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centos dedicated Server unresponsive for the first time

- by Ambrose Bwangatto

server was unresponsive for an hour so i rebooted it and checked /var/log/messages and found this. can anybody point out whats wrong ? Sep 28 07:39:35 www kernel: INFO: task mysqld:22749 blocked for more than 120 seconds. Sep 28 07:39:35 www kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. Sep 28 07:39:35 www kernel: mysqld D ffff810001015120 0 22749 3266 22792 22659 (NOTLB) Sep 28 07:39:35 www kernel: ffff810139d21e58 0000000000000086 ffff810036217000 ffffffff8000f758 Sep 28 07:39:35 www kernel: ffff81020dfd1408 0000000000000007 ffff8101cfbaf7e0 ffff81020fca5080 Sep 28 07:39:35 www kernel: 00017a451524782a 00000000000043b2 ffff8101cfbaf9c8 0000000280009a22 Sep 28 07:39:35 www kernel: Call Trace: Sep 28 07:39:35 www kernel: [<ffffffff8000f758>] generic_permission+0x52/0xca Sep 28 07:39:35 www kernel: [<ffffffff80063c63>] __mutex_lock_slowpath+0x60/0x9b Sep 28 07:39:35 www kernel: [<ffffffff8000cea2>] do_path_lookup+0x294/0x310 Sep 28 07:39:35 www kernel: [<ffffffff80063cad>] .text.lock.mutex+0xf/0x14 Sep 28 07:39:35 www kernel: [<ffffffff8003c618>] do_unlinkat+0x66/0x141 Sep 28 07:39:35 www kernel: [<ffffffff8005d229>] tracesys+0x71/0xe0 Sep 28 07:39:57 www kernel: [<ffffffff8005d28d>] tracesys+0xd5/0xe0 Sep 28 07:39:58 www kernel: Sep 28 07:39:59 www kernel: INFO: task httpd:22679 blocked for more than 120 seconds. Sep 28 07:40:04 www kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. Sep 28 07:40:08 www kernel: httpd D ffff81000100caa0 0 22679 22413 22680 22678 (NOTLB) Sep 28 07:40:51 www kernel: ffff81018b0dbc78 0000000000000086 ffff81018b0dbc88 0000004480063002 Sep 28 07:41:52 www kernel: ffff81000001cc00 0000000000000007 ffff81013ac5e860 ffff81020fc96100 Sep 28 07:43:10 www kernel: 00017a44de6376c8 000000000000a89f ffff81013ac5ea48 000000010001cc00 Sep 28 07:43:38 www kernel: Call Trace: Sep 28 07:44:06 www kernel: [<ffffffff80063c63>] __mutex_lock_slowpath+0x60/0x9b Sep 28 07:44:09 www kernel: [<ffffffff80063cad>] .text.lock.mutex+0xf/0x14 Sep 28 07:44:10 www kernel: [<ffffffff8000d0b2>] do_lookup+0x90/0x1e6 Sep 28 07:44:13 www kernel: [<ffffffff8000a2e9>] __link_path_walk+0xa3a/0xfd1 Sep 28 07:44:16 www kernel: [<ffffffff8000eb8e>] link_path_walk+0x45/0xb8 Sep 28 07:44:16 www kernel: [<ffffffff8000cea2>] do_path_lookup+0x294/0x310 Sep 28 07:44:29 www kernel: [<ffffffff800129ad>] getname+0x15b/0x1c2 Sep 28 07:44:38 www kernel: [<ffffffff80023b60>] __user_walk_fd+0x37/0x4c Sep 28 07:44:42 www kernel: [<ffffffff80028ada>] vfs_stat_fd+0x1b/0x4a Sep 28 07:44:43 www kernel: [<ffffffff8003c69a>] do_unlinkat+0xe8/0x141 Sep 28 07:45:02 www kernel: [<ffffffff80023890>] sys_newstat+0x19/0x31 Sep 28 07:46:18 www kernel: [<ffffffff8005d229>] tracesys+0x71/0xe0 Sep 28 07:46:43 