Specifies the log file. For daemonization (-d), either this or syslog need to be set.

The log file is kept open, so after rotation, kill -HUP or on console RELOAD; should be done. On Windows, the service must be stopped and started.

Note that setting logfile does not by itself turn off logging to stderr. Use the command-line option -q or -d for that.

Default: not set

Specifies the PID file. Without pidfile set, daemonization (-d) is not allowed.

Default: not set

Specifies a list (comma-separated) of addresses where to listen for TCP connections. You may also use * meaning “listen on all addresses”. When not set, only Unix socket connections are accepted.

Addresses can be specified numerically (IPv4/IPv6) or by name.

Default: not set

Which port to listen on. Applies to both TCP and Unix sockets.

Default: 6432

Specifies the location for Unix sockets. Applies to both the listening socket and to server connections. If set to an empty string, Unix sockets are disabled. A value that starts with @ specifies that a Unix socket in the abstract namespace should be created (currently supported on Linux and Windows).

For online reboot (-R) to work, a Unix socket needs to be configured, and it needs to be in the file-system namespace.

Default: /tmp (empty on Windows)

File system mode for Unix socket. Ignored for sockets in the abstract namespace. Not supported on Windows.

Default: 0777

Group name to use for Unix socket. Ignored for sockets in the abstract namespace. Not supported on Windows.

Default: not set

If set, specifies the Unix user to change to after startup. Works only if PgBouncer is started as root or if it’s already running as the given user. Not supported on Windows.

Default: not set

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

Maximum number of client connections allowed.

When this setting is increased, then the file descriptor limits in the operating system might also have to be increased. Note that the number of file descriptors potentially used is more than max_client_conn. If each user connects under its own user name to the server, the theoretical maximum used is:

max_client_conn + (max pool_size * total databases * total users)

If a database user is specified in the connection string (all users connect under the same user name), the theoretical maximum is:

max_client_conn + (max pool_size * total databases)

The theoretical maximum should never be reached, unless somebody deliberately crafts a special load for it. Still, it means you should set the number of file descriptors to a safely high number.

Search for ulimit in your favorite shell man page.

Default: 100

How many server connections to allow per user/database pair. Can be overridden in the per-database configuration.

Default: 20

Add more server connections to pool if below this number. Improves behavior when the normal load suddenly comes back after a period of total inactivity. The value is effectively capped at the pool size.

Only enforced for pools where at least one of the following is true:

Default: 0 (disabled)

How many additional connections to allow to a pool (see reserve_pool_timeout). 0 disables.

Default: 0 (disabled)

If a client has not been serviced in this time, use additional connections from the reserve pool. 0 disables. [seconds]

Default: 5.0

Do not allow more than this many server connections per database (regardless of user). This considers the PgBouncer database that the client has connected to, not the Tantor BE database of the outgoing connection.

This can also be set per database in the [databases] section.

Note that when you hit the limit, closing a client connection to one pool will 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 immediately be opened for the waiting pool.

Default: 0 (unlimited)

Do not allow more than this many server connections per user (regardless of database). This considers the PgBouncer user that is associated with a pool, which is either the user specified for the server connection or in absence of that the user the client has connected as.

This can also be set per user in the [users] section.

Note that when you hit the limit, closing a client connection to one pool will 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 immediately be opened for the waiting pool.

Default: 0 (unlimited)

By default, PgBouncer reuses server connections in LIFO (last-in, first-out) manner, so that few connections get the most load. This gives best performance if you have a single server serving a database. But if there is a round-robin system behind a database address (TCP, DNS, or host list), then it is better if PgBouncer also uses connections in that manner, thus achieving uniform load.

Default: 0

By default, PgBouncer tracks client_encoding, datestyle, timezone, standard_conforming_strings and application_name parameters per client. To allow other parameters to be tracked, they can be specified here, so that PgBouncer knows that they should be maintained in the client variable cache and restored in the server whenever the client becomes active.

