Run Yorc in High Availability (HA) mode

High level view of a typical HA installation

The bellow figure illustrates how a typical Yorc setup for enabling High Availability looks like.

Typical Yorc HA setup

This setup is composed by the following main components:

  • A POSIX distributed file system (NFS as an example in the figure above) to store deployments recipes (Shell scripts, Ansible recipes, binaries…)
  • A cluster of Consul servers
  • A cluster of Yorc servers each one collocated with a Consul agent and connected to the distributed filesystem
  • A Alien4Cloud with the Yorc plugin collocated with a Consul agent

The next sections describes how to setup those components.

Yorc HA setup

Distributed File System

Describing how to setup a Distributed File System (DSF) is out of the scope of this document. When choosing your DSF please take care to verify that it is POSIX compatible and can be mounted as linux partition.

Consul servers

To setup a cluster of Consul servers please refer to the Consul online documentation. One important thing to note is that you will need 3 or 5 Consul servers to ensure HA.

Yorc servers

Each Yorc server should be installed on its own host with a local Consul agent and a partition mounted on the Distributed File System. The Consul agent should run in client mode (by opposition to the server mode). Here is how to run a Consul agent in client mode and connect it to a running Consul server cluster.

consul agent -config-dir ./consul-conf -data-dir ./consul-data -retry-join <ConsulServer1IP> -retry-join <ConsulServer2IP> -retry-join <ConsulServer3IP>

When starting the Yorc server instance, a Consul service is automatically created with a defined TCP check on Yorc port.

When running Yorc you should use the –server_id command line flag (or equivalent configuration options or environment variable) to specify the server ID used to identify the server node in a cluster.

When running Yorc you should use the –working_directory command line flag (or equivalent configuration options or environment variable) to specify a working directory on the Distributed File System.


Please refer to the dedicated Yorc plugin for Alien4Cloud documentation for its typical installation and configuration.

Install and run Consul agent in client mode.

consul agent -config-dir ./consul-conf -data-dir ./consul-data -retry-join <ConsulServer1IP> -retry-join <ConsulServer2IP> -retry-join <ConsulServer3IP> -recursor <ConsulServer1IP> -recursor <ConsulServer2IP> -recursor <ConsulServer3IP>

Configure Consul DNS forwarding in order to be able to resolve yorc.service.consul DNS domain name.

In the Yorc plugin for Alien4Cloud configuration use http://yorc.service.consul:8800 as Yorc URL instead of using a IP address. This DNS name will be resolved by Consul (using a round-robin algorithm) to available Yorc servers.

If a Yorc server becomes unavailable, then Consul will detect it by using the service check and will stop to resolve the DNS requests to this Yorc instance, allowing seamless failover.