www kernel: [<ffffffff8005d28d>] tracesys+0xd5/0xe0 Sep 28 07:46:55 www kernel: Sep 28 07:46:58 www kernel: INFO: task php:28906 blocked for more than 120 seconds. Sep 28 07:46:59 www kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. Sep 28 07:47:00 www kernel: php D ffff810165127000 0 28906 28905 (NOTLB) Sep 28 07:47:37 www kernel: ffff810078431e58 0000000000000082 ffff810165127000 ffffffff8000f758 Sep 28 07:48:29 www kernel: ffff81020dfd1408 0000000000000007 ffff8101247b9860 ffff810207d0e100 Sep 28 07:48:36 www kernel: 00017a4218932fae 0000000000377111 ffff8101247b9a48 0000000280009a22 Sep 28 07:48:37 www kernel: Call Trace: Sep 28 07:48:37 www kernel: [<ffffffff8000f758>] generic_permission+0x52/0xca Sep 28 07:48:37 www kernel: [<ffffffff80063c63>] __mutex_lock_slowpath+0x60/0x9b Sep 28 07:48:37 www kernel: [<ffffffff8000cea2>] do_path_lookup+0x294/0x310 Sep 28 07:48:41 www kernel: [<ffffffff80063cad>] .text.lock.mutex+0xf/0x14 Sep 28 07:48:41 www kernel: [<ffffffff8003c618>] do_unlinkat+0x66/0x141 Sep 28 07:48:42 www kernel: [<ffffffff8005d229>] tracesys+0x71/0xe0 Sep 28 07:48:42 www kernel: [<ffffffff8005d28d>] tracesys+0xd5/0xe0 Sep 28 07:48:42 www kernel: Sep 28 07:48:43 www kernel: INFO: task php:29032 blocked for more than 120 seconds. Sep 28 07:48:45 www kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. Sep 28 07:48:46 www kernel: php D 0000000000000004 0 29032 1 29050 29024 (NOTLB) Sep 28 07:48:46 www kernel: ffff81006b465dc8 0000000000000086 ffff81020dfd1408 ffffffff80009a22 Sep 28 07:48:46 www kernel: 0000000000000000 0000000000000007 ffff81002946e860 ffff81003c943100 Sep 28 07:48:46 www kernel: 00017a4211450766 000000000024be3d ffff81002946ea48 000000020e42b300 Sep 28 07:48:52 www kernel: Call Trace: Sep 28 07:48:54 www kernel: [<ffffffff80009a22>] __link_path_walk+0x173/0xfd1 Sep 28 07:48:54 www kernel: [<ffffffff8002cc58>] mntput_no_expire+0x19/0x89 Sep 28 07:48:55 www kernel: [<ffffffff8000ebf5>] link_path_walk+0xac/0xb8 Sep 28 07:48:55 www kernel: [<ffffffff80063c63>] __mutex_lock_slowpath+0x60/0x9b Sep 28 07:48:55 www kernel: [<ffffffff80023974>] __path_lookup_intent_open+0x56/0x97 Sep 28 07:48:55 www kernel: [<ffffffff80063cad>] .text.lock.mutex+0xf/0x14 Sep 28 07:48:55 www kernel: [<ffffffff8001b260>] open_namei+0xea/0x718 Sep 28 07:48:59 www kernel: [<ffffffff80067235>] do_page_fault+0x4cc/0x842 Sep 28 07:49:01 www kernel: [<ffffffff80027726>] do_filp_open+0x1c/0x38 Sep 28 07:49:01 www kernel: [<ffffffff8001a09c>] do_sys_open+0x44/0xbe Sep 28 07:49:02 www kernel: [<ffffffff8005d28d>] tracesys+0xd5/0xe0 Sep 28 07:49:03 www kernel: Sep 28 07:49:07 www kernel: INFO: task mysqld:22749 blocked for more than 120 seconds. Sep 28 07:49:09 www kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. Sep 28 07:49:09 www kernel: mysqld D ffff810001015120 0 22749 3266 22792 22659 (NOTLB) Sep 28 