Merge "Update haht docs" into stable/newton
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@ -215,7 +215,7 @@ A bare-bones congress.conf is as follows (adapt MySQL root password):
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drivers = congress.datasources.neutronv2_driver.NeutronV2Driver,congress.datasources.glancev2_driver.GlanceV2Driver,congress.datasources.nova_driver.NovaDriver,congress.datasources.keystone_driver.KeystoneDriver,congress.datasources.ceilometer_driver.CeilometerDriver,congress.datasources.cinder_driver.CinderDriver,congress.datasources.swift_driver.SwiftDriver,congress.datasources.plexxi_driver.PlexxiDriver,congress.datasources.vCenter_driver.VCenterDriver,congress.datasources.murano_driver.MuranoDriver,congress.datasources.ironic_driver.IronicDriver
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auth_strategy = noauth
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[database]
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connection = mysql://root:password@127.0.0.1/congress?charset=utf8
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connection = mysql+pymysql://root:password@127.0.0.1/congress?charset=utf8
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For a detailed sample, please follow README-congress.conf.txt
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@ -88,5 +88,15 @@ are specified in the [DEFAULT] section of the configuration file.
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``debug``
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Whether or not the DEBUG-level of logging is enabled. Default is false.
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``transport_url``
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URL to the shared messaging service. It is not needed in a single-process
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Congress deployment, but must be specified in a multi-process Congress
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deployment.
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.. code-block:: text
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[DEFAULT]
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transport_url = rabbit://<rabbit-userid>:<rabbit-password>@<rabbit-host-address>:<port>
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.. include:: ha-overview.rst
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.. include:: ha-deployment.rst
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@ -8,72 +8,122 @@ HA Deployment
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-------------
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Overview
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--------
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==================
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This section shows how to deploy Congress with High Availability (HA).
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Congress is divided to 2 parts in HA. First part is API and PolicyEngine
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Node which is replicated with Active-Active style. Another part is
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DataSource Node which is deployed with warm-standby style. Please see the
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:ref:`HA Overview <ha_overview>` for details.
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This section shows how to deploy Congress with High Availability (HA). For an
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architectural overview, please see the :ref:`HA Overview <ha_overview>`.
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An HA deployment of Congress involves five main steps.
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#. Deploy messaging and database infrastructure to be shared by all the
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Congress nodes.
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#. Prepare the hosts to run Congress nodes.
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#. Deploy N (at least 2) policy-engine nodes.
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#. Deploy one datasource-drivers node.
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#. Deploy a load-balancer to load-balance between the N policy-engine nodes.
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The following sections describe each step in more detail.
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Shared Services
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==================
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All the Congress nodes share a database backend. To setup a database backend
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for Congress, please follow the database portion of
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`separate install instructions`__.
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__ http://docs.openstack.org/developer/congress/README.html?highlight=readme#separate-install
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Various solutions exist to avoid creating a single point of failure with the
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database backend.
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Note: If a replicated database solution is used, it must support table
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locking. Galera, for example, would not work. This limitation is expected to
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be removed in the Ocata release.
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A shared messaging service is also required. Refer to `Shared Messaging`__ for
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instructions for installing and configuring RabbitMQ.
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__ http://docs.openstack.org/ha-guide/shared-messaging.html
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Hosts Preparation
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==================
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Congress should be installed on each host expected to run a Congress node.
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Please follow the directions in `separate install instructions`__ to install
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Congress on each host, skipping the local database portion.
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__ http://docs.openstack.org/developer/congress/README.html?highlight=readme#separate-install
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In the configuration file, a ``transport_url`` should be specified to use the
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RabbitMQ messaging service configured in step 1.
