In the general case, upgrading from etcd 3.4 to 3.5 can be a zero-downtime, rolling upgrade:

  • one by one, stop the etcd v3.4 processes and replace them with etcd v3.5 processes
  • after running all v3.5 processes, new features in v3.5 are available to the cluster

Before starting an upgrade, read through the rest of this guide to prepare.

Upgrade checklists

NOTE: When migrating from v2 with no v3 data, etcd server v3.2+ panics when etcd restores from existing snapshots but no v3 ETCD_DATA_DIR/member/snap/db file. This happens when the server had migrated from v2 with no previous v3 data. This also prevents accidental v3 data loss (e.g. db file might have been moved). etcd requires that post v3 migration can only happen with v3 data. Do not upgrade to newer v3 versions until v3.0 server contains v3 data.

Highlighted breaking changes in 3.5.

Deprecate etcd_debugging_mvcc_db_total_size_in_bytes Prometheus metrics

v3.4 promoted etcd_debugging_mvcc_db_total_size_in_bytes Prometheus metrics to etcd_mvcc_db_total_size_in_bytes, in order to encourage etcd storage monitoring. And v3.5 completely deprcates etcd_debugging_mvcc_db_total_size_in_bytes.

  1. -etcd_debugging_mvcc_db_total_size_in_bytes
  2. +etcd_mvcc_db_total_size_in_bytes

Note that etcd_debugging_* namespace metrics have been marked as experimental. As we improve monitoring guide, we will promote more metrics.

Deprecated in etcd --logger capnslog

v3.4 defaults to --logger=zap in order to support multiple log outputs and structured logging.

etcd --logger=capnslog has been deprecated in v3.5, and now --logger=zap is the default.

  1. -etcd --logger=capnslog
  2. +etcd --logger=zap --log-outputs=stderr
  4. +# to write logs to stderr and a.log file at the same time
  5. +etcd --logger=zap --log-outputs=stderr,a.log

TODO(add more monitoring guides); v3.4 adds etcd --logger=zap support for structured logging and multiple log outputs. Main motivation is to promote automated etcd monitoring, rather than looking back server logs when it starts breaking. Future development will make etcd log as few as possible, and make etcd easier to monitor with metrics and alerts. etcd --logger=capnslog will be deprecated in v3.5.

Deprecated in etcd --log-output

v3.4 renamed etcd --log-output to --log-outputs to support multiple log outputs.

etcd --log-output has been deprecated in v3.5.

  1. -etcd --log-output=stderr
  2. +etcd --log-outputs=stderr

Deprecated etcd --log-package-levels

etcd --log-package-levels flag for capnslog has been deprecated.

Now, etcd --logger=zap is the default.

  1. -etcd --log-package-levels 'etcdmain=CRITICAL,etcdserver=DEBUG'
  2. +etcd --logger=zap --log-outputs=stderr

Deprecated [CLIENT-URL]/config/local/log

/config/local/log endpoint is being deprecated in v3.5, as is etcd --log-package-levels flag.

  1. -$ curl http://127.0.0.1:2379/config/local/log -XPUT -d '{"Level":"DEBUG"}'
  2. -# debug logging enabled

Changed gRPC gateway HTTP endpoints (deprecated /v3beta)

Before

  1. curl -L http://localhost:2379/v3beta/kv/put \
  2.   -X POST -d '{"key": "Zm9v", "value": "YmFy"}'

After

  1. curl -L http://localhost:2379/v3/kv/put \
  2.   -X POST -d '{"key": "Zm9v", "value": "YmFy"}'

/v3beta has been removed in 3.5 release.

Server upgrade checklists

Upgrade requirements

To upgrade an existing etcd deployment to 3.5, the running cluster must be 3.4 or greater. If it’s before 3.4, please upgrade to 3.4 before upgrading to 3.5.

Also, to ensure a smooth rolling upgrade, the running cluster must be healthy. Check the health of the cluster by using the etcdctl endpoint health command before proceeding.

Preparation

Before upgrading etcd, always test the services relying on etcd in a staging environment before deploying the upgrade to the production environment.

