Managing PostgreSQL with PgCenter

Managing PostgreSQL with pgCenterPgConf EU 2016, Estonia, Tallinn

Alexey [email protected]

I am a PostgreSQL DBA:

● Linux administration, internals;

● and PostgreSQL of course.

Work in PostgreSQL-Consulting:

● Consulting, support, troubleshooting, profiling, training, etc...

https://goo.gl/NYRFQV

About me

PostgreSQL statistics overview.

PgCenter – quick overview.

Management and troubleshoot with pgCenter.

Outline

+ The most subsystems and objects have stats.

+ Getting stats is quite easy.

– Stats are provided as counters.

– No history or what happened X minutes ago?

– No builtin tools, only psql and hand-made queries.

PostgreSQL statistics

Write Ahead Log

SharedBuffers

Buffers IO Autovacuum Workers

Autovacuum Launcher

Background Workers

Indexes IO

Query Execution

Query Planning

Client Backends Postmaster

Tables IO

Logger Process Stats Collector

LogicalReplication

WAL SenderProcess

ArchiverProcess

BackgroundWriter

CheckpointerProcess

Network Storage

Recovery Process

WAL Receiver ProcessTables/Indexes Data Files

pg_stat_all_tables

pg_current_xlog_location

pg_replication_slots

pg_stat_replication

pg_stat_archiver

pg_stat_database_conflicts

pg_buffercachepg_stat_database

pg_stat_activitypg_stat_user_tables

pg_stat_database

pg_stat_bgwrier

pgstattuplepg_table_size

pg_database_size

pg_index_size

pg_stat_activity

EXPLAIN

pg_stat_statements

pg_locks

pg_stat_user_functions

pg_stat_all_indexes

pg_stat_database

pg_statio_all_indexes

pg_statio_all_tablespg_xlog_location_diff

nicstat* iostat*

pg_stat_kcache

pg_stat_statements

* system tools

pg_stat_progress_vacuum

pg_stat_wal_receiver

pg_blocking_pids

Written in the C, uses libpq and ncurses.

Support PostgreSQL 9.x (9.0 ... 9.6).

Linux only.

Sources on Github.

Packages:

● ALT Linux;

● RedHat/CentOS/Fedora (pgdg, epel-testing);

● Ubuntu (Launchpad);

What is the pgCenter

Top-like interface for viewing stats.

System resource utilization (cpu, memory, storage, networking).

PostgreSQL general utilization (connections, autovacuum, qps).

Common admin tasks.

Major features

The same options as in the psql:

● pgcenter -h 127.0.0.1 -p 5432 -U postgres -d mydb

● pgcenter -U postgres mydb

● pgcenter mydb

Environment variables:

● PGHOST, PGPORT, PGUSER, PGDATABASE, PGPASSWORD

Connections file (~/.pgcenterrc).

How to run pgCenter

pgcenter: 2016-09-28 11:45:42, load average: 8.65, 8.80, 8.17 conn1 [ok]: 127.0.0.1:5432 postgres@postgres (ver: 9.6.0, up 00:29:28) %cpu: 26.5 us, 2.6 sy, 0.0 ni, 69.8 id, 1.1 wa, 0.0 hi, 0.0 si, 0.0 st activity: 25 total, 17 idle, 1 idle_in_xact, 7 active, 0 waiting, 0 others MiB mem: 30679 total, 258 free, 1130 used, 29291 buff/cached autovacuum: 1/8 workers/max, 0 manual, 0 wraparound, 00:08:15 vac_maxtimeMiB swap: 5119 total, 5119 free, 0 used, 3/0 dirty/writeback statements: 0 stmt/s, 0.000 stmt_avgtime, 00:08:15 xact_maxtime

datname commit rollback reads hits returned fetched inserts updates deletes conflicts deadlocks tmp_files tmp_bytes read_t write_tprod_db 1752 0 805 29173 197095 3504 1752 5256 0 0 0 0 0 13 0appcast 832 0 183 12448 93215 1664 832 2496 0 0 0 0 0 2 0template1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0template0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0postgres 5 1 0 0 0 0 0 0 0 0 0 0 0 0 0

