PostgreSQL Server Exporter

Prometheus exporter for PostgreSQL server metrics.

CI Tested PostgreSQL versions: 9.4, 9.5, 9.6, 10, 11

Quick Start

This package is available for Docker:

# Start an example database
docker run --net=host -it --rm -e POSTGRES_PASSWORD=password postgres
# Connect to it
docker run --net=host -e DATA_SOURCE_NAME="postgresql://postgres:password@localhost:5432/postgres?sslmode=disable" wrouesnel/postgres_exporter

Building and running

The build system is based on Mage

The default make file behavior is to build the binary:

$ go get github.com/wrouesnel/postgres_exporter
$ cd ${GOPATH-$HOME/go}/src/github.com/wrouesnel/postgres_exporter
$ go run mage.go binary
$ export DATA_SOURCE_NAME="postgresql://#:password@hostname:port/dbname"
$ ./postgres_exporter <flags>

To build the dockerfile, run go run mage.go docker.

This will build the docker image as wrouesnel/postgres_exporter:latest. This is a minimal docker image containing just postgres_exporter. By default no SSL certificates are included, if you need to use SSL you should either bind-mount /etc/ssl/certs/ca-certificates.crt or derive a new image containing them.

Vendoring

Package vendoring is handled with govendor

Flags

• web.listen-address Address to listen on for web interface and telemetry. Default is :9187.

• web.telemetry-path Path under which to expose metrics. Default is /metrics.

• disable-default-metrics Use only metrics supplied from queries.yaml via --extend.query-path.

• disable-settings-metrics Use the flag if you don't want to scrape pg_settings.

• extend.query-path Path to a YAML file containing custom queries to run. Check out queries.yaml for examples of the format.

• dumpmaps Do not run - print the internal representation of the metric maps. Useful when debugging a custom queries file.

• log.level Set logging level: one of debug, info, warn, error, fatal

• log.format Set the log output target and format. e.g. logger:syslog?appname=bob&local=7 or logger:stdout?json=true Defaults to logger:stderr.

• constantLabels Labels to set in all metrics. A list of label=value pairs, separated by commas.

Environment Variables

The following environment variables configure the exporter:

• DATA_SOURCE_NAME the default legacy format. Accepts URI form and key=value form arguments. The URI may contain the username and password to connect with.

• DATA_SOURCE_URI an alternative to DATA_SOURCE_NAME which exclusively accepts the raw URI without a username and password component.

• DATA_SOURCE_USER When using DATA_SOURCE_URI, this environment variable is used to specify the username.

• DATA_SOURCE_USER_FILE The same, but reads the username from a file.

• DATA_SOURCE_PASS When using DATA_SOURCE_URI, this environment variable is used to specify the password to connect with.

• DATA_SOURCE_PASS_FILE The same as above but reads the password from a file.

• PG_EXPORTER_WEB_LISTEN_ADDRESS Address to listen on for web interface and telemetry. Default is :9187.

• PG_EXPORTER_WEB_TELEMETRY_PATH Path under which to expose metrics. Default is /metrics.

• PG_EXPORTER_DISABLE_DEFAULT_METRICS Use only metrics supplied from queries.yaml. Value can be true or false. Default is false.

• PG_EXPORTER_DISABLE_SETTINGS_METRICS Use the flag if you don't want to scrape pg_settings. Value can be true or false. Defauls is false.

• PG_EXPORTER_EXTEND_QUERY_PATH Path to a YAML file containing custom queries to run. Check out queries.yaml for examples of the format.

• PG_EXPORTER_CONSTANT_LABELS Labels to set in all metrics. A list of label=value pairs, separated by commas.

Settings set by environment variables starting with PG_ will be overwritten by the corresponding CLI flag if given.

Setting the Postgres server's data source name

The PostgreSQL server's data source name must be set via the DATA_SOURCE_NAME environment variable.

For running it locally on a default Debian/Ubuntu install, this will work (transpose to init script as appropriate):

sudo -u postgres DATA_SOURCE_NAME="user=postgres host=/var/run/postgresql/ sslmode=disable" postgres_exporter

Also, you can set a list of sources to scrape different instances from the one exporter setup. Just define a comma separated string.

sudo -u postgres DATA_SOURCE_NAME="port=5432,port=6432" postgres_exporter

See the github.com/lib/pq module for other ways to format the connection string.

