual Machine. In this demo, I will be used a Cloud Services app with a Web Role and a Worker Role. To enable the Auto Scaling, select t your Windows Azure app in the Windows Azure management portal, and choose “SCLALE” tab. The Scale tab will show the all information regards with Auto Scaling. The below image shows that we have currently disabled the AutoScale service. To enable Auto Scaling, you need to choose either CPU or QUEUE. The QUEUE option is not available for Web Sites. The image below demonstrates how to configure Auto Scaling for a Web Role based on the utilization of CPU. We have configured the web role app for running with 1 to 5 Virtual Machine instances based on the CPU utilization with a range of 50 to 80%. If the aggregate utilization is becoming above above 80%, it will scale up instances and it will scale down instances when utilization is becoming below 50%. The image below demonstrates how to configure Auto Scaling for a Worker Role app based on the messages added into the Windows Azure storage Queue. We configured the worker role app for running with 1 to 3 Virtual Machine instances based on the Queue messages added into the Windows Azure storage Queue. Here we have specified the number of messages target per machine is 2000. The image below shows the summary of the Auto Scaling for the Cloud Service after configuring auto scaling service. Summary Auto Scaling is an extremely important behaviour of the Cloud applications for providing on-demand scalability without any manual intervention. Windows Azure provides greater support for enabling Auto Scaling for the apps deployed on the Windows Azure cloud platform. The new Auto Scaling service in Windows Azure lets you add automatic scaling capability to your Windows Azure Compute Services such as Cloud Services, Web Sites and Virtual Machine. In the new Auto Scaling service, you don’t have to host any monitor service like you have had in WASABi block. The Auto Scaling service is an excellent alternative to the manually hosting WASABi block in a Worker Role app.

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  • SQL SERVER – ASYNC_IO_COMPLETION – Wait Type – Day 11 of 28

    - by pinaldave
    For any good system three things are vital: CPU, Memory and IO (disk). Among these three, IO is the most crucial factor of SQL Server. Looking at real-world cases, I do not see IT people upgrading CPU and Memory frequently. However, the disk is often upgraded for either improving the space, speed or throughput. Today we will look at another IO-related wait type. From Book On-Line: Occurs when a task is waiting for I/Os to finish. ASYNC_IO_COMPLETION Explanation: Any tasks are waiting for I/O to finish. If by any means your application that’s connected to SQL Server is processing the data very slowly, this type of wait can occur. Several long-running database operations like BACKUP, CREATE DATABASE, ALTER DATABASE or other operations can also create this wait type. Reducing ASYNC_IO_COMPLETION wait: When it is an issue related to IO, one should check for the following things associated to IO subsystem: Look at the programming and see if there is any application code which processes the data slowly (like inefficient loop, etc.). Note that it should be re-written to avoid this  wait type. Proper placing of the files is very important. We should check the file system for proper placement of the files – LDF and MDF on separate drive, TempDB on another separate drive, hot spot tables on separate filegroup (and on separate disk), etc. Check the File Statistics and see if there is a higher IO Read and IO Write Stall SQL SERVER – Get File Statistics Using fn_virtualfilestats. Check event log and error log for any errors or warnings related to IO. If you are using SAN (Storage Area Network), check the throughput of the SAN system as well as configuration of the HBA Queue Depth. In one of my recent projects, the SAN was performing really badly and so the SAN administrator did not accept it. After some investigations, he agreed to change the HBA Queue Depth on the development setup (test environment). As soon as we changed the HBA Queue Depth to quite a higher value, there was a sudden big improvement in the performance. It is very likely to happen that there are no proper indexes on the system and yet there are lots of table scans and heap scans. Creating proper index can reduce the IO bandwidth considerably. If SQL Server can use appropriate cover index instead of clustered index, it can effectively reduce lots of CPU, Memory and IO (considering cover index has lesser columns than cluster table and all other; it depends upon the situation). You can refer to the following two articles I wrote that talk about how to optimize indexes: Create Missing Indexes Drop Unused Indexes Checking Memory Related Perfmon Counters SQLServer: Memory Manager\Memory Grants Pending (Consistent higher value than 0-2) SQLServer: Memory Manager\Memory Grants Outstanding (Consistent higher value, Benchmark) SQLServer: Buffer Manager\Buffer Hit Cache Ratio (Higher is better, greater than 90% for usually smooth running system) SQLServer: Buffer Manager\Page Life Expectancy (Consistent lower value than 300 seconds) Memory: Available Mbytes (Information only) Memory: Page Faults/sec (Benchmark only) Memory: Pages/sec (Benchmark only) Checking Disk Related Perfmon Counters Average Disk sec/Read (Consistent higher value than 4-8 millisecond is not good) Average Disk sec/Write (Consistent higher value than 4-8 millisecond is not good) Average Disk Read/Write Queue Length (Consistent higher value than benchmark is not good) Read all the post in the Wait Types and Queue series. Note: The information presented here is from my experience and there is no way that I claim it to be accurate. I suggest reading Book OnLine for further clarification. All the discussions of Wait Stats in this blog are generic and vary from system to system. It is recommended that you test this on a development server before implementing it to a production server. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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  • Laptop monitor stopped working and can't be re-enabled on a Dell Latitude E6410

