# pgbouncer(1)

## 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: Works only if OS supports Unix sockets and the `unix_socket_dir` is not disabled in config. 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 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.

http://wiki.postgresql.org/wiki/PgBouncer