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  • How to convert the amount of indentation in a source code file?

    - by toby
    I find that I now often work with code bases that have different amounts of indentation. Some use 2 spaces, some use 4 space, some even use tabs! Once in a while, I have to share code between these codebases, or, sometimes I use an incorrect amount of indentation by mistake. Is there a tool or a text editor feature that will convert between different amounts of indentation?

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  • Is there any way static block is executed more than once? if so then how?

    - by learner
    My Understanding Static block is executed during class loading, If a class is already loaded then there is no way to load the class other than class reloading Doubt/Question 1) Is there any time JVM reloads the class? My Understanding In Class Loading JVM loads source of the Java file, so it can not keep all thousands files source is a memory, it should discard the rarely used code and reload again when it is necessary and during reload JVM is not initializing static variables and locks again(may be using some tracking mechanism) Doubt/Question 2) If my above understanding is incorrect then please correct me

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  • Why can't I write just a try with no catch or finally?

    - by Camilo Martin
    Sometimes I do this and I've seen others doing it too: VB: Try DontWannaCatchIt() Catch End Try C#: try { DontWannaCatchIt(); } catch {} I know I should catch every important exception and do something about it, but sometimes it's not important to - or am I doing something wrong? Is this usage of the try block incorrect, and the requirement of at least one catch or finally block an indication of it?

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  • Concatenate a table name from a variable in a FROM clause

    - by idieeasy
    I'm trying to use a dynamically generated fully-qualified table name in sql server 2008. For example, this does not work: select max([id]) from @dbName+N'.[T1]' This will give an error like: Msg 102, Level 15, State 1, Line 73 Incorrect syntax near '+'. I know that something like this works: declare @qualifiedTable varchar(200) = @dbName+N'.[T1]' select max([id]) from @qualifiedTable But I have to do this LOTS of times so I would really like to do it in line. Is it possible?

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  • C++/CLI DLL on C# doesn't compile

    - by Mishgun_
    I wrote a wrapper DLL for some native c++ functions and compiled it in c++/CLI, then I added a reference to C# project, functions indicates there, but when I try compile project I get this error: "Additional information: Could not load file or assembly 'lib, Version=1.0.3742.39593, Culture=neutral, PublicKeyToken=null' or one of its dependencies. An attempt was made to load a program with an incorrect format. " What's the problem ? Thanks.

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  • SQL Syntax for testing objects before creating views & functions

    - by Scott Weinstein
    I'm trying to figure out the syntax for creating a view (or function) but only if a dependent CLR assembly exits. I've tried both IF EXISTS (SELECT name FROM sys.assemblies WHERE name = 'MyCLRAssembly') begin create view dbo.MyView as select GETDATE() as C1 end and IF EXISTS (SELECT name FROM sys.assemblies WHERE name = 'MyCLRAssembly') create view dbo.MyView as select GETDATE() as C1 go Neither work. I get Msg 156, Level 15, State 1, Line 2 Incorrect syntax near the keyword 'view'. How can this be done?

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  • How to run dubug file on another computer

    - by Pazzy
    I have a debug .exe file that i want to run on other machines that don't have MS Visual Studio 2008 installed on them. How can this be done? The release option doesn't work as the application does not function correctly when build in release (not sure why). At the moment I'm getting a message saying "This application has failed to start because the application configuration is incorrect". An ideas? Cheers.

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  • Mistake in the Asc() VB function?

    - by Alexander
    Hello! Could you please tell why the Asc() function returns incorrect result? Dim TestChar = Chr(128) Dim CharInt = Asc(TestChar) ' this is a mistake on Windows 7 x64. Asc(TestChar) returns 136 instead of 128 I executed this code on another computer and the result was 128. Thanks.

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  • How do i use the top keyword in an insert statement?

    - by acidzombie24
    I was using it as LIMIT when i got the exception Incorrect syntax near the keyword 'TOP'. Maybe i can omit it in this case without problem? but if i couldnt where do i put top? INSERT INTO [user_data] (...) SELECT ... @14 WHERE not exists (SELECT * FROM [user_data] WHERE [email] = @15 OR [name] = @16 OR [unconfirmed_email] = @17 TOP 1);

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  • What is the command-line input to produce the javadoc?

    - by Bernard
    After writing all the comments inside the code about the javadoc such as /** * This method compares the student's answer to the standard answer * @param ans The student's answer * @return True for correct answer; False for incorrect answer */ boolean compareAnswer(int ans); I guess it starts with : javadoc [optionss] [packages|files] I'm not sure what is the regular or default [option] and how can I say to produce it in my current home directory?

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  • XML XQUERY Problem with NTEXT data type

    - by johnfa
    Hello I want to use XQuery on a column of data type NTEXT (I have no choice!). I have tried converting the column to XML using CONVERT but it gives the error: Incorrect syntax near the keyword 'CONVERT'. Here's the query SELECT y.item.value('@UserID', 'varchar(50)') AS UnitID, y.item.value('@ListingID', 'varchar(100)') AS @ListingID FROM dbo.KB_XMod_Modules CROSS APPLY CONVERT(xml, instancedata).nodes('//instance') AS y(item) (instancedata is my column) Can anyone think of a work around for this ? Thanks

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  • Mpd as pppoe server with authorisation by freeradius2

