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Operator Tasks

Operational guides for deploying, configuring, and maintaining an etcd cluster.

1 - How to Set Up a Demo etcd Cluster

Guide to setting up a cluster in etcd
01_etcd_clustering_2016050601

On each etcd node, specify the cluster members:

TOKEN=token-01
CLUSTER_STATE=new
NAME_1=machine-1
NAME_2=machine-2
NAME_3=machine-3
HOST_1=10.240.0.17
HOST_2=10.240.0.18
HOST_3=10.240.0.19
CLUSTER=${NAME_1}=http://${HOST_1}:2380,${NAME_2}=http://${HOST_2}:2380,${NAME_3}=http://${HOST_3}:2380

Run this on each machine:

# For machine 1
THIS_NAME=${NAME_1}
THIS_IP=${HOST_1}
etcd --data-dir=data.etcd --name ${THIS_NAME} \
	--initial-advertise-peer-urls http://${THIS_IP}:2380 --listen-peer-urls http://${THIS_IP}:2380 \
	--advertise-client-urls http://${THIS_IP}:2379 --listen-client-urls http://${THIS_IP}:2379 \
	--initial-cluster ${CLUSTER} \
	--initial-cluster-state ${CLUSTER_STATE} --initial-cluster-token ${TOKEN}

# For machine 2
THIS_NAME=${NAME_2}
THIS_IP=${HOST_2}
etcd --data-dir=data.etcd --name ${THIS_NAME} \
	--initial-advertise-peer-urls http://${THIS_IP}:2380 --listen-peer-urls http://${THIS_IP}:2380 \
	--advertise-client-urls http://${THIS_IP}:2379 --listen-client-urls http://${THIS_IP}:2379 \
	--initial-cluster ${CLUSTER} \
	--initial-cluster-state ${CLUSTER_STATE} --initial-cluster-token ${TOKEN}

# For machine 3
THIS_NAME=${NAME_3}
THIS_IP=${HOST_3}
etcd --data-dir=data.etcd --name ${THIS_NAME} \
	--initial-advertise-peer-urls http://${THIS_IP}:2380 --listen-peer-urls http://${THIS_IP}:2380 \
	--advertise-client-urls http://${THIS_IP}:2379 --listen-client-urls http://${THIS_IP}:2379 \
	--initial-cluster ${CLUSTER} \
	--initial-cluster-state ${CLUSTER_STATE} --initial-cluster-token ${TOKEN}

Or use our public discovery service:

curl https://discovery.etcd.io/new?size=3
https://discovery.etcd.io/a81b5818e67a6ea83e9d4daea5ecbc92

# grab this token
TOKEN=token-01
CLUSTER_STATE=new
NAME_1=machine-1
NAME_2=machine-2
NAME_3=machine-3
HOST_1=10.240.0.17
HOST_2=10.240.0.18
HOST_3=10.240.0.19
DISCOVERY=https://discovery.etcd.io/a81b5818e67a6ea83e9d4daea5ecbc92

THIS_NAME=${NAME_1}
THIS_IP=${HOST_1}
etcd --data-dir=data.etcd --name ${THIS_NAME} \
	--initial-advertise-peer-urls http://${THIS_IP}:2380 --listen-peer-urls http://${THIS_IP}:2380 \
	--advertise-client-urls http://${THIS_IP}:2379 --listen-client-urls http://${THIS_IP}:2379 \
	--discovery ${DISCOVERY} \
	--initial-cluster-state ${CLUSTER_STATE} --initial-cluster-token ${TOKEN}

THIS_NAME=${NAME_2}
THIS_IP=${HOST_2}
etcd --data-dir=data.etcd --name ${THIS_NAME} \
	--initial-advertise-peer-urls http://${THIS_IP}:2380 --listen-peer-urls http://${THIS_IP}:2380 \
	--advertise-client-urls http://${THIS_IP}:2379 --listen-client-urls http://${THIS_IP}:2379 \
	--discovery ${DISCOVERY} \
	--initial-cluster-state ${CLUSTER_STATE} --initial-cluster-token ${TOKEN}

THIS_NAME=${NAME_3}
THIS_IP=${HOST_3}
etcd --data-dir=data.etcd --name ${THIS_NAME} \
	--initial-advertise-peer-urls http://${THIS_IP}:2380 --listen-peer-urls http://${THIS_IP}:2380 \
	--advertise-client-urls http://${THIS_IP}:2379 --listen-client-urls http://${THIS_IP}:2379 \
	--discovery ${DISCOVERY} \
	--initial-cluster-state ${CLUSTER_STATE} --initial-cluster-token ${TOKEN}

Now etcd is ready! To connect to etcd with etcdctl:

export ETCDCTL_API=3
HOST_1=10.240.0.17
HOST_2=10.240.0.18
HOST_3=10.240.0.19
ENDPOINTS=$HOST_1:2379,$HOST_2:2379,$HOST_3:2379

etcdctl --endpoints=$ENDPOINTS member list

2 - How to conduct leader election in etcd cluster

Steps for conducting a leader election through the etcdctl client

Prerequisites

  • Ensure etcd and etcdctl is installed.
  • Check for active etcd cluster.

