Document Kolla image API
A first shot at documenting the kolla image API. Not perfect but this should at least provide a good overview for the projects that want to consume kolla images. Change-Id: I10943a050e4d21dfcdebb75084a26c12845d322b
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Martin André
Mark Goddard
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1b0f4197f9
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@ -16,3 +16,15 @@ or build some images using ``--template-override``.
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image-building
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template-override/*
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Kolla Images API
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----------------
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Take advantage of the Kolla API to configure containers at runtime.
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.. toctree::
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:maxdepth: 2
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:glob:
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kolla_api
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@ -0,0 +1,174 @@
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.. _kolla_api:
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================
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Kolla Images API
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================
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Kolla offers two different ways to make changes to containers at runtime.
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The first is via a :ref:`configuration file <kolla_api_external_config>`
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exposed to the container and processed by the init scripts, and the second
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is via more traditional
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:ref:`environment variables <kolla_api_environment_variables>`.
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.. _kolla_api_external_config:
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External Config
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===============
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All of the Kolla images understand a JSON-formatted configuration
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describing a set of actions the container needs to perform at runtime before it
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executes the (potentially) long running process. This configuration also
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specifies the command to execute to run the service.
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When a container runs `kolla_start`_, the default entry-point, it processes
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the configuration file using `kolla_set_configs`_ with escalated privileges,
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meaning it is able to set file ownership and permissions.
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.. _kolla_start: https://github.com/openstack/kolla/blob/master/docker/base/start.sh
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.. _kolla_set_configs: https://github.com/openstack/kolla/blob/master/docker/base/set_configs.py
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Format of the configuration file
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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The `kolla_set_configs`_ script understands the following attributes:
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* **command** (required): the command the container runs once it finishes the
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initialization step.
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* **config_files**: copies files and directories inside the container. A list
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of dicts, each containing the following attributes:
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* **source** (required): path to the file or directory that needs to be
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copied. Understands shell wildcards.
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* **dest** (required): path to where the file or directory will be copied.
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does not need to exist, destination is deleted if it exists.
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* **owner** (required, unless ``preserve_properties`` is set to true): the
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``user:group`` to change ownership to. ``user`` is synonymous to
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``user:user``. Must be user and group names, not uid/gid.
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* **perm** (required, unless `preserve_properties` is set to true): the unix
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permissions to set to the target files and directories. Must be passed in
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the numeric octal form.
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* **preserve_properties**: copies the ownership and permissions from the
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original files and directory. Boolean, defaults to ``false``.
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* **optional**: do not raise an error when the source file is not present on
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the filesystem. Boolean, defaults to ``false``.
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* **merge**: merges the source directory into the target directory instead of
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replacing it. Boolean, defaults to ``false``.
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* **permissions**: change the permissions and/or ownership of files or
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directories inside the container. A list of dicts, each containing the
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following attributes:
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* **path** (required): the path to the file or directory to update.
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* **owner** (required): the ``user:group`` to change ownership to. ``user``
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is synonymous to ``user:user``. Must be user and group names, not uid/gid.
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* **perm**: the unix permissions to set to the target files and directories.
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Must be passed in the numeric octal form.
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* **recurse**: whether to apply the change recursively over the target
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directory. Boolean, defaults to ``false``.
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Here is an example configuration file:
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.. code-block:: json
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{
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"command": "trove-api --config-file=/etc/trove/trove.conf",
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"config_files": [
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{
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"source": "/var/lib/kolla/config_files/trove.conf",
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"dest": "/etc/trove/trove.conf",
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"owner": "trove",
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"perm": "0600",
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"optional": false
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}
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],
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"permissions": [
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{
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"path": "/var/log/kolla/trove",
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"owner": "trove:trove",
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"recurse": true
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}
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]
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}
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Passing the configuration file to the container
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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The configuration can be either passed via the ``KOLLA_CONFIG`` environment
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variable or as a file bind-mounted into the container. When bind-mounting the
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configuration file, the ``KOLLA_CONFIG_FILE`` environment variable controls
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where the file is located in the container, the default path being
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``/var/lib/kolla/config_files/config.json``.
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Passing the configuration file as environment variable:
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.. code-block:: console
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docker run -e KOLLA_CONFIG_STRATEGY=COPY_ALWAYS \
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-e KOLLA_CONFIG='{ "command": "...", "permissions": [ { "path": "...", } ] }' \
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kolla-image
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Mounting the configuration file in the container:
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.. code-block:: console
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docker run -e KOLLA_CONFIG_STRATEGY=COPY_ALWAYS \
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-e KOLLA_CONFIG_FILE=/config.json \
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-v /path/to/config.json:/config.json kolla-image
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.. _kolla_api_environment_variables:
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Environment Variables
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=====================
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Variables to pass to the containers
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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The Kolla containers also understand some environment variables to change their
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behavior at runtime:
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* **KOLLA_CONFIG**: load kolla config from the environment, takes precedence
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over ``KOLLA_CONFIG_FILE``.
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* **KOLLA_CONFIG_FILE**: path to kolla json config file, defaults to
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``/var/lib/kolla/config_files/config.json``.
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* **KOLLA_CONFIG_STRATEGY** (required): Defines how the :ref:`kolla_start
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script <kolla_api_external_config>` copies the configuration file. Must be
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one of:
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* **COPY_ONCE**: the configuration files are copied just once, the first time
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the container is started. In this scenario the container is perfectly
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immutable.
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* **COPY_ALWAYS**: the configuration files are copied each time the container
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starts. If a config file changes on the host, the change is applied in the
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container the next time it restarts.
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* **KOLLA_SKIP_EXTEND_START**: if set, bypass the ``extend_start.sh`` script.
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Not set by default.
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* **KOLLA_SERVICE_NAME**: if set, shows the value of the variable on the
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``PS1`` inside the container. Not set by default.
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* **KOLLA_BOOTSTRAP**: if set, and supported by the image, runs the bootstrap
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code defined in the images ``extend_start.sh`` scripts. Not set by default.
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* **KOLLA_UPGRADE**: if set, and supported by the image, runs the upgrade code
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defined in the images ``extend_start.sh`` scripts. Not set by default.
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* **KOLLA_OSM**: if set, and supported by the image, runs the online database
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migration code defined in the images ``extend_start.sh`` scripts. Not set by
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default.
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The containers may expose other environment variables for turning features on
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or off, such as the horizon container that looks for ``ENABLE_XXX`` variables
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where ``XXX`` is a horizon plugin name. These are generally defined in the
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container-specific ``extend_start.sh`` script, example for `horizon`_.
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.. _horizon: https://github.com/openstack/kolla/blob/master/docker/horizon/extend_start.sh
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Variables available in the containers
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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The following variables available in all images and can be evaluated in
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scripts:
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* **KOLLA_BASE_DISTRO**: ``base_distro`` used to build the image (e.g. centos,
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ubuntu)
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* **KOLLA_INSTALL_TYPE**: ``install_type`` used to build the image (binary,
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source)
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* **KOLLA_INSTALL_METATYPE**: ``install_metatype`` used to build the image
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(rdo, ...)
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