path: root/doc/usage.rst

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_mode=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_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.

remote_pid
    Pid of backend server process.  In case connection is made over
    unix socket and OS supports getting process ID info, it's
    OS pid.  Otherwise it's extracted from cancel packet server sent,
    which should be PID in case server is Postgres, but it's a random
    number in case server it another PgBouncer.

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.

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

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.

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.

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.

SHOW FDS;
---------

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

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.

This command also blocks 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 boot-time.

SHOW DNS_HOSTS;
---------------

Show hostnames in DNS cache.

hostname
    Host name.

ttl
    How meny 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
    Hostnames 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.

DISABLE db;
-----------

Reject all new client connections on the given database.

ENABLE db;
----------

Allow new client connections after a previous **DISABLE** command.

KILL db;
--------

Immediately drop all client and server connections on given database.

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 [db];
------------

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.

https://pgbouncer.github.io/

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