Database Connection Parameters

The following parameters may be included in the value to specify the location of the database.

dbname

The destination database name.

Default: the client-specified database name

host

The name or IP address of the Greenplum master host. Host names are resolved at connect time. If DNS returns several results, they are used in a round-robin manner. The DNS result is cached and the dns_max_ttl parameter determines when the cache entry expires.

Default: not set; the connection is made through a Unix socket

port

The Greenplum Database master port.

Default: 5432

user, password

If user= is set, all connections to the destination database are initiated as the specified user, resulting in a single connection pool for the database.

If the user= parameter is not set, PgBouncer attempts to log in to the destination database with the user name passed by the client. In this situation, there will be one pool for each user who connects to the database.

auth_user

If auth_user is set, any user who is not specified in auth_file is authenticated by querying the pg_shadow database view. PgBouncer performs this query as the auth_user Greenplum Database user. auth_user's password must be set in the auth_file.

client_encoding

Ask for specific client_encoding from server.

datestyle

Ask for specific datestyle from server.

timezone

Ask for specific timezone from server.

Pool Configuration

You can use the following parameters for database-specific pool configuration.

pool_size

Set the maximum size of pools for this database. If not set, the default_pool_size is used.

connect_query

Query to be executed after a connection is established, but before allowing the connection to be used by any clients. If the query raises errors, they are logged but ignored otherwise.

pool_mode

Set the pool mode for this database. If not set, the default pool_mode is used.

max_db_connections

Set a database-wide maximum number of PgBouncer connections for this database. The total number of connections for all pools for this database will not exceed this value.

Generic Settings

logfile

The location of the log file. The log file is kept open. After log rotation, execute kill -HUP pgbouncer or run the RELOAD; command in the PgBouncer Administration Console.

Default: not set

pidfile

The name of the pid file. Without a pidfile, you cannot run PgBouncer as a background (daemon) process.

Default: not set

listen_addr

A list of interface addresses where PgBouncer listens for TCP connections. You may also use *, which means to listen on all interfaces. If not set, only Unix socket connections are allowed.

Specify addresses numerically (IPv4/IPv6) or by name.

Default: not set

listen_port

The port PgBouncer listens on. Applies to both TCP and Unix sockets.

Default: 6432

unix_socket_dir

Specifies the location for the Unix sockets. Applies to both listening socket and server connections. If set to an empty string, Unix sockets are disabled. Required for online restart (-R option) to work.

Default: /tmp

unix_socket_mode

Filesystem mode for the Unix socket.

Default: 0777

unix_socket_group

Group name to use for Unix socket.

Default: not set

user

If set, specifies the Unix user to change to after startup. This works only if PgBouncer is started as root or if user is the same as the current user.

Default: not set

auth_file

The name of the file containing the user names and passwords to load. The file format is the same as the Greenplum Database pg_auth file.

Default: not set

auth_hba_file

HBA configuration file to use when auth_type is hba. Refer to the HBA file format discussion in the PgBouncer documentation for information about PgBouncer support of the HBA authentication file format.

Default: not set

auth_type

How to authenticate users.

pam

Use PAM to authenticate users. auth_file is ignored. This method is not compatible with databases using the auth_user option. The service name reported to PAM is “pgbouncer”. PAM is not supported in the HBA configuration file.

hba

The actual authentication type is loaded from the auth_hba_file. This setting allows different authentication methods different access paths.

cert

Clients must connect with TLS using a valid client certificate. The client's username is taken from CommonName field in the certificate.

md5

Use MD5-based password check. auth_file may contain both MD5-encrypted or plain-text passwords. This is the default authentication method.

plain

Clear-text password is sent over wire. Deprecated.

trust

No authentication is performed. The username must still exist in the auth_file.

any

Like the trust method, but the username supplied is ignored. Requires that all databases are configured to log in with a specific user. Additionally, the console database allows any user to log in as admin.

auth_query

Query to load a user's password from the database. If a user does not exist in the auth_file and the database entry includes an auth_user, this query is run in the database as auth_user to lookup up the user.

Note that the query is run inside target database, so if a function is used it needs to be installed into each database.

Default: SELECT usename, passwd FROM pg_shadow WHERE usename=$1

auth_user

If auth_user is set, any user who is not specified in auth_file is authenticated through the auth_query query from the pg_shadow database view. PgBouncer performs this query as the auth_user Greenplum Database user. auth_user's password must be set in the auth_file.

