Hi which result you get from the following query:
SELECT CASE WHEN pg_last_wal_receive_lsn() = pg_last_wal_replay_lsn() THEN 0 ELSE EXTRACT (EPOCH FROM now() - pg_last_xact_replay_timestamp()) END AS log_delay; source: https://severalnines.com/blog/postgresql-streaming-replication-deep-dive El mar., 23 de oct. de 2018 a la(s) 11:28, Boris Sagadin ( bo...@infosplet.com) escribió: > Nothing special, just: > > standby_mode = 'on' > primary_conninfo = 'host=... user=repmgr application_name=nodex' > recovery_target_timeline = 'latest' > > > Boris > > On Tue, Oct 23, 2018 at 3:10 PM, Hellmuth Vargas <hiv...@gmail.com> wrote: > >> Hi >> >> can share recovery.conf file settings?? >> >> El mar., 23 de oct. de 2018 a la(s) 00:28, Boris Sagadin ( >> bo...@infosplet.com) escribió: >> >>> Yes, turning wal_compression off improves things. Slave that was >>> mentioned unfortunately lagged too much before this setting was applied and >>> was turned off. However the remaining slave lags less now, although still >>> occasionally up to a few minutes. I think single threadedness of recovery >>> is a big slowdown for write heavy databases. Maybe an option to increase >>> wal_size beyond 16MB in v11 will help. >>> >>> In the meantime we'll solve this by splitting the DB to 2 or 3 clusters >>> or maybe trying out some sharding solution like Citus. >>> >>> >>> Boris >>> >>> On Sun, Oct 21, 2018 at 9:06 AM, Boris Sagadin <bo...@infosplet.com> >>> wrote: >>> >>>> Hello, >>>> >>>> I have a database running on i3.8xlarge (256GB RAM, 32 CPU cores, 4x >>>> 1.9TB NVMe drive) AWS instance with about 5TB of disk space occupied, ext4, >>>> Ubuntu 16.04. >>>> >>>> Multi-tenant DB with about 40000 tables, insert heavy. >>>> >>>> I started a new slave with identical HW specs, SR. DB started syncing >>>> from master, which took about 4 hours, then it started applying the WALs. >>>> However, it seems it can't catch up. Delay is still around 3 hours >>>> (measured with now() - pg_last_xact_replay_timestamp()), even a day later. >>>> It goes a few 100s up and down, but it seems to float around 3h mark. >>>> >>>> Disk IO is low at about 10%, measured with iostat, no connected >>>> clients, recovery process is at around 90% CPU single core usage. >>>> >>>> Tried tuning the various parameters, but with no avail. Only thing I >>>> found suspicious is stracing the recovery process constantly produces many >>>> errors such as: >>>> >>>> lseek(428, 0, SEEK_END) = 780124160 >>>> lseek(30, 0, SEEK_END) = 212992 >>>> read(9, 0x7ffe4001f557, 1) = -1 EAGAIN (Resource >>>> temporarily unavailable) >>>> lseek(680, 0, SEEK_END) = 493117440 >>>> read(9, 0x7ffe4001f557, 1) = -1 EAGAIN (Resource >>>> temporarily unavailable) >>>> lseek(774, 0, SEEK_END) = 583368704 >>>> >>>> ...[snip]... >>>> >>>> read(9, 0x7ffe4001f557, 1) = -1 EAGAIN (Resource >>>> temporarily unavailable) >>>> lseek(774, 0, SEEK_END) = 583368704 >>>> read(9, 0x7ffe4001f557, 1) = -1 EAGAIN (Resource >>>> temporarily unavailable) >>>> lseek(277, 0, SEEK_END) = 502882304 >>>> lseek(6, 516096, SEEK_SET) = 516096 >>>> read(6, >>>> "\227\320\5\0\1\0\0\0\0\340\7\246\26\274\0\0\315\0\0\0\0\0\0\0}\0178\5&/\260\r"..., >>>> 8192) = 8192 >>>> read(9, 0x7ffe4001f557, 1) = -1 EAGAIN (Resource >>>> temporarily unavailable) >>>> lseek(735, 0, SEEK_END) = 272809984 >>>> read(9, 0x7ffe4001f557, 1) = -1 EAGAIN (Resource >>>> temporarily unavailable) >>>> lseek(277, 0, SEEK_END) = 502882304 >>>> >>>> ls -l fd/9 >>>> lr-x------ 1 postgres postgres 64 Oct 21 06:21 fd/9 -> pipe:[46358] >>>> >>>> >>>> Perf top on recovery produces: >>>> >>>> 27.76% postgres [.] pglz_decompress >>>> 9.90% [kernel] [k] entry_SYSCALL_64_after_swapgs >>>> 7.09% postgres [.] hash_search_with_hash_value >>>> 4.26% libpthread-2.23.so [.] llseek >>>> 3.64% libpthread-2.23.so [.] __read_nocancel >>>> 2.80% [kernel] [k] __fget_light >>>> 2.67% postgres [.] 0x000000000034d3ba >>>> 1.85% [kernel] [k] ext4_llseek >>>> 1.84% postgres [.] pg_comp_crc32c_sse42 >>>> 1.44% postgres [.] hash_any >>>> 1.35% postgres [.] 0x000000000036afad >>>> 1.29% postgres [.] MarkBufferDirty >>>> 1.21% postgres [.] XLogReadRecord >>>> [...] >>>> >>>> Tried changing the process limits with prlimit to unlimited, but no >>>> change. >>>> >>>> I can turn off the WAL compression but I doubt this is the main >>>> culprit. Any ideas appreciated. >>>> >>>> Regards, >>>> Boris >>>> >>>> >>> >> >> -- >> Cordialmente, >> >> Ing. Hellmuth I. Vargas S. >> Esp. Telemática y Negocios por Internet >> Oracle Database 10g Administrator Certified Associate >> EnterpriseDB Certified PostgreSQL 9.3 Associate >> >> > -- Cordialmente, Ing. Hellmuth I. Vargas S.