Before beginning, download the snapshot backup. Should something go wrong with the upgrade, it is possible to use this backup to downgrade back to existing etcd version. Please note that the snapshot command only backs up the v3 data. For v2 data, see backing up v2 datastore.

Mixed versions

While upgrading, an etcd cluster supports mixed versions of etcd members, and operates with the protocol of the lowest common version. The cluster is only considered upgraded once all of its members are upgraded to version 3.5. Internally, etcd members negotiate with each other to determine the overall cluster version, which controls the reported version and the supported features.

Limitations

Note: If the cluster only has v3 data and no v2 data, it is not subject to this limitation.

If the cluster is serving a v2 data set larger than 50MB, each newly upgraded member may take up to two minutes to catch up with the existing cluster. Check the size of a recent snapshot to estimate the total data size. In other words, it is safest to wait for 2 minutes between upgrading each member.

For a much larger total data size, 100MB or more , this one-time process might take even more time. Administrators of very large etcd clusters of this magnitude can feel free to contact the etcd team before upgrading, and we’ll be happy to provide advice on the procedure.

Downgrade

If all members have been upgraded to v3.5, the cluster will be upgraded to v3.5, and downgrade from this completed state is not possible. If any single member is still v3.4, however, the cluster and its operations remains “v3.4”, and it is possible from this mixed cluster state to return to using a v3.4 etcd binary on all members.

Please download the snapshot backup to make downgrading the cluster possible even after it has been completely upgraded.

Upgrade procedure

This example shows how to upgrade a 3-member v3.4 ectd cluster running on a local machine.

Step 1: check upgrade requirements

Is the cluster healthy and running v3.4.x?

  1. etcdctl --endpoints=localhost:2379,localhost:22379,localhost:32379 endpoint health
  2. <<COMMENT
  3. localhost:2379 is healthy: successfully committed proposal: took = 2.118638ms
  4. localhost:22379 is healthy: successfully committed proposal: took = 3.631388ms
  5. localhost:32379 is healthy: successfully committed proposal: took = 2.157051ms
  6. COMMENT
  8. curl http://localhost:2379/version
  9. <<COMMENT
  10. {"etcdserver":"3.4.0","etcdcluster":"3.4.0"}
  11. COMMENT
  13. curl http://localhost:22379/version
  14. <<COMMENT
  15. {"etcdserver":"3.4.0","etcdcluster":"3.4.0"}
  16. COMMENT
  18. curl http://localhost:32379/version
  19. <<COMMENT
  20. {"etcdserver":"3.4.0","etcdcluster":"3.4.0"}
  21. COMMENT

Step 2: download snapshot backup from leader

Download the snapshot backup to provide a downgrade path should any problems occur.

etcd leader is guaranteed to have the latest application data, thus fetch snapshot from leader:

  1. curl -sL http://localhost:2379/metrics | grep etcd_server_is_leader
  2. <<COMMENT
  3. # HELP etcd_server_is_leader Whether or not this member is a leader. 1 if is, 0 otherwise.
  4. # TYPE etcd_server_is_leader gauge
  5. etcd_server_is_leader 1
  6. COMMENT
  8. curl -sL http://localhost:22379/metrics | grep etcd_server_is_leader
  9. <<COMMENT
  10. etcd_server_is_leader 0
  11. COMMENT
  13. curl -sL http://localhost:32379/metrics | grep etcd_server_is_leader
  14. <<COMMENT
  15. etcd_server_is_leader 0
  16. COMMENT
  18. etcdctl --endpoints=localhost:2379 snapshot save backup.db
  19. <<COMMENT
  20. {"level":"info","ts":1526585787.148433,"caller":"snapshot/v3_snapshot.go:109","msg":"created temporary db file","path":"backup.db.part"}
  21. {"level":"info","ts":1526585787.1485257,"caller":"snapshot/v3_snapshot.go:120","msg":"fetching snapshot","endpoint":"localhost:2379"}
  22. {"level":"info","ts":1526585787.1519694,"caller":"snapshot/v3_snapshot.go:133","msg":"fetched snapshot","endpoint":"localhost:2379","took":0.003502721}
  23. {"level":"info","ts":1526585787.1520295,"caller":"snapshot/v3_snapshot.go:142","msg":"saved","path":"backup.db"}
  24. Snapshot saved at backup.db
  25. COMMENT