Direct access to pg_shadow requires Greenplum Database administrative privileges. It is preferable to use a non-admin user that calls SECURITY DEFINER function instead.

pool_mode

Specifies when a server connection can be reused by other clients.

session

Connection is returned to the pool when the client disconnects. Default.

transaction

Connection is returned to the pool when the transaction finishes.

statement

Connection is returned to the pool when the current query finishes. Long transactions with multiple statements are disallowed in this mode.

max_client_conn

Maximum number of client connections allowed. When increased, you should also increase the file descriptor limits. The actual number of file descriptors used is more than max_client_conn. The theoretical maximum used, when each user connects with its own username to the server is:

max_client_conn + (max_pool_size * total_databases * total_users)

If a database user is specified in the connect string, all users connect using the same username. Then the theoretical maximum connections is:

max_client_conn + (max_pool_size * total_databases)

(The theoretical maximum should be never reached, unless someone deliberately crafts a load for it. Still, it means you should set the number of file descriptors to a safely high number. Search for ulimit in your operating system documentation.)

Default: 100

default_pool_size

The number of server connections to allow per user/database pair. This can be overridden in the per-database configuration.

Default: 20

min_pool_size

Add more server connections to the pool when it is lower than this number. This improves behavior when the usual load drops and then returns suddenly after a period of total inactivity.

Default: 0 (disabled)

reserve_pool_size

The number of additional connections to allow for a pool. 0 disables.

Default: 0 (disabled)

reserve_pool_timeout

If a client has not been serviced in this many seconds, PgBouncer enables use of additional connections from the reserve pool. 0 disables.

Default: 5.0

max_db_connections

The maximum number of connections per database. If you hit the limit, closing a client connection to one pool does not immediately allow a server connection to be established for another pool, because the server connection for the first pool is still open. Once the server connection closes (due to idle timeout), a new server connection will be opened for the waiting pool.

Default: unlimited

max_user_connections

The maximum number of connections per-user. When you hit the limit, closing a client connection to one pool does not immediately allow a connection to be established for another pool, because the connection for the first pool is still open. After the connection for the first pool has closed (due to idle timeout), a new server connection is opened for the waiting pool.

server_round_robin

By default, PgBouncer reuses server connections in LIFO (last-in, first-out) order, so that a few connections get the most load. This provides the best performance when a single server serves a database. But if there is TCP round-robin behind a database IP, then it is better if PgBouncer also uses connections in that manner to achieve uniform load.

Default: 0

ignore_startup_parameters

By default, PgBouncer allows only parameters it can keep track of in startup packets: client_encoding, datestyle, timezone, and standard_conforming_strings.

All others parameters raise an error. To allow other parameters, specify them here so that PgBouncer can ignore them.

Default: empty

disable_pqexec

Disable Simple Query protocol (PQexec). Unlike Extended Query protocol, Simple Query protocol allows multiple queries in one packet, which allows some classes of SQL-injection attacks. Disabling it can improve security. This means that only clients that exclusively use Extended Query protocol will work.

Default: 0

application_name_add_host

Add the client host address and port to the application name setting set on connection start. This helps in identifying the source of bad queries. The setting is overwritten without detection if the application executes SET application_name after connecting.

Default: 0

conffile

Show location of the current configuration file. Changing this parameter will result in PgBouncer using another config file for next RELOAD / SIGHUP.

Default: file from command line

service_name

Used during win32 service registration.

Default: pgbouncer

job_name

Alias for service_name.

Log Settings

syslog

Toggles syslog on and off.

Default: 0

syslog_ident

Under what name to send logs to syslog.

Default: pgbouncer

syslog_facility

Under what facility to send logs to syslog. Some possibilities are: auth, authpriv, daemon, user, local0-7

Default: daemon

log_connections

Log successful logins.

Default: 1

log_disconnections

Log disconnections, with reasons.

Default: 1

log_pooler_errors

Log error messages that the pooler sends to clients.

Default: 1

log_stats

Write aggregated statistics into the log, every stats_period. This can be disabled if external monitoring tools are used to grab the same data from SHOW commands.

Default: 1

stats_period

How often to write aggregated statistics to the log.

Default: 60

Console Access Control

admin_users

Comma-separated list of database users that are allowed to connect and run all commands on the PgBouncer Administration Console. Ignored when auth_type=any, in which case any username is allowed in as admin.

Default: empty

stats_users

Comma-separated list of database users that are allowed to connect and run read-only queries on the console. This includes all SHOW commands except SHOW FDS.

Default: empty

Connection Sanity Checks, Timeouts

server_reset_query

Query sent to server on connection release, before making it available to other clients. At that moment no transaction is in progress so it should not include ABORT or ROLLBACK.

The query should clean any changes made to a database session so that the next client gets a connection in a well-defined state. Default is DISCARD ALL which cleans everything, but that leaves the next client no pre-cached state.

Note: Greenplum Database does not support DISCARD ALL.

You can use other commands to clean up the session state. For example, DEALLOCATE ALL drops prepared statements, and DISCARD TEMP drops temporary tables.

