GSoC 2025: Extension Support for pgexporter¶

Project Title: Extension Support for pgexporter
Contributor: Bassam Adnan
Organization: PostgreSQL
Mentors: Jesper Pedersen (My-Wine-Cellar), Saurav Pal (resyfer)
Progress Report: https://github.com/pgexporter/pgexporter/discussions/221
Proposal: PostgreSQL extensions can offer detailed views of query performance, storage usage, and system health but this would need frequent manual setup to be used with monitoring systems. Our proposal improves upon pgexporter through automatic detection of supported extensions and the output of pre-configured metrics for vital extensions such as pg_stat_statements, pg_buffercache, and pg_stat_monitor. It allows easy observability, diminishes the role of manual setup, and helps for optimal data-driven database performance monitoring. Please find my detailed proposal here.

Project Overview¶

pgexporter is a Prometheus exporter for PostgreSQL that provides database metrics. This project adds extension support to pgexporter, enabling automatic detection, version handling, and metric collection from popular PostgreSQL extensions. See Discussion Forum: GSoC 2025 Extension Support #221 for an extensive discussion of how the project played out.

The Problem¶

While pgexporter had extensive ammount of core queries and supported custom queries, it lacked extension support, this becomes important because the extension versioning may have different semantics (per extension itself that too). We wanted to add out-of-the box metric support for most popular Postgres extensions.

What We Built¶

• Extension Detection System: Automatic discovery of installed extensions with version tracking
• Semantic Versioning: Unified comparison system supporting different versioning formats (e.g., 2.19.3 vs 1.10)
• Comprehensive Extension Library: Metric files for 15+ popular PostgreSQL extensions
• Configuration System: Enable/disable extensions globally or per-server
• Test Infrastructure: HTTP-based test suite for validating metrics and server behavior

Contributions¶

Here I discuss the contributions I have made whlie providing support for pgexporter.

Extensions Added (with version support)¶

Features added¶

1. Semantic Versioning

// Supports comparing 2.19.3 with 2.19.2 AND 1.10 with 1.9, handles alphanumeric cases too. Atleast the ones we encountered :D
struct version {
    int major;
    int minor;
    int patch;
};

2. Extension Detection on Startup Queries pg_available_extensions and stores metadata in AVL tree structures for version-based query selection.

3. Extension Configuration Section

[pgexporter]
extensions = pg_stat_statements, timescaledb  # Global enable

[primary]
extensions = citus  # Server-specific override

4. View Evolution Tracking Created scripts to extract and diff extension views across PostgreSQL versions, documenting schema changes for compatibility. These are available here. With verification scripts and ouputs apart from the view patches accross versions.

Infrastructure Improvements¶

• Duplicate Detection: YAML/JSON validation using ART (Adaptive Radix Tree) to prevent metric name collisions
• HTTP API Refactor: Enhanced request/response handling with deque-based header lookups (ported to pgmoneta/pgagroal)
• Test Suite: Comprehensive test cases covering startup, HTTP endpoints, metric validation
• Memory Leak Fixes: Multiple rounds of valgrind-based leak detection and fixes
• Documentation: Updated Prometheus chapter, added extra.info for all projects

Some Numbers¶

• 30+ PRs merged across pgexporter, pgmoneta, and pgagroal
• 14 extensions with comprehensive metric coverage (11 external + 3 PostGIS variants)
• 100+ metrics added for extension monitoring alone, added metrics for PostgreSQL 18 as well.
• PostgreSQL 13+ version support with ongoing compatibility work

Challenges Faced¶

No project (atleast the ones you learn from!) come without challenges. For me personally memory leaks have always been a problem when working with C. Even more when you have a constantly running program such as pgexporter. When they surface due to reasons which arent even deterministic sometimes, it can be quite tough to figure your way around it. I have gained enough exposure to ASan, something I never worked with before to help me deal with such issues. A constant pain was waiting on CI results only for them to fail in a few systems while pass in other, lets just say, dealing with this has helped me with patience.

Learning Outcomes¶

Through this project, I had a great time developing my skills in C. Engaging with syscalls for the first time outside an academic project, I got to learn much more about how shared memory space works, transferring data via HTTP (by building my own HTTP suite!) and where exactly is encryption used in the network. Apart from that, PostgreSQL wire protocol was a very fun read. Abit of a nightmare to deal with was GitHub Actions, I still remember the time we had one failing test case only in FreeBSD systems while every other system seemed just okay.

Apart from that, one major thing which I will always hold on to from this project is engaging in constant discussions, reaching out to help and make good quality PRs so as to not waste the mentors time. To me, the most important thing i've learned out of this project is communication.

Future Work¶

• More Extensions: pg_partman, pg_qualstats, hstore metrics
• Monitoring Solutions: Alternative to Grafana more fine tuned for pgexporter use cases.

Acknowledgements¶

Huge thanks to my mentors Jesper Pedersen and Saurav Pal for their guidance, code reviews, and patience throughout this journey. Special thanks to @Userfrom1995 and @ashu3103 for engaging with me in discussions for test suite and the entire pgexporter community for their support.

Links¶

• Discussion Forum: GSoC 2025 Extension Support
• Project Repository: pgexporter/pgexporter
• Documentation: pgexporter.github.io
• Releases: Extension support integrated in pgexporter releases

This project was completed as part of Google Summer of Code 2025 with pgexporter.