07:49:14 www kernel: ffff810139d21e58 0000000000000086 ffff810036217000 ffffffff8000f758 Sep 28 07:49:14 www kernel: ffff81020dfd1408 0000000000000007 ffff8101cfbaf7e0 ffff81020fca5080 Sep 28 07:49:15 www kernel: 00017a451524782a 00000000000043b2 ffff8101cfbaf9c8 0000000280009a22 Sep 28 07:49:15 www kernel: Call Trace: Sep 28 07:49:22 www kernel: [<ffffffff8000f758>] generic_permission+0x52/0xca Sep 28 07:49:23 www kernel: [<ffffffff80063c63>] __mutex_lock_slowpath+0x60/0x9b Sep 28 07:49:23 www kernel: [<ffffffff8000cea2>] do_path_lookup+0x294/0x310 Sep 28 07:49:23 www kernel: [<ffffffff80063cad>] .text.lock.mutex+0xf/0x14 Sep 28 07:49:23 www kernel: [<ffffffff8003c618>] do_unlinkat+0x66/0x141 Sep 28 07:49:23 www kernel: [<ffffffff8005d229>] tracesys+0x71/0xe0 Sep 28 07:49:23 www kernel: [<ffffffff8005d28d>] tracesys+0xd5/0xe0 Sep 28 07:49:23 www kernel: Sep 28 07:49:23 www kernel: INFO: task php:29024 blocked for more than 120 seconds. Sep 28 07:49:23 www kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. Sep 28 07:49:24 www kernel: php D ffff8101920a0000 0 29024 1 29032 29001 (NOTLB) Sep 28 07:49:26 www kernel: ffff8101cca8fe58 0000000000000086 ffff8101920a0000 ffffffff8000f758 Sep 28 07:49:26 www kernel: ffff81020dfd1408 0000000000000007 ffff81000b64b040 ffff8101e05337e0 Sep 28 07:49:26 www kernel: 00017a552aef9f35 0000000000009513 ffff81000b64b228 0000000180009a22 Sep 28 07:49:27 www kernel: Call Trace: Sep 28 07:49:27 www kernel: [<ffffffff8000f758>] generic_permission+0x52/0xca Sep 28 07:49:27 www kernel: [<ffffffff80063c63>] __mutex_lock_slowpath+0x60/0x9b Sep 28 07:49:27 www kernel: [<ffffffff8000cea2>] do_path_lookup+0x294/0x310 Sep 28 07:49:27 www kernel: [<ffffffff80063cad>] .text.lock.mutex+0xf/0x14 Sep 28 07:49:27 www kernel: [<ffffffff8003c618>] do_unlinkat+0x66/0x141 Sep 28 07:49:27 www kernel: [<ffffffff8005d229>] tracesys+0x71/0xe0 Sep 28 07:49:27 www kernel: [<ffffffff8005d28d>] tracesys+0xd5/0xe0 Sep 28 07:49:27 www kernel: Sep 28 07:49:27 www kernel: INFO: task php:29050 blocked for more than 120 seconds. Sep 28 07:49:28 www kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. Sep 28 07:49:28 www kernel: php D ffff810201d95000 0 29050 1 29032 (NOTLB) Sep 28 07:49:28 www kernel: ffff810051e45e58 0000000000000086 ffff810201d95000 ffffffff8000f758 Sep 28 07:49:28 www kernel: ffff81020dfd1408 0000000000000007 ffff81001c23f080 ffff81020f5e2080 Sep 28 07:49:29 www kernel: 00017a5d0bc2aa75 0000000000d0ecfe ffff81001c23f268 0000000280009a22 Sep 28 07:49:29 www kernel: Call Trace: Sep 28 07:49:29 www kernel: [<ffffffff8000f758>] generic_permission+0x52/0xca Sep 28 07:49:29 www kernel: [<ffffffff80063c63>] __mutex_lock_slowpath+0x60/0x9b Sep 28 07:49:29 www kernel: [<ffffffff8000cea2>] do_path_lookup+0x294/0x310 Sep 28 07:49:34 www kernel: [<ffffffff80063cad>] .text.lock.mutex+0xf/0x14 Sep 28 07:49:35 