Monasca Database Persister
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Hervé Beraud 37411e792a Add doc/requirements 2 years ago
README.rst Tool to migrate existing data to db per tenant 3 years ago Add doc/requirements 2 years ago


The general plan for the monasca project is to move in the direction of having a database per tenant because: - Not only give a finer grain control over retention policy per tenant but also possibly speed up tenants queries by scoping them within their project. - Security is improved though better isolation. For example, a previous bug in InfluxDB where the tenant ID was ignored in the query exposed data from outside a tenants project. This is less likely to happen with a separate DB per tenant.) - We move in a direction of improving scalability for InfluxDB users without the Enterprise license. In the future a dedicated InfluxDB instance could optionally be used per project.

For further reading -!/story/2006331

All effort has been made to ensure this is a safe process. And it should be safe to run the tool multiple times. However, it is provided AS IS and you should use it at your own risk.


Steps to use this tool:

  • Log in to one node where monasca-persister is deployed.
  • Identify installation path to monasca-persister. This may be a virtual environment such as /opt/stack/venv/monasca-<version>/lib/python2.7/site-packages/monasca_persister or as in devstack /opt/stack/monasca-persister/monasca_persister/ which you may need to activate.
  • Identify the existing configuration for monasca-persister. The likely location for this is /etc/monasca/persister.conf if using devstack.
  • Optionally, make a backup of your database in case something goes wrong but your original database should be left intact.
  • Open and edit and edit mapping between your existing projects to retention policies if you so wish. You may also want to change end_time_offset_override to the length of history you want the migration tool to consider.
  • Invoke the tool to migrate to database per tenant. The arguments inside the square bracket default to the values shown when undefined.
sudo -u mon-persister python --config-file /etc/monasca/persister.conf --migrate-retention-policy project:2w,project2:1d --migrate-skip-regex ^log\\..+ [--migrate-time-unit w --migrate-start-time-offset 0 --migrate-end-time-offset 520]
  • The progress of the migration will be logged to persister log file specifed in the persister config.


1. Will this interrupt the operation of Monasca? - In theory, you can run this migration query on a live Monasca system because the migration leaves the original database untouched. However, in practice, it may degrade performance while the migration is taking place. 2. How do I ensure that I migrate all metrics to the new scheme? i.e. Do I need to stop all persisters writing to InfluxDB and let Kafka buffer for a bit while the migration is taking place? - If you stop the persister and the migration takes longer than the Kafka buffer duration, this may cause data loss. It may be best to do the first batch of migration on the entire dataset and perform iterative migration of smaller chucks collected in the duration migration was taking place. 3. Will the original index be left intact so that I can fall back if it doesn't work? - Yes. 4. What do I do after I have run the tool? I need to enable the feature before starting the persisters right? - If you enable the feature by flipping on db_per_tenant flag before starting the migration and restart your persister service, your persister will start writing to a database per tenant model. It may be best to switch this feature on after the first round of migration, restart the persister so that it starts writing to database per tenancy and migrate the remainder of the data. Note that in the second run, you may need to delete migrate-success so that the metrics are not skipped. You may also want to try with smaller --migrate-time-unit option (default: w for week) if larger chunks of migration fail. Other option are d for day and h for hours. 5. How long does it take (rough estimate per GB of metrics?) - This depends on your storage backend. On one of the systems in which this tool was tested on, it was an overnight job to move 40GB of metrics. 6. Is the tool idempotent? i.e. could I migrate the bulk of the data with the persisters running, stop the persisters, and then migrate the delta in a short interval to minimise downtime? Can I run it again if it fails? - Yes, InfluxDB ensures that same time indices with the same tags, fields and values are not duplicated. Copying things over twice is perfectly safe. 7. Will it set fire to my cat? - Depends if you cat is well behaved.


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