Sunday, November 27, 2016

Oracle Linux - Consul failed to sync remote state: No cluster leader

Whenever you are installing and running Consul from HashiCorp on Oracle Linux you might run into some strange errors. Even though your configuration JSON file passes the configuration validation the log file contains a long repetitive lst of the same error complaining about "failed to sync remote state: No cluster leader" and " coordinate update error: No cluster leader".

Consul is a tool for service discovery and configuration. It provides high level features such as service discovery, health checking and key/value storage. It makes use of a group of strongly consistent servers to manage the datacenter. Consul is developed by HasiCorp and is available from its own website.

It might be that you have the below output when you start consul:

    2016/11/25 21:03:50 [INFO] raft: Initial configuration (index=0): []
    2016/11/25 21:03:50 [INFO] raft: Node at 127.0.0.1:8300 [Follower] entering Follower state (Leader: "")
    2016/11/25 21:03:50 [INFO] serf: EventMemberJoin: consul_1 127.0.0.1
    2016/11/25 21:03:50 [INFO] serf: EventMemberJoin: consul_1.private_dc 127.0.0.1
    2016/11/25 21:03:50 [INFO] consul: Adding LAN server consul_1 (Addr: tcp/127.0.0.1:8300) (DC: private_dc)
    2016/11/25 21:03:50 [INFO] consul: Adding WAN server consul_1.private_dc (Addr: tcp/127.0.0.1:8300) (DC: private_dc)
    2016/11/25 21:03:55 [WARN] raft: no known peers, aborting election
    2016/11/25 21:03:57 [ERR] agent: failed to sync remote state: No cluster leader
    2016/11/25 21:04:14 [ERR] agent: coordinate update error: No cluster leader
    2016/11/25 21:04:30 [ERR] agent: failed to sync remote state: No cluster leader
    2016/11/25 21:04:50 [ERR] agent: coordinate update error: No cluster leader
    2016/11/25 21:05:01 [ERR] agent: failed to sync remote state: No cluster leader
    2016/11/25 21:05:26 [ERR] agent: coordinate update error: No cluster leader
    2016/11/25 21:05:34 [ERR] agent: failed to sync remote state: No cluster leader
    2016/11/25 21:06:02 [ERR] agent: coordinate update error: No cluster leader
    2016/11/25 21:06:10 [ERR] agent: failed to sync remote state: No cluster leader
    2016/11/25 21:06:35 [ERR] agent: coordinate update error: No cluster leader

The main reason for the above is that you try to start consul in an environment where there is no cluster available, or it is the first node of the cluster. In case you start it as the first node of the cluster or as the only node of the cluster you have to ensure that you include -bootstrap-expect 1 as a command line option when starting (in case you will only have one node).

You can also include "bootstrap_expect": 1 in the json configuration file if you use a configuration file to start Consul.

As an example, the below start of Consult will prevent the above errors:

consul agent -server -bootstrap-expect 1 -data-dir /tmp/consul
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