    - by xektrum
    I'm using Ubuntu 12.04 (upgraded from 11.10), everything seemed to work fine until today when my laptop monitor suddenly stopped working. Here are the facts: My laptop is a Dell Latitude E6410, Intel graphics. External Monitor is attached through a docking station. Everything worked fine for about 6-7 month, then upgraded to 12.04 Issue started today after a week of upgrade. I think the issue started after I ran CounterStrike 1.6, both monitors blinked and then only the attached monitor which is connected to a docking station continued to work I thought at first that was a transient issue but then I've rebooted, removed the battery but the same happens. Laptop Monitor and external monitor work fine up to login screen, but after I login it goes black Whenever I try to re-enable laptop monitor from Display Manager I get errors: The selected configuration for displays could not be applied could not set the configuration for CRTC 63 Not sure what technical details are required but here are some: $ xrandr Screen 0: minimum 320 x 200, current 3120 x 1050, maximum 8192 x 8192 eDP1 connected (normal left inverted right x axis y axis) 1440x900 60.0 + 40.0 VGA1 disconnected (normal left inverted right x axis y axis) HDMI1 connected 1680x1050+0+0 (normal left inverted right x axis y axis) 474mm x 296mm 1680x1050 60.0*+ 1280x1024 75.0 60.0 1152x864 75.0 1024x768 75.1 60.0 800x600 75.0 60.3 640x480 75.0 60.0 720x400 70.1 DP1 disconnected (normal left inverted right x axis y axis) HDMI2 disconnected (normal left inverted right x axis y axis) DP2 disconnected (normal left inverted right x axis y axis) $ tail /var/log/Xorg.0.log [ 8367.132] (WW) intel(0): flip queue failed: Device or resource busy [ 8367.132] (WW) intel(0): Page flip failed: Device or resource busy [ 8367.174] (WW) intel(0): flip queue failed: Device or resource busy [ 8367.174] (WW) intel(0): Page flip failed: Device or resource busy [ 8367.174] (WW) intel(0): flip queue failed: Device or resource busy [ 8367.174] (WW) intel(0): Page flip failed: Device or resource busy [ 8367.265] (WW) intel(0): flip queue failed: Device or resource busy [ 8367.265] (WW) intel(0): Page flip failed: Device or resource busy [ 8367.265] (WW) intel(0): flip queue failed: Device or resource busy [ 8367.265] (WW) intel(0): Page flip failed: Device or resource busy I'm using gnome-shell, and the only ways I've been able to get both display working have been: 1) Booting with laptop disconnected from docking and then re attach external with VGA instead of DVI, but only worked for a session. 2) Removing xserver-xorg-video-intel, but then I gnome-shell is gone as well as dri I would appreciate any suggestions. Regards, ============================= WORKAROUND FOUND ============================= So I have tried few things and here is what worked: I've installed a newer version of xserver-xorg-video-intel (2.19 vs 2.17) from ppa:xorg-edgers/ppa, it didn't work at first, it was only showing low graphics mode, so I tried with a different linux-image 3.0.0-19-generic-pae instead of 3.2.0-24-generic-pae, which I believe is 12.04 precise default, then everything started to work again, Now I've installed 3.4.0-1-generic-pae from same ppa and everything goes flawless so I believe the issue is either with linux-image 3.0.0-19-generic-pae or xserver-xorg-video-intel 2.17. Hope this helps someone in the future. PS: Now xrandr shows multiple modes for my laptop monitor $ xrandr Screen 0: minimum 320 x 200, current 3120 x 1050, maximum 8192 x 8192 eDP1 connected 1440x900+1680+0 (normal left inverted right x axis y axis) 303mm x 189mm 1440x900 60.0*+ 59.9 40.0 1360x768 59.8 60.0 1152x864 60.0 1024x768 60.0 800x600 60.3 56.2 640x480 59.9 VGA1 disconnected (normal left inverted right x axis y axis) HDMI1 connected 1680x1050+0+0 (normal left inverted right x axis y axis) 474mm x 296mm 1680x1050 60.0*+ 1280x1024 75.0 60.0 1152x864 75.0 1024x768 75.1 60.0 800x600 75.0 60.3 640x480 75.0 60.0 720x400 70.1 DP1 disconnected (normal left inverted right x axis y axis) HDMI2 disconnected (normal left inverted right x axis y axis) DP2 disconnected (normal left inverted right x axis y axis)

