Install and configure

This section describes how to install and configure the Workflow Service, code-named mistral, on the controller node.

Note

Mistral can be used in standalone mode or it can work with OpenStack.

If Mistral is used with OpenStack, you must already have a working OpenStack environment with at least the following components installed:

• Keystone with API v3 support

Note that installation and configuration may vary by distribution.

Overview

The Workflow service consists of the following components:

Mistral API service

Provides a REST API for operating and monitoring workflow executions.

mistral-dashboard service

Mistral Dashboard is a Horizon plugin.

Mistral Engine service

Controls workflow executions and handles their data flow, places finished tasks in a queue, transfers data from task to task, and deals with condition transitions, and so on.

Mistral Executor service

Executes task actions, picks up the tasks from the queue, runs actions, and sends results back to the engine.

Mistral Notifier service

Send notifications based on state of workflow executions.

python-mistralclient

Python client API and Command Line Interface.

mistral-lib

A library used by mistral internals.

mistral-extra

A collection of extra actions that could be installed to extend mistral standard actions with openstack ones.

Prerequisites

Install the following dependencies:

On apt based distributions:

$ apt-get update
$ apt-get install python3 python3-venv python3-pip git

On dnf based distributions:

$ dnf update
$ dnf install python3 python3-venv python3-pip git

Note

you may need to adapt the previous commands based on your distribution.

Installation

Note

For instructions on how to install Mistral using devstack, refer to Mistral Devstack Installation

Clone the repo and go to the repo directory:

$ git clone https://opendev.org/openstack/mistral
$ cd mistral

Create a venv:

$ python3 -m venv venv
$ source venv/bin/activate

Now install mistral:

$ pip install \
  -c https://releases.openstack.org/constraints/upper/master \
  -r requirements.txt \
  .

Note

You may need to adjust the constraints file based on the release of mistral you are installing

Generate the configuration file:

$ pip install tox
$ tox -egenconfig

Create the mistral directory and copy the example configuration file:

$ mkdir /etc/mistral
$ cp etc/mistral.conf.sample /etc/mistral/mistral.conf

Edit the configuration file:

$ vi /etc/mistral/mistral.conf

You may also want to install the mistral-extra package to have the opentack actions available (but this is not mandatory):

$ pip install mistral-extra

Configuring Mistral

Refer Configuration and Policy Guide to find general information on how to configure Mistral server.

Before The First Run

After the installation, you will see the mistral-server and mistral-db-manage commands in your virtual env.

The mistral-db-manage command can be used for database migrations.

Update the database to the latest revision:

# For MySQL / MariaDB / PostgreSQL
$ mistral-db-manage --config-file /etc/mistral/mistral.conf upgrade head

# For SQLite - do not use sqlite in production!
# e.g. connection = 'sqlite:////var/lib/mistral.sqlite'
$ python tools/sync_db.py --config-file /etc/mistral/mistral.conf

Before starting the Mistral server, run the mistral-db-manage populate command. It creates the DB with all the standard actions and standard workflows that Mistral provides to all Mistral users.:

$ mistral-db-manage --config-file /etc/mistral/mistral.conf populate

For more detailed information on the mistral-db-manage script, see the Mistral Upgrade Guide.

Running Mistral API server

To run the Mistral API server, execute the following command in a shell:

$ mistral-server --server api --config-file /etc/mistral/mistral.conf

Running Mistral Engines

To run the Mistral Engine, execute the following command in a shell:

$ mistral-server --server engine --config-file /etc/mistral/mistral.conf

Running Mistral Executors

To run the Mistral Executor instance, execute the following command in a shell:

$ mistral-server --server executor --config-file /etc/mistral/mistral.conf

Note that at least one Engine instance and one Executor instance should be running so that workflow tasks are processed by Mistral.

Mistral Notifier

To run the Mistral Notifier, execute the following command in a shell:

$ mistral-server --server notifier --config-file /etc/mistral/mistral.conf

Running Multiple Mistral Servers Under the Same Process

To run more than one server (API, Engine, or Task Executor) on the same process, execute the following command in a shell:

$ mistral-server --server api,engine --config-file /etc/mistral/mistral.conf

The –server command line option can be a comma delimited list. The valid options are “all” (by default if not specified) or any combination of “api”, “engine”, and “executor”. It is important to note that the “fake” transport for the rpc_backend defined in the config file should only be used if “all” the Mistral servers are launched on the same process. Otherwise, messages do not get delivered if the Mistral servers are launched on different processes because the “fake” transport is using an in-process queue.