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For example:
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.. code-block:: text
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+-------------------------------------+ +--------------+
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| Load Balancer (eg. HAProxy) | <----+ Push client |
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+----+-------------+-------------+----+ +--------------+
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| | |
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PE | PE | PE | all+DSDs node
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+---------+ +---------+ +---------+ +-----------------+
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| +-----+ | | +-----+ | | +-----+ | | +-----+ +-----+ |
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| | API | | | | API | | | | API | | | | DSD | | DSD | |
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| +-----+ | | +-----+ | | +-----+ | | +-----+ +-----+ |
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| +-----+ | | +-----+ | | +-----+ | | +-----+ +-----+ |
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| | PE | | | | PE | | | | PE | | | | DSD | | DSD | |
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| +-----+ | | +-----+ | | +-----+ | | +-----+ +-----+ |
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+---------+ +---------+ +---------+ +--------+--------+
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| | | |
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| | | |
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+--+----------+-------------+--------+--------+
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| |
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| |
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+-------+----+ +------------------------+-----------------+
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| Oslo Msg | | DBs (policy, config, push data, exec log)|
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+------------+ +------------------------------------------+
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[DEFAULT]
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transport_url = rabbit://<rabbit-userid>:<rabbit-password>@<rabbit-host-address>:5672
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All hosts should be configured with a database connection that points to the
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shared database deployed in step 1, not the local address shown in
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`separate install instructions`__.
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__ http://docs.openstack.org/developer/congress/README.html?highlight=readme#separate-install
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For example:
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.. code-block:: text
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[database]
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connection = mysql+pymysql://root:<database-password>@<shared-database-ip-address>/congress?charset=utf8
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HA for API and Policy Engine Node
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---------------------------------
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Policy Engine Nodes
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=====================
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New config settings for setting the DSE node type:
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- N (>=2 even okay) nodes of PE+API node
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In this step, we deploy N (at least 2) policy-engine nodes, each with an
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associated API server. Each node can be started as follows:
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.. code-block:: console
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$ python /usr/local/bin/congress-server --api --policy-engine --node-id=<api_unique_id>
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$ python /usr/local/bin/congress-server --api --policy-engine --node-id=<unique_node_id>
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- One single DSD node
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Each node must have a unique node-id specified as a commandline option.
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For high availability, each node is usually deployed on a different host. If
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multiple nodes are to be deployed on the same host, each node must have a
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different port specified using the ``bind_port`` configuration option in the
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congress configuration file.
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Datasource Drivers Node
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========================
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In this step, we deploy a single datasource-drivers node in warm-standby style.
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The datasource-drivers node can be started directly with the following command:
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.. code-block:: console
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$ python /usr/local/bin/congress-server --datasources --node-id=<datasource_unique_id>
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$ python /usr/local/bin/congress-server --datasources --node-id=<unique_node_id>
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HA for DataSource Node
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----------------------
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A unique node-id (distinct from all the policy-engine nodes) must be specified.
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Nodes which DataSourceDriver runs on takes warm-standby style. Congress assumes
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cluster manager handles the active-standby cluster. In this document, we describe
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how to make HA of DataSourceDriver node by `Pacemaker`_ .
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For warm-standby deployment, an external manager is used to launch and manage
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the datasource-drivers node. In this document, we sketch how to deploy the
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datasource-drivers node with `Pacemaker`_ .
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See the `OpenStack High Availability Guide`__ for general usage of Pacemaker
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and how to deploy Pacemaker cluster stack. The guide has some HA configuration
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for other OpenStack projects.
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and how to deploy Pacemaker cluster stack. The guide also has some HA
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configuration guidance for other OpenStack projects.
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__ http://docs.openstack.org/ha-guide/index.html
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.. _Pacemaker: http://clusterlabs.org/
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Prepare OCF resource agent
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==========================
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----------------------------
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You need a custom Resource Agent (RA) for DataSoure Node HA. The custom RA is
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located in Congress repository, ``/path/to/congress/script/ocf/congress-datasource``.
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@ -87,8 +137,8 @@ Install the RA with following steps.
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$ cp /path/to/congress/script/ocf/congress-datasource ./congress-datasource
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$ chmod a+rx congress-datasource
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Configure RA
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============
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Configuring the Resource Agent
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-------------------------------
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You can now add the Pacemaker configuration for Congress DataSource Node resource.
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Connect to the Pacemaker cluster with the *crm configure* command and add the
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@ -111,4 +161,18 @@ The RA has following configurable parameters.
