View Issue Details
| ID | Project | Category | View Status | Date Submitted | Last Update |
|---|---|---|---|---|---|
| 0000633 | Pgpool-II | Bug | public | 2020-08-18 07:48 | 2020-08-24 10:08 |
| Reporter | pgdude | Assigned To | hoshiai | ||
| Priority | normal | Severity | minor | Reproducibility | always |
| Status | feedback | Resolution | open | ||
| Platform | linux | OS | ubuntu | OS Version | 20.04 |
| Product Version | 4.1.2 | ||||
| Summary | 0000633: Getting random, but frequent "failed to unlock semaphore" errors | ||||
| Description | I am using postgresql 12. 3. I am using pgpool2 only in connection pooling and load balancing mode with one primary and one standby. Watchdog is turned off. pgpool2 and postgresql are on the same host. I get these messages frequently in pgpool.log file on both primary and standby hosts. Aug 17 12:06:56 ltpgsql11 pgpool[19549]: 2020-08-17 12:06:56 pid: 19558 db: postgres usr: postgres LOCATION: pool_proto_modules.c:3348 Aug 17 12:06:56 ltpgsql11 pgpool[19549]: 2020-08-17 12:06:56 pid: 19558 db: postgres usr: postgres WARNING: failed to lock semaphore error:"Invalid argument" Aug 17 12:06:56 ltpgsql11 pgpool[19549]: 2020-08-17 12:06:56 pid: 19558 db: postgres usr: postgres CONTEXT: while searching system catalog, When relcache is missed Aug 17 12:06:56 ltpgsql11 pgpool[19549]: 2020-08-17 12:06:56 pid: 19558 db: postgres usr: postgres LOCATION: pool_sema.c:129 Aug 17 12:06:56 ltpgsql11 pgpool[19549]: 2020-08-17 12:06:56 pid: 19558 db: postgres usr: postgres WARNING: failed to unlock semaphore error:"Invalid argument" Aug 17 12:06:56 ltpgsql11 pgpool[19549]: 2020-08-17 12:06:56 pid: 19558 db: postgres usr: postgres CONTEXT: while searching system catalog, When relcache is missed Aug 17 12:06:56 ltpgsql11 pgpool[19549]: 2020-08-17 12:06:56 pid: 19558 db: postgres usr: postgres LOCATION: pool_sema.c:158 Aug 17 12:06:56 ltpgsql11 pgpool[19549]: 2020-08-17 12:06:56 pid: 19558 db: postgres usr: postgres LOG: DB node id: 0 backend pid: 3587 statement: create database testing; Aug 17 12:06:56 ltpgsql11 pgpool[19549]: 2020-08-17 12:06:56 pid: 19558 db: postgres usr: postgres LOCATION: pool_proto_modules.c:3348 | ||||
| Steps To Reproduce | Just issue normal sql statements and you will see these error messages spitting out. | ||||
| Tags | No tags attached. | ||||
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psql -U postgres -p 5433 -h myprimaryhost -c "SHOW pool_cache" WARNING: failed to lock semaphore error:"Invalid argument" WARNING: failed to unlock semaphore error:"Invalid argument" WARNING: failed to lock semaphore error:"Invalid argument" WARNING: failed to unlock semaphore error:"Invalid argument" num_cache_hits | num_selects | cache_hit_ratio | num_hash_entries | used_hash_entries | num_cache_entries | used_cache_entries_size | free_cache_entries_size | fragment_cache_entries_size ----------------+-------------+-----------------+------------------+-------------------+-------------------+-------------------------+-------------------------+----------------------------- 0 | 0 | 0.00 | 0 | 0 | 0 | 0 | 0 | 0 |
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I think that we need more details. Do this problem reappear with after pgpool restart? And, I would like to need more information. Could you share logs of pgpool which is started with '--debug' option (debug mode) and your pgpool.conf file. |
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Yes it reappears after a pgpool restart. when you say start with --debug option, is that the same as setting client_min_message and log_min_message to one of the debug levels? |
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I will get the debug logs to you in a few hours... |
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The source code for this error is in src/utils/pool_sema.c in function, pool_semaphore_lock(). No interesting comments here either. It does not adversely affect anything that I am aware of, and when i turn on more debugging levels, debug1, debug2, it goes away. So if you want to close this, be my guest. |
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Ok, I recognized that this problem is not happened currently. If this problem is not reproduced by you, I will close this ticket. Please let me know If there is any new update. |
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Actually I still get these warnings sporadically, sometimes they come out of a psql session in stdout/stderr and not just in the pgpool.log. |
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If you can get this warning sporadically, we may be able to know this cause by comparing WARNINIG happend log with not WARNING happend log, with debug mode. For example, it may only occur with a particular semaphore lock. |
| Date Modified | Username | Field | Change |
|---|---|---|---|
| 2020-08-18 07:48 | pgdude | New Issue | |
| 2020-08-18 08:08 | pgdude | Note Added: 0003474 | |
| 2020-08-18 17:13 | hoshiai | Assigned To | => hoshiai |
| 2020-08-18 17:13 | hoshiai | Status | new => assigned |
| 2020-08-18 17:49 | hoshiai | Status | assigned => feedback |
| 2020-08-18 17:49 | hoshiai | Note Added: 0003476 | |
| 2020-08-18 22:36 | pgdude | Note Added: 0003477 | |
| 2020-08-18 22:36 | pgdude | Status | feedback => assigned |
| 2020-08-18 23:19 | pgdude | Note Added: 0003482 | |
| 2020-08-19 05:47 | pgdude | Note Added: 0003483 | |
| 2020-08-21 16:37 | hoshiai | Status | assigned => feedback |
| 2020-08-21 16:37 | hoshiai | Note Added: 0003494 | |
| 2020-08-22 03:12 | pgdude | Note Added: 0003497 | |
| 2020-08-22 03:12 | pgdude | Status | feedback => assigned |
| 2020-08-24 10:08 | hoshiai | Status | assigned => feedback |
| 2020-08-24 10:08 | hoshiai | Note Added: 0003506 |