Conduct Leader election

The etcdctl command is used to conduct leader elections in an etcd cluster. It makes sure that only one client can become leader at a time.

etcdctl --endpoints=$ENDPOINTS elect <election-name> [proposal]

etcdctl --endpoints=$ENDPOINTS elect election-name p1

Options

  • --endpoints : $ENDPOINTS

Address of each etcd cluster members.

  • election-name string

A string identifier for the election. All participants competing for leadership must use the same election name.

  • leader-name string

Proposal value of the new leader.

Example

./etcdctl elect my-election proposal1
my-election/694d99fafea88404
proposal1

another election:
./etcdctl elect new-election proposal1
new-election/694d99fafea8840f
proposal1

3 - How to check Cluster status

Guide to checking etcd cluster status

Prerequisites

Check Overall Status

endpoint status to check the overall status of each endpoint specified in --endpoints flag:

etcdctl endpoint status (--endpoints=$ENDPOINTS|--cluster)

Options

--cluster[=false]: use all endpoints from the cluster member list

Check Health

endpoint health to check the healthiness of each endpoint specified in --endpoints flag:

etcdctl endpoint health (--endpoints=$ENDPOINTS|--cluster)

Options

--cluster[=false]: use all endpoints from the cluster member list

Check KV Hash

endpoint hashkv to check the KV history hash of each endpoint specified in --endpoints flag:

etcdctl endpoint hashkv (--endpoints=$ENDPOINTS|--cluster) [rev=$REV]

Options

--cluster[=false]: use all endpoints from the cluster member list
--rev=0: maximum revision to hash (default: latest revision)

Options inherited from parent commands

--endpoints="127.0.0.1:2379": gRPC endpoints
-w, --write-out="simple": set the output format (fields, json, protobuf, simple, table)

Examples

etcdctl --write-out=table --endpoints=$ENDPOINTS endpoint status

+------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
|    ENDPOINT      |        ID        | VERSION | DB SIZE | IS LEADER | IS LEARNER | RAFT TERM | RAFT INDEX | RAFT APPLIED INDEX | ERRORS |
+------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
| 10.240.0.17:2379 | 4917a7ab173fabe7 |  3.5.0  |   45 kB |      true |      false |         4 |      16726 |              16726 |        |
| 10.240.0.18:2379 | 59796ba9cd1bcd72 |  3.5.0  |   45 kB |     false |      false |         4 |      16726 |              16726 |        |
| 10.240.0.19:2379 | 94df724b66343e6c |  3.5.0  |   45 kB |     false |      false |         4 |      16726 |              16726 |        |
+------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------|
etcdctl --endpoints=$ENDPOINTS endpoint health

10.240.0.17:2379 is healthy: successfully committed proposal: took = 3.345431ms
10.240.0.19:2379 is healthy: successfully committed proposal: took = 3.767967ms
10.240.0.18:2379 is healthy: successfully committed proposal: took = 4.025451ms
etcdctl --cluster endpoint hashkv  --write-out=table

+------------------+------------+---------------+
|     ENDPOINT     |    HASH    | HASH REVISION |
+------------------+------------+---------------+
| 10.240.0.17:2379 | 3892279174 |             3 |
| 10.240.0.18:2379 | 3892279174 |             3 |
| 10.240.0.19:2379 | 3892279174 |             3 |
+------------------+------------+---------------+

4 - How to save the database

Guide to taking a snapshot of the etcd database

Pre-requisites

Snapshot a database

snapshot to save point-in-time snapshot of etcd database:

etcdctl --endpoints=$ENDPOINT snapshot save DB_NAME

Global Options

etcdctl

--endpoints=[127.0.0.1:2379], gRPC endpoints

Snapshot can only be requested from one etcd node, so --endpoints flag should contain only one endpoint.

etcdutl

-w, --write-out string   set the output format (fields, json, protobuf, simple, table) (default "simple")

Example

11_etcdctl_snapshot_2016051001
ENDPOINTS=$HOST_1:2379
etcdctl --endpoints=$ENDPOINTS snapshot save my.db

Snapshot saved at my.db
etcdutl --write-out=table snapshot status my.db

+---------+----------+------------+------------+
|  HASH   | REVISION | TOTAL KEYS | TOTAL SIZE |
+---------+----------+------------+------------+
| c55e8b8 |        9 |         13 | 25 kB      |
+---------+----------+------------+------------+