Interface overview



Interface overview

System metrics



Interface overview

System metrics PostgreSQL metrics



Interface overview


Statistics values



Interface overview


Statistics valuesAdditional information

pgcenter: 2016-09-28 11:45:42, load average: 8.65, 8.80, 8.17 %cpu: 26.5 us, 2.6 sy, 0.0 ni, 69.8 id, 1.1 wa, 0.0 hi, 0.0 si, 0.0 st MiB mem: 30679 total, 258 free, 1130 used, 29291 buff/cachedMiB swap: 5119 total, 5119 free, 0 used, 3/0 dirty/writeback

Interface overview

program name current time load average

cpu usage memory usage swap usage

conn1 [ok]: 127.0.0.1:5432 postgres@postgres (ver: 9.6.0, up 00:29:28) activity: 25 total, 17 idle, 1 idle_in_xact, 7 active, 0 waiting, 0 othersautovacuum: 1/8 workers/max, 0 manual, 0 wraparound, 00:08:15 vac_maxtimestatements: 689 stmt/s, 1.857 stmt_avgtime, 00:00:01 xact_maxtime

Interface overview

tab number current connection postgres version

connections vacuum operations queries/xact info

postgres uptime

datname commit rollback reads hits returned fetched inserts updates >prod_db 1752 0 805 29173 197095 3504 1752 5256 >appcast 832 0 183 12448 93215 1664 832 2496 >template1 0 0 0 0 0 0 0 0 >template0 0 0 0 0 0 0 0 0 >Postgres 5 1 0 0 0 0 0 0 >

Interface overview

datname commit rollback reads hits returned fetched inserts updates >prod_db 1752 0 805 29173 197095 3504 1752 5256 >appcast 832 0 183 12448 93215 1664 832 2496 >template1 0 0 0 0 0 0 0 0 >template0 0 0 0 0 0 0 0 0 >Postgres 5 1 0 0 0 0 0 0 >

Left, Right: change sort.

F: Enable filter.

/: Change sort order – desc or asc.

Interface overview

N: open new connection in a new tab

Ctrl+D: close current tab.

1..8: switch between tabs.

W: save opened connections settings to the connfile.

General actions

d: pg_stat_databases

r: pg_stat_replication

t: pg_stat_all_tables

T: pg_statio_all_tables

i: pg_stat_all_indexes, pg_statio_all_indexes

f: pg_stat_user_functions

a: pg_stat_activity

v: pg_stat_progress_vacuum

x: pg_stat_statements

s: Relations size

Available stats

C: show config menu.

E: edit config menu.

R: reload postgres service.

Admin tasks




l: show log file.

Admin tasks


E: edit config menu


l: show log file.

-: сancel query using pid.

_: terminate backend using pid.

Del: cancel group of queries using mask.

Shift+Del: terminate group of backends using mask.

.: show current mask, >: set new mask.

Admin tasks




l: show log file.

-: cancel query using pid.

_: terminate backend using pid.

Del: cancel group of queries using mask.

Shift+Del: terminate group of backends using mask.

.: show current mask, >: set new mask.

p: open psql session.

Admin tasks

B: open iostat.

I: open nicstat.

L: tail postgres log (show the latest log lines).

Additional Information

B: open iostat.Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz avgqu-sz await r_await w_await %util

sda: 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

sda1: 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

sdb: 0.00 1.98 0.00 106.93 0.00 53.85 1031.33 141.19 1472.32 0.00 1472.32 100.00

sdb1: 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

sdb2: 0.00 1.98 0.00 106.93 0.00 53.85 1031.33 141.19 1472.32 0.00 1472.32 100.00

I: open nicstat.



B: open iostat.

