089f63bc7e
Our legacy database doesn't provide alarm capability any more, however, there is a table in document still mentions it. Also update this table for hbase statistic limitation. Change-Id: I195106b23024a289196d9b5ec7cc891f251040e4
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90 lines
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Copyright 2013 Nicolas Barcet for eNovance
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Licensed under the Apache License, Version 2.0 (the "License"); you may
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not use this file except in compliance with the License. You may obtain
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a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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License for the specific language governing permissions and limitations
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under the License.
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.. _choosing_db_backend:
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============================
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Choosing a database backend
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============================
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.. note::
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Ceilometer's native database capabilities is intended for post processing
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and auditing purposes where responsiveness is not a requirement. It
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captures the full fidelity of each datapoint and thus is not designed
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for low latency use cases. For more responsive use cases, it's recommended
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to store data in an alternative source such as Gnocchi_. Please see
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`Moving from Ceilometer to Gnocchi`_ to find more information.
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.. note::
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As of Liberty, alarming support, and subsequently its database, is handled
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by Aodh_.
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.. _Aodh: http://docs.openstack.org/developer/aodh/
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Selecting a database backend for Ceilometer should not be done lightly for
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numerous reasons:
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1. Not all backend drivers are equally implemented and tested. To help you
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make your choice, the table below will give you some idea of the
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status of each of the drivers available in trunk. Note that we do welcome
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patches to improve completeness and quality of drivers.
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2. It may not be a good idea to use the same host as another database as
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Ceilometer can generate a LOT OF WRITES. For this reason it is generally
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recommended, if the deployment is targeting going into production, to use
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a dedicated host, or at least a VM which will be migratable to another
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physical host if needed. The following spreadsheet can help you get an
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idea of the volumes that ceilometer can generate:
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`Google spreadsheet <https://docs.google.com/a/enovance.com/spreadsheet/ccc?key=0AtziNGvs-uPudDhRbEJJOHFXV3d0ZGc1WE9NLTVPX0E#gid=0>`_
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3. If you are relying on this backend to bill customers, you will note that
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your capacity to generate revenue is very much linked to its reliability,
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which seems to be a factor dear to many managers.
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The following is a table indicating the status of each database drivers:
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================== ============================= ===========================================
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Driver API querying API statistics
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================== ============================= ===========================================
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MongoDB Yes Yes
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MySQL Yes Yes
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PostgreSQL Yes Yes
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HBase Yes Yes, except groupby & selectable aggregates
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================== ============================= ===========================================
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Moving from Ceilometer to Gnocchi
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=================================
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Gnocchi represents a fundamental change in how data is represented and stored.
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Installation and configuration can be found in :ref:`installing_manually`.
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Differences between APIs can be found here_.
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There currently exists no migration tool between the services. To transition
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to Gnocchi, multiple dispatchers can be enabled in the Collector to capture
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data in both the native Ceilometer database and Gnocchi. This will allow you
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to test Gnocchi and transition to it fully when comfortable. The following
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should be included in addition to the required configurations for each
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backend::
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[DEFAULT]
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meter_dispatchers=database
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meter_dispatchers=gnocchi
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.. _Gnocchi: http://gnocchi.xyz
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.. _here: https://docs.google.com/presentation/d/1PefouoeMVd27p2OGDfNQpx18mY-Wk5l0P1Ke2Vt5LwA/edit?usp=sharing
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