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  • JDeveloper 11.1.2 : Command Link in Table Column Work Around

    - by Frank Nimphius
    Just figured that in Oracle JDeveloper 11.1.2, clicking on a command link in a table does not mark the table row as selected as it is the behavior in previous releases of Oracle JDeveloper. For the time being, the following work around can be used to achieve the "old" behavior: To mark the table row as selected, you need to build and queue the table selection event in the code executed by the command link action listener. To queue a selection event, you need to know about the rowKey of the row that the command link that you clicked on is located in. To get to this information, you add an f:attribute tag to the command link as shown below <af:column sortProperty="#{bindings.DepartmentsView1.hints.DepartmentId.name}" sortable="false"    headerText="#{bindings.DepartmentsView1.hints.DepartmentId.label}" id="c1">   <af:commandLink text="#{row.DepartmentId}" id="cl1" partialSubmit="true"       actionListener="#{BrowseBean.onCommandItemSelected}">     <f:attribute name="rowKey" value="#{row.rowKey}"/>   </af:commandLink>   ... </af:column> The f:attribute tag references #{row.rowKey} wich in ADF translates to JUCtrlHierNodeBinding.getRowKey(). This information can be used in the command link action listener to compose the RowKeySet you need to queue the selected row. For simplicitly reasons, I created a table "binding" reference to the managed bean that executes the command link action. The managed bean code that is referenced from the af:commandLink actionListener property is shown next: public void onCommandItemSelected(ActionEvent actionEvent) {   //get access to the clicked command link   RichCommandLink comp = (RichCommandLink)actionEvent.getComponent();   //read the added f:attribute value   Key rowKey = (Key) comp.getAttributes().get("rowKey");     //get the current selected RowKeySet from the table   RowKeySet oldSelection = table.getSelectedRowKeys();   //build an empty RowKeySet for the new selection   RowKeySetImpl newSelection = new RowKeySetImpl();     //RowKeySets contain List objects with key objects in them   ArrayList list = new ArrayList();   list.add(rowKey);   newSelection.add(list);     //create the selectionEvent and queue it   SelectionEvent selectionEvent = new SelectionEvent(oldSelection, newSelection, table);   selectionEvent.queue();     //refresh the table   AdfFacesContext.getCurrentInstance().addPartialTarget(table); }

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  • MVC Communication Pattern