I: open nicstat.Interface: rMbps wMbps rPk/s wPk/s rAvs wAvs IErr OErr Coll Sat %rUtil %wUtil %Util

eth0: 592.33 7.29 52350.50 16897.03 1483.04 56.52 0.00 0.00 0.00 0.00 44.05 0.54 44.59

eth1: 119.04 1.85 10728.71 4290.10 1454.32 56.39 0.00 0.00 0.00 0.00 8.85 0.14 8.99

lo: 0.13 0.13 49.50 49.50 351.96 351.96 0.00 0.00 0.00 0.00 0.00 0.00 0.00



B: open iostat.

I: open nicstat.

L: tail postgres log (show the latest log lines).ERROR: cannot execute SELECT FOR UPDATE in a read-only transaction

ERROR: cannot execute SELECT FOR UPDATE in a read-only transaction

LOG: checkpoint starting: time

LOG: checkpoint complete: wrote 40 buffers (0.0%); 0 transaction log file(s) added, 0 removed, 26 recycled; write=3.924 s, sync=0.

ERROR: cannot execute SELECT FOR UPDATE in a read-only transaction


Troubleshoot:

● quick overview, resource utilization and postgresql activity;

● autovacuum issues;

● replication problems;

● database anomalies;

● tables, indexes and functions;

● where is the space?

● bad company;

● queries investigation.

Troubleshoot

Quick overview:

● run pgCenter;

● check resources usage (cpu, mem, disk, net);

● check the postgresql usage;

● make a plan what's next.

Troubleshoot

pgcenter: 2016-09-28 12:21:45, load average: 19.81, 5.15, 3.35

%cpu: 68.6 us, 5.5 sy, 0.0 ni, 15.1 id, 10.8 wa, 0.0 hi, 0.0 si, 0.0 st

MiB mem: 30679 total, 1508 free, 1130 used, 28041 buff/cached

MiB swap: 5119 total, 552 free, 4567 used, 834/198 dirty/writeback

Troubleshoot

pgcenter: 2016-09-28 12:21:45, load average: 19.81, 5.15, 3.35

%cpu: 68.6 us, 5.5 sy, 0.0 ni, 15.1 id, 10.8 wa, 0.0 hi, 0.0 si, 0.0 st

MiB mem: 30679 total, 1508 free, 1130 used, 28041 buff/cached

MiB swap: 5119 total, 552 free, 4567 used, 834/198 dirty/writeback

load average? – check cpu/disks usage.

us – check queries/activity.

sy, si, hi – check system/kernel/hardware.

wa – check queries, disks activity.

mem/swap – revise shared_buffers/work_mem.

dirty/writeback – write activity, disks utilization.

Troubleshoot

PostgreSQL general state:

● too many connections;

● too many bad connections (waiting, idle_in_xact);

● too many vacuums, long vacuum;

● too many queries, long transactions/queries;

Troubleshoot

conn1 [ok]: 127.0.0.1:5432 postgres@postgres (ver: 9.6.0, up 05:02:50)

activity: 44 total, 2 idle, 2 idle_in_xact, 9 active, 31 waiting, 0 others

autovacuum: 6/8 workers/max, 0 manual, 6 wraparound, 02:13:02 vac_maxtime

statements: 172 stmt/s, 5.390 stmt_avgtime, 00:18:37 xact_maxtime

Troubleshoot

conn1 [ok]: 127.0.0.1:5432 postgres@postgres (ver: 9.6.0, up 05:02:50)

activity: 44 total, 2 idle, 2 idle_in_xact, 9 active, 31 waiting, 0 others

autovacuum: 6/8 workers/max, 0 manual, 6 wraparound, 02:13:02 vac_maxtime

statements: 172 stmt/s, 5.390 stmt_avgtime, 00:18:37 xact_maxtime

too many active – check activity.

idle in transactions, waiting – check activity, cancel or terminate that.

what about autovacuum worker limit? – increase the limit, play with cost parameters.

check pg_stat_progress_vacuum, disks utilization.

long transactions – cancel or terminate.