www kernel: [<ffffffff8003c618>] do_unlinkat+0x66/0x141 Sep 28 07:49:37 www kernel: [<ffffffff8005d229>] tracesys+0x71/0xe0 Sep 28 07:49:37 www kernel: [<ffffffff8005d28d>] tracesys+0xd5/0xe0 Sep 28 07:49:37 www kernel: Sep 28 07:49:37 www kernel: INFO: task php:29064 blocked for more than 120 seconds. Sep 28 07:49:37 www kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. Sep 28 07:49:37 www kernel: php D ffff81009c231000 0 29064 29057 (NOTLB) Sep 28 07:49:38 www kernel: ffff8100a5dc7e58 0000000000000086 ffff81009c231000 ffffffff8000f758 Sep 28 07:49:38 www kernel: ffff81020dfd1408 0000000000000007 ffff81000a850820 ffff8102038037a0 Sep 28 07:49:38 www kernel: 00017a5bb5c6846e 000000000000861a ffff81000a850a08 0000000080009a22 Sep 28 07:49:38 www kernel: Call Trace: Sep 28 07:49:38 www kernel: [<ffffffff8000f758>] generic_permission+0x52/0xca Sep 28 07:49:38 www kernel: [<ffffffff80063c63>] __mutex_lock_slowpath+0x60/0x9b Sep 28 07:49:38 www kernel: [<ffffffff8000cea2>] do_path_lookup+0x294/0x310 Sep 28 07:49:38 www kernel: [<ffffffff80063cad>] .text.lock.mutex+0xf/0x14 Sep 28 07:49:38 www kernel: [<ffffffff8003c618>] do_unlinkat+0x66/0x141 Sep 28 07:49:38 www kernel: [<ffffffff8005d229>] tracesys+0x71/0xe0 Sep 28 07:49:40 www kernel: [<ffffffff8005d28d>] tracesys+0xd5/0xe0 Sep 28 07:49:42 www kernel: Sep 28 07:49:42 www kernel: INFO: task mysqld:24612 blocked for more than 120 seconds. Sep 28 07:49:43 www kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. Sep 28 07:49:46 www kernel: mysqld D ffff81020dfd14c0 0 24612 3266 19643 3599 (NOTLB) Sep 28 07:49:46 www kernel: ffff81019e517c78 0000000000000086 ffff81019e517c88 ffffffff80063002 Sep 28 07:49:47 www kernel: ffff810201966558 0000000000000009 ffff81015fa560c0 ffff8101c263b860 Sep 28 07:49:51 www kernel: 00017a9d113e27fe 0000000000008d5a ffff81015fa562a8 000000018006ec9f Sep 28 07:49:52 www kernel: Call Trace: Sep 28 07:49:52 www kernel: [<ffffffff80063002>] thread_return+0x62/0xfe Sep 28 07:49:52 www kernel: [<ffffffff8005a46a>] getnstimeofday+0x10/0x29 Sep 28 07:49:53 www kernel: [<ffffffff80063c63>] __mutex_lock_slowpath+0x60/0x9b Sep 28 07:49:54 www kernel: [<ffffffff80063cad>] .text.lock.mutex+0xf/0x14 Sep 28 07:49:54 www kernel: [<ffffffff8000d0b2>] do_lookup+0x90/0x1e6 Sep 28 07:49:56 www kernel: [<ffffffff8000a2e9>] __link_path_walk+0xa3a/0xfd1 Sep 28 07:50:00 www kernel: [<ffffffff8000eb8e>] link_path_walk+0x45/0xb8 Sep 28 07:50:03 www kernel: [<ffffffff8000cea2>] do_path_lookup+0x294/0x310 Sep 28 07:50:04 www kernel: [<ffffffff800129ad>] getname+0x15b/0x1c2 Sep 28 07:50:06 www kernel: [<ffffffff80023b60>] __user_walk_fd+0x37/0x4c Sep 28 07:50:06 www kernel: [<ffffffff8003f013>] vfs_lstat_fd+0x18/0x47 Sep 28 07:50:08 www kernel: [<ffffffff8002ad91>] sys_newlstat+0x19/0x31 Sep 28 07:50:10 www kernel: [<ffffffff8005d229>] tracesys+0x71/0xe0 Sep 