    - by Kedu
    This is kind of a follow up question to this http://stackoverflow.com/questions/23743285/model-view-controller-and-callbacks, but I wanted to post it separately, because its kind of a different topic. I'm working on a multiplayer cardgame for the Android platform. I split the project into MVC which fits the needs pretty good, but I'm currently stuck because I can't figure out a good way to communicate between the different parts. I have everything setup and working with the controller being a big state machine, which is called over and over from the gameloop, and calls getter methods from the GUI and the android/network part to get the input. The input itself in the GUI and network is set by inputlisteners that set a local variable which I read in the getter method. So far so good, this is working. But my problem is, the controller has to check every input separately,so if I want to add an input I have to check in which states its valid and call the getter method from all these states. This is not good, and lets the code look pretty ugly, makes additions uncomfortable and adds redundance. So what I've got from the question I mentioned above is that some kind of command or event pattern will fit my needs. What I want to do is to create a shared and threadsafe queue in the controller and instead of calling all these getter methods, I just check the queue for new input and proceed it. On the other side, the GUI and network don't have all these getters, but instead create an event or command and send it to the controller through, for example, observer/observable. Now my problem: I can't figure out a way, for these commands/events to fit a common interface (which the queue can store) and still transport different kind of data (button clicks, cards that are played, the player id the command comes from, synchronization data etc.). If I design the communication as command pattern, I have to stick all the information that is needed to execute the command into it when its created, that's impossible because the GUI or network has no knowledge of all the things the controller needs to execute stuff that needs to be done when for example a card is played. I thought about getting this stuff into the command when executing it. But over all the different commands I have, I would need all the information the controller has, and thus give the command a reference to the controller which would make everything in it public, which is real bad design I guess. So, I could try some kind of event pattern. I have to transport data in the event. So, like the command, I would have an interface, which all events have in common, and can be stored in the shared queue. I could create a big enum with all the different events that a are possible, save one of these enums in the actual event, and build a big switch case for the events, to proceed different stuff for different events. The problem here: I have different data for all the events. But I need a common interface, to store the events in a queue. How do I get the specific data, if I can only access the event through the interface? Even if that wouldn't be a problem, I'm creating another big switch case, which looks ugly, and when i want to add a new event, I have to create the event itself, the case, the enum, and the method that's called with the data. I could of course check the event with the enum and cast it to its type, so I can call event type specific methods that give me the data I need, but that looks like bad design too.

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  • Load Balance WCF and Share a Remote MSMQ for High Throughput

    - by BarDev
    After a ton of reading in books and on the web, I have noticed hints of information that WCF and MSMQ can be used in achieving high throughput. The information I have seen mentions using multiple WCF services in a farm that reads from a single MSMQ queue. The problem is that I have found paragraphs here and there that mentions that high throughput can be done, but I cannot seem to find a document of how to implement it. The following is an excerpt from a MSDN article. The following paragraph is from Best Practices for Queued Communication http://msdn.microsoft.com/en-us/library/ms731093.aspx To achieve higher throughput and availability, use a farm of WCF services that read from the queue. This requires that all of these services expose the same contract on the same endpoint. The farm approach works best for applications that have high production rates of messages because it enables a number of services to all read from the same queue. This is what I'm trying to solve. I have an intranet application where a client sends a request to a WCF service. But I want the ability to load balance the WCF services on multiple servers in a farm. I also want these WCF services in the farm to do transactional reads from a remote MSMQ when an item is available in the Queue. If this is possible, an issue I have is that I do not understand the activation process of WCF to retrieve messages from a remote queue. If this is possible, does anyone know of any articles or Webcasts that would explain it in detail? BarDev

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  • Python-daemon doesn't kill its kids

    - by Brian M. Hunt
    When using python-daemon, I'm creating subprocesses likeso: import multiprocessing class Worker(multiprocessing.Process): def __init__(self, queue): self.queue = queue # we wait for things from this in Worker.run() ... q = multiprocessing.Queue() with daemon.DaemonContext(): for i in xrange(3): Worker(q) while True: # let the Workers do their thing q.put(_something_we_wait_for()) When I kill the parent daemonic process (i.e. not a Worker) with a Ctrl-C or SIGTERM, etc., the children don't die. How does one kill the kids? My first thought is to use atexit to kill all the workers, likeso: with daemon.DaemonContext(): workers = list() for i in xrange(3): workers.append(Worker(q)) @atexit.register def kill_the_children(): for w in workers: w.terminate() while True: # let the Workers do their thing q.put(_something_we_wait_for()) However, the children of daemons are tricky things to handle, and I'd be obliged for thoughts and input on how this ought to be done. Thank you.

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  • Use Delayed::Job to manage multiple job queues

    - by Alex
    I want to use Delayed::Job (or perhaps a more appropriate job queue to my problem) to dispatch jobs to multiple background daemons. I have several background daemons that carry out different responsibilities. Each one is interested in different jobs in the queue from the Rails app. Is this possible using Delayed::Job, or perhaps there is a different job queue that better fits this task?

