PGBOUNCER(1)

NAME
pgbouncer - lightweight connection pooler for PostgreSQL

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.

1.  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

2.  Create a userlist.txt file that contains the 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 the PostgreSQL server:

             $ psql -p 6432 -U someuser template1

5.  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
               [...]

6.  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 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.

total_client_parse_count
    Total number of prepared statements created by clients. Only applicable in named prepared statement tracking mode, see max_prepared_statements.

total_server_parse_count
    Total number of prepared statements created by pgbouncer on a server. Only applicable in named prepared statement tracking mode, see max_prepared_statements.

total_bind_count
    Total number of prepared statements readied for execution by clients and forwarded to PostgreSQL by pgbouncer. Only applicable in named prepared statement tracking mode, see max_prepared_statements.

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).

avg_client_parse_count
    Average number of prepared statements created by clients. Only applicable in named prepared statement tracking mode, see max_prepared_statements.

avg_server_parse_count
    Average number of prepared statements created by pgbouncer on a server. Only applicable in named prepared statement tracking mode, see max_prepared_statements.

avg_bind_count
    Average number of prepared statements readied for execution by clients and forwarded to PostgreSQL by pgbouncer. Only applicable in named prepared statement tracking mode, see max_prepared_statements.

  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.

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.

id  Unique ID for server.

  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 (Client connections that are linked to server connections), idle (Client connections with no queries waiting to be processed), 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.

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

id  Unique ID for client.

  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.

load_balance_hosts
    The load_balance_hosts in use if the pool’s host contains a comma-separated list.

  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.

reserve_pool_size
    The user’s override reserve_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 server connections that this user has open to all servers.

max_user_client_connections
    The user’s max_user_client_connections setting. If this setting is not set for this specific user, then the default value will be displayed.

current_client_connections
    Current number of client connections that this user has open to PgBouncer.

  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_size
    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.

load_balance_hosts
    The database’s load_balance_hosts if the host contains a comma-separated list.

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

current_connections
    Current number of server connections for this database.

max_client_connections
    Maximum number of allowed client connections for this PgBouncer instance, as set by max_db_client_connections per database.

current_client_connections
    Current number of client 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 the given database or all databases, excluding the admin database.

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

  KILL_CLIENT id
Immediately kill specified client connection along with any server connections for the given client. The client to kill, is identified by the id value that can be found using the SHOW CLIENTS command.

An example command will look something like KILL_CLIENT 1234.

  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. Please note that UNIX sockets will remain open during the shutdown but will only accept connections to the PgBouncer admin console.

  SHUTDOWN WAIT_FOR_CLIENTS
Stop accepting new connections and shutdown the process once all existing clients have disconnected. Please note that UNIX sockets will remain open during the shutdown but will only accept connections to the pgbouncer admin console. This command can be used to do zero-downtime rolling restart of two PgBouncer processes using the following procedure:

1.  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.

2.  Pick a process to restart first, let’s call it A.

3.  Run SHUTDOWN WAIT_FOR_CLIENTS (or send SIGTERM) to process A.

4.  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.

5.  Start process A again.

6.  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/