    - by Korjavin Ivan
    I install freeradius2, add to raddb/users: test Cleartext-Password := "test1" Service-Type = Framed-User, Framed-Protocol = PPP, Framed-IP-Address = 10.36.0.2, Framed-IP-Netmask = 255.255.255.0, start radiusd, and check auth: radtest test test1 127.0.0.1 1002 testing123 Sending Access-Request of id 199 to 127.0.0.1 port 1812 User-Name = "test" User-Password = "test1" NAS-IP-Address = 127.0.0.1 NAS-Port = 1002 Message-Authenticator = 0x00000000000000000000000000000000 rad_recv: Access-Accept packet from host 127.0.0.1 port 1812, id=199, length=44 Service-Type = Framed-User Framed-Protocol = PPP Framed-IP-Address = 10.36.0.2 Framed-IP-Netmask = 255.255.255.0 Works fine. Next step. Add to mpd.conf: radius: set auth disable internal set auth max-logins 1 CI set auth enable radius-auth set radius timeout 90 set radius retries 2 set radius server 127.0.0.1 testing123 1812 1813 set radius me 127.0.0.1 create link template L pppoe set link action bundle B set link max-children 1000 set link no multilink set link no shortseq set link no pap chap-md5 chap-msv1 chap-msv2 set link enable chap set pppoe acname Internet load radius create link template em1 L set pppoe iface em1 set link enable incoming And trying to connect, auth failed, here is mpd log: mpd: [em1-2] LCP: auth: peer wants nothing, I want CHAP mpd: [em1-2] CHAP: sending CHALLENGE #1 len: 21 mpd: [em1-2] LCP: LayerUp mpd: [em1-2] CHAP: rec'd RESPONSE #1 len: 58 mpd: [em1-2] Name: "test" mpd: [em1-2] AUTH: Trying RADIUS mpd: [em1-2] RADIUS: Authenticating user 'test' mpd: [em1-2] RADIUS: Rec'd RAD_ACCESS_REJECT for user 'test' mpd: [em1-2] AUTH: RADIUS returned: failed mpd: [em1-2] AUTH: ran out of backends mpd: [em1-2] CHAP: Auth return status: failed mpd: [em1-2] CHAP: Reply message: ^AE=691 R=1 mpd: [em1-2] CHAP: sending FAILURE #1 len: 14 mpd: [em1-2] LCP: authorization failed Then i start freeradius as radiusd -fX, and get this log: rad_recv: Access-Request packet from host 127.0.0.1 port 46400, id=223, length=282 NAS-Identifier = "rubin.svyaz-nt.ru" NAS-IP-Address = 127.0.0.1 Message-Authenticator = 0x14d36639bed8074ec2988118125367ea Acct-Session-Id = "815965-em1-2" NAS-Port = 2 NAS-Port-Type = Ethernet Service-Type = Framed-User Framed-Protocol = PPP Calling-Station-Id = "00e05290b3e3 / 00:e0:52:90:b3:e3 / em1" NAS-Port-Id = "em1" Vendor-12341-Attr-12 = 0x656d312d32 Tunnel-Medium-Type:0 = IEEE-802 Tunnel-Client-Endpoint:0 = "00:e0:52:90:b3:e3" User-Name = "test" MS-CHAP-Challenge = 0xbb1e68d5bbc30f228725a133877de83e MS-CHAP2-Response = 0x010088746ae65b68e435e9d045ad6f9569b60000000000000000b56991b4f20704cb6c68e5982eec5e98a7f4b470c109c1b9 # Executing section authorize from file /usr/local/etc/raddb/sites-enabled/default +- entering group authorize {...} ++[preprocess] returns ok ++[chap] returns noop [mschap] Found MS-CHAP attributes. Setting 'Auth-Type = mschap' ++[mschap] returns ok [eap] No EAP-Message, not doing EAP ++[eap] returns noop [files] users: Matched entry DEFAULT at line 172 ++[files] returns ok Found Auth-Type = MSCHAP # Executing group from file /usr/local/etc/raddb/sites-enabled/default +- entering group MS-CHAP {...} [mschap] No Cleartext-Password configured. Cannot create LM-Password. [mschap] No Cleartext-Password configured. Cannot create NT-Password. [mschap] Creating challenge hash with username: test [mschap] Client is using MS-CHAPv2 for test, we need NT-Password [mschap] FAILED: No NT/LM-Password. Cannot perform authentication. [mschap] FAILED: MS-CHAP2-Response is incorrect ++[mschap] returns reject Failed to authenticate the user. Login incorrect: [test] (from client localhost port 2 cli 00e05290b3e3 / 00:e0:52:90:b3:e3 / em1) Using Post-Auth-Type REJECT # Executing group from file /usr/local/etc/raddb/sites-enabled/default +- entering group REJECT {...} [attr_filter.access_reject] expand: %{User-Name} -> test attr_filter: Matched entry DEFAULT at line 11 ++[attr_filter.access_reject] returns updated Delaying reject of request 2 for 1 seconds Going to the next request Waking up in 0.9 seconds. Sending delayed reject for request 2 Sending Access-Reject of id 223 to 127.0.0.1 port 46400 MS-CHAP-Error = "\001E=691 R=1" Why i have error "[mschap] No Cleartext-Password configured. Cannot create LM-Password." ? I define cleartext-password in users. I check raddb/sites-enabled/default authorize { chap mschap eap { ok = return } files } looks ok for me. Whats wrong with mpd/chap/radius ?

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  • Error during GENERAL_REQUEST_ENTITY for POST results in ASP .NET session state never getting unlocked

    - by Jesse
    I have been trying to chase down the root cause of a condition where ASP .NET session state remains locked after a web request has been terminated due to an unexpected error. We use the SQL Server session state provider for session because we have several servers in a web farm. This issue first presented itself in the form of many requests getting stuck on the 'AcquireRequestState' event of their lifecycle for no apparent reason. I was able to finding corresponding entries for these requests in the session state database in SQL server that were all locked (column Locked = 1). I was also able to correlate these requests to entries in the IIS log with HTTP status codes of 500 (with a sub status of 0). These findings lead me to believe that, in some cases, a request was erroring out but was NOT releasing its lock on session state like it should. I enabled Failed Request Tracing in IIS for the website in question for status code 500 with all available providers selected each with the 'Verbose' setting for verbosity. I've since gathered several failed traces that have caused permanently locked ASP .NET sessions. They all share the same characteristics: They are all 'POST' requests where the browser is posting data to be processed/saved. They all have events indicating that the 'Session' module was invoked during the REQUEST_ACQUIRE_STATE event. At this point the request would have marked the row in the session state database as being "locked". This is normal and expected. They all have GENERAL_READ_ENTITY_START, GENERAL_READ_ENTITY_END, and GENERAL_REQUEST_ENTITY entries that appear to be reading in the data that was posted to the server as part of the request. This appears to be a buffered operation as these events get repeated over and over with each one reading in some subset of the posted data. At some point during the 'read entity' related events and error occurs. Some have the error code "Incorrect function. (0x80070001)" and others have "The I/O operation has been aborted because of either a thread exit or an application request. (0x800703e3)". Once the error has been encountered, they all jump directly to the END_REQUEST events. The issue here is that, under normal circumstances, there should be a RELEASE_REQUEST_STATE event that will allow the Session module to release the lock it has on the session. This event is being skipped in this scenario. Just to be sure, I enabled failed request tracing for the '200' status code as well and generated several traces of successful requests that do have the RELEASE_REQUEST_STATE event being handled by the Session module. My theory at this point is that some kind of network issue is causing the 'Incorrect function' and 'I/O operation has been aborted because of either a thread exit or an application request' errors, but I don't understand why this seems to be causing the request handling to skip over the RELEASE_REQUEST_STATE event. If the request went through REQUEST_ACQUIRE_STATE it seems like it should also hit RELEASE_REQUEST_STATE as well. I'm loathe to say that this is a bug in IIS or ASP .NET, but it certainly appears that way to me at this point. Are there any configuration changes I could make to help ensure that 'RELEASE_REQUEST_STATE' is fired under all error conditions?

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  • How to export SQL Server data from corrupted database (with disk write error)