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  • Passing events in JMS

    - by sam
    I'm new in JMS. In my program, My Problem is that , I want to pass 4 events(classes) (callEvent, agentEvent, featureEvent, eventListenerExit) from the JMSQueue Program , who i m mention below. How can I do this? // (JmsSender.java) package com.apac.control.helper; import java.util.Calendar; import javax.jms.Queue; import javax.jms.QueueConnection; import javax.jms.QueueConnectionFactory; import javax.jms.QueueSender; import javax.jms.QueueSession; import javax.jms.Session; import javax.jms.TextMessage; import javax.naming.InitialContext; import com.apac.control.api.CallData; import com.apac.control.exception.CtiException; import library.cti.CtiEventDocument; import library.cti.impl.CtiEventDocumentImpl; public final class JmsSender { private QueueConnectionFactory factory; private Queue queue; private QueueConnection connection; private QueueSession session; private QueueSender sender; private String sessionId; private String deviceId; private String centerId; private String switchId; public JmsSender(String queueJndiName, String sessionId, String deviceId, String centerId, String switchId) throws CtiException { this.sessionId = sessionId; this.deviceId = deviceId; this.centerId = centerId; this.switchId = switchId; try { InitialContext ic = new InitialContext(); factory = (QueueConnectionFactory) ic.lookup("javax/jms/QueueConnectionFactory"); queue = (Queue) ic.lookup(queueJndiName); } catch (Exception e) { throw new CtiException("CTI. Error creating JmsSender.", e); } } public String getCenterId() { return centerId; } public String getDeviceId() { return deviceId; } public String getSwitchId() { return switchId; } public void connect() throws CtiException { try { connection = factory.createQueueConnection(); } catch (Exception e) { throw new CtiException("CTI000. Error connecting to cti queue."); } } public void close() throws CtiException { try { connection.close(); } catch (Exception e) { throw new CtiException("CTI000. Error closing queue."); } } public void send(String eventType, CallData call, long seqId) throws CtiException { // prepare the message CtiEventDocument ced = this.createBaseCtiDocument(); CtiEventDocument ce = ced.getCtiEvent(); ce.setSequenceId(seqId); ce.setCallId("" + call.getCallId()); ce.setUcid(call.getUCID()); ce.setEventType(eventType); ce.setDnisNumber(call.getDnisNumber()); ce.setAniNumber(call.getAniNumber()); ce.setApplicationData(call.getApplicationData()); ce.setQueueNumber(call.getQueueNumber()); ce.setCallingNumber(call.getCallingNumber()); if (call instanceof ManualCall) { ce.setManual("yes"); } try { sendMessage(ced.toString()); } catch (Exception e) { throw new CtiException("CTI051. Error sending message.", e); } } public void send(String eventType, String agentId, String agentMode, long seqId) throws CtiException { CtiEventDocument ced = this.createBaseCtiDocument(); CtiEventDocument ce = ced.getCtiEvent(); ce.setSequenceId(seqId); ce.setEventType(eventType); ce.setAgentId(agentId); ce.setAgentMode(agentMode); try { sendMessage(ced.toString()); } catch (Exception e) { throw new CtiException("CTI051. Error sending message.", e); } } public void sendError(String errCode, String errMsg) throws CtiException { CtiEventDocument ced = this.createBaseCtiDocument(); CtiEventDocument ce = ced.getCtiEvent(); ce.setEventType("Error"); ce.setErrorCode(errCode); ce.setErrorMessage(errMsg); try { sendMessage(ced.toString()); } catch (Exception e) { throw new CtiException("CTI051. Error sending message.", e); } } private CtiEventDocument createBaseCtiDocument() { CtiEventDocument ced = CtiEventDocument.Factory.newInstance(); CtiEventDocument ce = ced.addNewCtiEvent(); ce.setSessionId(sessionId); ce.setSwitchId(switchId); ce.setCenterId(centerId); ce.setDeviceId(deviceId); ce.setTime(Calendar.getInstance()); return ced; } // Synchronization protects session, which cannot be // accessed by more than one thread. We may more than // one thread here from Cti in some cases (for example // when customer is being transfered out and hangs the call // at the same time. synchronized void sendMessage(String msg) throws Exception { session = connection.createQueueSession(true, Session.AUTO_ACKNOWLEDGE); sender = session.createSender(queue); TextMessage txtMsg = session.createTextMessage(msg); sender.send(txtMsg); sender.close(); session.commit(); } }