If you need to specify multiple values, use a comma-separated list (e.g. default_transaction_read_only, IntervalStyle)

The Postgres protocol allows specifying parameters settings, both directly as a parameter in the startup packet, or inside the options startup packet. Parameters specified using both of these methods are supported by track_extra_parameters. However, it’s not possible to include options itself in track_extra_parameters, only the parameters contained in options.

Default: IntervalStyle

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 will raise an error. To allow others parameters, they can be specified here, so that PgBouncer knows that they are handled by the admin and it can ignore them.

If you need to specify multiple values, use a comma-separated list (e.g. options,extra_float_digits)

The Postgres protocol allows specifying parameters settings, both directly as a parameter in the startup packet, or inside the options startup packet. Parameters specified using both of these methods are supported by ignore_startup_parameters. It’s even possible to include options itself in track_extra_parameters, which results in any unknown parameters contained inside options to be ignored.

Default: empty

The peer id used to identify this PgBouncer process in a group of PgBouncer processes that are peered together. The peer_id value should be unique within a group of peered PgBouncer processes. When set to 0 pgbouncer peering is disabled. See the docs for the [peers] section for more information. The maximum value that can be used for the peer_id is 16383.

Default: 0

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

Default: 0

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 etc. This logic applies only at the start of a connection. If application_name is later changed with SET, PgBouncer does not change it again.

Default: 0

Show location of current config file. Changing it will make PgBouncer use another config file for next RELOAD / SIGHUP.

Default: file from command line

Used on win32 service registration.

Default: pgbouncer

Alias for service_name.

Sets how often the averages shown in various SHOW commands are updated and how often aggregated statistics are written to the log (but see log_stats). [seconds]

Default: 60

When this is set to a non-zero value PgBouncer tracks protocol-level named prepared statements related commands sent by the client in transaction and statement pooling mode. PgBouncer makes sure that any statement prepared by a client is available on the backing server connection. Even when the statement was originally prepared on another server connection.

PgBouncer internally examines all the queries that are sent by clients as a prepared statement, and gives each unique query string an internal name with the format PGBOUNCER_{unique_id}. If the same query string is prepared multiple times (possibly by different clients), then these queries share the same internal name. PgBouncer only prepares the statement on the actual Tantor BE server using the internal name (so not the name provided by the client). PgBouncer keeps track of the name that the client gave to each prepared statement. It then rewrites each command that uses a prepared statement to by replacing the client side name with the the internal name (e.g. replacing my_prepared_statement with PGBOUNCER_123) before forwarding that command to the server. More importantly, if the prepared statement that the client wants to execute is not yet prepared on the server (e.g. because a different server is now assigned to the client than when the client prepared the statement), then PgBouncer transparently prepares the statement before executing it.

The actual value of this setting controls the number of prepared statements kept active in an LRU cache on a single server connection. When the setting is set to 0 prepared statement support for transaction and statement pooling is disabled. To get the best performance you should try to make sure that this setting is larger than the amount of commonly used prepared statements in your application. Keep in mind that the higher this value, the larger the memory footprint of each PgBouncer connection will be on your Tantor BE server, because it will keep more queries prepared on those connections. It also increases the memory footprint of PgBouncer itself, because it now needs to keep track of query strings.

The impact on PgBouncer memory usage is not that big though:

So if you consider the following as an example scenario:

Then, PgBouncer needs at most the following amount of memory to handle these prepared statements:

200 x 5kB + 1000 x 4 x 4kB = ~17MB of memory.

Tracking prepared statements does not only come with a memory cost, but also with increased CPU usage, because PgBouncer needs to inspect and rewrite the queries. Multiple PgBouncer instances can listen on the same port to use more than one core for processing, see the documentation for the so_reuseport option for details.

But of course there are also performance benefits to prepared statements. Just as when connecting to Tantor BE directly, by preparing a query that is executed many times, it reduces the total amount of parsing and planning that needs to be done. The way that PgBouncer tracks prepared statements is especially beneficial to performance when multiple clients prepare the same queries. Because client connections automatically reuse a prepared statement on a server connection, even if it was prepared by another client. As an example, if you have a pool_size of 20 and you have 100 clients that all prepare the exact same query, then the query is prepared (and thus parsed) only 20 times on the Tantor BE server.