    - by damitamit
    IT realised there was a disk write error on our production SQL Server 2005 and hence was causing the backups to fail. By the time they had realised this the nightly backup was old, so were not able to just restore the backup on another server. The database is still running and being used constantly. However DBCC CheckDB fails. Also the SQL Server backup task fails, Copy Database fails, Export Data Wizard fails. However it seems all the data can be read from the tables (i.e using bcp etc) Another observation I have made is that the Transaction Log is nearly double the size of the Database. (Does that mean all the changes arent being written to the MDF?) What would be the best plan of attack to get the database to a state where backups are working and the data is safe? Take the database offline and use the MDF/LDF to somehow create the database on another sql server? Export the data from the database using bcp. Create the database (use the Generate Scripts function on the corrupt db to create the schema on the new db) on another sql server and use bcp again to import the data. Some other option that is the right course of action in this situation? The IT manager says the data is safe as if the server fails, the data can be restored from the mdf/ldf. I'm not sure so insisted that we start exporting the data each night as a failsafe (using bcp for example). IT are also having issues on the hardware side of things as supposedly the disk error in on a virtualized disk and can't be rebuilt like a normal raid array (or something like that). Please excuse my use of incorrect terminology and incorrect assumptions on how Sql Server operates. I'm the application developer and have been called to help (as it seems IT know less about SQL Server than I do). Many Thanks, Amit Results of DBBC CheckDB: Msg 1823, Level 16, State 2, Line 1 A database snapshot cannot be created because it failed to start. Msg 7928, Level 16, State 1, Line 1 The database snapshot for online checks could not be created. Either the reason is given in a previous error or one of the underlying volumes does not support sparse files or alternate streams. Attempting to get exclusive access to run checks offline. Msg 5030, Level 16, State 12, Line 1 The database could not be exclusively locked to perform the operation. Msg 7926, Level 16, State 1, Line 1 Check statement aborted. The database could not be checked as a database snapshot could not be created and the database or table could not be locked. See Books Online for details of when this behavior is expected and what workarounds exist. Also see previous errors for more details. Msg 823, Level 24, State 3, Line 1 The operating system returned error 1(error not found) to SQL Server during a write at offset 0x00000674706000 in file 'G:\AX40_Dynamics_Live.mdf'. Additional messages in the SQL Server error log and system event log may provide more detail. This is a severe system-level error condition that threatens database integrity and must be corrected immediately. Complete a full database consistency check (DBCC CHECKDB). This error can be caused by many factors; for more information, see SQL Server Books Online.

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  • SSH new connection begins to hang (not reject or terminate) after a day or so on Ubuntu 13.04 server

    - by kross
    Recently we upgraded the server from 12.04 LTS server to 13.04. All was well, including after a reboot. With all packages updated we began to see a strange issue, ssh works for a day or so (unclear on timing) then a later request for SSH hangs (cannot ctrl+c, nothing). It is up and serving webserver traffic etc. Port 22 is open (ips etc altered slightly for posting): nmap -T4 -A x.acme.com Starting Nmap 6.40 ( http://nmap.org ) at 2013-09-12 16:01 CDT Nmap scan report for x.acme.com (69.137.56.18) Host is up (0.026s latency). rDNS record for 69.137.56.18: c-69-137-56-18.hsd1.tn.provider.net Not shown: 998 filtered ports PORT STATE SERVICE VERSION 22/tcp open ssh OpenSSH 6.1p1 Debian 4 (protocol 2.0) | ssh-hostkey: 1024 54:d3:e3:38:44:f4:20:a4:e7:42:49:d0:a7:f1:3e:21 (DSA) | 2048 dc:21:77:3b:f4:4e:74:d0:87:33:14:40:04:68:33:a6 (RSA) |_256 45:69:10:79:5a:9f:0b:f0:66:15:39:87:b9:a1:37:f7 (ECDSA) 80/tcp open http Jetty 7.6.2.v20120308 | http-title: Log in as a Bamboo user - Atlassian Bamboo |_Requested resource was http://x.acme.com/userlogin!default.action;jsessionid=19v135zn8cl1tgso28fse4d50?os_destination=%2Fstart.action Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel Service detection performed. Please report any incorrect results at http://nmap.org/submit/ . Nmap done: 1 IP address (1 host up) scanned in 12.89 seconds Here is the ssh -vvv: ssh -vvv x.acme.com OpenSSH_5.9p1, OpenSSL 0.9.8x 10 May 2012 debug1: Reading configuration data /Users/tfergeson/.ssh/config debug1: Reading configuration data /etc/ssh_config debug1: /etc/ssh_config line 20: Applying options for * debug2: ssh_connect: needpriv 0 debug1: Connecting to x.acme.com [69.137.56.18] port 22. debug1: Connection established. debug3: Incorrect RSA1 identifier debug3: Could not load "/Users/tfergeson/.ssh/id_rsa" as a RSA1 public key debug1: identity file /Users/tfergeson/.ssh/id_rsa type 1 debug1: identity file /Users/tfergeson/.ssh/id_rsa-cert type -1 debug1: identity file /Users/tfergeson/.ssh/id_dsa type -1 debug1: identity file /Users/tfergeson/.ssh/id_dsa-cert type -1 debug1: Remote protocol version 2.0, remote software version OpenSSH_6.1p1 Debian-4 debug1: match: OpenSSH_6.1p1 Debian-4 pat OpenSSH* debug1: Enabling compatibility mode for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_5.9 debug2: fd 3 setting O_NONBLOCK debug3: load_hostkeys: loading entries for host "x.acme.com" from file "/Users/tfergeson/.ssh/known_hosts" debug3: load_hostkeys: found key type RSA in file /Users/tfergeson/.ssh/known_hosts:10 debug3: load_hostkeys: loaded 1 keys debug3: order_hostkeyalgs: prefer hostkeyalgs: [email protected],[email protected],ssh-rsa debug1: SSH2_MSG_KEXINIT sent debug1: SSH2_MSG_KEXINIT received debug2: kex_parse_kexinit: diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1 debug2: kex_parse_kexinit: [email protected],[email protected],ssh-rsa,[email protected],[email protected],ssh-dss debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected] debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected] debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-sha2-256,hmac-sha2-256-96,hmac-sha2-512,hmac-sha2-512-96,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96 debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-sha2-256,hmac-sha2-256-96,hmac-sha2-512,hmac-sha2-512-96,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96 debug2: kex_parse_kexinit: none,[email protected],zlib debug2: kex_parse_kexinit: none,[email protected],zlib debug2: kex_parse_kexinit: debug2: kex_parse_kexinit: debug2: kex_parse_kexinit: first_kex_follows 0 debug2: kex_parse_kexinit: reserved 0 debug2: kex_parse_kexinit: ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1 debug2: kex_parse_kexinit: ssh-rsa,ssh-dss,ecdsa-sha2-nistp256 debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected] debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected] debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96 debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96 debug2: kex_parse_kexinit: none,[email protected] debug2: kex_parse_kexinit: none,[email protected] debug2: kex_parse_kexinit: debug2: kex_parse_kexinit: debug2: kex_parse_kexinit: first_kex_follows 0 debug2: kex_parse_kexinit: reserved 0 debug2: mac_setup: found hmac-md5 debug1: kex: server->client aes128-ctr hmac-md5 none debug2: mac_setup: found hmac-md5 debug1: kex: client->server aes128-ctr hmac-md5 none debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP debug2: dh_gen_key: priv key bits set: 130/256 debug2: bits set: 503/1024 debug1: SSH2_MSG_KEX_DH_GEX_INIT sent debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY debug1: Server host key: RSA dc:21:77:3b:f4:4e:74:d0:87:33:14:40:04:68:33:a6 debug3: load_hostkeys: loading entries for host "x.acme.com" from file "/Users/tfergeson/.ssh/known_hosts" debug3: load_hostkeys: found key type RSA in file /Users/tfergeson/.ssh/known_hosts:10 debug3: load_hostkeys: loaded 1 keys debug3: load_hostkeys: loading entries for host "69.137.56.18" from file "/Users/tfergeson/.ssh/known_hosts" debug3: load_hostkeys: found key type RSA in file /Users/tfergeson/.ssh/known_hosts:6 debug3: load_hostkeys: loaded 1 keys debug1: Host 'x.acme.com' is known and matches the RSA host key. debug1: Found key in /Users/tfergeson/.ssh/known_hosts:10 debug2: bits set: 493/1024 debug1: ssh_rsa_verify: signature correct debug2: kex_derive_keys debug2: set_newkeys: mode 1 debug1: SSH2_MSG_NEWKEYS sent debug1: expecting SSH2_MSG_NEWKEYS debug2: set_newkeys: mode 0 debug1: SSH2_MSG_NEWKEYS received debug1: Roaming not allowed by server debug1: SSH2_MSG_SERVICE_REQUEST sent debug2: service_accept: ssh-userauth debug1: SSH2_MSG_SERVICE_ACCEPT received debug2: key: /Users/tfergeson/.ssh/id_rsa (0x7ff189c1d7d0) debug2: key: /Users/tfergeson/.ssh/id_dsa (0x0) debug1: Authentications that can continue: publickey debug3: start over, passed a different list publickey debug3: preferred publickey,keyboard-interactive,password debug3: authmethod_lookup publickey debug3: remaining preferred: keyboard-interactive,password debug3: authmethod_is_enabled publickey debug1: Next authentication method: publickey debug1: Offering RSA public key: /Users/tfergeson/.ssh/id_rsa debug3: send_pubkey_test debug2: we sent a publickey packet, wait for reply debug1: Server accepts key: pkalg ssh-rsa blen 277 debug2: input_userauth_pk_ok: fp 3c:e5:29:6c:9d:27:d1:7d:e8:09:a2:e8:8e:6e:af:6f debug3: sign_and_send_pubkey: RSA 3c:e5:29:6c:9d:27:d1:7d:e8:09:a2:e8:8e:6e:af:6f debug1: read PEM private key done: type RSA debug1: Authentication succeeded (publickey). Authenticated to x.acme.com ([69.137.56.18]:22). debug1: channel 0: new [client-session] debug3: ssh_session2_open: channel_new: 0 debug2: channel 0: send open debug1: Requesting [email protected] debug1: Entering interactive session. debug2: callback start debug2: client_session2_setup: id 0 debug2: fd 3 setting TCP_NODELAY debug2: channel 0: request pty-req confirm 1 debug1: Sending environment. debug3: Ignored env ATLAS_OPTS debug3: Ignored env rvm_bin_path debug3: Ignored env TERM_PROGRAM debug3: Ignored env GEM_HOME debug3: Ignored env SHELL debug3: Ignored env TERM debug3: Ignored env CLICOLOR debug3: Ignored env IRBRC debug3: Ignored env TMPDIR debug3: Ignored env Apple_PubSub_Socket_Render debug3: Ignored env TERM_PROGRAM_VERSION debug3: Ignored env MY_RUBY_HOME debug3: Ignored env TERM_SESSION_ID debug3: Ignored env USER debug3: Ignored env COMMAND_MODE debug3: Ignored env rvm_path debug3: Ignored env COM_GOOGLE_CHROME_FRAMEWORK_SERVICE_PROCESS/USERS/tfergeson/LIBRARY/APPLICATION_SUPPORT/GOOGLE/CHROME_SOCKET debug3: Ignored env JPDA_ADDRESS debug3: Ignored env APDK_HOME debug3: Ignored env SSH_AUTH_SOCK debug3: Ignored env Apple_Ubiquity_Message debug3: Ignored env __CF_USER_TEXT_ENCODING debug3: Ignored env rvm_sticky_flag debug3: Ignored env MAVEN_OPTS debug3: Ignored env LSCOLORS debug3: Ignored env rvm_prefix debug3: Ignored env PATH debug3: Ignored env PWD debug3: Ignored env JAVA_HOME debug1: Sending env LANG = en_US.UTF-8 debug2: channel 0: request env confirm 0 debug3: Ignored env JPDA_TRANSPORT debug3: Ignored env rvm_version debug3: Ignored env M2_HOME debug3: Ignored env HOME debug3: Ignored env SHLVL debug3: Ignored env rvm_ruby_string debug3: Ignored env LOGNAME debug3: Ignored env M2_REPO debug3: Ignored env GEM_PATH debug3: Ignored env AWS_RDS_HOME debug3: Ignored env rvm_delete_flag debug3: Ignored env EC2_PRIVATE_KEY debug3: Ignored env RUBY_VERSION debug3: Ignored env SECURITYSESSIONID debug3: Ignored env EC2_CERT debug3: Ignored env _ debug2: channel 0: request shell confirm 1 debug2: callback done debug2: channel 0: open confirm rwindow 0 rmax 32768 I can hard reboot (only mac monitors at that location) and it will again be accessible. This now happens every single time. It is imperative that I get it sorted. The strange thing is that it behaves initially then starts to hang after several hours. I perused logs previously and nothing stood out. From the auth.log, I can see that it has allowed me in, but still I get nothing back on the client side: Sep 20 12:47:50 cbear sshd[25376]: Accepted publickey for tfergeson from 10.1.10.14 port 54631 ssh2 Sep 20 12:47:50 cbear sshd[25376]: pam_unix(sshd:session): session opened for user tfergeson by (uid=0) UPDATES: Still occurring even after setting UseDNS no and commenting out #session optional pam_mail.so standard noenv This does not appear to be a network/dns related issue, as all services running on the machine are as responsive and accessible as ever, with the exception of sshd. Any thoughts on where to start?

