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etcd/CHANGELOG-3.4.md

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v3.4.0 (TBD 2018-05-01)

See code changes and v3.4 upgrade guide for any breaking changes.

Improved

  • TODO: Rewrite client balancer with new gRPC balancer interface.
  • Add jitter to watch progress notify to prevent spikes in etcd_network_client_grpc_sent_bytes_total.
  • Add warnings on requests taking too long.
    • e.g. etcdserver: read-only range request "key:\"\\000\" range_end:\"\\000\" " took too long [3.389041388s] to execute
  • Improve long-running concurrent read transactions under light write workloads.
    • Previously, periodic commit on pending writes blocks incoming read transactions, even if there is no pending write.
    • Now, periodic commit operation does not block concurrent read transactions, thus improves long-running read transaction performance.
  • Adjust election timeout on server restart to reduce disruptive rejoining servers.
    • Previously, etcd fast-forwards election ticks on server start, with only one tick left for leader election. This is to speed up start phase, without having to wait until all election ticks elapse. Advancing election ticks is useful for cross datacenter deployments with larger election timeouts. However, it was affecting cluster availability if the last tick elapses before leader contacts the restarted node.
    • Now, when etcd restarts, it adjusts election ticks with more than one tick left, thus more time for leader to prevent disruptive restart.
  • Add Raft Pre-Vote feature to reduce disruptive rejoining servers.
    • For instance, a flaky(or rejoining) member may drop in and out, and start campaign. This member will end up with a higher term, and ignore all incoming messages with lower term. In this case, a new leader eventually need to get elected, thus disruptive to cluster availability. Raft implements Pre-Vote phase to prevent this kind of disruptions. If enabled, Raft runs an additional phase of election to check if pre-candidate can get enough votes to win an election.
  • Adjust periodic compaction retention window.
    • e.g. --auto-compaction-mode=revision --auto-compaction-retention=1000 automatically Compact on "latest revision" - 1000 every 5-minute (when latest revision is 30000, compact on revision 29000).
    • e.g. Previously, --auto-compaction-mode=periodic --auto-compaction-retention=24h automatically Compact with 24-hour retention windown for every 2.4-hour. Now, Compact happens for every 1-hour.
    • e.g. Previously, --auto-compaction-mode=periodic --auto-compaction-retention=30m automatically Compact with 30-minute retention windown for every 3-minute. Now, Compact happens for every 30-minute.
    • Periodic compactor keeps recording latest revisions for every compaction period when given period is less than 1-hour, or for every 1-hour when given compaction period is greater than 1-hour (e.g. 1-hour when --auto-compaction-mode=periodic --auto-compaction-retention=24h).
    • For every compaction period or 1-hour, compactor uses the last revision that was fetched before compaction period, to discard historical data.
    • The retention window of compaction period moves for every given compaction period or hour.
    • For instance, when hourly writes are 100 and --auto-compaction-mode=periodic --auto-compaction-retention=24h, v3.2.x, v3.3.0, v3.3.1, and v3.3.2 compact revision 2400, 2640, and 2880 for every 2.4-hour, while v3.3.3 or later compacts revision 2400, 2500, 2600 for every 1-hour.
    • Futhermore, when --auto-compaction-mode=periodic --auto-compaction-retention=30m and writes per minute are about 1000, v3.3.0, v3.3.1, and v3.3.2 compact revision 30000, 33000, and 36000, for every 3-minute, while v3.3.3 or later compacts revision 30000, 60000, and 90000, for every 30-minute.
  • Make Lease Lookup non-blocking with concurrent Grant/Revoke.

Breaking Changes

Dependency

Metrics, Monitoring

Security, Authentication

See security doc for more details.

  • Add etcd --host-whitelist flag, etcdserver.Config.HostWhitelist, and embed.Config.HostWhitelist, to prevent "DNS Rebinding" attack.
    • Any website can simply create an authorized DNS name, and direct DNS to "localhost" (or any other address). Then, all HTTP endpoints of etcd server listening on "localhost" becomes accessible, thus vulnerable to DNS rebinding attacks (CVE-2018-5702).
    • Client origin enforce policy works as follow:
      • If client connection is secure via HTTPS, allow any hostnames..
      • If client connection is not secure and "HostWhitelist" is not empty, only allow HTTP requests whose Host field is listed in whitelist.
    • By default, "HostWhitelist" is empty, which means insecure server allows all client HTTP requests.
    • Note that the client origin policy is enforced whether authentication is enabled or not, for tighter controls.
    • When specifying hostnames, loopback addresses are not added automatically. To allow loopback interfaces, add them to whitelist manually (e.g. "localhost", "127.0.0.1", etc.).
    • e.g. etcd --host-whitelist example.com, then the server will reject all HTTP requests whose Host field is not example.com (also rejects requests to "localhost").
  • TODO: Support TLS cipher suite lists.
  • Support ttl field for etcd Authentication JWT token.
    • e.g. etcd --auth-token jwt,pub-key=<pub key path>,priv-key=<priv key path>,sign-method=<sign method>,ttl=5m.
  • Allow empty token provider in etcdserver.ServerConfig.AuthToken.

Added: etcd

  • Add --pre-vote flag to enable to run an additional Raft election phase.
    • For instance, a flaky(or rejoining) member may drop in and out, and start campaign. This member will end up with a higher term, and ignore all incoming messages with lower term. In this case, a new leader eventually need to get elected, thus disruptive to cluster availability. Raft implements Pre-Vote phase to prevent this kind of disruptions. If enabled, Raft runs an additional phase of election to check if pre-candidate can get enough votes to win an election.
    • --pre-vote=false by default.
    • v3.5 will enable --pre-vote=true by default.
  • TODO: --initial-corrupt-check flag is now stable (--experimental-initial-corrupt-check is deprecated).
    • --initial-corrupt-check=true by default, to check cluster database hashes before serving client/peer traffic.
  • TODO: --corrupt-check-time flag is now stable (--experimental-corrupt-check-time is deprecated).
    • --corrupt-check-time=12h by default, to check cluster database hashes for every 12-hour.
  • TODO: --enable-v2v3 flag is now stable (--experimental-enable-v2v3 is deprecated).
    • --enable-v2=true --enable-v2v3='' by default, to enable v2 API server that is backed by v2 store.
    • --enable-v2=true --enable-v2v3=/aaa to enable v2 API server that is backed by v3 storage.
    • --enable-v2=false --enable-v2v3='' to disable v2 API server.
    • --enable-v2=false --enable-v2v3=/aaa to disable v2 API server. TODO: error?
    • v4.0 will configure --enable-v2=true --enable-v2v3=/aaa to enable v2 API server that is backed by v3 storage.
  • Add --discovery-srv-name flag to support custom DNS SRV name with discovery.
    • If not given, etcd queries _etcd-server-ssl._tcp.[YOUR_HOST] and _etcd-server._tcp.[YOUR_HOST].
    • If --discovery-srv-name="foo", then query _etcd-server-ssl-foo._tcp.[YOUR_HOST] and _etcd-server-foo._tcp.[YOUR_HOST].
    • Useful for operating multiple etcd clusters under the same domain.

Added: embed

Added: API

Added: v3 etcdctl

Added: gRPC gateway

Package raft

Fixed: v3

Go

  • Require Go 1.10+.
  • Compile with Go 1.10.