pgmb

pgmb : A simple PostgreSQL Message Broker system

Overview

Packages

Source

pig build pkg pgmb;		# build rpm/deb

Install

Make sure PGDG and PIGSTY repo available:

pig repo add pgsql -u   # add both repo and update cache

Install this extension with pig:

pig install pgmb;		# install via package name, for the active PG version

pig install pgmb -v 18;   # install for PG 18
pig install pgmb -v 17;   # install for PG 17
pig install pgmb -v 16;   # install for PG 16
pig install pgmb -v 15;   # install for PG 15
pig install pgmb -v 14;   # install for PG 14

Create this extension with:

CREATE EXTENSION pgmb CASCADE; -- requires pg_cron, http

Usage

Sources:

• README
• Control
• SQL
• META.json

pgmb implements a SQL message broker with worker endpoints, routing-key patterns, queues and HTTP dispatch scheduled through pg_cron. The upstream repository is archived.

Installation and compatibility

The RPM revision 1.0.0-2PGSTY requires pgsql_http_N and removes a redundant schema-creation statement. Earlier RPMs and existing DEB packages retain the upstream SQL and can fail at CREATE EXTENSION pgmb because the control file and install script both create the schema. Package installation alone does not establish that the extension can be created.

Install as a superuser. The required extensions are pg_cron and http; pgmb itself does not require preload. Configure the scheduler for the database in which the extension will be used:

shared_preload_libraries = 'pg_cron'
cron.database_name = 'postgres'

Restart PostgreSQL, connect to that database, and create the dependencies before the extension:

CREATE EXTENSION pg_cron;
CREATE EXTENSION http;
CREATE EXTENSION pgmb;

Register a queue and send a message

The worker endpoint receives HTTP requests from the database server. Use a trusted endpoint and restrict who can register workers.

SELECT pgmb.create(
    'orders', 'order.*', 3,
    pgmb.worker('order_worker', 'http://127.0.0.1:8080/worker', 100)
);

SELECT pgmb.send(
    gen_random_uuid(), 'order.created', '{"order_id": 123}'::jsonb
);

SELECT * FROM pgmb.workers;
SELECT * FROM pgmb.queues;
SELECT * FROM pgmb.orders_queue;
SELECT * FROM pgmb.orders_dead_letter_queue;

The argument order for pgmb.create is name, binding pattern, maximum retries, then worker UUID. A trigger routes messages to matching queues, and queue creation registers a scheduler job.

API

Limits of version 1.0.0

• Delays populate enqueued_at, but the dispatcher does not filter out future timestamps; the overloads do not guarantee delayed delivery.
• Headers are stored with messages, but the dispatcher sends only the body using http_post; they are not forwarded as custom HTTP headers.
• Retries use a counter on subsequent dispatches. The SQL does not implement exponential backoff.
• HTTP effects are external to the database transaction. Review delivery and retention requirements before relying on this archived project.