ETCD node failover

左手的ㄟ右手 2022-03-02 07:58 173阅读 0赞

# Unreachable member #

A cluster with etcd containers is created successfully.  
Check the cluster status with the following command.

# etcdctl --endpoint cluster-health

If the cluster is running normally, the output looks like:

member xxx is healthy: got healthy result from https://10.23.2.109:3379
    member xxx is healthy: got healthy result from https://10.23.2.108:3379
    member xxx is healthy: got healthy result from https://10.23.2.110:3379
    cluster is healthy

If one member failed, the output may look like:

failed to check the health of member xxx on https://10.23.2.109:3379: Get https://10.23.2.109:3379/health: dial tcp 10.23.2.109:3379: connect: connection refused
    member xxx is unreachable: [https://10.23.2.109:3379] are all unreachable
    member xxx is healthy: got healthy result from https://10.23.2.108:3379
    member xxx is healthy: got healthy result from https://10.23.2.110:3379
    cluster is healthy

The reason may meet one of the following four cases.

## Case 1: The whole environment of an etcd container was destroyed. ##

## Solution ##

*  Remove the destroyed member with etcdctl.

# etcdctl member remove xxx

xxx is memberID of the unreachable member.

*  Create a new etcd container with adding the following environment variables to env in config file.

"ETCD_INITIAL_CLUSTER_STATE": "existing"
    "ETCD_INITIAL_CLUSTER": <The cluster peer urls with the new etcd container>

"hostname2=[https://10.23.2.108][https_10.23.2.108]:3380,hostname3=[https://10.23.2.110][https_10.23.2.110]:3380" in *ETCD\_INITIAL\_CLUSTER* are the peer urls of the cluster after removing the destroyed member.

*  Add the new container to the existing cluster.

# etcdctl --endpoint member add <name> <peerURL>

<name> is hostname in its config file.

<peerURL> is one of ETCD\_INITIAL\_ADVERTISE\_PEER\_URLS in its config file.

## Case 2: The etcd container doesn't exist. ##

## Solution ##

*  Add ***"ETCD\_INITIAL\_CLUSTER\_STATE": "existing"*** to the container creation config file.
 *  Create the container with the new config file, but keep the other configurations as same as before.

## Case 3: The etcd container was stopped. ##

## Solution ##

Start the container.

# docker start <container>

## Case 4: The etcd service was stopped in its container. ##

## Solution ##

Restart the stopped etcd container.

# docker restart <container>

# Unhealthy member #

If a member is unhealthy, we can refer to above case 2 to remove its container with metadata, then create a new one to fix it.

[https_10.23.2.108]: https://10.23.2.108
[https_10.23.2.110]: https://10.23.2.110