Troubleshoot

Replication problems:

● replication lag – queries with different results;

● network utilization, errors;

● disk utilization, bandwidth.

Troubleshoot

client user name state mode pending write flush replay total_lag

10.13.0.5 replica walreceiver streaming async 256 0 0 227754 228009



Troubleshoot

client user name state mode pending write flush replay total_lag




high pending – busy master/network.

high write/flush/replay – busy standby, long running queries.

Troubleshoot

Database anomalies:

● rollbacks;

● deadlocks;

● recovery conflicts;

● temporary files.

Troubleshoot

datname commit rollback reads hits returned fetched inserts updates deletes conflicts deadlocks tmp_files tmp_bytes read_t write_t

pgbench 11845 0 0 61663 11845 0 0 11845 0 0 0 4 85725 0 0

staging 1854 10 0 128 1844 0 1844 0 0 0 0 0 0 0 0

template1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

template0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Postgres 5 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Troubleshoot

datname commit rollback reads hits returned fetched inserts updates deletes conflicts deadlocks tmp_files tmp_bytes read_t write_t

pgbench 11845 0 0 61663 11845 0 0 11845 0 0 0 4 85725 0 0

staging 1854 10 0 128 1844 0 1844 0 0 0 0 0 0 0 0

template1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

template0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Postgres 5 0 0 0 0 0 0 0 0 0 0 0 0 0 0

rollbacks – check postgres and application logs for errors.

deadlocks – check postgres log, review pg_locks.

conflicts – check pg_stat_database_conflicts, raise delays, enable feedback.

temporary files – check logs, pg_stat_statements, work_mem (carefully).

Troubleshoot

Tables activity:

● sequential scans;

● abnormal activity;

Troubleshoot

relation seq_scan seq_read idx_scan idx_fetch inserts updates deletes hot_updates live dead

public.job_stats 94 116090 0 0 0 0 0 0 0 0

public.feed_settings 10924 10924 0 0 0 10924 0 10924 0 7

public.feed_actions 0 0 35 1275 0 68 3 0 0 3

public.job_boards 0 0 0 0 0 0 0 0 0 0

Troubleshoot

relation seq_scan seq_read idx_scan idx_fetch inserts updates deletes hot_updates live dead

public.job_stats 94 116090 0 0 0 0 0 0 0 0

public.feed_settings 924 924 0 0 0 924 0 924 0 7

public.feed_actions 0 0 35 1275 0 68 3 0 0 3

public.job_boards 0 0 0 0 0 0 0 0 0 0

sequential scans – no index or broken planner stats.

abnormal activity – too many CRUD, check pg_statio_all_tables.

Troubleshoot

Index activity:

● unused indexes;

Troubleshoot

relation index idx_scan idx_tup_read idx_tup_fetch idx_read idx_hit

public.job_bodies job_bodies_pkey 850 850 850 0 14560

public.job_bodies job_bodies_refcount_idx 850 880 850 0 14960

public.job_bodies job_bodies_reftype_idx 170 255 170 1136 7024

public.job_bodies job_bodies_spc2_idx 0 0 0 0 0


Troubleshoot

relation index idx_scan idx_tup_read idx_tup_fetch idx_read idx_hit

public.job_bodies job_bodies_pkey 850 850 850 0 14560

public.job_bodies job_bodies_refcount_idx 850 880 850 0 14960

public.job_bodies job_bodies_reftype_idx 170 255 170 1136 7024



zero idx_scan – unused indexes;

tip: before drop them, check its usage on standbys.

Troubleshoot

Functions usage:

● long running functions;

● run psql, edit function with \ef funcname.

Troubleshoot

Where is the space Postgres ?

● check tables sizes (with and without indexes);

● check tables size changes;

● use filters to see interesting tables.

