Multiple engine workers

URL of launchpad blueprint:

This specification is to implement multiple workers to murano-engine.

Problem description

murano-engine is currently single process. It’s a problem for scalability.

Proposed change

Implement multiple workers to murano-engine by oslo.service library. When starting service, murano-engine forks the number of workers which is written in configuration file. When a configuration reload is required, restart service is needed. If child process is killed, murano-engine forks new worker. Most of the OpenStack projects use oslo.service.


There are some external tools.

Configuration management tool such as Puppet, Chef, Ansible

Configuration management tool controls services which is managed by init systems like systemd, upstart. Configuration management tool does not manage processes.

Init systems

Systemd, upstart are init systems of Unix like systems. Upstart is default init system until Ubuntu 14.10 or RHEL6. Systemd is default init system of Ubuntu 15.04 or RHEL7, and other Linux systems.

Systemd manages processes based on configuration file. If process spawns child processes, systemd recognizes child processes properly and manages under single control group by a configuration file. Systemd can be configured automatically restart process on crash but does not have ability to spawn process.


Supervisor is time-proven process management tool written in python. Supervisor can control a number of processes on UNIX-like operating systems. Supervisor starts processes as subprocesses , so can true up/down and can be configured automatically restart them on a crash.

Supervisor has good function itself, but must managed by init systems and considered high availability. Supervisor is not working under Python 3. The whole Openstack and murano are going to support python 3. This is not appropriate for alternatives.

Combination of configuration management tool and systemd can be altenative for implementing multiple processes. configuration management tool deploys services, each service manages single murano-engine process.

Both proposed change and alternative can process restart if process crashed.

Proposed change can manage multi processes easier than alternative. Proposed change has main process which spawns child processes. If you change the number of processes, update configuration file and then restart service. On the other hand, alternative needs to rewrite conf file of configuration managenment tool and redeploy.

Proposed change can manage control group of murano-engine processes easier than alternative. Because proposed change can change control group settings by update a configuration file of systemd. On the other hand, alternative needs to update each confifiguration file of systemd.

Data model impact


REST API impact


Versioning impact


Other end user impact


Deployer impact

The number of murano-engine workers config option is added in murano.conf under engine section named workers. The default value is oslo_concurrency.processutils.get_worker_count().

Developer impact


Murano-dashboard / Horizon impact




Primary assignee:

Work Items

  • Add the number of murano-engine workers config option to murano.conf
  • Replace oslo_service.service.ServiceLauncher with oslo_service.service.launch in murano.engine.cmd module. Worker parameter of oslo_service.service.launch method takes the number of murano-engine workers config option.


  • oslo_concurrency


  • Unit tests on murano-engine

Documentation Impact