A dynamic configurable reverse proxy for use within Galaxy

Invoking

This project can be invoked from `lib/main.js script in the source or
installed and invoked through its published package via npm or npx.

`console
$ npx @galaxyproject/gx-it-proxy --version
$ npx @galaxyproject/gx-it-proxy --sessions test.sqlite --port 8001 # use SQLite
$ npx @galaxyproject/gx-it-proxy --sessions test.json --port 8001 # use a JSON file
$ npx @galaxyproject/gx-it-proxy --sessions postgresql:///galaxy?host=/var/run/postgresql --port 8001 # use PostgreSQL
`

Double Proxy

To double-proxy (e.g. from Galaxy to a remote proxy that proxies to the application):

`console
host1$ ./lib/main.js --sessions test.sqlite --forwardIP host2 --forwardPort 8001
host2$ ./lib/main.js --port 8001
`

Sessions

The proxy loads sessions from the file or database passed with the --sessions
option. SQLite and JSON files are watched and reloaded on every change.
PostgreSQL databases are polled every five seconds by default. The polling
interval can be configured via the --pollingInterval option (in ms).

Faster updates for PostgreSQL databases are possible via
PostgreSQL asynchronous notifications.
To enable them, create a PostgreSQL trigger that sends a
NOTIFY message to the channel gxitproxy every time the table gxitproxy
changes.

`SQL
CREATE OR REPLACE FUNCTION notify_gxitproxy()
RETURNS trigger AS $$
BEGIN
PERFORM pg_notify('gxitproxy', 'Table "gxitproxy" changed');
RETURN NEW;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER gxitproxy_notify
AFTER INSERT OR UPDATE OR DELETE ON gxitproxy
FOR EACH ROW EXECUTE FUNCTION notify_gxitproxy();
`

Although it is possible to disable polling using --pollingInterval 0`, it is
strongly discouraged, as the delivery of asynchronous notifications is not
guaranteed.