Step 3: stop one existing etcd server

When each etcd process is stopped, expected errors will be logged by other cluster members. This is normal since a cluster member connection has been (temporarily) broken:

  1. {"level":"info","ts":1526587281.2001143,"caller":"etcdserver/server.go:2249","msg":"updating cluster version","from":"3.0","to":"3.4"}
  2. {"level":"info","ts":1526587281.2010646,"caller":"membership/cluster.go:473","msg":"updated cluster version","cluster-id":"7dee9ba76d59ed53","local-member-id":"7339c4e5e833c029","from":"3.0","from":"3.4"}
  3. {"level":"info","ts":1526587281.2012327,"caller":"api/capability.go:76","msg":"enabled capabilities for version","cluster-version":"3.4"}
  4. {"level":"info","ts":1526587281.2013083,"caller":"etcdserver/server.go:2272","msg":"cluster version is updated","cluster-version":"3.4"}
  8. ^C{"level":"info","ts":1526587299.0717514,"caller":"osutil/interrupt_unix.go:63","msg":"received signal; shutting down","signal":"interrupt"}
  9. {"level":"info","ts":1526587299.0718873,"caller":"embed/etcd.go:285","msg":"closing etcd server","name":"s1","data-dir":"/tmp/etcd/s1","advertise-peer-urls":["http://localhost:2380"],"advertise-client-urls":["http://localhost:2379"]}
  10. {"level":"info","ts":1526587299.0722554,"caller":"etcdserver/server.go:1341","msg":"leadership transfer starting","local-member-id":"7339c4e5e833c029","current-leader-member-id":"7339c4e5e833c029","transferee-member-id":"729934363faa4a24"}
  11. {"level":"info","ts":1526587299.0723994,"caller":"raft/raft.go:1107","msg":"7339c4e5e833c029 [term 3] starts to transfer leadership to 729934363faa4a24"}
  12. {"level":"info","ts":1526587299.0724802,"caller":"raft/raft.go:1113","msg":"7339c4e5e833c029 sends MsgTimeoutNow to 729934363faa4a24 immediately as 729934363faa4a24 already has up-to-date log"}
  13. {"level":"info","ts":1526587299.0737045,"caller":"raft/raft.go:797","msg":"7339c4e5e833c029 [term: 3] received a MsgVote message with higher term from 729934363faa4a24 [term: 4]"}
  14. {"level":"info","ts":1526587299.0737681,"caller":"raft/raft.go:656","msg":"7339c4e5e833c029 became follower at term 4"}
  15. {"level":"info","ts":1526587299.073831,"caller":"raft/raft.go:882","msg":"7339c4e5e833c029 [logterm: 3, index: 9, vote: 0] cast MsgVote for 729934363faa4a24 [logterm: 3, index: 9] at term 4"}
  16. {"level":"info","ts":1526587299.0738947,"caller":"raft/node.go:312","msg":"raft.node: 7339c4e5e833c029 lost leader 7339c4e5e833c029 at term 4"}
  17. {"level":"info","ts":1526587299.0748374,"caller":"raft/node.go:306","msg":"raft.node: 7339c4e5e833c029 elected leader 729934363faa4a24 at term 4"}
  18. {"level":"info","ts":1526587299.1726425,"caller":"etcdserver/server.go:1362","msg":"leadership transfer finished","local-member-id":"7339c4e5e833c029","old-leader-member-id":"7339c4e5e833c029","new-leader-member-id":"729934363faa4a24","took":0.100389359}
  19. {"level":"info","ts":1526587299.1728148,"caller":"rafthttp/peer.go:333","msg":"stopping remote peer","remote-peer-id":"b548c2511513015"}
  20. {"level":"warn","ts":1526587299.1751974,"caller":"rafthttp/stream.go:291","msg":"closed TCP streaming connection with remote peer","stream-writer-type":"stream MsgApp v2","remote-peer-id":"b548c2511513015"}