5 - How to Add and Remove Members

Guide to dealing with membership in etcd cluster

member to add,remove,update membership:

13_etcdctl_member_2016062301
# For each machine
TOKEN=my-etcd-token-1
CLUSTER_STATE=new
NAME_1=etcd-node-1
NAME_2=etcd-node-2
NAME_3=etcd-node-3
HOST_1=10.240.0.13
HOST_2=10.240.0.14
HOST_3=10.240.0.15
CLUSTER=${NAME_1}=http://${HOST_1}:2380,${NAME_2}=http://${HOST_2}:2380,${NAME_3}=http://${HOST_3}:2380

# For node 1
THIS_NAME=${NAME_1}
THIS_IP=${HOST_1}
etcd --data-dir=data.etcd --name ${THIS_NAME} \
	--initial-advertise-peer-urls http://${THIS_IP}:2380 \
	--listen-peer-urls http://${THIS_IP}:2380 \
	--advertise-client-urls http://${THIS_IP}:2379 \
	--listen-client-urls http://${THIS_IP}:2379 \
	--initial-cluster ${CLUSTER} \
	--initial-cluster-state ${CLUSTER_STATE} \
	--initial-cluster-token ${TOKEN}

# For node 2
THIS_NAME=${NAME_2}
THIS_IP=${HOST_2}
etcd --data-dir=data.etcd --name ${THIS_NAME} \
	--initial-advertise-peer-urls http://${THIS_IP}:2380 \
	--listen-peer-urls http://${THIS_IP}:2380 \
	--advertise-client-urls http://${THIS_IP}:2379 \
	--listen-client-urls http://${THIS_IP}:2379 \
	--initial-cluster ${CLUSTER} \
	--initial-cluster-state ${CLUSTER_STATE} \
	--initial-cluster-token ${TOKEN}

# For node 3
THIS_NAME=${NAME_3}
THIS_IP=${HOST_3}
etcd --data-dir=data.etcd --name ${THIS_NAME} \
	--initial-advertise-peer-urls http://${THIS_IP}:2380 \
	--listen-peer-urls http://${THIS_IP}:2380 \
	--advertise-client-urls http://${THIS_IP}:2379 \
	--listen-client-urls http://${THIS_IP}:2379 \
	--initial-cluster ${CLUSTER} \
	--initial-cluster-state ${CLUSTER_STATE} \
	--initial-cluster-token ${TOKEN}

Then replace a member with member remove and member add commands:

# get member ID
export ETCDCTL_API=3
HOST_1=10.240.0.13
HOST_2=10.240.0.14
HOST_3=10.240.0.15
etcdctl --endpoints=${HOST_1}:2379,${HOST_2}:2379,${HOST_3}:2379 member list

# remove the member
MEMBER_ID=278c654c9a6dfd3b
etcdctl --endpoints=${HOST_1}:2379,${HOST_2}:2379,${HOST_3}:2379 \
	member remove ${MEMBER_ID}

# add a new member (node 4)
export ETCDCTL_API=3
NAME_1=etcd-node-1
NAME_2=etcd-node-2
NAME_4=etcd-node-4
HOST_1=10.240.0.13
HOST_2=10.240.0.14
HOST_4=10.240.0.16 # new member
etcdctl --endpoints=${HOST_1}:2379,${HOST_2}:2379 \
	member add ${NAME_4} \
	--peer-urls=http://${HOST_4}:2380

Next, start the new member with --initial-cluster-state existing flag:

# [WARNING] If the new member starts from the same disk space,
# make sure to remove the data directory of the old member
#
# restart with 'existing' flag
TOKEN=my-etcd-token-1
CLUSTER_STATE=existing
NAME_1=etcd-node-1
NAME_2=etcd-node-2
NAME_4=etcd-node-4
HOST_1=10.240.0.13
HOST_2=10.240.0.14
HOST_4=10.240.0.16 # new member
CLUSTER=${NAME_1}=http://${HOST_1}:2380,${NAME_2}=http://${HOST_2}:2380,${NAME_4}=http://${HOST_4}:2380

THIS_NAME=${NAME_4}
THIS_IP=${HOST_4}
etcd --data-dir=data.etcd --name ${THIS_NAME} \
	--initial-advertise-peer-urls http://${THIS_IP}:2380 \
	--listen-peer-urls http://${THIS_IP}:2380 \
	--advertise-client-urls http://${THIS_IP}:2379 \
	--listen-client-urls http://${THIS_IP}:2379 \
	--initial-cluster ${CLUSTER} \
	--initial-cluster-state ${CLUSTER_STATE} \
	--initial-cluster-token ${TOKEN}