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  • Reading,Writing, Editing BLOBS through DataTables and DataRows

    - by Soham
    Consider this piece of code: DataSet ds = new DataSet(); SQLiteDataAdapter Da = new SQLiteDataAdapter(Command); Da.Fill(ds); DataTable dt = ds.Tables[0]; bool PositionExists; if (dt.Rows.Count > 0) { PositionExists = true; } else { PositionExists = false; } if (PositionExists) { //dt.Rows[0].Field<>("Date") } Here the "Date" field is a BLOB. My question is, a. Will reading through the DataAdapter create any problems later on, when I am working with BLOBS? More, specifically, will it read the BLOB properly? b. This was the read part.Now when I am writing the BLOB to the DB,its a queue actually. I.e I am trying to store a queue in MySQLite using a BLOB. Will Conn.ExecuteNonQuery() serve my purpose? c. When I am reading the BLOB back from the DB, can I edit it as the original datatype, it used to be in C# environment i.e { Queue - BLOB - ? } {C# -MySQL - C# } So in this context, Date field was a queue, I wrote it back as a BLOB, when reading it back, can I access it(and edit) as a queue? Thank You. Soham

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  • long polling netty nio framework java

    - by Alfred
    Hi, How can I do long-polling using netty framework? Say for example I fetch http://localhost/waitforx but waitforx is asynchronous because it has to wait for an event? Say for example it fetches something from a blocking queue(can only fetch when data in queue). When getting item from queue I would like to sent data back to client. Hopefully somebody can give me some tips how to do this. Many thanks

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  • Start oracle dequeue on startup

    - by Geln
    Hi, I got the following error of Oracle, ORA-25226: dequeue failed, queue string.string is not enabled for dequeue And the following is the Cause and Action for it from the official document: Cause: The queue has not been enabled for dequeue. Action: Enable the queue using START_QUEUE. But this error occurs every time when restart the database, is there any configuration to set to start the dequeue on database startup? thanks!

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  • activemq round robin between queues or topics

    - by forkit
    I'm trying to achieve load balancing between different types of messages. I would not know in advance what the messages coming in might be until they hit the queue. I know I can try resequencing the messages, but I was thinking that maybe if there was a way to have the various consumers round robin between either queues or between topics, this would solve my problem. The main problem i'm trying to solve is that I have many services sending messages to one queue with many consumers feeding off one queue. I do not want one type of service monopolizing the entire worker cluster. Again I don't know in advance what the messages that are going to hit the queue are going to be. To try to clearly repeat my question: Is there a way to tell the consumers to round robin between either existing queues or topics? Thank you in advance.

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  • Messaging pattern question

    - by Al Bundy
    Process A is calculating values for objects a1, a2, a3 etc. and is sending results to the middleware queue (RabbitMQ). Consumers read the queue and process these results further. Periodically process A has to send a snapshot of these values, so consumers could do some other calculations. Values for these objects might change independently. The queue might look like this a1, a1, a2, a1, a2, a2, a3... Consumers process each item in the queue. The snapshot has to contain all objects and consumers will process this message for all objects in one go. So the requirement is to have a queue like this: a1, a1, a3, a2, a2, [snapshot, a1, a2, a3], a3, a1 ... The problem is that these items are of different types: one type for objects like a1, a2 and other for a snapshot. This means that they should be processed in a diferent queues, but in that case there is a race condition: consumers might process objects before processing a snapshot. Is there any pattern to solve this (quite common) problem? We are using RabbitMQ for message queueing.

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  • C++ MySQL++ Delete query statement brain killer question