Adding new metrics

The exporter will attempt to dynamically export additional metrics if they are added in the future, but they will be marked as "untyped". Additional metric maps can be easily created from Postgres documentation by copying the tables and using the following Python snippet:

x = """tab separated raw text of a documentation table"""
for l in StringIO(x):
    column, ctype, description = l.split('\t')
    print """"{0}" : {{ prometheus.CounterValue, prometheus.NewDesc("pg_stat_database_{0}", "{2}", nil, nil) }}, """.format(column.strip(), ctype, description.strip())

Adjust the value of the resultant prometheus value type appropriately. This helps build rich self-documenting metrics for the exporter.

Adding new metrics via a config file

The -extend.query-path command-line argument specifies a YAML file containing additional queries to run. Some examples are provided in queries.yaml.

Disabling default metrics

To work with non-officially-supported postgres versions you can try disabling (e.g. 8.2.15) or a variant of postgres (e.g. Greenplum) you can disable the default metrics with the --disable-default-metrics flag. This removes all built-in metrics, and uses only metrics defined by queries in the queries.yaml file you supply (so you must supply one, otherwise the exporter will return nothing but internal statuses and not your database).

Automatically discover databases

To scrape metrics from all databases on a database server, the database DSN's can be dynamically discovered via the --auto-discover-databases flag. When true, SELECT datname FROM pg_database WHERE datallowconn = true AND datistemplate = false is run for all configured DSN's. From the result a new set of DSN's is created for which the metrics are scraped.

In addition, the option --exclude-databases adds the possibily to filter the result from the auto discovery to discard databases you do not need.

Running as non-superuser

To be able to collect metrics from pg_stat_activity and pg_stat_replication as non-superuser you have to create functions and views as a superuser, and assign permissions separately to those.

In PostgreSQL, views run with the permissions of the user that created them so they can act as security barriers. Functions need to be created to share this data with the non-superuser. Only creating the views will leave out the most important bits of data.

-- To use IF statements, hence to be able to check if the user exists before
-- attempting creation, we need to switch to procedural SQL (PL/pgSQL)
-- instead of standard SQL.
-- More: https://www.postgresql.org/docs/9.3/plpgsql-overview.html
-- To preserve compatibility with <9.0, DO blocks are not used; instead,
-- a function is created and dropped.
CREATE OR REPLACE FUNCTION __tmp_create_user() returns void as $$
BEGIN
  IF NOT EXISTS (
          SELECT                       -- SELECT list can stay empty for this
          FROM   pg_catalog.pg_user
          WHERE  usename = 'postgres_exporter') THEN
    CREATE USER postgres_exporter;
  END IF;
END;
$$ language plpgsql;

SELECT __tmp_create_user();
DROP FUNCTION __tmp_create_user();

ALTER USER postgres_exporter WITH PASSWORD 'password';
ALTER USER postgres_exporter SET SEARCH_PATH TO postgres_exporter,pg_catalog;

-- If deploying as non-superuser (for example in AWS RDS), uncomment the GRANT
-- line below and replace <MASTER_USER> with your root user.
-- GRANT postgres_exporter TO <MASTER_USER>;
CREATE SCHEMA IF NOT EXISTS postgres_exporter;
GRANT USAGE ON SCHEMA postgres_exporter TO postgres_exporter;
GRANT CONNECT ON DATABASE postgres TO postgres_exporter;

CREATE OR REPLACE FUNCTION get_pg_stat_activity() RETURNS SETOF pg_stat_activity AS
$$ SELECT * FROM pg_catalog.pg_stat_activity; $$
LANGUAGE sql
VOLATILE
SECURITY DEFINER;

CREATE OR REPLACE VIEW postgres_exporter.pg_stat_activity
AS
  SELECT * from get_pg_stat_activity();

GRANT SELECT ON postgres_exporter.pg_stat_activity TO postgres_exporter;

CREATE OR REPLACE FUNCTION get_pg_stat_replication() RETURNS SETOF pg_stat_replication AS
$$ SELECT * FROM pg_catalog.pg_stat_replication; $$
LANGUAGE sql
VOLATILE
SECURITY DEFINER;

CREATE OR REPLACE VIEW postgres_exporter.pg_stat_replication
AS
  SELECT * FROM get_pg_stat_replication();

GRANT SELECT ON postgres_exporter.pg_stat_replication TO postgres_exporter;

NOTE
Remember to use postgres database name in the connection string:

DATA_SOURCE_NAME=postgresql://postgres_exporter:password@localhost:5432/postgres?sslmode=disable

Hacking

• To build a copy for your current architecture run go run mage.go binary or just go run mage.go This will create a symlink to the just built binary in the root directory.
• To build release tar balls run go run mage.go release.
• Build system is a bit temperamental at the moment since the conversion to mage - I am working on getting it to be a perfect out of the box experience, but am time-constrained on it at the moment.