When transaction pooling is used, the server_reset_query should be empty, as clients should not use any session features. If clients do use session features, they will be broken because transaction pooling does not guarantee that the next query will run on the same connection.

Default: DISCARD ALL; (Not supported by Greenplum Database.)

server_reset_query_always

Whether server_reset_query should be run in all pooling modes. When this setting is off (default), the server_reset_query will be run only in pools that are in sessions pooling mode. Connections in transaction pooling mode should not have any need for reset query.

Default: 0

server_check_delay

How long to keep released connections available for re-use without running sanity-check queries on it. If 0, then the query is run always.

Default: 30.0

server_check_query

A simple do-nothing query to test the server connection.

If an empty string, then sanity checking is disabled.

Default: SELECT 1;

server_fast_close

Disconnect a server in session pooling mode immediately or after the end of the current transaction if it is in “close_needed” mode (set by RECONNECT, RELOAD that changes connection settings, or DNS change), rather than waiting for the session end. In statement or transaction pooling mode, this has no effect since that is the default behavior there.

If because of this setting a server connection is closed before the end of the client session, the client connection is also closed. This ensures that the client notices that the session has been interrupted.

This setting makes connection configuration changes take effect sooner if session pooling and long-running sessions are used. The downside is that client sessions are liable to be interrupted by a configuration change, so client applications will need logic to reconnect and reestablish session state. But note that no transactions will be lost, because running transactions are not interrupted, only idle sessions.

Default: 0

server_lifetime

The pooler tries to close server connections that have been connected longer than this number of seconds. Setting it to 0 means the connection is to be used only once, then closed.

Default: 3600.0

server_idle_timeout

If a server connection has been idle more than this many seconds it is dropped. If this parameter is set to 0, timeout is disabled. [seconds]

Default: 600.0

server_connect_timeout

If connection and login will not finish in this number of seconds, the connection will be closed.

Default: 15.0

server_login_retry

If a login fails due to failure from connect() or authentication, the pooler waits this many seconds before retrying to connect.

Default: 15.0

client_login_timeout

If a client connects but does not manage to login in this number of seconds, it is disconnected. This is needed to avoid dead connections stalling SUSPEND and thus online restart.

Default: 60.0

autodb_idle_timeout

If database pools created automatically (via *) have been unused this many seconds, they are freed. Their statistics are also forgotten.

Default: 3600.0

dns_max_ttl

How long to cache DNS lookups, in seconds. If a DNS lookup returns several answers, PgBouncer round-robins between them in the meantime. The actual DNS TTL is ignored.

Default: 15.0

dns_nxdomain_ttl

How long error and NXDOMAIN DNS lookups can be cached, in seconds.

Default: 15.0

dns_zone_check_period

Period to check if zone serial numbers have changed.

PgBouncer can collect DNS zones from hostnames (everything after first dot) and then periodically check if the zone serial numbers change. If changes are detected, all hostnames in that zone are looked up again. If any host IP changes, its connections are invalidated.

Works only with UDNS and c-ares backend (--with-udns or --with-cares to configure).

Default: 0.0 (disabled)

TLS settings

client_tls_sslmode

TLS mode to use for connections from clients. TLS connections are disabled by default. When enabled, client_tls_key_file and client_tls_cert_file must be also configured to set up the key and certificate PgBouncer uses to accept client connections.

• disable: Plain TCP. If client requests TLS, it’s ignored. Default.
• allow: If client requests TLS, it is used. If not, plain TCP is used. If client uses client-certificate, it is not validated.
• prefer: Same as allow.
• require: Client must use TLS. If not, client connection is rejected. If client uses client-certificate, it is not validated.
• verify-ca: Client must use TLS with valid client certificate.
• verify-full: Same as verify-ca.

client_tls_key_file

Private key for PgBouncer to accept client connections.

Default: not set

client_tls_cert_file

Root certificate file to validate client certificates.

Default: unset

client_tls_ca_file

Root certificate to validate client certificates.

Default: unset

client_tls_protocols

Which TLS protocol versions are allowed.

Valid values: are tlsv1.0, tlsv1.1, tlsv1.2.

Shortcuts: all (tlsv1.0,tlsv1.1,tlsv1.2), secure (tlsv1.2), legacy (all).

Default: secure

client_tls_ciphers

Default: fast

client_tls_ecdhcurve

Elliptic Curve name to use for ECDH key exchanges.

Allowed values: none (DH is disabled), auto (256-bit ECDH), curve name.

Default: auto

client_tls_dheparams

DHE key exchange type.

Allowed values: none (DH is disabled), auto (2048-bit DH), legacy (1024-bit DH).