  21. {"level":"warn","ts":1526587299.1752589,"caller":"rafthttp/stream.go:301","msg":"stopped TCP streaming connection with remote peer","stream-writer-type":"stream MsgApp v2","remote-peer-id":"b548c2511513015"}
  22. {"level":"warn","ts":1526587299.177348,"caller":"rafthttp/stream.go:291","msg":"closed TCP streaming connection with remote peer","stream-writer-type":"stream Message","remote-peer-id":"b548c2511513015"}
  23. {"level":"warn","ts":1526587299.1774004,"caller":"rafthttp/stream.go:301","msg":"stopped TCP streaming connection with remote peer","stream-writer-type":"stream Message","remote-peer-id":"b548c2511513015"}
  24. {"level":"info","ts":1526587299.177515,"caller":"rafthttp/pipeline.go:86","msg":"stopped HTTP pipelining with remote peer","local-member-id":"7339c4e5e833c029","remote-peer-id":"b548c2511513015"}
  25. {"level":"warn","ts":1526587299.1777067,"caller":"rafthttp/stream.go:436","msg":"lost TCP streaming connection with remote peer","stream-reader-type":"stream MsgApp v2","local-member-id":"7339c4e5e833c029","remote-peer-id":"b548c2511513015","error":"read tcp 127.0.0.1:34636->127.0.0.1:32380: use of closed network connection"}
  26. {"level":"info","ts":1526587299.1778402,"caller":"rafthttp/stream.go:459","msg":"stopped stream reader with remote peer","stream-reader-type":"stream MsgApp v2","local-member-id":"7339c4e5e833c029","remote-peer-id":"b548c2511513015"}
  27. {"level":"warn","ts":1526587299.1780295,"caller":"rafthttp/stream.go:436","msg":"lost TCP streaming connection with remote peer","stream-reader-type":"stream Message","local-member-id":"7339c4e5e833c029","remote-peer-id":"b548c2511513015","error":"read tcp 127.0.0.1:34634->127.0.0.1:32380: use of closed network connection"}
  28. {"level":"info","ts":1526587299.1780987,"caller":"rafthttp/stream.go:459","msg":"stopped stream reader with remote peer","stream-reader-type":"stream Message","local-member-id":"7339c4e5e833c029","remote-peer-id":"b548c2511513015"}
  29. {"level":"info","ts":1526587299.1781602,"caller":"rafthttp/peer.go:340","msg":"stopped remote peer","remote-peer-id":"b548c2511513015"}
  30. {"level":"info","ts":1526587299.1781986,"caller":"rafthttp/peer.go:333","msg":"stopping remote peer","remote-peer-id":"729934363faa4a24"}
  31. {"level":"warn","ts":1526587299.1802843,"caller":"rafthttp/stream.go:291","msg":"closed TCP streaming connection with remote peer","stream-writer-type":"stream MsgApp v2","remote-peer-id":"729934363faa4a24"}
  32. {"level":"warn","ts":1526587299.1803446,"caller":"rafthttp/stream.go:301","msg":"stopped TCP streaming connection with remote peer","stream-writer-type":"stream MsgApp v2","remote-peer-id":"729934363faa4a24"}
  33. {"level":"warn","ts":1526587299.1824749,"caller":"rafthttp/stream.go:291","msg":"closed TCP streaming connection with remote peer","stream-writer-type":"stream Message","remote-peer-id":"729934363faa4a24"}
  34. {"level":"warn","ts":1526587299.18255,"caller":"rafthttp/stream.go:301","msg":"stopped TCP streaming connection with remote peer","stream-writer-type":"stream Message","remote-peer-id":"729934363faa4a24"}