28 07:50:15 www kernel: [<ffffffff8005d28d>] tracesys+0xd5/0xe0 Sep 28 07:50:19 www kernel: Sep 28 07:50:19 www kernel: INFO: task php:29178 blocked for more than 120 seconds. Sep 28 07:50:23 www kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. Sep 28 07:50:23 www kernel: php D 0000000000000003 0 29178 29123 (NOTLB) Sep 28 07:50:23 www kernel: ffff81004a95bdc8 0000000000000086 ffff81020dfd1408 ffffffff80009a22 Sep 28 07:50:24 www kernel: ffffffff800a2fd0 0000000000000007 ffff8101937a4040 ffff81010bde27a0 Sep 28 07:50:26 www kernel: 00017aa3a1d89c9b 000000000000d66e ffff8101937a4228 000000020e42b300 Sep 28 07:50:26 www kernel: Call Trace: Sep 28 07:50:26 www kernel: [<ffffffff80009a22>] __link_path_walk+0x173/0xfd1 Sep 28 07:50:27 www kernel: [<ffffffff800a2fd0>] wake_bit_function+0x0/0x23 Sep 28 07:50:27 www kernel: [<ffffffff8002cc58>] mntput_no_expire+0x19/0x89 Sep 28 07:50:27 www kernel: [<ffffffff8000ebf5>] link_path_walk+0xac/0xb8 Sep 28 07:50:28 www kernel: [<ffffffff80063c63>] __mutex_lock_slowpath+0x60/0x9b Sep 28 07:50:32 www kernel: [<ffffffff80023974>] __path_lookup_intent_open+0x56/0x97 Sep 28 07:50:32 www kernel: [<ffffffff80063cad>] .text.lock.mutex+0xf/0x14 Sep 28 07:50:34 www kernel: [<ffffffff8001b260>] open_namei+0xea/0x718 Sep 28 07:50:34 www kernel: [<ffffffff80067235>] do_page_fault+0x4cc/0x842 Sep 28 07:50:35 www kernel: [<ffffffff80027726>] do_filp_open+0x1c/0x38 Sep 28 07:50:35 www kernel: [<ffffffff8001a09c>] do_sys_open+0x44/0xbe Sep 28 07:50:35 www kernel: [<ffffffff8005d28d>] tracesys+0xd5/0xe0 Sep 28 07:50:35 www kernel: Sep 28 07:56:41 www kernel: proftpd invoked oom-killer: gfp_mask=0x201d2, order=0, oomkilladj=0 Sep 28 07:56:41 www kernel: Sep 28 07:56:41 www kernel: Call Trace: Sep 28 07:56:41 www kernel: [<ffffffff800c9f35>] out_of_memory+0x8e/0x2f3 Sep 28 07:56:41 www kernel: [<ffffffff800a2fa2>] autoremove_wake_function+0x0/0x2e Sep 28 07:56:41 www kernel: [<ffffffff8000f67d>] __alloc_pages+0x27f/0x308 Sep 28 07:56:41 www kernel: [<ffffffff80013047>] __do_page_cache_readahead+0x96/0x17b Sep 28 07:56:41 www kernel: [<ffffffff80013984>] filemap_nopage+0x14c/0x360 Sep 28 07:56:41 www kernel: [<ffffffff80008972>] __handle_mm_fault+0x1fd/0x103b Sep 28 07:56:41 www kernel: [<ffffffff800a4fe1>] ktime_get_ts+0x1a/0x4e Sep 28 07:56:41 www kernel: [<ffffffff80067202>] do_page_fault+0x499/0x842 Sep 28 07:56:41 www kernel: [<ffffffff8003ad91>] hrtimer_try_to_cancel+0x4a/0x53 Sep 28 07:58:10 www kernel: [<ffffffff80033541>] do_setitimer+0xd0/0x689 Sep 28 08:26:22 www syslogd 1.4.1: restart. Sep 28 08:26:22 www kernel: klogd 1.4.1, log source = /proc/kmsg started. Sep 28 08:26:22 www kernel: Linux version 2.6.18-274.17.1.el5 ([email protected]) (gcc version 4.1.2 20080704 (Red Hat 4.1.2-51)) #1 SMP Tue Jan 10 17:25:58 EST 2012 Sep 28 08:26:22 www kernel: Command line: ro root=LABEL=/