The reuse of prepared statements has one downside. If the return or argument types of a prepared statement changes across executions then Tantor BE currently throws an error such as:

ERROR:  cached plan must not change result type

You can avoid such errors by not having multiple clients that use the exact same query string in a prepared statement, but expecting different argument or result types. One of the most common ways of running into this issue is during a DDL migration where you add a new column or change a column type on an existing table. In those cases you can run RECONNECT on the PgBouncer admin console after doing the migration to force a re-prepare of the query and make the error go away.

Default: 0

How to authenticate users.

HBA configuration file to use when auth_type is hba. See section HBA file format below about details.

Default: not set

Identity map file to use when auth_type is hba and a user map will be defined. See section Ident map file format below about details.

Default: not set

The name of the file to load user names and passwords from. See section Authentication file format below about details.

Most authentication types (see above) require that either auth_file or auth_user be set; otherwise there would be no users defined.

Default: not set

If auth_user is set, then any user not specified in auth_file will be queried through the auth_query query from pg_shadow in the database, using auth_user. The password of auth_user will be taken from auth_file. (If the auth_user does not require a password then it does not need to be defined in auth_file.)

Direct access to pg_shadow requires admin rights. It’s preferable to use a non-superuser that calls a SECURITY DEFINER function instead.

Default: not set

Query to load user’s password from database.

Direct access to pg_shadow requires admin rights. It’s preferable to use a non-superuser that calls a SECURITY DEFINER function instead.

Note that the query is run inside the 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

Database name in the [database] section to be used for authentication purposes. This option can be either global or overridden in the connection string if this parameter is specified.

Toggles syslog on/off. On Windows, the event log is used instead.

Default: 0

Under what name to send logs to syslog.

Default: pgbouncer (program name)

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

Default: daemon

Log successful logins.

Default: 1

Log disconnections with reasons.

Default: 1

Log error messages the pooler sends to clients.

Default: 1

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

Increase verbosity. Mirrors the “-v” switch on the command line. For example, using “-v -v” on the command line is the same as verbose=2.

Default: 0

Comma-separated list of database users that are allowed to connect and run all commands on the console. Ignored when auth_type is any, in which case any user name is allowed in as admin.

Default: empty

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

Default: empty

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

The query is supposed to clean any changes made to the database session so that the next client gets the connection in a well-defined state. The default is DISCARD ALL, which cleans everything, but that leaves the next client no pre-cached state. It can be made lighter, e.g. DEALLOCATE ALL to just drop prepared statements, if the application does not break when some state is kept around.

When transaction pooling is used, the server_reset_query is not used, because in that mode, clients must not use any session-based features, since each transaction ends up in a different connection and thus gets a different session state.

Default: DISCARD ALL

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 a reset query.

This setting is for working around broken setups that run applications that use session features over a transaction-pooled PgBouncer. It changes non-deterministic breakage to deterministic breakage: Clients always lose their state after each transaction.

Default: 0

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

Default: 30.0

Simple do-nothing query to check if the server connection is alive.

If an empty string, then sanity checking is disabled.

Default: select 1

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

The pooler will close an unused (not currently linked to any client connection) server connection that has been connected longer than this. Setting it to 0 means the connection is to be used only once, then closed. [seconds]

This can also be set per database in the [databases] section.

Default: 3600.0

If a server connection has been idle more than this many seconds it will be closed. If 0 then this timeout is disabled. [seconds]

Default: 600.0

If connection and login don’t finish in this amount of time, the connection will be closed. [seconds]

Default: 15.0

If login to the server failed, because of failure to connect or from authentication, the pooler waits this much before retrying to connect. During the waiting interval, new clients trying to connect to the failing server will get an error immediately without another connection attempt. [seconds]

The purpose of this behavior is that clients don’t unnecessarily queue up waiting for a server connection to become available if the server is not working. However, it also means that if a server is momentarily failing, for example during a restart or if the configuration was erroneous, then it will take at least this long until the pooler will consider connecting to it again. Planned events such as restarts should normally be managed using the PAUSE command to avoid this.

