.. Copyright 2013 Nicolas Barcet for eNovance Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. .. _choosing_db_backend: ============================ Choosing a database backend ============================ .. note:: Ceilometer's native database capabilities is intended for post processing and auditing purposes where responsiveness is not a requirement. It captures the full fidelity of each datapoint and thus is not designed for low latency use cases. For more responsive use cases, it's recommended to store data in an alternative source such as Gnocchi_. Please see `Moving from Ceilometer to Gnocchi`_ to find more information. .. note:: As of Liberty, alarming support, and subsequently its database, is handled by Aodh_. .. _Aodh: http://docs.openstack.org/developer/aodh/ Selecting a database backend for Ceilometer should not be done lightly for numerous reasons: 1. Not all backend drivers are equally implemented and tested. To help you make your choice, the table below will give you some idea of the status of each of the drivers available in trunk. Note that we do welcome patches to improve completeness and quality of drivers. 2. It may not be a good idea to use the same host as another database as Ceilometer can generate a LOT OF WRITES. For this reason it is generally recommended, if the deployment is targeting going into production, to use a dedicated host, or at least a VM which will be migratable to another physical host if needed. The following spreadsheet can help you get an idea of the volumes that ceilometer can generate: `Google spreadsheet `_ 3. If you are relying on this backend to bill customers, you will note that your capacity to generate revenue is very much linked to its reliability, which seems to be a factor dear to many managers. The following is a table indicating the status of each database drivers: ================== ============================= =========================================== Driver API querying API statistics ================== ============================= =========================================== MongoDB Yes Yes MySQL Yes Yes PostgreSQL Yes Yes HBase Yes Yes, except groupby & selectable aggregates ================== ============================= =========================================== Moving from Ceilometer to Gnocchi ================================= Gnocchi represents a fundamental change in how data is represented and stored. Installation and configuration can be found in :ref:`installing_manually`. Differences between APIs can be found here_. There currently exists no migration tool between the services. To transition to Gnocchi, multiple dispatchers can be enabled in the Collector to capture data in both the native Ceilometer database and Gnocchi. This will allow you to test Gnocchi and transition to it fully when comfortable. The following should be included in addition to the required configurations for each backend:: [DEFAULT] meter_dispatchers=database meter_dispatchers=gnocchi event_dispatchers=gnocchi .. _Gnocchi: http://gnocchi.xyz .. _here: https://docs.google.com/presentation/d/1PefouoeMVd27p2OGDfNQpx18mY-Wk5l0P1Ke2Vt5LwA/edit?usp=sharing