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Simplest way to add stills to MP3 audio soundtrack

- by Ambrose

I have some audio and want to add visuals to it and upload to YouTube. Nothing fancy, just like slides, image_A from 00:00:00 to 00:00:05 then image_B from 00:00:50 to 00:00:30 and so on. I have recent Mac and Windows machines to do this on. I'd like to do it on free or demo software if I can. Please give a bit of a hint how to get started if you can. I took a look a iMovie, but ... where to start, if you haven't actually got video?

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What does "every two minutes" mean in cron?

- by Ambrose

I've got two scripts in cron set to run every two minutes: */2 -- the thing is, they're out of step. One runs at 1,3,5,7,9 minutes, etc. and the other at 0,2,4,6,8. This is not a mission-critical problem, but means I've got two status reports, one a bit stale compared to the other. What does cron do exactly? Run the first one in crontab document order, waiting till it's finished to run the second one? Is there any way I can make the run at the same time, or as close as possible?

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Parse the HTTP_COOKIES string from Apache for use in #if clause

- by Ambrose

I want to be able to read the cookies from Apache's HTTP_COOKIE string and then add includes based on the contents of that string. I've got this far:  <p>COOKIES: </p> which gives me a string with all the cookies in it. Now I want to be able to parse the string for something like Name=Bob. I thought I'd be able to do this:  <p>Your name is </p>  But it doesn't seem to work. What should I be doing -- or isn't this possible?

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mod_rewrite to find missing /img/foo.jpg in /img/f/

- by Ambrose

I've got a folder of images which is reaching a critical mass after a few years. I want to move images into alphabetical folders, so that /img/foo.jpg goes into /img/f/foo.jpg and /img/bar.jpg goes into /img/b/bar.jpg and so on. In order to make the transition smooth, and to allow the manual uploaders to put stuff into the top level, I'd like to use mod_rewrite to do this: if /img/foo.jpg exists, serve it up, if not look for it in /img/f/foo.jpg thanks for any suggestions. For the record, no, I don't think we need to go /img/f/fo/foo.jpg just yet.

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What does [a|b|c] evaluate to in Prolog?

- by Ambrose

The pipe operator in prolog returns one or more atomic Heads and a Tail list. ?- [a,b,c] = [a,b|[c]]. true. Nesting multiple pipes in a single match can be done similar to this: ?- [a,b,c] = [a|[b|[c]]]. true. What does the statement [a|b|c] infer about a, b and c?

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WebLogic history an interview with Laurie Pitman by Qualogy

- by JuergenKress

All those years that I am working with WebLogic, the BEA and Oracle era are the most well known about WebLogic evolving into a worldwide Enterprise platform for Java applications, being used by multinationals around the globe. But how did it all begin? Besides from the spare info you find on some Internet pages, I was eager to hear it in person from one of the founders of WebLogic back in 1995, before the BEA era, Laurie Pitman. Four young people, Carl Resnikoff, Paul Ambrose, Bob Pasker, and Laurie Pitman, became friends and colleagues about the time of the first release of Java in 1995. Between the four of them, they had an MA in American history, an MA in piano, an MS in library systems, a BS in chemistry, and a BS in computer science. They had come together kind of serendipitously, interested in building some web tools exclusively in Java for the emerging Internet web application market. They found many things to like about each other, some overlap in our interests, but also a lot of well-placed differences which made a partnership particularly interesting. They made it formal in January 1996 by incorporating. Read the complete article here. WebLogic Partner Community For regular information become a member in the WebLogic Partner Community please visit: http://www.oracle.com/partners/goto/wls-emea ( OPN account required). If you need support with your account please contact the Oracle Partner Business Center. Blog Twitter LinkedIn Mix Forum Wiki Technorati Tags: WebLogic history,Qualogy,WebLogic,WebLogic Community,Oracle,OPN,Jürgen Kress

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Represent multiple Null/Generic objects in an ActiveRecord association?

- by slothbear

I have a Casefile model that belongs_to a Doctor. In additional to all the "real" doctors, there are several generic Doctors: "self-treated", "not specified", and "removed" (it used to have a real doctor, but no longer does). I suspect there will be even more generic values in the future. I started with special "doctors" in the database, generated from seed. The generic Doctors only need to respond to the "name" and "real_doctor?" methods. This worked with one, was strained with two, and now feels completely broken. I want to change the behavior and can't figure out how to test it, a bad sign. Creating all the generic objects for testing is also trouble, including fake values to pass validation of the required Doctor attributes. The Null Object pattern works well for one generic object. The "name" method could check casefile.doctor.nil? and return "self-treated", as demonstrated by Craig Ambrose. What pattern should I use when there are multiple generic objects with very limited state?

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