Linux Certif

Toute la documentation sur la certification Linux LPI

pgbouncer

NAME

pgbouncer - Lightweight connection pooler for PostgreSQL.

SYNOPSIS

 pgbouncer [-d][-R][-v][-u user] <pgbouncer.ini>
 pgbouncer -V|-h
 

On Windows computers, the options are:

 pgbouncer.exe [-v][-u user] <pgbouncer.ini>
 pgbouncer.exe -V|-h
 

Additional options for setting up a Windows service:

 pgbouncer.exe -regservice   <pgbouncer.ini>
 pgbouncer.exe -unregservice <pgbouncer.ini>
 

DESCRIPTION

pgbouncer is a PostgreSQL connection pooler. Any target application can be connected to pgbouncer as if it were a PostgreSQL server, and pgbouncer will create a connection to the actual server, or it will reuse one of its existing connections.

The aim of pgbouncer is to lower the performance impact of opening new connections to PostgreSQL.

In order not to compromise transaction semantics for connection pooling, pgbouncer supports several types of pooling when rotating connections:

Session pooling

Most polite method. When client connects, a server connection will be assigned to it for the whole duration the client stays connected. When the client disconnects, the server connection will be put back into the pool. This is the default method.

Transaction pooling

A server connection is assigned to client only during a transaction. When PgBouncer notices that transaction is over, the server connection will be put back into the pool.

Statement pooling

Most aggressive method. The server connection will be put back into pool immediately after a query completes. Multi-statement transactions are disallowed in this mode as they would break.

The administration interface of pgbouncer consists of some new SHOW commands available when connected to a special virtual database pgbouncer.

QUICK-START

Basic setup and usage as following.

1. Create a pgbouncer.ini file. Details in pgbouncer(5). Simple example:

 [databases]
 template1 = host=127.0.0.1 port=5432 dbname=template1
 

 [pgbouncer]
 listen_port = 6543
 listen_addr = 127.0.0.1
 auth_type = md5
 auth_file = users.txt
 logfile = pgbouncer.log
 pidfile = pgbouncer.pid
 admin_users = someuser
 

2. Create a users.txt file:

 "someuser" "same_password_as_in_server"
 

3. Launch pgbouncer:

 $ pgbouncer -d pgbouncer.ini
 

4. Have your application (or the psql client) connect to pgbouncer instead of directly to PostgreSQL server.

 $ psql -p 6543 -U someuser template1
 

5. Manage pgbouncer by connecting to the special administration database pgbouncer and issuing show help; to begin:

 $ psql -p 6543 -U someuser pgbouncer
 pgbouncer=# show help;
 NOTICE:  Console usage
 DETAIL:
   SHOW [HELP|CONFIG|DATABASES|FDS|POOLS|CLIENTS|SERVERS|SOCKETS|LISTS|VERSION]
   SET key = arg
   RELOAD
   PAUSE
   SUSPEND
   RESUME
   SHUTDOWN
 

6. If you made changes to the pgbouncer.ini file, you can reload it with:

 pgbouncer=# RELOAD;
 

COMMAND LINE SWITCHES

-d

Run in background. Without it the process will run in foreground. Note: Does not work on Windows, pgbouncer need to run as service there.

-R

Do an online restart. That means connecting to the running process, loading the open sockets from it, and then using them. If there is no active process, boot normally. Note: Does not work on Windows machines.

-u user

Switch to the given user on startup.

-v

Increase verbosity. Can be used multiple times.

-q

Be quiet - do not log to stdout. Note this does not affect logging verbosity, only that stdout is not to be used. For use in init.d scripts.

-V

Show version.

-h

Show short help.

-regservice

Win32: Register pgbouncer to run as Windows service. The service_name config parameter value is used as name to register under.

-unregservice

Win32: Unregister Windows service.

ADMIN CONSOLE

The console is available by connecting as normal to the database pgbouncer

 $ psql -p 6543 pgbouncer
 

Only users listed in configuration parameters admin_users or stats_users are allowed to login to the console. (Except when auth_mode=any, then any user is allowed in as an admin.)

Additionally, the username pgbouncer is allowed to log in without password, if the login comes via Unix socket and the client has same Unix user uid as the running process.

SHOW COMMANDS

The SHOW commands output information. Each command is described below.

SHOW STATS;

Shows statistics.
database

Statistics are presented per database.

total_requests

Total number of SQL requests pooled by pgbouncer.

total_received

Total volume in bytes of network traffic received by pgbouncer.

total_sent

Total volume in bytes of network traffic sent by pgbouncer.

total_query_time

Total number of microseconds spent by pgbouncer when actively connected to PostgreSQL.

avg_req

Average requests per second in last stat period.

avg_recv

Average received (from clients) bytes per second.

avg_sent

Average sent (to clients) bytes per second.

avg_query

Average query duration in microseconds.