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* config: a path of Congress's config file
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* node_id(Option): a node id of the datasource node. Default is "datasource-node".
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* binary(Option): a path of Congress binary Default is "/usr/local/bin/congress-server".
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* additional_parameters(Option): additional parameters of congress-server
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* additional_parameters(Option): additional parameters of congress-server
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Load-balancer
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==============
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A load-balancer should be used to distribute incoming API requests to the N
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policy-engine (and API service) nodes deployed in step 3.
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It is recommended that a sticky configuration be used to avoid exposing a user
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to out-of-sync artifacts when the user hits different policy-engine nodes.
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`HAProxy <http://www.haproxy.org/>`_ is a popular load-balancer for this
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purpose. The HAProxy section of the `OpenStack High Availability Guide`__
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has instructions for deploying HAProxy for high availability.
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__ http://docs.openstack.org/ha-guide/index.html
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@ -20,7 +20,7 @@ HA Types
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========
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Warm Standby
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~~~~~~~~~~~~
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-------------
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Warm Standby is when a software component is installed and available on the
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secondary node. The secondary node is up and running. In the case of a
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failure on the primary node, the software component is started on the
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@ -29,7 +29,7 @@ Data is regularly mirrored to the secondary system using disk based replication
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or shared disk. This generally provides a recovery time of a few minutes.
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Active-Active (Load-Balanced)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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------------------------------
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In this method, both the primary and secondary systems are active and
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processing requests in parallel. Data replication happens through software
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capabilities and would be bi-directional. This generally provides a recovery
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@ -72,24 +72,9 @@ oslo-messaging to all policy engines.
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| Oslo Msg | | DBs (policy, config, push data, exec log)|
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+------------+ +------------------------------------------+
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- Performance impact of HAHT deployment:
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- Downtime: < 1s for queries, ~2s for reactive enforcement
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- Throughput and latency: leverages multi-process and multi-node parallelism
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- DSDs nodes are separated from PE, allowing high load DSDs to operate more
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smoothly and avoid affecting PE performance.
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- PE nodes are symmetric in configuration, making it easy to load balance
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evenly.
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- No redundant data-pulling load on datasources
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- Requirements for HAHT deployment
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- Cluster manager (eg. Pacemaker + Corosync) to manage warm
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standby
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- Does not require global leader election
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Details
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~~~~~~~
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-------------
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- Datasource Drivers (DSDs):
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@ -156,24 +141,30 @@ Details
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caller to a particular node. This configuration avoids the experience of
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going back in time.
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- External components (load balancer, DBs, and oslo messaging bus) can be made
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highly available using standard solutions (e.g. clustered LB, Galera MySQL
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cluster, HA rabbitMQ)
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highly available using standard solutions (e.g. clustered LB, HA rabbitMQ)
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Performance Impact
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==================
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- In single node deployment, there is generally no performance impact.
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- Increased latency due to network communication required by multi-node
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deployment
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- Increased reactive enforcement latency if action executions are persistently
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logged to facilitate smoother failover
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- PE replication can achieve greater query throughput
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End User Impact
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===============
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Different PE instances may be out-of-sync in their data and policies (eventual
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consistency). The issue is generally made transparent to the end user by
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making each user sticky to a particular PE instance. But if a PE instance
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goes down, the end user reaches a different instance and may experience
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out-of-sync artifacts.
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Cautions and Limitations
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============================
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- Replicated PE deployment is new in the Newton release and a major departure
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from the previous model. As a result, the deployer may be more likely to
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experience unexpected issues.
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- In the Newton release, creating a new policy requires locking a database
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table. As a result, it should not be deployed with a database backend that
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does not support table locking (e.g., Galera). The limitation is expected to
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be removed in the Ocata release.
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- Different PE instances may be out-of-sync in their data and policies
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(eventual consistency).
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The issue is generally made transparent to the end user by
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configuring the load balancer to make each user sticky to a particular PE
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instance. But if a user reaches a different PE instance (say because of load
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balancer configuration or because the original instance went down), the end
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user reaches a different instance and may experience out-of-sync artifacts.
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