Overview

Module that provides a client connection with transaction support to a PostgreSQL database.

Usage

Environment Variables

Variable	Description	Default
PGHOST	DB hostname	::1
PGPORT	DB port	5432
PGDATABASE	DB name
PGUSER	DB username
PGPASSWORD	DB password
PG_MAX_CLIENT	Maximum number of open connections	10
PG_IDLE_TIMEOUT_MS	Idle timeout in milliseconds	10000
PG_CNXN_TIMEOUT_MS	Connection timeout in milliseconds	0

The idle timeout closes an open connection after the specified period of inactivity.
A connect request shall fail if the maximum number of connections are still in use after the specified connection timeout.

Example Usage

const { connect, end } = require( '@rhoweb.js/pg-client');

const dbClient = await connect();
. . .
do stuff with the DB client
. . .
await dbClient.release();

// When closing down
await end(); // Terminate the connection pool

Methods

connect

Create a client connection object.

const dbClient = await pgClient.connect( customPool = null );

Defaults to the regular pool if no argument is specified.

Exceptions shall be thrown if:

• any of the required environment variables are not defined (i.e., the ones without default values);
• the specified environment variables are invalid or do not define a valid connection;
• if it is not possible to connect the database for any reason;
• if the maximumum number of active client connections are currently in use.

end

Terminate the DB connection pool.

async pgClient.end();

Call this to terminate the connection pool when shutting down the application.
If this is not called, the connection pool shall terminate automatically after about 5 seconds.

createCustomPool

const customPool = await pgClient.createCustomPool();

Create a new connection pool configured from different environment variables.
The custom pool must be explicitly closed by the caller.

... updated environment variables ...
const customPool = await pgClient.createCustomPool();
const dbClient   = await pgClient.connect( customPool );
... do stuff ...
await dbClient.release();
await customPool.close();

Regular Pool and Custom Pool

Custom pools are used for non-standard use cases, typically administrative.
The regular connection pool is created when "connect()" is first called.
If "connect()" has not yet been called, changing the environment variables dynamically shall result in the regular connection pool being configured incorrectly, e.g.,

process.env.PG_IDLE_TIMEOUT_MS = 0;
const customPool = await pgClient.createCustomPool();
. . .
await pgClient.connect();
. . .

Either restore the modified environment variables, e.g.,

const oldTimeout = process.env.PG_IDLE_TIMEOUT_MS;
process.env.PG_IDLE_TIMEOUT_MS = 0;
const customPool = await pgClient.createCustomPool();
process.env.PG_IDLE_TIMEOUT_MS = oldTimeout;
. . .

or connect and disconnect a regular client first, e.g.,

await pgClient.connect();
await pgClient.release();
process.env.PG_IDLE_TIMEOUT_MS = 0;
const customPool = await pgClient.createCustomPool();
. . .

getConfig

Returns the configuration as loaded from the environment, e.g.,

const pgConfig = pgClient.getConfig();

would return something like:

{
  PGHOST:              'pghost.com',
  PGPORT:              '5432',
  PGDATABASE:          'pgdb',
  PGUSER:              'pguser',
  PGPASSWORD:          'pgpass'
  PG_MAX_CLIENT:       null,
  PG_IDLE_TIMEOUT_MS': null,
  PG_CNXN_TIMEOUT_MS': null,
}

Run Tests

Either define the DB environment variables or modify the defaults defined in test/unit/pg-client.js.

export PGHOST=myhost
export PGPORT=5432
export PGDATABASE=mydb
export PGUSER=myuser
export PGPASSWORD=mypassword
npm install
npm install mocha --global
npm run test
npm run test-coverage