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  • External usb 3.0 hard drive is not recognised when plugged into usb 3 port (ubuntu natty 64 bit).

    - by kimangroo
    I have an Iomega Prestige Portable External Hard Drive 1TB USB 3.0. It works fine on windows 7 as a usb 3.0 drive. It isn't detected on ubuntu natty 64bit, 2.6.38-8-generic. fdisk -l cannot see it at all: Disk /dev/sda: 500.1 GB, 500107862016 bytes 255 heads, 63 sectors/track, 60801 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x1bed746b Device Boot Start End Blocks Id System /dev/sda1 1 1689 13560832 27 Unknown /dev/sda2 * 1689 1702 102400 7 HPFS/NTFS /dev/sda3 1702 19978 146805760 7 HPFS/NTFS /dev/sda4 19978 60802 327914497 5 Extended /dev/sda5 25555 60802 283120640 7 HPFS/NTFS /dev/sda6 19978 23909 31571968 83 Linux /dev/sda7 23909 25555 13218816 82 Linux swap / Solaris Partition table entries are not in disk order lsusb can see it: Bus 003 Device 003: ID 059b:0070 Iomega Corp. Bus 003 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 002 Device 004: ID 05fe:0011 Chic Technology Corp. Browser Mouse Bus 002 Device 003: ID 0a12:0001 Cambridge Silicon Radio, Ltd Bluetooth Dongle (HCI mode) Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 001 Device 005: ID 0489:e00f Foxconn / Hon Hai Bus 001 Device 004: ID 0c45:64b5 Microdia Bus 001 Device 003: ID 08ff:168f AuthenTec, Inc. Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub And dmesg | grep -i xhci (I may have unplugged the drive and plugged it back in again after booting): [ 1.659060] pci 0000:04:00.0: xHCI HW did not halt within 2000 usec status = 0x0 [ 11.484971] xhci_hcd 0000:04:00.0: PCI INT A -> GSI 18 (level, low) -> IRQ 18 [ 11.484997] xhci_hcd 0000:04:00.0: setting latency timer to 64 [ 11.485002] xhci_hcd 0000:04:00.0: xHCI Host Controller [ 11.485064] xhci_hcd 0000:04:00.0: new USB bus registered, assigned bus number 3 [ 11.636149] xhci_hcd 0000:04:00.0: irq 18, io mem 0xc5400000 [ 11.636241] xhci_hcd 0000:04:00.0: irq 43 for MSI/MSI-X [ 11.636246] xhci_hcd 0000:04:00.0: irq 44 for MSI/MSI-X [ 11.636251] xhci_hcd 0000:04:00.0: irq 45 for MSI/MSI-X [ 11.636256] xhci_hcd 0000:04:00.0: irq 46 for MSI/MSI-X [ 11.636261] xhci_hcd 0000:04:00.0: irq 47 for MSI/MSI-X [ 11.639654] xHCI xhci_add_endpoint called for root hub [ 11.639655] xHCI xhci_check_bandwidth called for root hub [ 11.956366] usb 3-1: new SuperSpeed USB device using xhci_hcd and address 2 [ 12.001073] xhci_hcd 0000:04:00.0: WARN: short transfer on control ep [ 12.007059] xhci_hcd 0000:04:00.0: WARN: short transfer on control ep [ 12.012932] xhci_hcd 0000:04:00.0: WARN: short transfer on control ep [ 12.018922] xhci_hcd 0000:04:00.0: WARN: short transfer on control ep [ 12.049139] xhci_hcd 0000:04:00.0: WARN: short transfer on control ep [ 12.056754] xhci_hcd 0000:04:00.0: WARN: short transfer on control ep [ 12.131607] xhci_hcd 0000:04:00.0: WARN no SS endpoint bMaxBurst [ 12.179717] xhci_hcd 0000:04:00.0: WARN: short transfer on control ep [ 12.686876] xhci_hcd 0000:04:00.0: WARN: babble error on endpoint [ 12.687058] xhci_hcd 0000:04:00.0: WARN Set TR Deq Ptr cmd invalid because of stream ID configuration [ 12.687152] xhci_hcd 0000:04:00.0: ERROR Transfer event for disabled endpoint or incorrect stream ring [ 43.330737] usb 3-1: reset SuperSpeed USB device using xhci_hcd and address 2 [ 43.422579] xhci_hcd 0000:04:00.0: WARN: short transfer on control ep [ 43.422658] xhci_hcd 0000:04:00.0: xHCI xhci_drop_endpoint called with disabled ep ffff88014669af00 [ 43.422665] xhci_hcd 0000:04:00.0: xHCI xhci_drop_endpoint called with disabled ep ffff88014669af40 [ 43.422671] xhci_hcd 0000:04:00.0: xHCI xhci_drop_endpoint called with disabled ep ffff88014669af80 [ 43.422677] xhci_hcd 0000:04:00.0: xHCI xhci_drop_endpoint called with disabled ep ffff88014669afc0 [ 43.531159] xhci_hcd 0000:04:00.0: WARN no SS endpoint bMaxBurst [ 125.160248] xhci_hcd 0000:04:00.0: WARN no SS endpoint bMaxBurst [ 903.766466] usb 3-1: new SuperSpeed USB device using xhci_hcd and address 3 [ 903.807789] xhci_hcd 0000:04:00.0: WARN: short transfer on control ep [ 903.813530] xhci_hcd 0000:04:00.0: WARN: short transfer on control ep [ 903.819400] xhci_hcd 0000:04:00.0: WARN: short transfer on control ep [ 903.825104] xhci_hcd 0000:04:00.0: WARN: short transfer on control ep [ 903.855067] xhci_hcd 0000:04:00.0: WARN: short transfer on control ep [ 903.862314] xhci_hcd 0000:04:00.0: WARN: short transfer on control ep [ 903.862597] xhci_hcd 0000:04:00.0: WARN no SS endpoint bMaxBurst [ 903.913211] xhci_hcd 0000:04:00.0: WARN: short transfer on control ep [ 904.424416] xhci_hcd 0000:04:00.0: WARN: babble error on endpoint [ 904.424599] xhci_hcd 0000:04:00.0: WARN Set TR Deq Ptr cmd invalid because of stream ID configuration [ 904.424700] xhci_hcd 0000:04:00.0: ERROR Transfer event for disabled endpoint or incorrect stream ring [ 935.139021] usb 3-1: reset SuperSpeed USB device using xhci_hcd and address 3 [ 935.226075] xhci_hcd 0000:04:00.0: WARN: short transfer on control ep [ 935.226140] xhci_hcd 0000:04:00.0: xHCI xhci_drop_endpoint called with disabled ep ffff880148186b00 [ 935.226148] xhci_hcd 0000:04:00.0: xHCI xhci_drop_endpoint called with disabled ep ffff880148186b40 [ 935.226153] xhci_hcd 0000:04:00.0: xHCI xhci_drop_endpoint called with disabled ep ffff880148186b80 [ 935.226159] xhci_hcd 0000:04:00.0: xHCI xhci_drop_endpoint called with disabled ep ffff880148186bc0 [ 935.343339] xhci_hcd 0000:04:00.0: WARN no SS endpoint bMaxBurst I thought it might be that the firmware wasn't compatible with linux or something, but when booting a live image of partedmagic, (2.6.38.4-pmagic), the drive was detected fine, I could mount it and got usb 3.0 speeds (at least they double the speeds I got from plugging same drive in usb 2 ports). dmesg in partedmagic did say something about no SuperSpeed endpoint which was an error I saw in a previous dmesg of ubuntu: Jun 27 15:49:02 (none) user.info kernel: [ 2.978743] xhci_hcd 0000:04:00.0: PCI INT A -> GSI 18 (level, low) -> IRQ 18 Jun 27 15:49:02 (none) user.debug kernel: [ 2.978771] xhci_hcd 0000:04:00.0: setting latency timer to 64 Jun 27 15:49:02 (none) user.info kernel: [ 2.978781] xhci_hcd 0000:04:00.0: xHCI Host Controller Jun 27 15:49:02 (none) user.info kernel: [ 2.978856] xhci_hcd 0000:04:00.0: new USB bus registered, assigned bus number 3 Jun 27 15:49:02 (none) user.info kernel: [ 3.089458] xhci_hcd 0000:04:00.0: irq 18, io mem 0xc5400000 Jun 27 15:49:02 (none) user.debug kernel: [ 3.089541] xhci_hcd 0000:04:00.0: irq 42 for MSI/MSI-X Jun 27 15:49:02 (none) user.debug kernel: [ 3.089544] xhci_hcd 0000:04:00.0: irq 43 for MSI/MSI-X Jun 27 15:49:02 (none) user.debug kernel: [ 3.089546] xhci_hcd 0000:04:00.0: irq 44 for MSI/MSI-X Jun 27 15:49:02 (none) user.debug kernel: [ 3.089548] xhci_hcd 0000:04:00.0: irq 45 for MSI/MSI-X Jun 27 15:49:02 (none) user.debug kernel: [ 3.089550] xhci_hcd 0000:04:00.0: irq 46 for MSI/MSI-X Jun 27 15:49:02 (none) user.warn kernel: [ 3.092857] usb usb3: No SuperSpeed endpoint companion for config 1 interface 0 altsetting 0 ep 129: using minimum values Jun 27 15:49:02 (none) user.info kernel: [ 3.092864] usb usb3: New USB device found, idVendor=1d6b, idProduct=0003 Jun 27 15:49:02 (none) user.info kernel: [ 3.092866] usb usb3: New USB device strings: Mfr=3, Product=2, SerialNumber=1 Jun 27 15:49:02 (none) user.info kernel: [ 3.092867] usb usb3: Product: xHCI Host Controller Jun 27 15:49:02 (none) user.info kernel: [ 3.092869] usb usb3: Manufacturer: Linux 2.6.38.4-pmagic xhci_hcd Jun 27 15:49:02 (none) user.info kernel: [ 3.092870] usb usb3: SerialNumber: 0000:04:00.0 Jun 27 15:49:02 (none) user.debug kernel: [ 3.092961] xHCI xhci_add_endpoint called for root hub Jun 27 15:49:02 (none) user.debug kernel: [ 3.092963] xHCI xhci_check_bandwidth called for root hub Well I have no idea what's going wrong, and I haven't had much luck from google and the forums so far. A number of unanswered threads with people with similar error messages and problems only. Hopefully someone here can help or point me in the right direction?!