Troubleshoot

relation total_size rel_size idx_size total_change rel_change idx_change

public.job_bodies 7656200 6557568 1098632 312 260 58

public.job_stats_20161004 1629232 1285764 343468 37928 29920 8008

public.rules 3000 2744 256 0 0 0

public.resumes 384 224 160 0 0 0

public.versions 112 40 72 0 0 0

Troubleshoot

Bad company:

● long running queries or idle transactions;

● waiting queries/transactions;

● cancel queries or terminate backends using pid or mask;

● change age threshold to hide unwanted things.

Troubleshoot

pid cl_addr cl_port datname usename state wait_etype wait_event xact_age query_age change_age query

6942 -1 shopdb shop_app active Lock transactionid 00:10:14 00:00:17 00:00:17 update >

6930 -1 shopdb shop_app active 00:08:17 00:00:12 00:00:12 update >


3857 -1 shopdb shop_app active 00:00:00 00:00:00 00:00:00 select >

5781 -1 shopdb shop_bg active 00:03:29 00:00:01 00:00:01 select >


Troubleshoot

pid cl_addr cl_port datname usename state wait_etype wait_event xact_age query_age change_age query


6930 -1 shopdb shop_app active 00:08:17 00:00:12 00:00:12 update >


3857 -1 shopdb shop_app active 00:00:00 00:00:00 00:00:00 select >



idle in transaction, waiting – cancel or terminate.

use age thresholds and filters.

Troubleshoot

Query investigation:

● cpu- or disk hog queries;

● most called queries;

● queries doing a lot of IO;

● pg_stat_statements;

● query reports;

● looking for a query example;

● run psql and EXPLAIN ANALYZE query;

● rewrite a query, build an index, move a query to the standby, blame developers...

Troubleshoot

user database t_all_t t_read_t t_write_t t_cpu_t all_t read_t write_t cpu_t calls queryid query

postgres pgbench 00:56:05 00:00:00 00:00:00 00:56:05 254 0 0 254 10790 e19c70cd44 update >

postgres pgbench 00:00:32 00:00:00 00:00:00 00:00:32 4 0 0 4 10790 cfc329b478 commit;

postgres pgbench 00:00:28 00:00:00 00:00:00 00:00:28 4 0 0 4 10790 731392f8ec begin;

postgres pgbench 00:35:03 00:14:01 00:00:00 00:21:02 85 22 0 107 1587 a357c10e55 select >

postgres pgbench 00:22:27 00:08:15 00:00:00 00:14:12 51 10 0 61 854 4db337810e update >

postgres pgbench 00:07:23 00:00:00 00:00:00 00:07:23 11 0 0 11 59 6acc738af9 select >

Troubleshoot

summary:

total_time: 01:03:47, cpu_time: 00:59:38, io_time: 00:04:09 (ALL: 100.00%, CPU: 93.47%, IO: 6.53%),

total queries: 258,798,086

query info:

usename: streamcast,

datname: outpost,

calls (relative to all queries): 86,250,226 (33.33%),

rows (relative to all queries): 86,250,226 (94.46%),

total time (relative to all queries): 00:58:14 (ALL: 91.3%, CPU: 97.7%, IO: 0.0%),

average time (only for this query): 0.04ms, cpu_time: 0.04ms, io_time: 0.00ms, (ALL: 100.0%, CPU: 100.0%, IO: 0.0%),

query text (id: 14a58a3b9f):

SELECT tags.tg_id FROM tags WHERE tags.id IN (?, ?, ?) AND (id NOT IN (?)) GROUP BY id HAVING count(distinct tg_id) > ? LIMIT ?

Troubleshoot

pgCenter has many features but:

● psql is always available – 'p' hotkey.

● use the help – 'h' hotkey.

In the end

pgCenter is useful:

● to check what's going on;

● for quick overview;

● to make simple admin operations;

● to manage postgres easier and faster (I hope).

In the end

Alexey [email protected]

PostgreSQL–Consulting: Data maintenance as its best.http://postgresql-consulting.com

Questions?

mailto:[email protected]

http://postgresql-consulting.com/

Managing PostgreSQL with PgCenter

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