pgbouncer

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 users.txt file that contains users allowed in:

    "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: Works only if OS supports Unix sockets and the unix_socket_dir is not disabled in config. Does not work on Windows machines. Does not work with TLS connections, they are dropped.

-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_type=any, then any user is allowed in as a stats_user.)

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_xact_count

Total number of SQL transactions pooled by pgbouncer.

total_query_count

Total number of SQL queries 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_xact_time

Total number of microseconds spent by pgbouncer when connected to PostgreSQL in a transaction, either idle in transaction or executing queries.

total_query_time

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

total_wait_time

Time spent by clients waiting for a server in microseconds.

avg_xact_count

Average transactions per second in last stat period.

avg_query_count

Average queries 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_xact_time

Average transaction duration in microseconds.

avg_query_time

Average query duration in microseconds.

avg_wait_time

Time spent by clients waiting for a server in microseconds (average per second).

SHOW STATS_TOTALS;

Subset of SHOW STATS showing the total values (total_).

SHOW STATS_AVERAGES;

Subset of SHOW STATS showing the average values (avg_).

SHOW SERVERS;

type

S, for server.

user

User name 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.

wait

Current waiting time in seconds.

wait_us

Microsecond part of the current waiting time.

close_needed

1 if the connection will be closed as soon as possible, because a configuration file reload or DNS update changed the connection information or RECONNECT was issued.

ptr

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

link

Address of client connection the server is paired with.

remote_pid

PID of backend server process. In case connection is made over Unix socket and OS supports getting process ID info, its OS PID. Otherwise it’s extracted from cancel packet server sent, which should be PID in case server is PostgreSQL, but it’s a random number in case server it is another PgBouncer.

tls

A string with TLS connection information, or empty if not using TLS.

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.

wait

Current waiting time in seconds.

wait_us

Microsecond part of the current waiting time.

close_needed

not used for clients

ptr

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

link

Address of server connection the client is paired with.

remote_pid

Process ID, in case client connects over Unix socket and OS supports getting it.

tls

A string with TLS connection information, or empty if not using TLS.

SHOW POOLS;

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

database

Database name.

user

User name.

cl_active

Client connections that are linked to server connection and can process queries.

cl_waiting

Client connections have sent queries but have not yet got a server connection.

sv_active

Server connections that linked to client.

sv_idle

Server connections that unused and immediately usable for client queries.

sv_used

Server connections that have been idle more than server_check_delay, so they needs server_check_query to run on it before it can be used.

sv_tested

Server connections that are currently running either server_reset_query or server_check_query.

sv_login

Server connections currently in logging in process.

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.

maxwait_us

Microsecond part of the maximum waiting time.

pool_mode

The pooling mode in use.

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.

dns_names

Count of DNS names in the cache.

dns_zones

Count of DNS zones in the cache.

dns_queries

Count of in-flight DNS queries.

dns_pending

not used

SHOW USERS;

name

The user name

pool_mode

The user’s override pool_mode, or NULL if the default will be used instead.

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.

pool_mode

The database’s override pool_mode, or NULL if the default will be used instead.

max_connections

Maximum number of allowed connections for this database, as set by max_db_connections, either globally or per database.

current_connections

Current number of connections for this database.

paused

1 if this database is currently paused, else 0.

disabled

1 if this database is currently disabled, else 0.

SHOW FDS;

Internal command - shows list of file descriptors in use with internal state attached to them.

When the connected user has user name “pgbouncer”, connects through Unix socket and has same UID as the 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.

This command also blocks the internal event loop, so it should not be used while PgBouncer is in use.

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 at boot time. Use SET to change a variable at run time.

SHOW DNS_HOSTS;

Show host names in DNS cache.

hostname

Host name.

ttl

How many seconds until next lookup.

addrs

Comma separated list of addresses.

SHOW DNS_ZONES;

Show DNS zones in cache.

zonename

Zone name.

serial

Current serial.

count

Host names belonging to this zone.

Process controlling commands

PAUSE [db];

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.

If database name is given, only that database will be paused.

New client connections to a paused database will wait until RESUME is called.

DISABLE db;

Reject all new client connections on the given database.

ENABLE db;

Allow new client connections after a previous DISABLE command.

RECONNECT [db];

Close each open server connection for the given database, or all databases, after it is released (according to the pooling mode), even if its lifetime is not up yet. New server connections can be made immediately and will connect as necessary according to the pool size settings.

This command is useful when the server connection setup has changed, for example to perform a gradual switchover to a new server. It is not necessary to run this command when the connection string in pgbouncer.ini has been changed and reloaded (see RELOAD) or when DNS resolution has changed, because then the equivalent of this command will be run automatically. This command is only necessary if something downstream of PgBouncer routes the connections.

After this command is run, there could be an extended period where some server connections go to an old destination and some server connections go to a new destination. This is likely only sensible when switching read-only traffic between read-only replicas, or when switching between nodes of a multimaster replication setup. If all connections need to be switched at the same time, PAUSE is recommended instead. To close server connections without waiting (for example, in emergency failover rather than gradual switchover scenarios), also consider KILL.

KILL db;

Immediately drop all client and server connections on given database.

New client connections to a killed database will wait until RESUME is called.

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.

New client connections to a suspended database will wait until RESUME is called.

RESUME [db];

Resume work from previous KILL, PAUSE, or SUSPEND command.

SHUTDOWN;

The PgBouncer process will exit.

RELOAD;

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

PgBouncer notices when a configuration file reload changes the connection parameters of a database definition. An existing server connection to the old destination will be closed when the server connection is next released (according to the pooling mode), and new server connections will immediately use the updated connection parameters.

WAIT_CLOSE [];

Wait until all server connections, either of the specified database or of all databases, have cleared the “close_needed” state (see SHOW SERVERS). This can be called after aRECONNECT** or RELOAD to wait until the respective configuration change has been fully activated, for example in switchover scripts.

Other commands

SET key = arg;

Changes a configuration setting (see also SHOW CONFIG). For example:

SET log_connections = 1;
SET server_check_query = 'select 2';

(Note that this command is run on the PgBouncer admin console and sets PgBouncer settings. A SET command run on another database will be passed to the PostgreSQL backend like any other SQL command.)

Signals

SIGHUP

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

SIGINT

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

SIGTERM

Immediate shutdown. Same as issuing SHUTDOWN; on the console.

SIGUSR1

Same as issuing PAUSE; on the console.

SIGUSR2

Same as issuing RESUME; on the 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) - man page of configuration settings descriptions.

https://pgbouncer.github.io/

https://wiki.postgresql.org/wiki/PgBouncer