|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.|
|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.|
|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
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:
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:
-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.
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.
The SHOW commands output information. Each command is described below.
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.
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, its OS pid. Otherwise its extracted from cancel packet server sent, which should be PID in case server is Postgres, but its a random number in case server it another PgBouncer.
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.
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 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.
name The user name pool_mode The users override pool_mode, or NULL if the default will be used instead.
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 databases override pool_mode, or NULL if the default will be used instead.
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 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 hostnames in DNS cache.
hostname Host name. ttl How meny seconds until next lookup. addrs Comma separated list of addresses.
Show DNS zones in cache.
zonename Zone name. serial Current serial. count Hostnames belonging to this zone.
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.
Reject all new client connections on the given database.
Allow new client connections after a previous DISABLE command.
Immediately drop all client and server connections on given database.
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 work from previous PAUSE or SUSPEND command.
The PgBouncer process will exit.
The PgBouncer process will reload its configuration file and update changeable settings.
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.
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.
pgbouncer(5) - manpage of configuration settings descriptions.