ae8952dea7
The worker now supports a DISCOVER message that can be sent to it to discover which version of the JSON message format that it supports. The Gearman function name that it registers is now simply the hostname and no longer includes 'lbaas-<VERSION>-' as a prefix. Change-Id: Ib34ae424e5461b3b1f8df601a6e7a1fd99c48c05
92 lines
3.1 KiB
ReStructuredText
92 lines
3.1 KiB
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Description
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===========
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Purpose
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-------
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A Python-based Gearman worker that handles messages for the Gearman job queue
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sharing the same name as the local hostname. The messages that it receives are
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JSON objects describing a load balancer, and returns this same JSON object, but
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with status fields added to describe the state of the LB.
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Installation
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------------
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Installing the Required Tools
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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You must have Python setuptools installed. On Ubuntu::
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$ sudo apt-get install python-setuptools
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Now you may install the Libra toolset::
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$ sudo python setup.py install
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The worker also needs some packages installed in order to be used with
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HAProxy. The commands below will install them on Ubuntu::
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$ sudo apt-get install haproxy
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$ sudo apt-get install socat
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The Ubuntu default is to have HAProxy disabled. You will need to edit the
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file */etc/default/haproxy* and set *ENABLED* to 1 if you want HAProxy to
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actually start (hint: you do).
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Edit /etc/sudoers
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^^^^^^^^^^^^^^^^^
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The worker needs to be able to run some commands as root without being
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prompted for a password. It is suggested that you run the worker as
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the `haproxy` user and `haproxy` group on Ubuntu systems. Then add the
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following line to /etc/sudoers::
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%haproxy ALL = NOPASSWD: /usr/sbin/service, /bin/cp, /bin/mv, /bin/rm, /usr/bin/socat
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The above lets everyone in the *haproxy* group run those commands
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as root without being prompted for a password.
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Configuration File
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------------------
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It can be easier to give options via a configuration file. See the sample
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configuration file etc/sample_libra.cfg for an example and further
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documentation. Use the :option:`--config <libra_worker.py -c>` option
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to specify the configuration file to read.
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Running the Worker
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------------------
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The worker can run in either daemon or non-daemon mode. Daemon mode requires
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escalated privileges so that it can behave like a proper daemon. Non-daemon
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mode (:option:`--nodaemon <libra_worker.py -n>` option) is useful for testing.
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Basic commands::
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# Getting help
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$ libra_worker -h
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# Start up as a daemon running as the `haproxy` user and
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# connecting to the local Gearman job server.
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$ sudo libra_worker --user haproxy --group haproxy --server 127.0.0.1:4730
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# Start up with debugging output in non-daemon mode
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$ libra_worker --debug --nodaemon
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NOTE: When running the worker in daemon mode, you must make sure that the
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directory where the PID file will be (:option:`--pid <libra_worker.py -p>`
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option) and the directory where the log files will be written
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(:option:`--logfile <libra_worker.py -l>` option) exists and is writable
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by the user/group specified with the :option:`--user <libra_worker.py --user>`
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and :option:`--group <libra_worker.py --group>` options. Also, the
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Python module used to start the daemon process does not like it when the PID
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file already exists at startup.
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**IF THE WORKER IMMEDIATELY EXITS WHEN STARTED IN DAEMON MODE, AND NO ERROR
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MESSAGES ARE IN THE LOG, ONE OF THESE REASONS IS THE MOST LIKELY CAUSE!**
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You can verify that the worker is running by using the sample Gearman
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client in the bin/ directory::
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$ bin/client.py
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