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  • Refactoring a Single Rails Model with large methods & long join queries trying to do everything

    - by Kelseydh
    I have a working Ruby on Rails Model that I suspect is inefficient, hard to maintain, and full of unnecessary SQL join queries. I want to optimize and refactor this Model (Quiz.rb) to comply with Rails best practices, but I'm not sure how I should do it. The Rails app is a game that has Missions with many Stages. Users complete Stages by answering Questions that have correct or incorrect Answers. When a User tries to complete a stage by answering questions, the User gets a Quiz entry with many Attempts. Each Attempt records an Answer submitted for that Question within the Stage. A user completes a stage or mission by getting every Attempt correct, and their progress is tracked by adding a new entry to the UserMission & UserStage join tables. All of these features work, but unfortunately the Quiz.rb Model has been twisted to handle almost all of it exclusively. The callbacks began at 'Quiz.rb', and because I wasn't sure how to leave the Quiz Model during a multi-model update, I resorted to using Rails Console to have the @quiz instance variable via self.some_method do all the heavy lifting to retrieve every data value for the game's business logic; resulting in large extended join queries that "dance" all around the Database schema. The Quiz.rb Model that Smells: class Quiz < ActiveRecord::Base belongs_to :user has_many :attempts, dependent: :destroy before_save :check_answer before_save :update_user_mission_and_stage accepts_nested_attributes_for :attempts, :reject_if => lambda { |a| a[:answer_id].blank? }, :allow_destroy => true #Checks every answer within each quiz, adding +1 for each correct answer #within a stage quiz, and -1 for each incorrect answer def check_answer stage_score = 0 self.attempts.each do |attempt| if attempt.answer.correct? == true stage_score += 1 elsif attempt.answer.correct == false stage_score - 1 end end stage_score end def winner return true end def update_user_mission_and_stage ####### #Step 1: Checks if UserMission exists, finds or creates one. #if no UserMission for the current mission exists, creates a new UserMission if self.user_has_mission? == false @user_mission = UserMission.new(user_id: self.user.id, mission_id: self.current_stage.mission_id, available: true) @user_mission.save else @user_mission = self.find_user_mission end ####### #Step 2: Checks if current UserStage exists, stops if true to prevent duplicate entry if self.user_has_stage? @user_mission.save return true else ####### ##Step 3: if step 2 returns false: ##Initiates UserStage creation instructions #checks for winner (winner actions need to be defined) if they complete last stage of last mission for a given orientation if self.passed? && self.is_last_stage? && self.is_last_mission? create_user_stage_and_update_user_mission self.winner #NOTE: The rest are the same, but specify conditions that are available to add badges or other actions upon those conditions occurring: ##if user completes first stage of a mission elsif self.passed? && self.is_first_stage? && self.is_first_mission? create_user_stage_and_update_user_mission #creates user badge for finishing first stage of first mission self.user.add_badge(5) self.user.activity_logs.create(description: "granted first-stage badge", type_event: "badge", value: "first-stage") #If user completes last stage of a given mission, creates a new UserMission elsif self.passed? && self.is_last_stage? && self.is_first_mission? create_user_stage_and_update_user_mission #creates user badge for finishing first mission self.user.add_badge(6) self.user.activity_logs.create(description: "granted first-mission badge", type_event: "badge", value: "first-mission") elsif self.passed? create_user_stage_and_update_user_mission else self.passed? == false return true end end end #Creates a new UserStage record in the database for a successful Quiz question passing def create_user_stage_and_update_user_mission @nu_stage = @user_mission.user_stages.new(user_id: self.user.id, stage_id: self.current_stage.id) @nu_stage.save @user_mission.save self.user.add_points(50) end #Boolean that defines passing a stage as answering every question in that stage correct def passed? self.check_answer >= self.number_of_questions end #Returns the number of questions asked for that stage's quiz def number_of_questions self.attempts.first.answer.question.stage.questions.count end #Returns the current_stage for the Quiz, routing through 1st attempt in that Quiz def current_stage self.attempts.first.answer.question.stage end #Gives back the position of the stage relative to its mission. def stage_position self.attempts.first.answer.question.stage.position end #will find the user_mission for the current user and stage if it exists def find_user_mission self.user.user_missions.find_by_mission_id(self.current_stage.mission_id) end #Returns true if quiz was for the last stage within that mission #helpful for triggering actions related to a user completing a mission def is_last_stage? self.stage_position == self.current_stage.mission.stages.last.position end #Returns true if quiz was for the first stage within that mission #helpful for triggering actions related to a user completing a mission def is_first_stage? self.stage_position == self.current_stage.mission.stages_ordered.first.position end #Returns true if current user has a UserMission for the current stage def user_has_mission? self.user.missions.ids.include?(self.current_stage.mission.id) end #Returns true if current user has a UserStage for the current stage def user_has_stage? self.user.stages.include?(self.current_stage) end #Returns true if current user is on the last mission based on position within a given orientation def is_first_mission? self.user.missions.first.orientation.missions.by_position.first.position == self.current_stage.mission.position end #Returns true if current user is on the first stage & mission of a given orientation def is_last_mission? self.user.missions.first.orientation.missions.by_position.last.position == self.current_stage.mission.position end end My Question Currently my Rails server takes roughly 500ms to 1 sec to process single @quiz.save action. I am confident that the slowness here is due to sloppy code, not bad Database ERD design. What does a better solution look like? And specifically: Should I use join queries to retrieve values like I did here, or is it better to instantiate new objects within the model instead? Or am I missing a better solution? How should update_user_mission_and_stage be refactored to follow best practices? Relevant Code for Reference: quizzes_controller.rb w/ Controller Route Initiating Callback: class QuizzesController < ApplicationController before_action :find_stage_and_mission before_action :find_orientation before_action :find_question def show end def create @user = current_user @quiz = current_user.quizzes.new(quiz_params) if @quiz.save if @quiz.passed? if @mission.next_mission.nil? && @stage.next_stage.nil? redirect_to root_path, notice: "Congratulations, you have finished the last mission!" elsif @stage.next_stage.nil? redirect_to [@mission.next_mission, @mission.first_stage], notice: "Correct! Time for Mission #{@mission.next_mission.position}", info: "Starting next mission" else redirect_to [@mission, @stage.next_stage], notice: "Answer Correct! You passed the stage!" end else redirect_to [@mission, @stage], alert: "You didn't get every question right, please try again." end else redirect_to [@mission, @stage], alert: "Sorry. We were unable to save your answer. Please contact the admministrator." end @questions = @stage.questions.all end private def find_stage_and_mission @stage = Stage.find(params[:stage_id]) @mission = @stage.mission end def find_question @question = @stage.questions.find_by_id params[:id] end def quiz_params params.require(:quiz).permit(:user_id, :attempt_id, {attempts_attributes: [:id, :quiz_id, :answer_id]}) end def find_orientation @orientation = @mission.orientation @missions = @orientation.missions.by_position end end Overview of Relevant ERD Database Relationships: Mission - Stage - Question - Answer - Attempt <- Quiz <- User Mission - UserMission <- User Stage - UserStage <- User Other Models: Mission.rb class Mission < ActiveRecord::Base belongs_to :orientation has_many :stages has_many :user_missions, dependent: :destroy has_many :users, through: :user_missions #SCOPES scope :by_position, -> {order(position: :asc)} def stages_ordered stages.order(:position) end def next_mission self.orientation.missions.find_by_position(self.position.next) end def first_stage next_mission.stages_ordered.first end end Stage.rb: class Stage < ActiveRecord::Base belongs_to :mission has_many :questions, dependent: :destroy has_many :user_stages, dependent: :destroy has_many :users, through: :user_stages accepts_nested_attributes_for :questions, reject_if: :all_blank, allow_destroy: true def next_stage self.mission.stages.find_by_position(self.position.next) end end Question.rb class Question < ActiveRecord::Base belongs_to :stage has_many :answers, dependent: :destroy accepts_nested_attributes_for :answers, :reject_if => lambda { |a| a[:body].blank? }, :allow_destroy => true end Answer.rb: class Answer < ActiveRecord::Base belongs_to :question has_many :attempts, dependent: :destroy end Attempt.rb: class Attempt < ActiveRecord::Base belongs_to :answer belongs_to :quiz end User.rb: class User < ActiveRecord::Base belongs_to :school has_many :activity_logs has_many :user_missions, dependent: :destroy has_many :missions, through: :user_missions has_many :user_stages, dependent: :destroy has_many :stages, through: :user_stages has_many :orientations, through: :school has_many :quizzes, dependent: :destroy has_many :attempts, through: :quizzes def latest_stage_position self.user_missions.last.user_stages.last.stage.position end end UserMission.rb class UserMission < ActiveRecord::Base belongs_to :user belongs_to :mission has_many :user_stages, dependent: :destroy end UserStage.rb class UserStage < ActiveRecord::Base belongs_to :user belongs_to :stage belongs_to :user_mission end