    - by shauny
    Hello all, I'm relatively new to the MySQL++ connector in C++, and have an really annoying issue with it already! I've managed to get stored procedures working, however i'm having issues with the delete statements. I've looked high and low and have found no documentation with examples. First I thought maybe the code needs to free the query/connection results after calling the stored procedure, but of course MySQL++ doesn't have a free_result method... or does it? Anyways, here's what I've got: #include <iostream> #include <stdio.h> #include <queue> #include <deque> #include <sys/stat.h> #include <mysql++/mysql++.h> #include <boost/thread/thread.hpp> #include "RepositoryQueue.h" using namespace boost; using namespace mysqlpp; class RepositoryChecker { private: bool _isRunning; Connection _con; public: RepositoryChecker() { try { this->_con = Connection(false); this->_con.set_option(new MultiStatementsOption(true)); this->_con.set_option(new ReconnectOption(true)); this->_con.connect("**", "***", "***", "***"); this->ChangeRunningState(true); } catch(const Exception& e) { this->ChangeRunningState(false); } } /** * Thread method which runs and creates the repositories */ void CheckRepositoryQueues() { //while(this->IsRunning()) //{ std::queue<RepositoryQueue> queues = this->GetQueue(); if(queues.size() > 0) { while(!queues.empty()) { RepositoryQueue &q = queues.front(); char cmd[256]; sprintf(cmd, "svnadmin create /home/svn/%s/%s/%s", q.GetPublicStatus().c_str(), q.GetUsername().c_str(), q.GetRepositoryName().c_str()); if(this->DeleteQueuedRepository(q.GetQueueId())) { printf("query deleted?\n"); } printf("Repository created!\n"); queues.pop(); } } boost::this_thread::sleep(boost::posix_time::milliseconds(500)); //} } protected: /** * Gets the latest queue of repositories from the database * and returns them inside a cool queue defined with the * RepositoryQueue class. */ std::queue<RepositoryQueue> GetQueue() { std::queue<RepositoryQueue> queues; Query query = this->_con.query("CALL sp_GetRepositoryQueue();"); StoreQueryResult result = query.store(); RepositoryQueue rQ; if(result.num_rows() > 0) { for(unsigned int i = 0;i < result.num_rows(); ++i) { rQ = RepositoryQueue((unsigned int)result[i][0], (unsigned int)result[i][1], (String)result[i][2], (String)result[i][3], (String)result[i][4], (bool)result[i][5]); queues.push(rQ); } } return queues; } /** * Allows the thread to be shut off. */ void ChangeRunningState(bool isRunning) { this->_isRunning = isRunning; } /** * Returns the running value of the active thread. */ bool IsRunning() { return this->_isRunning; } /** * Deletes the repository from the mysql queue table. This is * only called once it has been created. */ bool DeleteQueuedRepository(unsigned int id) { char cmd[256]; sprintf(cmd, "DELETE FROM RepositoryQueue WHERE Id = %d LIMIT 1;", id); Query query = this->_con.query(cmd); return (query.exec()); } }; I've removed all the other methods as they're not needed... Basically it's the DeleteQueuedRepository method which isn't working, the GetQueue works fine. PS: This is on a Linux OS (Ubuntu server) Many thanks, Shaun

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  • conceptual question : what do performSelectorOnMainThread do?

    - by hib
    Hello all, I just come across this strange situation . I was using the technique of lazy image loading from apple examples . when I was used the class in my application it gave me topic to learn but don't what was actually happening there . So here goes the scenario : I think everybody has seen the apple lazytableimagesloading . I was reloading my table on finishing the parsing of data : - (void)didFinishParsing:(NSMutableArray *)appList { self.upcomingArray = [NSMutableArray arrayWithArray:loadedApps]; // we are finished with the queue and our ParseOperation [self.upcomingTableView reloadData]; self.queue = nil; // we are finished with the queue and our ParseOperation } but as a result the the connection was not starting and images were not loading . when I completely copy the lazyimageloading and I replaced the above code with the following code it works fine - (void)didFinishParsing:(NSMutableArray *)appList { [self performSelectorOnMainThread:@selector(handleLoadedApps:) withObject:appList waitUntilDone:NO]; self.queue = nil; // we are finished with the queue and our ParseOperation } So I want to know what is the concept behind this . Please let me know if you can not understand the question or details are not enough because I desperately want to know why it is like this ?

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  • EasyHook Windows Hooking problem/.dll injection