Default: auto

server_tls_sslmode

TLS mode to use for connections to Greenplum Database and PostgreSQL servers. TLS connections are disabled by default.

• disabled: Plain TCP. TLS is not requested from the server. Default.
• allow: If server rejects plain, try TLS. (PgBouncer Documentation is speculative on this..)
• prefer: TLS connection is always requested first. When connection is refused, plain TPC is used. Server certificate is not validated.
• require: Connection must use TLS. If server rejects it, plain TCP is not attempted. Server certificate is not validated.
• verify-ca: Connection must use TLS and server certificate must be valid according to server_tls_ca_file. The server hostname is not verfied against the certificate.
• verify-full: Connection must use TLS and the server certificate must be valid according to server_tls_ca_file. The server hostname must match the hostname in the certificate.

server_tls_ca_file

Path to the root certificate file used to validate Greenplum Database and PostgreSQL server certificates.

Default: unset

server_tls_key_file

The private key for PgBouncer to authenticate against Greenplum Database or PostgreSQL server.

Default: not set

server_tls_cert_file

Certificate for private key. Greenplum Database or PostgreSQL servers can validate it.

Default: not set

server_tls_protocols

Which TLS protocol versions are allowed.

Valid values are: tlsv1.0, tlsv1.1, tlsv1.2.

Shortcuts: all (tlsv1.0, tlsv1.1, tlsv1.2); secure (tlsv1.2); legacy (all).

Default: secure

server_tls_ciphers

Default: fast

Dangerous Timeouts

Setting the following timeouts can cause unexpected errors.

query_timeout

Queries running longer than this (seconds) are canceled. This parameter should be used only with a slightly smaller server-side statement_timeout, to trap queries with network problems. [seconds]

Default: 0.0 (disabled)

query_wait_timeout

The maximum time, in seconds, queries are allowed to wait for execution. If the query is not assigned a connection during that time, the client is disconnected. This is used to prevent unresponsive servers from grabbing up connections.

Default: 120

client_idle_timeout

Client connections idling longer than this many seconds are closed. This should be larger than the client-side connection lifetime settings, and only used for network problems.

Default: 0.0 (disabled)

idle_transaction_timeout

If client has been in "idle in transaction" state longer than this (seconds), it is disconnected.

Default: 0.0 (disabled)

Low-level Network Settings

pkt_buf

Internal buffer size for packets. Affects the size of TCP packets sent and general memory usage. Actual libpq packets can be larger than this so there is no need to set it large.

Default: 4096

max_packet_size

Maximum size for packets that PgBouncer accepts. One packet is either one query or one result set row. A full result set can be larger.

Default: 2147483647

listen_backlog

Backlog argument for the listen(2) system call. It determines how many new unanswered connection attempts are kept in queue. When the queue is full, further new connection attempts are dropped.

Default: 128

sbuf_loopcnt

How many times to process data on one connection, before proceeding. Without this limit, one connection with a big result set can stall PgBouncer for a long time. One loop processes one pkt_buf amount of data. 0 means no limit.

Default: 5

SO_REUSEPORT

Specifies whether to set the socket option SO_REUSEPORT on TCP listening sockets. On some operating systems, this allows running multiple PgBouncer instances on the same host listening on the same port and having the kernel distribute the connections automatically. This option is a way to get PgBouncer to use more CPU cores. (PgBouncer is single-threaded and uses one CPU core per instance.)

The behavior in detail depends on the operating system kernel. As of this writing, this setting has the desired effect on recent versions of Linux. On systems that don’t support the socket option at all, turning this setting on will result in an error.

Each PgBouncer instance on the same host needs different settings for at least unix_socket_dir and pidfile, as well as logfile if that is used. Also note that if you make use of this option, you can no longer connect to a specific PgBouncer instance via TCP/IP, which might have implications for monitoring and metrics collection.

Default: 0

suspend_timeout

How many seconds to wait for buffer flush during SUSPEND or restart (-R). Connection is dropped if flush does not succeed.

Default: 10

tcp_defer_accept

For details on this and other TCP options, please see the tcp(7) man page.

Default: 45 on Linux, otherwise 0

tcp_socket_buffer

Default: not set

tcp_keepalive

Turns on basic keepalive with OS defaults.

On Linux, the system defaults are tcp_keepidle=7200, tcp_keepintvl=75, tcp_keepcnt=9.

Default: 1

tcp_keepcnt

Default: not set

tcp_keepidle

Default: not set

tcp_keepintvl

Default: not set

tcp_user_timeout

Sets the TCP_USER_TIMEOUT socket option. This specifies the maximum amount of time in milliseconds that transmitted data may remain unacknowledged before the TCP connection is forcibly closed. If set to 0, then operating system’s default is used.

Default: 0