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  • Master-slave vs. peer-to-peer archictecture: benefits and problems

    - by Ashok_Ora
    Normal 0 false false false EN-US X-NONE X-NONE Almost two decades ago, I was a member of a database development team that introduced adaptive locking. Locking, the most popular concurrency control technique in database systems, is pessimistic. Locking ensures that two or more conflicting operations on the same data item don’t “trample” on each other’s toes, resulting in data corruption. In a nutshell, here’s the issue we were trying to address. In everyday life, traffic lights serve the same purpose. They ensure that traffic flows smoothly and when everyone follows the rules, there are no accidents at intersections. As I mentioned earlier, the problem with typical locking protocols is that they are pessimistic. Regardless of whether there is another conflicting operation in the system or not, you have to hold a lock! Acquiring and releasing locks can be quite expensive, depending on how many objects the transaction touches. Every transaction has to pay this penalty. To use the earlier traffic light analogy, if you have ever waited at a red light in the middle of nowhere with no one on the road, wondering why you need to wait when there’s clearly no danger of a collision, you know what I mean. The adaptive locking scheme that we invented was able to minimize the number of locks that a transaction held, by detecting whether there were one or more transactions that needed conflicting eyou could get by without holding any lock at all. In many “well-behaved” workloads, there are few conflicts, so this optimization is a huge win. If, on the other hand, there are many concurrent, conflicting requests, the algorithm gracefully degrades to the “normal” behavior with minimal cost. We were able to reduce the number of lock requests per TPC-B transaction from 178 requests down to 2! Wow! This is a dramatic improvement in concurrency as well as transaction latency. The lesson from this exercise was that if you can identify the common scenario and optimize for that case so that only the uncommon scenarios are more expensive, you can make dramatic improvements in performance without sacrificing correctness. So how does this relate to the architecture and design of some of the modern NoSQL systems? NoSQL systems can be broadly classified as master-slave sharded, or peer-to-peer sharded systems. NoSQL systems with a peer-to-peer architecture have an interesting way of handling changes. Whenever an item is changed, the client (or an intermediary) propagates the changes synchronously or asynchronously to multiple copies (for availability) of the data. Since the change can be propagated asynchronously, during some interval in time, it will be the case that some copies have received the update, and others haven’t. What happens if someone tries to read the item during this interval? The client in a peer-to-peer system will fetch the same item from multiple copies and compare them to each other. If they’re all the same, then every copy that was queried has the same (and up-to-date) value of the data item, so all’s good. If not, then the system provides a mechanism to reconcile the discrepancy and to update stale copies. So what’s the problem with this? There are two major issues: First, IT’S HORRIBLY PESSIMISTIC because, in the common case, it is unlikely that the same data item will be updated and read from different locations at around the same time! For every read operation, you have to read from multiple copies. That’s a pretty expensive, especially if the data are stored in multiple geographically separate locations and network latencies are high. Second, if the copies are not all the same, the application has to reconcile the differences and propagate the correct value to the out-dated copies. This means that the application program has to handle discrepancies in the different versions of the data item and resolve the issue (which can further add to cost and operation latency). Resolving discrepancies is only one part of the problem. What if the same data item was updated independently on two different nodes (copies)? In that case, due to the asynchronous nature of change propagation, you might land up with different versions of the data item in different copies. In this case, the application program also has to resolve conflicts and then propagate the correct value to the copies that are out-dated or have incorrect versions. This can get really complicated. My hunch is that there are many peer-to-peer-based applications that don’t handle this correctly, and worse, don’t even know it. Imagine have 100s of millions of records in your database – how can you tell whether a particular data item is incorrect or out of date? And what price are you willing to pay for ensuring that the data can be trusted? Multiple network messages per read request? Discrepancy and conflict resolution logic in the application, and potentially, additional messages? All this overhead, when all you were trying to do was to read a data item. Wouldn’t it be simpler to avoid this problem in the first place? Master-slave architectures like the Oracle NoSQL Database handles this very elegantly. A change to a data item is always sent to the master copy. Consequently, the master copy always has the most current and authoritative version of the data item. The master is also responsible for propagating the change to the other copies (for availability and read scalability). Client drivers are aware of master copies and replicas, and client drivers are also aware of the “currency” of a replica. In other words, each NoSQL Database client knows how stale a replica is. This vastly simplifies the job of the application developer. If the application needs the most current version of the data item, the client driver will automatically route the request to the master copy. If the application is willing to tolerate some staleness of data (e.g. a version that is no more than 1 second out of date), the client can easily determine which replica (or set of replicas) can satisfy the request, and route the request to the most efficient copy. This results in a dramatic simplification in application logic and also minimizes network requests (the driver will only send the request to exactl the right replica, not many). So, back to my original point. A well designed and well architected system minimizes or eliminates unnecessary overhead and avoids pessimistic algorithms wherever possible in order to deliver a highly efficient and high performance system. If you’ve every programmed an Oracle NoSQL Database application, you’ll know the difference! /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;}