    - by Tom
    Ok can someone try and find the error with this code, it should produce all the registry keys every time something accesses them but i keep getting: System.MissingMethodException: The given method does not exist at EasyHook.LocalHook.GetProcAdress(String InModule, String InChannelName) An example code can be found here: http://www.codeproject.com/KB/DLL/EasyHook64.aspx I can get the CcreateFileW example to work! My code is here: public class Main : EasyHook.IEntryPoint { FileMon.FileMonInterface Interface; LocalHook LocalHook; Stack<String> Queue = new Stack<String>(); public Main(RemoteHooking.IContext InContext,String InChannelName) { // connect to host... Interface = RemoteHooking.IpcConnectClient<FileMon.FileMonInterface>(InChannelName); Interface.Ping(); } public void Run(RemoteHooking.IContext InContext,String InChannelName) { // install hook... try { LocalHook localHook = LocalHook.Create(LocalHook.GetProcAddress("Advapi32.dll", "RegOpenKeyExW"),new DMyRegOpenKeyExW(MyRegOpenKeyExW),this); localHook.ThreadACL.SetExclusiveACL(new int[] { }); } catch (Exception ExtInfo) { Interface.ReportException(ExtInfo); return; } Interface.IsInstalled(RemoteHooking.GetCurrentProcessId()); RemoteHooking.WakeUpProcess(); // wait for host process termination... try { while (true) { Thread.Sleep(500); // transmit newly monitored file accesses... if (Queue.Count > 0) { String[] Package = null; lock (Queue) { Package = Queue.ToArray(); Queue.Clear(); } Interface.OnCreateFile(RemoteHooking.GetCurrentProcessId(), Package); } else Interface.Ping(); } } catch { // Ping() will raise an exception if host is unreachable } } [DllImport("Advapi32.dll", CharSet = CharSet.Unicode, SetLastError = true, CallingConvention = CallingConvention.StdCall)] static extern int RegOpenKeyExW(UIntPtr hKey,string subKey,int ulOptions,int samDesired,out UIntPtr hkResult); [UnmanagedFunctionPointer(CallingConvention.StdCall, CharSet = CharSet.Unicode, SetLastError = true)] delegate int DMyRegOpenKeyExW(UIntPtr hKey,string subKey,int ulOptions,int samDesired,out UIntPtr hkResult); int MyRegOpenKeyExW(UIntPtr hKey,string subKey,int ulOptions,int samDesired,out UIntPtr hkResult) { Console.WriteLine(string.Format("Accessing: {0}", subKey)); return RegOpenKeyExW(hKey, subKey, ulOptions, samDesired, out hkResult); } }

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  • activemessaging with stomp and activemq.prefetchSize=1

    - by Clint Miller
    I have a situation where I have a single activemq broker with 2 queues, Q1 and Q2. I have two ruby-based consumers using activemessaging. Let's call them C1 and C2. Both consumers subscribe to each queue. I'm setting activemq.prefetchSize=1 when subscribing to each queue. I'm also setting ack=client. Consider the following sequence of events: 1) A message that triggers a long-running job is published to queue Q1. Call this M1. 2) M1 is dispatched to consumer C1, kicking off a long operation. 3) Two messages that trigger short jobs are published to queue Q2. Call these M2 and M3. 4) M2 is dispatched to C2 which quickly runs the short job. 5) M3 is dispatched to C1, even though C1 is still running M1. It's able to dispatch to C1 because prefetchSize=1 is set on the queue subscription, not on the connection. So the fact that a Q1 message has already been dispatched doesn't stop one Q2 message from being dispatched. Since activemessaging consumers are single-threaded, the net result is that M3 sits and waits on C1 for a long time until C1 finishes processing M1. So, M3 is not processed for a long time, despite the fact that consumer C2 is sitting idle (since it quickly finishes with message M2). Essentially, whenever a long Q1 job is run and then a whole bunch of short Q2 jobs are created, exactly one of the short Q2 jobs gets stuck on a consumer waiting for the long Q1 job to finish. Is there a way to set prefetchSize at the connection level rather than at the subscription level? I really don't want any messages dispatched to C1 while it is processing M1. The other alternative is that I could create a consumer dedicated to processing Q1 and then have other consumers dedicated to processing Q2. But, I'd rather not do that since Q1 messages are infrequent--Q1's dedicated consumers would sit idle most of the day tying up memory.

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  • Best approach for a scalable PHP (AJAX based) chat system

    - by Simon
    Hi, I'm building a chat system for a company and I'm wondering as to what the best way to build the system would be? The current setup we have is a Nginx HTTP Server with PHP and Memcacheq (as a message queue that appends the chat messages to the user's own queue). We then poll the Nginx server (through a Comet style request) and query the message queue for updates. Is it a good idea to use a message queue such as Memcacheq to handle a chat system that has both user-to-user and site-wide chat or is it best to just stick to MySQL? Thanks!

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