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README.admin - Administration notes |
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This file contains notes related to administration of a working Synnefo |
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deployment. This document should be read *after* README.deploy, which contains |
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step-by-step Synnefo deployment instructions. |
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Reconciliation mechanism |
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On certain occasions, such as a Ganeti or RabbitMQ failure, the VM state in the |
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system's database may differ from that in the Ganeti installation. The |
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reconciliation process is designed to bring the system's database in sync with |
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what Ganeti knows about each VM. |
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The administrator can trigger reconciliation manually, by issuing a Ganeti |
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OP_INSTANCE_QUERY_DATA command, using gnt-instance info. |
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Alternatively, the reconciliation process can be triggered for all VMs using |
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the command |
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./manage.py reconcile --all |
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It is advised, though not strictly necessary, to run the reconciliation process |
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periodically, through cron. To avoid overloading the Ganeti master, the |
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periodic reconciliation process takes a staggered approach to updating the VMs, |
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which is configured through the following parameters: |
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* The settings.py RECONCILIATION_MIN parameter, which specifies the |
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maximum time a VM can remain ``non-reconciled''. (default: 30 mins) |
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* The --interval option to the reconcile command, which declares the |
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interval time between reconciliation attempts (default: 1 min) |
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On each invocation of the reconcile command, the system will trigger a |
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reconciliation for ((num_all_vms/RECONCILIATION_MIN) * interval) |
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machines. Obviously the lower the interval value and the higher the |
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setting of RECONCILIATION_MIN, the less load is going to be put on Ganeti. |
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