Default: 15.0

If a client connects but does not manage to log in in this amount of time, it will be disconnected. Mainly needed to avoid dead connections stalling SUSPEND and thus online restart. [seconds]

Default: 60.0

If the automatically created (via “*”) database pools have been unused this many seconds, they are freed. The negative aspect of that is that their statistics are also forgotten. [seconds]

Default: 3600.0

How long DNS lookups can be cached. The actual DNS TTL is ignored. [seconds]

Default: 15.0

How long DNS errors and NXDOMAIN DNS lookups can be cached. [seconds]

Default: 15.0

Period to check if a zone serial has changed.

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

Works only with c-ares backend (configure option --with-cares).

Default: 0.0 (disabled)

The location of a custom resolv.conf file. This is to allow specifying custom DNS servers and perhaps other name resolution options, independent of the global operating system configuration.

Requires evdns (>= 2.0.3) or c-ares (>= 1.15.0) backend.

The parsing of the file is done by the DNS backend library, not PgBouncer, so see the library’s documentation for details on allowed syntax and directives.

Default: empty (use operating system defaults)

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. The most common certificate file format usable by PgBouncer is pem.

Private key for PgBouncer to accept client connections.

Default: not set

Certificate for private key. Clients can validate it.

Default: not set

Root certificate file to validate client certificates.

Default: not set

Which TLS protocol versions are allowed. Allowed values: tlsv1.0, tlsv1.1, tlsv1.2, tlsv1.3. Shortcuts: all (tlsv1.0,tlsv1.1,tlsv1.2,tlsv1.3), secure (tlsv1.2,tlsv1.3), legacy (all).

Default: secure

Allowed TLS ciphers, in OpenSSL syntax. Shortcuts:

Only connections using TLS version 1.2 and lower are affected. There is currently no setting that controls the cipher choices used by TLS version 1.3 connections.

Default: default

Elliptic Curve name to use for ECDH key exchanges.

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

Default: auto

DHE key exchange type.

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

Default: auto

TLS mode to use for connections to Tantor BE servers. The default mode is prefer.

Root certificate file to validate Tantor BE server certificates.

Default: not set

Private key for PgBouncer to authenticate against Tantor BE server.

Default: not set

Certificate for private key. Tantor BE server can validate it.

Default: not set

Which TLS protocol versions are allowed. Allowed values: tlsv1.0, tlsv1.1, tlsv1.2, tlsv1.3. Shortcuts: all (tlsv1.0,tlsv1.1,tlsv1.2,tlsv1.3), secure (tlsv1.2,tlsv1.3), legacy (all).

Default: secure

Allowed TLS ciphers, in OpenSSL syntax. Shortcuts:

Only connections using TLS version 1.2 and lower are affected. There is currently no setting that controls the cipher choices used by TLS version 1.3 connections.

Default: default

Queries running longer than that are canceled. This should be used only with a slightly smaller server-side statement_timeout, to apply only for network problems. [seconds]

Default: 0.0 (disabled)

Maximum time queries are allowed to spend waiting for execution. If the query is not assigned to a server during that time, the client is disconnected. 0 disables. If this is disabled, clients will be queued indefinitely. [seconds]

This setting is used to prevent unresponsive servers from grabbing up connections. It also helps when the server is down or rejects connections for any reason.

Default: 120.0

Maximum time cancellation requests are allowed to spend waiting for execution. If the cancel request is not assigned to a server during that time, the client is disconnected. 0 disables. If this is disabled, cancel requests will be queued indefinitely. [seconds]

This setting is used to prevent a client locking up when a cancel cannot be forwarded due to the server being down.

