allas

Introduction

allas is a connection pooler for PostgreSQL which only supports LISTEN / NOTIFY. The idea is to allow the application to use e.g. pgbouncer in transaction pooling mode while only receiving notifications through allas. allas only uses a single PostgreSQL connection and takes care of LISTENing and UNLISTENing appropriately on that connection to make sure all of its clients get the set of notifications they're interested in.

How to build

Clone the repository, and run "go build" in the cloned directory. This should produce a binary called "allas".

Configuration

The configuration file uses a JSON format and is organized into sections. The top level structure is a JSON object, with the following keys ("sections"):

listen

listen specifies how allas listens to new connections. It has three possible options:

1. port (integer) specifies the port to listen on.
2. host (string) specifies the address to listen on. The asterisk ("*") can be used to listen on all TCP interfaces, or an absolute path can be used to listen on a UNIX domain socket.
3. keepalive (boolean) specifies whether TCP keepalives should be enabled or not.

connect

connect is a pq connection string. It supports many of libpq's options.

startup_parameters

startup_parameters is a JSON object specifying the list of "startup parameters" (such as the server's version number) to send to each client when they connect.

prometheus

prometheus is a JSON object with the following keys:

1. listen (object) specifies how allas listens to connections from the Prometheus scraping process. The keys are the same as used by the main listen section, documented above. The port 9226 has been allocated in the Prometheus wiki for allas's use.

databases

databases is an array of JSON objects with the following keys:

1. name (string) specifies the name of the database.
2. auth (object) is described in the section Database authentication, below.

Database authentication

The auth key of a database configuration section is a JSON object with a combination of the following keys:

1. method (string) is the authentication method used. There are only two values values: "trust" and "md5". Both match their respective counterpart in PostgreSQL HBA configuration.
2. user (string) is the user name the user has to pass to match the authentication method.
3. password (string) is a clear-text copy of the password the client should use for authentication.

Configuration example

Here's an example configuration file:

{
    "listen": {
        "port": 6433,
        "host": "localhost"
    },
    "connect": "host=localhost port=5432 sslmode=disable",
    "startup_parameters": {
        "server_version": "9.1.24",
        "client_encoding": "UTF8"
    },
    "prometheus": {
        "listen": {
            "port": 9226,
            "host": "*"
        }
    },
    "databases": [
        {
            "name": "allas",
            "auth": {
                "method": "md5",
                "user": "allas",
                "password": "s3cret"
            }
        }
    ]
}