pg_exporter

A PostgreSQL metric exporter for Prometheus written in Rust

Goals

pg_exporter is designed with a selective metrics approach:

• Modular collectors – Expose only the metrics you actually need instead of collecting everything by default.
• Avoid unnecessary metrics – Prevent exposing large numbers of unused metrics to Prometheus, reducing load and keeping monitoring efficient.
• Customizable collectors – Tailor the metrics to your specific requirements while maintaining compatibility with the official postgres_exporter.
• Low memory footprint – Designed to minimize memory usage and maximize efficiency while scraping metrics.

Download or build

Install via Cargo:

cargo install pg_exporter

Or download the latest release from the releases page.

Docker/Podman

Container images are available at ghcr.io/nbari/pg_exporter:

# Using Docker
docker run -d \
  -e PG_EXPORTER_DSN="postgresql://postgres_exporter@postgres-host:5432/postgres" \
  -p 9432:9432 \
  ghcr.io/nbari/pg_exporter:latest

# Using Podman
podman run -d \
  -e PG_EXPORTER_DSN="postgresql://postgres_exporter@postgres-host:5432/postgres" \
  -p 9432:9432 \
  ghcr.io/nbari/pg_exporter:latest

Connecting to host PostgreSQL from container:

• Docker Desktop (Mac/Windows): use host.docker.internal instead of localhost
• Podman: use host.containers.internal instead of localhost
• Linux with --network=host: use localhost directly

Example with host connection:

podman run -d \
  -e PG_EXPORTER_DSN="postgresql://postgres_exporter@host.containers.internal:5432/postgres" \
  -p 9432:9432 \
  ghcr.io/nbari/pg_exporter:latest

Usage

Run the exporter and use the socket directory:

pg_exporter --dsn postgresql:///postgres?host=/var/run/postgresql&user=postgres_exporter

in pg_hba.conf you need to allow the user postgres_exporter to connect, for example:

local  all  postgres_exporter  trust

Security Best Practices

Instead of using trust authentication (which allows connection without password), it is recommended to use peer authentication for local connections. This requires creating a system user named postgres_exporter.

1. Create the system user:

   sudo useradd -r -d /nonexistent -s /usr/bin/nologin postgres_exporter

2. Configure pg_hba.conf to use peer authentication:

   local  all  postgres_exporter  peer
   

3. Run the exporter as the postgres_exporter user:

   sudo -u postgres_exporter pg_exporter --dsn postgresql:///postgres?host=/var/run/postgresql&user=postgres_exporter

This ensures that only the system user postgres_exporter can connect to the database as the postgres_exporter role, significantly improving security.

You can also specify a custom port, for example 9187:

pg_exporter --dsn postgresql://postgres_exporter@localhost:5432/postgres --port 9187

Environment Variables

pg_exporter supports standard PostgreSQL environment variables for connection configuration. This is useful when you want to avoid putting sensitive information like passwords in the DSN or command line arguments.

Supported variables include:

• PGHOST
• PGPORT
• PGUSER
• PGPASSWORD
• PGDATABASE

Example usage with PGPASSWORD:

PGPASSWORD=secret pg_exporter --dsn postgresql://postgres@localhost:5432/postgres

You can also omit parts of the DSN and rely on environment variables:

PGUSER=postgres PGPASSWORD=secret pg_exporter --dsn postgresql://localhost:5432/postgres

Docker Secrets Support

For Docker Swarm or Kubernetes environments, you can use PG_EXPORTER_DSN_FILE to read the DSN from a file (e.g., Docker secrets):

# docker-compose.yml for Docker Swarm
services:
  pg_exporter:
    image: ghcr.io/nbari/pg_exporter:latest
    environment:
      PG_EXPORTER_DSN_FILE: /run/secrets/pg_dsn
    secrets:
      - pg_dsn
    ports:
      - "9432:9432"

secrets:
  pg_dsn:
    external: true

Create the secret:

echo "postgresql://postgres_exporter:password@postgres:5432/postgres" | docker secret create pg_dsn -

Priority order: PG_EXPORTER_DSN_FILE > PG_EXPORTER_DSN > --dsn flag > default value

Available collectors

The following collectors are available:

• --collector.default default
• --collector.activity activity
• --collector.database database
• --collector.vacuum vacuum
• --collector.locks locks
• --collector.stat stat
• --collector.replication replication
• --collector.index index
• --collector.statements statements - Query performance metrics from pg_stat_statements (see detailed guide)
• --collector.tls tls - SSL/TLS certificate monitoring, connection encryption stats (PostgreSQL 9.5+)
• --collector.exporter exporter - Exporter self-monitoring (process metrics, scrape performance, cardinality tracking)

You can enable --collector.<name> or disable --no-collector.<name> For example, to disable the vacuum collector:

pg_exporter --dsn postgresql:///postgres?host=/var/run/postgresql&user=postgres_exporter --no-collector.vacuum

Enabled by default

This collectors are enabled by default:

• default
• activity
• vacuum

Scrape Behavior

pg_exporter is designed to be resilient to PostgreSQL outages:

• High Availability – The exporter starts and stays available even if the database is down.
• HTTP 200 Always – The /metrics endpoint always responds with HTTP 200 to avoid triggering unnecessary Prometheus "down" alerts for the exporter itself.
• pg_up Metric – Use the pg_up metric (1 for up, 0 for down) to monitor database connectivity.
• Metric Omission – When the database is unreachable, database-dependent metrics are omitted from the output rather than being reported as zero.

Systemd Boot Ordering

For systemd deployments, ensure exporter startup is ordered after PostgreSQL to avoid early boot races:

[Unit]
After=network-online.target postgresql.service
Wants=network-online.target

If your distribution uses a versioned unit name (for example postgresql-16.service), replace postgresql.service accordingly.

Project layout

The project is structured as follows:

├── bin
├── cli
├── collectors
├── exporter
└── lib.rs

All the collectors are located in the collectors directory. Each collector is in its own subdirectory, making it easy to manage and extend.

collectors
├── activity
│   ├── connections.rs
│   ├── mod.rs
│   └── wait.rs
├── config.rs
├── database
│   ├── catalog.rs
│   ├── mod.rs
│   ├── README.md
│   └── stats.rs
├── default
│   ├── mod.rs
│   ├── postmaster.rs
│   ├── settings.rs
│   └── version.rs
├── locks
│   ├── mod.rs
│   └── relations.rs
├── mod.rs <-- main file to register collectors
├── register_macro.rs
├── registry.rs
├── stat
│   ├── mod.rs
│   └── user_tables.rs
├── util.rs
└── vacuum
    ├── mod.rs
    ├── progress.rs
    └── stats.rs

In mod.rs file inside the collectors directory, you can see how each collector is registered. This modular approach allows for easy addition or removal of collectors as needed.

Each collector can then be extended with more specific metrics. For example, the vacuum collector has two files: progress.rs and stats.rs, this allows for better organization and separation of concerns within the collector and better testability. (or that is the plan).

Testing

The project includes unit tests for each collector and integration tests for the exporter as a whole. You can run the tests using:

just test

need just installed, see just

For direct checks, these commands are also part of the normal validation flow:

cargo fmt --all -- --check
just clippy

To run with opentelemetry set the environment variable OTEL_EXPORTER_OTLP_ENDPOINT, for example:

OTEL_EXPORTER_OTLP_ENDPOINT="http://localhost:4317"

Then you can run the exporter and it will send traces to the specified endpoint.

To run postgres and jaeger locally

just postgres
just jaeger
just watch

For tracees add more verbosity with -v, for example:

cargo watch -x 'run -- --collector.vacuum -vv'

open jaeger at http://localhost:16686 and select the pg_exporter service to see the traces.

🤝 Contributing

We welcome contributions of all kinds.

1. Read the Agent & Contributor Contract. It contains repository-specific rules for AI and human contributors, including testing, safety, and release-flow expectations.
2. Read the Development Guide. It covers local PostgreSQL setup, test workflows, and safe collector patterns.
3. Run tests: just test runs the standard validation flow for this crate.
4. Formatting: run cargo fmt --all -- --check.
5. Linting: run just clippy before submitting changes.
6. Check recent release notes in CHANGELOG.md so documentation and release notes stay aligned.

Related docs:

• AGENTS.md
• CONTRIBUTING.md
• CHANGELOG.md
• tests/TESTING.md

Feedback

This project is a work in progress. Your feedback, suggestions, and contributions are always welcome!