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:
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:
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 commands pooled by pgbouncer.
- total_server_assignment_count
- Total times a server was assigned to a client
- 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_server_assignment_count
- Average number of times a server as assigned to a client per second in the
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
of the wait times for clients assigned a backend during the current
stats_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.
- replication
- If server connection uses replication. Can be none, logical or physical.
- 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.
- replication
- If client connection uses replication. Can be none, logical or physical.
- 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. These are clients that are disconnected, but
PgBouncer keeps the memory around that was allocated for them so it can be
reused for a future clients to avoid allocations.
- used_clients
- Count of used clients.
- login_clients
- Count of clients in login state.
- free_servers
- Count of free servers. These are servers that are disconnected, but
PgBouncer keeps the memory around that was allocated for them so it can be
reused for a future servers to avoid allocations.
- 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_size
- The user’s override pool_size. or NULL if not set.
- pool_mode
- The user’s override pool_mode, or NULL if not set.
- max_user_connections
- The user’s max_user_connections setting. If this setting is not set
for this specific user, then the default value will be displayed.
- current_connections
- Current number of connections that this user has open to all servers.
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.
- server_lifetime
- The maximum lifetime of a server connection 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.
SHUTDOWN WAIT_FOR_SERVERS
Stop accepting new connections and shutdown after all servers are released.
This is basically the same as issuing PAUSE and SHUTDOWN, except that
this also stops accepting new connections while waiting for the PAUSE as
well as eagerly disconnecting clients that are waiting to receive a server
connection.
SHUTDOWN WAIT_FOR_CLIENTS
Stop accepting new connections and shutdown the process once all existing
clients have disconnected. This command can be used to do zero-downtime rolling
restart of two PgBouncer processes using the following procedure:
- Have two or more PgBouncer processes running on the same port using
so_reuseport
(configuring peering is
recommended, but not required). To achieve zero downtime when
restarting we’ll restart these processes one-by-one, thus leaving the
others running to accept connections while one is being restarted.
- Pick a process to restart first, let’s call it A.
- Run
SHUTDOWN WAIT_FOR_CLIENTS
(or send SIGTERM
) to process A.
- Cause all clients to reconnect. Possibly by waiting some time until the
client side pooler causes reconnects due to its
server_idle_timeout
(or similar config). Or if no client side pooler is used, possibly by
restarting the clients. Once all clients have reconnected. Process A
will exit automatically, because no clients are connected to it anymore.
- Start process A again.
- Repeat step 3, 4 and 5 for each of the remaining processes, one-by-one
until you restarted all processes.
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.
- SIGTERM
- Super safe shutdown. Wait for all existing clients to disconnect, but don’t
accept new connections. This is the same as issuing
SHUTDOWN WAIT_FOR_CLIENTS on the console. If this signal is received while
there is already a shutdown in progress, then an “immediate shutdown” is
triggered instead of a “super safe shutdown”. In PgBouncer versions earlier
than 1.23.0, this signal would cause an “immediate shutdown”.
- SIGINT
- Safe shutdown. Same as issuing SHUTDOWN WAIT_FOR_SERVERS on the console.
If this signal is received while there is already a shutdown in progress,
then an “immediate shutdown” is triggered instead of a “safe shutdown”.
- SIGQUIT
- 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.
See also
pgbouncer(5) - man page of configuration settings descriptions
https://www.pgbouncer.org/