What is the precedence in qpid broker options?

Environment

Red Hat Enterprise MRG Messaging (any version)

Issue

Having qpid broker parameters specified in:

• environmental variables like export QPID_PORT=5672
• command line option (like --port=5672)
• configuration file (like port=5672)

what is their precedence? What setting for an option will be used, if the option is specified on multiple places?

Resolution

Options are set with this precedence:

1. command line option
2. environmental variable
3. configuration file

That means, if an option is specified e.g. in command line and in configuration file, the value from command line will be used.

This strictly applies also to log-enable option that can be specified multiple times - see this solution for details.

Diagnostic Steps

Example: having AMQP listening port defined on multiple configuration places and checking what port the broker will listen on:

$ export QPID_PORT=10001
$ echo "port=10002" > port.conf
$ qpidd --config=port.conf --port=10003 2>&1 | grep "Listening on"
2013-10-25 11:18:20 [Network] notice Listening on TCP/TCP6 port 10003
^C
$ qpidd --config=port.conf 2>&1 | grep "Listening on"
2013-10-25 11:18:56 [Network] notice Listening on TCP/TCP6 port 10001
^C
$ unset QPID_PORT
$ qpidd --config=port.conf 2>&1 | grep "Listening on"
2013-10-25 11:19:28 [Network] notice Listening on TCP/TCP6 port 10002
^C
$

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