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  • Big data: An evening in the life of an actual buyer

    - by Jean-Pierre Dijcks
    Here I am, and this is an actual story of one of my evenings, trying to spend money with a company and ultimately failing. I just gave up and bought a service from another vendor, not the incumbent. Here is that story and how I think big data could actually fix this (and potentially prevent some of this from happening). In the end this story should illustrate how big data can benefit me (get me what I want without causing grief) and the company I am trying to buy something from. Note: Lots of details left out, I have no intention of being the annoyed blogger moaning about a specific company. What did I want to get? We watch TV, we have internet and we do have a land line. The land line is from a different vendor then the TV and the internet. I have decided that this makes no sense and I was going to get a bundle (no need to infer who this is, I just picked the generic bundle word as this is what I want to get) of all three services as this seems to save me money. I also want to not talk to people, I just want to click on a website when I feel like it and get it all sorted. I do think that is reality. I want to just do my shopping at 9.30pm while watching silly reruns on TV. Problem 1 - Bad links So, I'm an existing customer of the company I want to buy my bundle from. I go to the website, I click on offers. Turns out they are offers for new customers. After grumbling about how good they are, I click on offers for existing customers. Bummer, it goes to offers for new customers, so I click again on the link for offers for existing customers. No cigar... it just does not work. Big data solutions: 1) Do not show an existing customer the offers for new customers unless they are the same => This is only partially doable without login, but if a customer logs in the application should always know that this is an existing customer. But in general, imagine I do this from my home going through the internet service of this vendor to their domain... an instant filter should move me into the "existing customer route". 2) Flag dead or incorrect links => I've clicked the link for "existing customer offers" at least 3 times in under 5 seconds... Identifying patterns like this is easy in Hadoop and can very quickly make a list of potentially incorrect links. No need for realtime fixing, just the fact that this link can be pro-actively fixed across my entire web domain is a good thing. Preventative maintenance! Problem 2 - Purchase cannot be completed Apart from the fact that the browsing pattern to actually get to what I want is poorly designed, my purchase never gets past a specific point. In other words, I put something into my shopping cart and when I want to move on the application either crashes (with me going to an error page) or hangs or goes into something like chat. So I try again, and again and again. I think I tried this entire path (while being logged in!!) at least 10 times over the course of 20 minutes. I also clicked on the feedback button and, frustrated as I was, tried to explain this did not work... Big Data Solutions: 1) This web site does shopping cart analysis. I got an email next day stating I have things in my shopping cart, just click here to complete my purchase. After the above experience, this just added insult to my pain... 2) What should have happened, is a Hadoop job going over all logged in customers that are on the buy flow. It should flag anyone who is trying (multiple attempts from the same user to do the same thing), analyze the shopping card, the clicks to identify what the customers wants, his feedback provided (note: always own your own website feedback, never just farm this out!!) and in a short turn around time (30 minutes to 2 hours or so) email me with a link to complete my purchase. Not with a link to my shopping cart 12 hours later, but a link to actually achieve what I wanted... Why should this company go through the big data effort? I do believe this is relatively easy to do using our Oracle Event Processing and Big Data Appliance solutions combined. It is almost so simple (to my mind) that it makes no sense that this is not in place? But, now I am ranting... Why is this interesting? It is because of $$$$. After trying really hard, I mean I did this all in the evening, and again in the morning before going to work. I kept on failing, But I really wanted this to work... so an email that said, sorry, we noticed you tried to get a bundle (the log knows what I wanted, where I failed, so easy to generate), here is the link to click and complete your purchase. And here is 2 movies on us as an apology would have kept me as a customer, and got the additional $$$$ per month for the next couple of years. It would also lead to upsell on my phone package etc. Instead, I went to a completely different company, bought service from them. Lost money for company A, negative sentiment for company A and me telling this story at the water cooler so I'm influencing more people to think negatively about company A. All in all, a loss of easy money, a ding in sentiment and image where a relatively simple solution exists and can be in place on the software I describe routinely in this blog... For those who are coming to Openworld and maybe see value in solving the above, or are thinking of how to solve this, come visit us in Moscone North - Oracle Red Lounge or in the Engineered Systems Showcase.

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  • Task Scheduler Cannot Apply My Changes - Adding a User with Permissions

    - by Aaron
    I can log in to the server using a domain account without administrator privileges and create a task in the Task Scheduler. I am allowed to do an initial save of the task but unable to modify it with the same user account. When changes are complete, a message box prompts for the user password (same domain user I logged in with), then fails with the following message. Task Scheduler cannot apply your changes. The user account is unknown, the password is incorrect, or the account does not have permission to modify the task. When I check Log on as Batch Job Properties (found this from the Help documentation): This policy is accessible by opening the Control Panel, Administrative Tools, and then Local Security Policy. In the Local Security Policy window, click Local Policy, User Rights Assignment, and then Logon as batch job. Everything is grayed out, so I can't add a user. How can I add a user?

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  • netsh.exe: Error 87

    - by Ben
    I'm having some trouble creating a urlacl reservation in Windows Server 2008; probably this a rookie mistake. The command line I'm using is: netsh http add urlacl url=http://+:99898/ user=ben The error that I see is: Url reservation add failed, Error: 87 The parameter is incorrect. There is a local user account named 'ben' that has admin privileges. I've made sure to put a trailing slash after the port number in the URL. Google and MSDN documentation are letting me down now - does anyone have any clue what I'm doing incorrectly?

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  • Cannot log to Proxmox GUI

    - by greg
    I'm running proxmox on debian 6.0.8 kernel 2.6.32-18-pve. When I try to log into the GUI with the root password, it lets me in for about 2 seconds then asks for the password again: <hostname>:8006/api2/json/cluster/resources 401 (permission denied - invalid ticket) This is not the same behavior as when I give an incorrect password. I suspect a hostname problem, but I can't sort it out. My /etc/hosts contains the following line: <ip> <shorthostname> <longhostname> pvelocalhost The folder /etc/pve/nodes contains a folder name The https certificates matches the hostname. Any idea? TIA greg

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  • Prevent RDP logon brute force in mikrotik router via winbox

    - by holian
    Masters, I need help, how to config our router to block RDP brute force attacks I would like to set our router to only allow RDP connection from a specified country (our specified IP ranges), plus i need to set up router to block (take ips to black list) and drop brute force attepmst to specified port numbers. I try to set this with changeing the ftp port to rdp port. http://wiki.mikrotik.com/wiki/Bruteforce_login_prevention_%28FTP_%26_SSH Any suggestion tnx. H Current configuration: I try to configure the router via Winbox. I set some NAT rules (from dyndns to local address, rdp port) In the filter rules tab: I'm not sure this configuration should do the trick?! Is the content text "530 login incorrect" is fit for RDP connection to? Because in the tutorial used for filtering FTP connection. How to set router to allow RDP attempts from specified IP ranges? Thank you // New config

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