Default: 10.0

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. [seconds]

Default: 0.0 (disabled)

If a client has been in “idle in transaction” state longer, it will be disconnected. [seconds]

Default: 0.0 (disabled)

How long to wait for buffer flush during SUSPEND or reboot (-R). A connection is dropped if the flush does not succeed. [seconds]

Default: 10

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

Default: 4096

Maximum size for Tantor BE packets that PgBouncer allows through. One packet is either one query or one result set row. The full result set can be larger.

Default: 2147483647

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

Default: 128

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

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 (sufficiently recent versions of) Linux, DragonFlyBSD, and FreeBSD. (On FreeBSD, it applies the socket option SO_REUSEPORT_LB instead.) Some other operating systems support the socket option but it won’t have the desired effect: It will allow multiple processes to bind to the same port but only one of them will get the connections. See your operating system’s setsockopt() documentation for details.

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.

To make sure query cancellations keep working, you should set up PgBouncer peering between the different PgBouncer processes. For details look at docs for the peer_id configuration option and the peers configuration section. There’s also an example that uses peering and so_reuseport in the example section of these docs.

Default: 0

Sets the TCP_DEFER_ACCEPT socket option; see man 7 tcp for details. (This is a Boolean option: 1 means enabled. The actual value set if enabled is currently hardcoded to 45 seconds.)

This is currently only supported on Linux.

Default: 1 on Linux, otherwise 0

Default: not set

Turns on basic keepalive with OS defaults.

On Linux, the system defaults are tcp_keepidle=7200, tcp_keepintvl=75, tcp_keepcnt=9. They are probably similar on other operating systems.

Default: 1

Default: not set

Default: not set

Default: not set

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.

This is currently only supported on Linux.

Default: 0

Destination database name.

Default: same as client-side database name

Host name or IP address to connect to. Host names are resolved at connection time, the result is cached per dns_max_ttl parameter. When a host name’s resolution changes, existing server connections are automatically closed when they are released (according to the pooling mode), and new server connections immediately use the new resolution. If DNS returns several results, they are used in a round-robin manner.

If the value begins with /, then a Unix socket in the file-system namespace is used. If the value begins with @, then a Unix socket in the abstract namespace is used.

A comma-separated list of host names or addresses can be specified. In that case, connections are made in a round-robin manner. (If a host list contains host names that in turn resolve via DNS to multiple addresses, the round-robin systems operate independently. This is an implementation dependency that is subject to change.) Note that in a list, all hosts must be available at all times: There are no mechanisms to skip unreachable hosts or to select only available hosts from a list or similar. (This is different from what a host list in libpq means.) Also note that this only affects how the destinations of new connections are chosen. See also the setting server_round_robin for how clients are assigned to already established server connections.

Examples:

host=localhost
host=127.0.0.1
host=2001:0db8:85a3:0000:0000:8a2e:0370:7334
host=/var/run/postgresql
host=192.168.0.1,192.168.0.2,192.168.0.3

Default: not set, meaning to use a Unix socket

Default: 5432

If user= is set, all connections to the destination database will be done with the specified user, meaning that there will be only one pool for this database.

Otherwise, PgBouncer logs into the destination database with the client user name, meaning that there will be one pool per user.

If no password is specified here, the password from the auth_file will be used for the user specified above. Dynamic forms of password discovery such as auth_query are not currently supported.

Override of the global auth_user setting, if specified.

Override of the global auth_query setting, if specified. The entire SQL statement needs to be enclosed in single quotes.

Override of the global auth_dbname setting, if specified.

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

Set the minimum pool size for this database. If not set, the global min_pool_size is used.

Only enforced if at least one of the following is true:

Set additional connections for this database. If not set, reserve_pool_size is used.

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.

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

Configure a database-wide maximum (i.e. all pools within the database will not have more than this many server connections).

Configure the server_lifetime per database. If not set the database will fall back to the instance wide configured value for server_lifetime

Ask specific client_encoding from server.

Ask specific datestyle from server.