SHOW SERVERS;

type

S, for server.

user

Username pgbouncer uses to connect to server.

database

Database name.

state

State of the pgbouncer server connection, one of active, used or idle.

addr

IP address of PostgreSQL server.

port

Port of PostgreSQL server.

local_addr

Connection start address on local machine.

local_port

Connection start port on local machine.

connect_time

When the connection was made.

request_time

When last request was issued.

ptr

Address of internal object for this connection. Used as unique ID.

link

Address of client connection the server is paired with.

SHOW CLIENTS;

type

C, for client.

user

Client connected user.

database

Database name.

state

State of the client connection, one of active, used, waiting or idle.

addr

IP address of client.

port

Port client is connected to.

local_addr

Connection end address on local machine.

local_port

Connection end port on local machine.

connect_time

Timestamp of connect time.

request_time

Timestamp of latest client request.

ptr

Address of internal object for this connection. Used as unique ID.

link

Address of server connection the client is paired with.

SHOW POOLS;

A new pool entry is made for each couple of (database, user).
database

Database name.

user

Username.

cl_active

Count of currently active client connections.

cl_waiting

Count of currently waiting client connections.

sv_active

Count of currently active server connections.

sv_idle

Count of currently idle server connections.

sv_used

Count of currently used server connections.

sv_tested

Count of currently tested server connections.

sv_login

Count of server connections currently logged in to PostgreSQL.

maxwait

How long the first (oldest) client in queue has waited, in seconds. If this starts increasing, then the current pool of servers does not handle requests quick enough. Reason may be either overloaded server or just too small of a pool_size setting.

SHOW LISTS;

Show following internal information, in columns (not rows):
databases

Count of databases.

users

Count of users.

pools

Count of pools.

free_clients

Count of free clients.

used_clients

Count of used clients.

login_clients

Count of clients in login state.

free_servers

Count of free servers.

used_servers

Count of used servers.

SHOW USERS;

Shows one line per user, under the name column name.

SHOW DATABASES;

name

Name of configured database entry.

host

Host pgbouncer connects to.

port

Port pgbouncer connects to.

database

Actual database name pgbouncer connects to.

force_user

When user is part of the connection string, the connection between pgbouncer and PostgreSQL is forced to the given user, whatever the client user.

pool_size

Maximum number of server connections.

SHOW FDS;

Shows list of fds in use. When the connected user has username "pgbouncer", connects through Unix socket and has same UID as running process, the actual fds are passed over the connection. This mechanism is used to do an online restart. Note: This does not work on Windows machines.
fd

File descriptor numeric value.

task

One of pooler, client or server.

user

User of the connection using the FD.

database

Database of the connection using the FD.

addr

IP address of the connection using the FD, unix if a unix socket is used.

port

Port used by the connection using the FD.

cancel

Cancel key for this connection.

link

fd for corresponding server/client. NULL if idle.

SHOW CONFIG;

Show the current configuration settings, one per row, with following columns:
key

Configuration variable name

value

Configuration value

changeable

Either yes or no, shows if the variable can be changed while running. If no, the variable can be changed only boot-time.

 

PROCESS CONTROLLING COMMANDS

PAUSE;

PgBouncer tries to disconnect from all servers, first waiting for all queries to complete. The command will not return before all queries are finished. To be used at the time of database restart.

SUSPEND;

All socket buffers are flushed and PgBouncer stops listening for data on them. The command will not return before all buffers are empty. To be used at the time of PgBouncer online reboot.

RESUME;

Resume work from previous PAUSE or SUSPEND command.

SHUTDOWN;

The PgBouncer process will exit.

RELOAD;

The PgBouncer process will reload its configuration file and update changeable settings.

 

SIGNALS

SIGHUP

Reload config. Same as issuing command RELOAD; on console.

SIGINT

Safe shutdown. Same as issuing PAUSE; and SHUTDOWN; on console.

SIGTERM

Immediate shutdown. Same as issuing SHUTDOWN; on console.

LIBEVENT SETTINGS

From libevent docs:

 It is possible to disable support for epoll, kqueue, devpoll, poll
 or select by setting the environment variable EVENT_NOEPOLL,
 EVENT_NOKQUEUE, EVENT_NODEVPOLL, EVENT_NOPOLL or EVENT_NOSELECT,
 respectively.
 

 By setting the environment variable EVENT_SHOW_METHOD, libevent
 displays the kernel notification method that it uses.
 

SEE ALSO

pgbouncer(5) - manpage of configuration settings descriptions.

m[blue]http://pgbouncer.projects.postgresql.org/doc/m[]

m[blue]https://developer.skype.com/SkypeGarage/DbProjects/PgBouncerm[]