Document Ephemeral Heat
Change-Id: I0e3ff5605b59a7a3ca527756271825f9a781e728 Signed-off-by: James Slagle <jslagle@redhat.com>
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.. _ephemeral_heat:
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Ephemeral Heat
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==============
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Introduction
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------------
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Ephemeral Heat is a means to install the overcloud by using an ephemeral Heat
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process instead of a system installed Heat process. This change is possible
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beginning in the Wallaby release.
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In a typical undercloud, Heat is installed on the undercloud and processes are
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run in podman containers for heat-api and heat-engine. When using ephemeral
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Heat, there is no longer a requirement that Heat is installed on the
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undercloud, instead these processes are started on demand by the deployment,
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update, and upgrade commands.
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This model has been in use within TripleO already for both the undercloud and
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:ref:`standalone <standalone>` installation methods, which start an on demand
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all in one heat-all process in order to perform only the installation. Using
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ephemeral Heat in this way allows for re-use of the Heat templates from
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tripleo-heat-templates without having to require an already fully installed
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undercloud.
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Description
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-----------
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Ephemeral Heat is enabled by passing the ``--heat-type`` argument to
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``openstack overcloud deploy``. The ephemeral process can also be launched
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outside of a deployment with the ``openstack tripleo launch heat`` command. The
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latter command also takes a ``--heat-type`` argument to enable selecting the
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type of Heat process to use.
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Heat types
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__________
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The ``--heat-type`` argument allows for the following options described below.
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installed
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Use the system Heat installation. This is the historical TripleO usage of
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Heat with Heat fully installed on the undercloud. This is the default
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value, and requires a fully installed undercloud.
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native
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Use an ephemeral ``heat-all`` process. The process will be started natively
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on the system executing tripleoclient commands by way of an OS (operating
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system) fork.
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container
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A podman container will be started on the executing system that runs a
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single ``heat-all`` process.
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pod
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A podman pod will be started on the executing system that runs containers
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for ``heat-api`` and ``heat-engine``.
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In all cases, the process(es) are terminated at the end of the deployment.
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.. note::
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The native and container methods are limited in scale due to being a single
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Heat process. Deploying more than 3 nodes or 2 roles will significantly
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impact the deployment time with these methods as Heat has only a single
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worker thread.
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Using the installed or pod methods enable scaling node and role counts as
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is typically required.
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Using
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-----
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The following example shows using ``--heat-type`` to enable ephemeral Heat::
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openstack overcloud deploy \
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--stack overcloud \
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--work-dir ~/overcloud-deploy/overcloud \
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--heat-type <pod|container|native> \
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<other cli arguments>
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With ephemeral Heat enabled, several additional deployment artifacts are
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generated related to the management of the Heat process(es). These artifacts
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are generated under the working directory of the deployment in a
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``heat-launcher`` subdirectory. The working directory can be overridden with
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the ``--work-dir`` argument.
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Using the above example, the Heat artifact directory would be located at
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``~/overcloud-deploy/overcloud/heat-launcher``. An example of the directory
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contents is shown below::
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[centos@ephemeral-heat ~]$ ls -l ~/overcloud-deploy/overcloud/heat-launcher/
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total 41864
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-rw-rw-r--. 1 centos centos 650 Mar 24 18:39 api-paste.ini
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-rw-rw-r--. 1 centos centos 1054 Mar 24 18:39 heat.conf
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-rw-rw-r--. 1 centos centos 42852118 Mar 24 18:31 heat-db-dump.sql
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-rw-rw-r--. 1 centos centos 2704 Mar 24 18:39 heat-pod.yaml
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drwxrwxr-x. 2 centos centos 49 Mar 24 16:02 log
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-rw-rw-r--. 1 centos centos 1589 Mar 24 18:39 token_file.json
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The directory contains the necessary files to inspect and debug the Heat
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process(es), and if necessary reproduce the deployment.
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.. note::
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The consolidated log file for the Heat process is the ``log`` file in the
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``heat-launcher`` directory.
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Launching Ephemeral Heat
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________________________
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Outside of a deployment, the ephemeral Heat process can also be started with the
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``openstack tripleo launch heat`` command. This can be used to interactively
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use the ephemeral Heat process or to debug a previous deployment.
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When combined with ``--heat-dir`` and ``--restore-db``, the command can be used
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to restore the Heat process and database from a previous deployment::
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openstack tripleo launch heat \
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--heat-type pod \
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--heat-dir ~/overcloud-deploy/overcloud/heat-launcher \
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--restore-db
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The command will exit after launching the Heat process, and the Heat process
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will continue to run in the background.
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Interacting with ephemeral Heat
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...............................
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With the ephemeral Heat process launched and running, ``openstackclient`` can be
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used to interact with the Heat API. The following shell environment
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configuration must be set in order to disable authentication::
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unset OS_PROJECT_NAME
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unset OS_PROJECT_DOMAIN_NAME
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unset OS_USER_DOMAIN_NAME
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OS_AUTH_TYPE=none
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OS_ENDPOINT=http://192.168.24.2:8006/v1/admin
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Once the environment is configured, ``openstackclient`` work as expected
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against the Heat API::
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[centos@ephemeral-heat ~]$ openstack stack list
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+--------------------------------------+------------+---------+-----------------+----------------------+--------------+
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| ID | Stack Name | Project | Stack Status | Creation Time | Updated Time |
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+--------------------------------------+------------+---------+-----------------+----------------------+--------------+
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| 761e2a54-c6f9-4e0f-abe6-c8e0ad51a76c | overcloud | admin | CREATE_COMPLETE | 2021-03-22T20:48:37Z | None |
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+--------------------------------------+------------+---------+-----------------+----------------------+--------------+
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Killing ephemeral Heat
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......................
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To stop the ephemeral Heat process previously started with ``openstack tripleo
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launch heat``, use the ``--kill`` argument::
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openstack tripleo launch heat \
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--heat-type pod \
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--heat-dir ~/overcloud-deploy/overcloud/heat-launcher \
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--kill
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Limitations
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-----------
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Ephemeral Heat currently only supports new deployments. Update and Upgrade
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support for deployments that previously used the system installed Heat will be
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coming.
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@ -26,6 +26,7 @@ This section has additional documentation around advanced deployment related top
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architecture
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build_single_image
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container_image_prepare
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ephemeral_heat
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instack_undercloud
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standalone
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template_deploy
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@ -1,3 +1,5 @@
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.. _standalone:
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Standalone Containers based Deployment
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======================================
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