Ask specific timezone from server.

Set the maximum size of pools for all connections from this user. If not set, the database or default_pool_size is used.

Set the pool mode to be used for all connections from this user. If not set, the database or default pool_mode is used.

Configure a maximum for the user (i.e. all pools with the user will not have more than this many server connections).

Host name or IP address to connect to. Host names are resolved at connection time, the result is cached per dns_max_ttl parameter. If DNS returns several results, they are used in a round-robin manner. But in general it’s not recommended to use a hostname that resolves to multiple IPs, because then the cancel request might still be forwarded to the wrong node and it would need to be forwarded again (which is only allowed up to three times).

If the value begins with /, then a Unix socket in the file-system namespace is used. If the value begins with @, then a Unix socket in the abstract namespace is used.

Examples:

host=localhost
host=127.0.0.1
host=2001:0db8:85a3:0000:0000:8a2e:0370:7334
host=/var/run/pgbouncer-1

Default: 6432

Set the maximum number of cancel requests that can be in flight to the peer at the same time. It’s quite normal for cancel requests to arrive in bursts, e.g. when the backing Postgres server slow or down. So it’s important for pool_size to not be so low that it cannot handle these bursts.

If not set, the default_pool_size is used.

If the password is stored in plain text, it can be used for any password-based authentication used in the backend server; plain text, MD5 or SCRAM (see Password Authentication for details).

MD5-hashed passwords can be used if backend server uses MD5 authentication (or specific users have MD5-hashed passwords).

SCRAM secrets can only be used for logging into a server if the client authentication also uses SCRAM, the PgBouncer database definition does not specify a user name, and the SCRAM secrets are identical in PgBouncer and the Tantor BE server (same salt and iterations, not merely the same password). This is due to an inherent security property of SCRAM: The stored SCRAM secret cannot by itself be used for deriving login credentials.

The authentication file can be written by hand, but it’s also useful to generate it from some other list of users and passwords. See ./etc/mkauth.py for a sample script to generate the authentication file from the pg_shadow system table. Alternatively, use auth_query instead of auth_file to avoid having to maintain a separate authentication file.

If the backend server is configured to use SCRAM password authentication PgBouncer cannot successfully authenticate if it does not know either a) user password in plain text or b) corresponding SCRAM secret.

Some cloud providers (i.e. AWS RDS) prohibit access to Tantor BE sensitive system tables for fetching passwords. Even for the most privileged user (i.e. member of rds_superuser) the select * from pg_authid; returns the ERROR: permission denied for table pg_authid. That is a known behaviour (blog).

Therefore, fetching an existing SCRAM secret once it has been stored in a managed server is impossible which makes it hard to configure PgBouncer to use the same SCRAM secret. Nevertheless, SCRAM secret can still be configured and used on both sides using the following trick:

Generate SCRAM secret for arbitrary password with a tool that is capable of printing out the secret. For example psql --echo-hidden and the command \password prints out the SCRAM secret to the console before sending it over to the server.

$ psql --echo-hidden <connection_string>
postgres=# \password <role_name>
Enter new password for user "<role_name>": 
Enter it again: 
********* QUERY **********
ALTER USER <role_name> PASSWORD 'SCRAM-SHA-256$<iterations>:<salt>$<storedkey>:<serverkey>'
**************************

Note down the SCRAM secret from the QUERY and set it in PgBouncer’s userlist.txt.

If you used a tool other than psql --echo-hidden then you need to set the SCRAM secret also in the server (you can use alter role <role_name> password '<scram_secret>' for that).

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

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.

The proper way to do it for JDBC is adding the prepareThreshold=0 parameter to the connection string.

To disable use of server-side prepared statements, the PDO attribute PDO::ATTR_EMULATE_PREPARES must be set to true. Either at connect-time:

$db = new PDO("dsn", "user", "pass", array(PDO::ATTR_EMULATE_PREPARES => true));

or later:

$db->setAttribute(PDO::ATTR_EMULATE_PREPARES, true);