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# PostgresSQL Server Exporter

Prometheus exporter for PostgresSQL server metrics.
Supported Postgres versions: 9.1 and up.

## 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 -e DATA_SOURCE_NAME="postgresql://postgres:password@localhost:5432/?sslmode=disable" -p 9113:9113 wrouesnel/postgres_exporter
```

## Building and running
The default make file behavior is to build the binary:
```
make
export DATA_SOURCE_NAME="postgresql://login:password@hostname:port/dbname"
./postgres_exporter <flags>
```

To build the dockerfile, run `make 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`](https://github.com/kardianos/govendor)

### Flags

* `web.listen-address` 
  Address to listen on for web interface and telemetry.

* `web.telemetry-path`
  Path under which to expose metrics.

* `config.expect-replication-stats`
  The target database has replication turned on - log errors when
  replication stats are missing.

### Setting the Postgres server's data source name

The PostgresSQL server's [data source name](http://en.wikipedia.org/wiki/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

See the [github.com/lib/pq](http://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:

```python
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](queries.yaml).

### 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 to do so.

```sql
CREATE USER postgres_exporter PASSWORD 'password';
ALTER USER postgres_exporter SET SEARCH_PATH TO postgres_exporter,pg_catalog;

CREATE SCHEMA postgres_exporter AUTHORIZATION postgres_exporter;

CREATE FUNCTION postgres_exporter.f_select_pg_stat_activity()
RETURNS setof pg_catalog.pg_stat_activity
LANGUAGE sql
SECURITY DEFINER
AS $$
  SELECT * from pg_catalog.pg_stat_activity;
$$;

CREATE FUNCTION postgres_exporter.f_select_pg_stat_replication()
RETURNS setof pg_catalog.pg_stat_replication
LANGUAGE sql
SECURITY DEFINER
AS $$
  SELECT * from pg_catalog.pg_stat_replication;
$$;

CREATE VIEW postgres_exporter.pg_stat_replication
AS
  SELECT * FROM postgres_exporter.f_select_pg_stat_replication();

CREATE VIEW postgres_exporter.pg_stat_activity
AS
  SELECT * FROM postgres_exporter.f_select_pg_stat_activity();

GRANT SELECT ON postgres_exporter.pg_stat_replication TO postgres_exporter;
GRANT SELECT ON postgres_exporter.pg_stat_activity TO postgres_exporter;
```