  35. {"level":"info","ts":1526587299.18261,"caller":"rafthttp/pipeline.go:86","msg":"stopped HTTP pipelining with remote peer","local-member-id":"7339c4e5e833c029","remote-peer-id":"729934363faa4a24"}
  36. {"level":"warn","ts":1526587299.1827736,"caller":"rafthttp/stream.go:436","msg":"lost TCP streaming connection with remote peer","stream-reader-type":"stream MsgApp v2","local-member-id":"7339c4e5e833c029","remote-peer-id":"729934363faa4a24","error":"read tcp 127.0.0.1:51482->127.0.0.1:22380: use of closed network connection"}
  37. {"level":"info","ts":1526587299.182845,"caller":"rafthttp/stream.go:459","msg":"stopped stream reader with remote peer","stream-reader-type":"stream MsgApp v2","local-member-id":"7339c4e5e833c029","remote-peer-id":"729934363faa4a24"}
  38. {"level":"warn","ts":1526587299.1830168,"caller":"rafthttp/stream.go:436","msg":"lost TCP streaming connection with remote peer","stream-reader-type":"stream Message","local-member-id":"7339c4e5e833c029","remote-peer-id":"729934363faa4a24","error":"context canceled"}
  39. {"level":"warn","ts":1526587299.1831107,"caller":"rafthttp/peer_status.go:65","msg":"peer became inactive","peer-id":"729934363faa4a24","error":"failed to read 729934363faa4a24 on stream Message (context canceled)"}
  40. {"level":"info","ts":1526587299.1831737,"caller":"rafthttp/stream.go:459","msg":"stopped stream reader with remote peer","stream-reader-type":"stream Message","local-member-id":"7339c4e5e833c029","remote-peer-id":"729934363faa4a24"}
  41. {"level":"info","ts":1526587299.1832306,"caller":"rafthttp/peer.go:340","msg":"stopped remote peer","remote-peer-id":"729934363faa4a24"}
  42. {"level":"warn","ts":1526587299.1837125,"caller":"rafthttp/http.go:424","msg":"failed to find remote peer in cluster","local-member-id":"7339c4e5e833c029","remote-peer-id-stream-handler":"7339c4e5e833c029","remote-peer-id-from":"b548c2511513015","cluster-id":"7dee9ba76d59ed53"}
  43. {"level":"warn","ts":1526587299.1840093,"caller":"rafthttp/http.go:424","msg":"failed to find remote peer in cluster","local-member-id":"7339c4e5e833c029","remote-peer-id-stream-handler":"7339c4e5e833c029","remote-peer-id-from":"b548c2511513015","cluster-id":"7dee9ba76d59ed53"}
  44. {"level":"warn","ts":1526587299.1842315,"caller":"rafthttp/http.go:424","msg":"failed to find remote peer in cluster","local-member-id":"7339c4e5e833c029","remote-peer-id-stream-handler":"7339c4e5e833c029","remote-peer-id-from":"729934363faa4a24","cluster-id":"7dee9ba76d59ed53"}
  45. {"level":"warn","ts":1526587299.1844475,"caller":"rafthttp/http.go:424","msg":"failed to find remote peer in cluster","local-member-id":"7339c4e5e833c029","remote-peer-id-stream-handler":"7339c4e5e833c029","remote-peer-id-from":"729934363faa4a24","cluster-id":"7dee9ba76d59ed53"}
  46. {"level":"info","ts":1526587299.2056687,"caller":"embed/etcd.go:473","msg":"stopping serving peer traffic","address":"127.0.0.1:2380"}
  47. {"level":"info","ts":1526587299.205819,"caller":"embed/etcd.go:480","msg":"stopped serving peer traffic","address":"127.0.0.1:2380"}
  48. {"level":"info","ts":1526587299.2058413,"caller":"embed/etcd.go:289","msg":"closed etcd server","name":"s1","data-dir":"/tmp/etcd/s1","advertise-peer-urls":["http://localhost:2380"],"advertise-client-urls":["http://localhost:2379"]}

