Synnefo

README.admin - Administration notes

This file contains notes related to administration of a working Synnefo

deployment. This document should be read *after* README.deploy, which contains

step-by-step Synnefo deployment instructions.

Reconciliation mechanism

========================

On certain occasions, such as a Ganeti or RabbitMQ failure, the VM state in the

system's database may differ from that in the Ganeti installation. The

reconciliation process is designed to bring the system's database in sync with

what Ganeti knows about each VM.

The administrator can trigger reconciliation manually, by issuing a Ganeti

OP_INSTANCE_QUERY_DATA command, using gnt-instance info.

Alternatively, the reconciliation process can be triggered for all VMs using the

command

  ./manage.py reconcile --all

It is advised, though not strictly necessary, to run the reconciliation process

periodically, through cron. To avoid overloading the Ganeti master, the periodic

reconciliation process takes a staggered approach to updating the VMs, which is

configured through the following parameters:

* The settings.py RECONCILIATION_MIN parameter, which specifies the maximum time

  a VM can remain ``non-reconciled''. (default: 30 mins)

* The --interval option to the reconcile command, which declares the interval

  time between reconciliation attempts (default: 1 min)

On each invocation of the reconcile command, the system will trigger a

reconciliation for ((num_all_vms/RECONCILIATION_MIN) * interval) machines.

Obviously the lower the interval value and the higher the setting of

RECONCILIATION_MIN, the less load is going to be put on Ganeti.

Logging

=======

Logging in Synnefo is using Python's logging module. The module is configured

using a configuration file, whose format is described here:

http://docs.python.org/library/logging.config.html

By default, the log initialization code will look for the logging.conf file

in the following locations in order:

1. /etc/synnefo/logging.conf

2. os.getcwd()/logging.conf

3. synnefo.logic.__path__[0]/logging.conf (<-- this is the default)

The default configuration is using Linux conventions: it logs to /dev/log for

all loggers. The default configuration can be changed by copying the default

file to any of the above mentioned locations and changing it appropriately.

* Logging and demonization: If the logging is configured to print to the console

  (using the consoleHandler handler) then daemon processes (notably, the

  dispatcher) will not work as it should. This only happens after the daemon

  has lost its controlling terminal (e.g. because the terminal was closed);

  in this case the dispatcher does not know where to log to and depending on

  the system it either crashes or stalls. This can be avoided if the logging

  module is not configured to output to the console.