PgBouncer

pgbouncer

Synopsis

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

On Windows, 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 a 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 a 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 the 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 is as follows.

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

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

 [pgbouncer]
 listen_port = 6432
 listen_addr = localhost
 auth_type = md5
 auth_file = userlist.txt
 logfile = pgbouncer.log
 pidfile = pgbouncer.pid
 admin_users = someuser

Create a userlist.txt file that contains the users allowed in:
```
 "someuser" "same_password_as_in_server"
```
Launch pgbouncer:
```
 $ pgbouncer -d pgbouncer.ini
```
Have your application (or the psql client) connect to pgbouncer instead of directly to the PostgreSQL server:
```
 $ psql -p 6432 -U someuser template1
```

Manage pgbouncer by connecting to the special administration database pgbouncer and issuing SHOW HELP; to begin:

 $ psql -p 6432 -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
   [...]

If you made changes to the pgbouncer.ini file, you can reload it with:
```
 pgbouncer=# RELOAD;
```

Command line switches

-d, --daemon: Run in the background. Without it, the process will run in the foreground. + In daemon mode, setting pidfile as well as logfile or syslog is required. No log messages will be written to stderr after going into the background. + Note: Does not work on Windows; pgbouncer need to run as service there.
-R, --reboot: DEPRECATED: Instead of this option use a rolling restart with multiple pgbouncer processes listening on the same port using so_reuseport instead 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 configuration. Does not work on Windows. Does not work with TLS connections, they are dropped.
-u USERNAME, `--user=`USERNAME: Switch to the given user on startup.
-v, --verbose: Increase verbosity. Can be used multiple times.
-q, --quiet: Be quiet: do not log to stderr. This does not affect logging verbosity, only that stderr is not to be used. For use in init.d scripts.
-V, --version: Show version.
-h, --help: Show short help.
--regservice: Win32: Register pgbouncer to run as Windows service. The service_name configuration parameter value is used as the 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 6432 pgbouncer

Only users listed in the configuration parameters admin_users or stats_users are allowed to log in to the console. (Except when auth_type=any, then any user is allowed in as a stats_user.)

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

The admin console currently only supports the simple query protocol. Some drivers use the extended query protocol for all commands; these drivers will not work for this.

Show commands

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

SHOW STATS

Shows statistics. In this and related commands, the total figures are since process start, the averages are updated every stats_period.

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. Updated when a client connection is assigned a backend connection.
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: Average time spent by clients waiting for a server that were assigned a backend connection within the current stats_period, in microseconds (averaged per second within that period).

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 TOTALS

Like SHOW STATS but aggregated across all databases.

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, idle, used, tested, new, active_cancel, being_canceled.
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: Not used for server connections.
wait_us: Not used for server connections.
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 the server sent, which should be the PID in case the server is PostgreSQL, but it’s a random number in case the server it is another PgBouncer.
tls: A string with TLS connection information, or empty if not using TLS.
application_name: A string containing the application_name set on the linked client connection, or empty if this is not set, or if there is no linked connection.
prepared_statements: The amount of prepared statements that are prepared on the server. This number is limited by the max_prepared_statements setting.

SHOW CLIENTS

type: C, for client.
user: Client connected user.
database: Database name.
state: State of the client connection, one of active, waiting, active_cancel_req, or waiting_cancel_req.
addr: IP address of client.
port: Source port of client.
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.
application_name: A string containing the application_name set by the client for this connection, or empty if this was not set.
prepared_statements: The amount of prepared statements that the client has prepared

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 either linked to server connections or are idle with no queries waiting to be processed.
cl_waiting: Client connections that have sent queries but have not yet got a server connection.
cl_active_cancel_req: Client connections that have forwarded query cancellations to the server and are waiting for the server response.
cl_waiting_cancel_req: Client connections that have not forwarded query cancellations to the server yet.
sv_active: Server connections that are linked to a client.
sv_active_cancel: Server connections that are currently forwarding a cancel request.
sv_being_canceled: Servers that normally could become idle but are waiting to do so until all in-flight cancel requests have completed that were sent to cancel a query on this server.
sv_idle: Server connections that are unused and immediately usable for client queries.
sv_used: Server connections that have been idle for more than server_check_delay, so they need server_check_query to run on them before they can be used again.
sv_tested: Server connections that are currently running either server_reset_query or server_check_query.
sv_login: Server connections currently in the process of logging in.
maxwait: How long the first (oldest) client in the queue has waited, in seconds. If this starts increasing, then the current pool of servers does not handle requests quickly enough. The reason may be either an 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 PEER_POOLS

A new peer_pool entry is made for each configured peer.

database: ID of the configured peer entry.
cl_active_cancel_req: Client connections that have forwarded query cancellations to the server and are waiting for the server response.
cl_waiting_cancel_req: Client connections that have not forwarded query cancellations to the server yet.
sv_active_cancel: Server connections that are currently forwarding a cancel request.
sv_login: Server connections currently in the process of logging in.

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 the 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.
min_pool_size: Minimum number of server connections.
reserve_pool: Maximum number of additional connections for this database.
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 PEERS

peer_id: ID of the configured peer entry.
host: Host pgbouncer connects to.
port: Port pgbouncer connects to.
pool_size: Maximum number of server connections that can be made to this peer

SHOW FDS

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

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

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 SOCKETS, SHOW ACTIVE_SOCKETS

Shows low-level information about sockets or only active sockets. This includes the information shown under SHOW CLIENTS and SHOW SERVERS as well as other more low-level information.

SHOW CONFIG

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

key: Configuration variable name
value: Configuration value
default: Configuration default 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 MEM

Shows low-level information about the current sizes of various internal memory allocations. The information presented is subject to change.

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.

SHOW VERSION

Show the PgBouncer version string.

SHOW STATE

Show the PgBouncer state settings. Current states are active, paused and suspended.

Process controlling commands

PAUSE [db]

PgBouncer tries to disconnect from all servers. Disconnecting each server connection waits for that server connection to be released according to the server pool’s pooling mode (in transaction pooling mode, the transaction must complete, in statement mode, the statement must complete, and in session pooling mode the client must disconnect). The command will not return before all server connections have been disconnected. 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 files and update changeable settings. This includes the main configuration file as well as the files specified by the settings auth_file and auth_hba_file.

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 [db]

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 a RECONNECT 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 the Libevent documentation:

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.