Step 4: restart the etcd server with same configuration

Restart the etcd server with same configuration but with the new etcd binary.

  1. -etcd-old --name s1 \
  2. +etcd-new --name s1 \
  3.   --data-dir /tmp/etcd/s1 \
  4.   --listen-client-urls http://localhost:2379 \
  5.   --advertise-client-urls http://localhost:2379 \
  6.   --listen-peer-urls http://localhost:2380 \
  7.   --initial-advertise-peer-urls http://localhost:2380 \
  8.   --initial-cluster s1=http://localhost:2380,s2=http://localhost:22380,s3=http://localhost:32380 \
  9.   --initial-cluster-token tkn \
  10.   --initial-cluster-state new

The new v3.5 etcd will publish its information to the cluster. At this point, cluster still operates as v3.4 protocol, which is the lowest common version.

{"level":"info","ts":1526586617.1647713,"caller":"membership/cluster.go:485","msg":"set initial cluster version","cluster-id":"7dee9ba76d59ed53","local-member-id":"7339c4e5e833c029","cluster-version":"3.0"}

{"level":"info","ts":1526586617.1648536,"caller":"api/capability.go:76","msg":"enabled capabilities for version","cluster-version":"3.0"}

{"level":"info","ts":1526586617.1649303,"caller":"membership/cluster.go:473","msg":"updated cluster version","cluster-id":"7dee9ba76d59ed53","local-member-id":"7339c4e5e833c029","from":"3.0","from":"3.4"}

{"level":"info","ts":1526586617.1649797,"caller":"api/capability.go:76","msg":"enabled capabilities for version","cluster-version":"3.4"}

{"level":"info","ts":1526586617.2107732,"caller":"etcdserver/server.go:1770","msg":"published local member to cluster through raft","local-member-id":"7339c4e5e833c029","local-member-attributes":"{Name:s1 ClientURLs:[http://localhost:2379]}","request-path":"/0/members/7339c4e5e833c029/attributes","cluster-id":"7dee9ba76d59ed53","publish-timeout":7}

Verify that each member, and then the entire cluster, becomes healthy with the new v3.5 etcd binary:

  1. etcdctl endpoint health --endpoints=localhost:2379,localhost:22379,localhost:32379
  2. <<COMMENT
  3. localhost:32379 is healthy: successfully committed proposal: took = 2.337471ms
  4. localhost:22379 is healthy: successfully committed proposal: took = 1.130717ms
  5. localhost:2379 is healthy: successfully committed proposal: took = 2.124843ms
  6. COMMENT

Un-upgraded members will log warnings like the following until the entire cluster is upgraded.

This is expected and will cease after all etcd cluster members are upgraded to v3.5:

  1. :41.942121 W | etcdserver: member 7339c4e5e833c029 has a higher version 3.5.0
  2. :45.945154 W | etcdserver: the local etcd version 3.4.0 is not up-to-date

Step 5: repeat step 3 and step 4 for rest of the members

When all members are upgraded, the cluster will report upgrading to 3.5 successfully:

Member 1:

{"level":"info","ts":1526586949.0920913,"caller":"api/capability.go:76","msg":"enabled capabilities for version","cluster-version":"3.5"} {"level":"info","ts":1526586949.0921566,"caller":"etcdserver/server.go:2272","msg":"cluster version is updated","cluster-version":"3.5"}

Member 2:

{"level":"info","ts":1526586949.092117,"caller":"membership/cluster.go:473","msg":"updated cluster version","cluster-id":"7dee9ba76d59ed53","local-member-id":"729934363faa4a24","from":"3.4","from":"3.5"} {"level":"info","ts":1526586949.0923078,"caller":"api/capability.go:76","msg":"enabled capabilities for version","cluster-version":"3.5"}

Member 3:

{"level":"info","ts":1526586949.0921423,"caller":"membership/cluster.go:473","msg":"updated cluster version","cluster-id":"7dee9ba76d59ed53","local-member-id":"b548c2511513015","from":"3.4","from":"3.5"} {"level":"info","ts":1526586949.0922918,"caller":"api/capability.go:76","msg":"enabled capabilities for version","cluster-version":"3.5"}

  1. endpoint health --endpoints=localhost:2379,localhost:22379,localhost:32379
  2. <<COMMENT
  3. localhost:2379 is healthy: successfully committed proposal: took = 492.834µs
  4. localhost:22379 is healthy: successfully committed proposal: took = 1.015025ms
  5. localhost:32379 is healthy: successfully committed proposal: took = 1.853077ms
  6. COMMENT
  8. curl http://localhost:2379/version
  9. <<COMMENT
  10. {"etcdserver":"3.5.0","etcdcluster":"3.5.0"}
  11. COMMENT
  13. curl http://localhost:22379/version
  14. <<COMMENT
  15. {"etcdserver":"3.5.0","etcdcluster":"3.5.0"}
  16. COMMENT
  18. curl http://localhost:32379/version
  19. <<COMMENT
  20. {"etcdserver":"3.5.0","etcdcluster":"3.5.0"}
  21. COMMENT