See [code changes](https://github.com/etcd-io/etcd/compare/v3.3.13...v3.3.14) and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md) for any breaking changes. **Again, before running upgrades from any previous release, please make sure to read change logs below and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md).**
### etcd server
- Fix [race condition in `rafthttp` transport pause/resume](https://github.com/etcd-io/etcd/pull/10826).
See [code changes](https://github.com/etcd-io/etcd/compare/v3.3.12...v3.3.13) and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md) for any breaking changes. **Again, before running upgrades from any previous release, please make sure to read change logs below and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md).**
- Add [`Verify` function to perform corruption check on WAL contents](https://github.com/etcd-io/etcd/pull/10603).
### Dependency
- Migrate [`github.com/ugorji/go/codec`](https://github.com/ugorji/go/releases) to [**`github.com/json-iterator/go`**](https://github.com/json-iterator/go) (See [#10667](https://github.com/etcd-io/etcd/pull/10667) for more).
- Migrate [`github.com/ghodss/yaml`](https://github.com/ghodss/yaml/releases) to [**`sigs.k8s.io/yaml`**](https://github.com/kubernetes-sigs/yaml) (See [#10718](https://github.com/etcd-io/etcd/pull/10718) for more).
See [code changes](https://github.com/etcd-io/etcd/compare/v3.3.11...v3.3.12) and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md) for any breaking changes. **Again, before running upgrades from any previous release, please make sure to read change logs below and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md).**
### etcdctl
- [Strip out insecure endpoints from DNS SRV records when using discovery](https://github.com/etcd-io/etcd/pull/10443) with etcdctl v2
See [code changes](https://github.com/etcd-io/etcd/compare/v3.3.10...v3.3.11) and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md) for any breaking changes. **Again, before running upgrades from any previous release, please make sure to read change logs below and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md).**
- Disable [CommonName authentication for gRPC-gateway](https://github.com/etcd-io/etcd/pull/10366) gRPC-gateway proxy requests to etcd server use the etcd client server TLS certificate. If that certificate contains CommonName we do not want to use that for authentication as it could lead to permission escalation.
See [code changes](https://github.com/etcd-io/etcd/compare/v3.3.9...v3.3.10) and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md) for any breaking changes. **Again, before running upgrades from any previous release, please make sure to read change logs below and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md).**
- Add [gRPC interceptor for debugging logs](https://github.com/etcd-io/etcd/pull/9990); enable `etcd --debug` flag to see per-request debug information.
See [code changes](https://github.com/etcd-io/etcd/compare/v3.3.8...v3.3.9) and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md) for any breaking changes. **Again, before running upgrades from any previous release, please make sure to read change logs below and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md).**
- Compile with [*Go 1.10.3*](https://golang.org/doc/devel/release.html#go1.10) to support [crypto/x509 "Name Constraints"](https://github.com/etcd-io/etcd/issues/9912).
- Use it with `etcd_mvcc_db_total_size_in_bytes` and `etcd_mvcc_db_total_size_in_use_in_bytes`.
-`etcd_server_quota_backend_bytes 2.147483648e+09` means current quota size is 2 GB.
-`etcd_mvcc_db_total_size_in_bytes 20480` means current physically allocated DB size is 20 KB.
-`etcd_mvcc_db_total_size_in_use_in_bytes 16384` means future DB size if defragment operation is complete.
-`etcd_mvcc_db_total_size_in_bytes - etcd_mvcc_db_total_size_in_use_in_bytes` is the number of bytes that can be saved on disk with defragment operation.
- Use it with `etcd_mvcc_db_total_size_in_bytes` and `etcd_mvcc_db_total_size_in_use_in_bytes`.
-`etcd_server_quota_backend_bytes 2.147483648e+09` means current quota size is 2 GB.
-`etcd_mvcc_db_total_size_in_bytes 20480` means current physically allocated DB size is 20 KB.
-`etcd_mvcc_db_total_size_in_use_in_bytes 16384` means future DB size if defragment operation is complete.
-`etcd_mvcc_db_total_size_in_bytes - etcd_mvcc_db_total_size_in_use_in_bytes` is the number of bytes that can be saved on disk with defragment operation.
- Fix [lease keepalive interval updates when response queue is full](https://github.com/etcd-io/etcd/pull/9952).
- If `<-chan *clientv3LeaseKeepAliveResponse` from `clientv3.Lease.KeepAlive` was never consumed or channel is full, client was [sending keepalive request every 500ms](https://github.com/etcd-io/etcd/issues/9911) instead of expected rate of every "TTL / 3" duration.
See [code changes](https://github.com/etcd-io/etcd/compare/v3.3.7...v3.3.8) and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md) for any breaking changes. **Again, before running upgrades from any previous release, please make sure to read change logs below and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md).**
See [code changes](https://github.com/etcd-io/etcd/compare/v3.3.6...v3.3.7) and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md) for any breaking changes. **Again, before running upgrades from any previous release, please make sure to read change logs below and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md).**
See [code changes](https://github.com/etcd-io/etcd/compare/v3.3.5...v3.3.6) and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md) for any breaking changes. **Again, before running upgrades from any previous release, please make sure to read change logs below and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md).**
- Previously, when auth token is an empty string, it returns [`failed to initialize the etcd server: auth: invalid auth options` error](https://github.com/etcd-io/etcd/issues/9349).
- Fix [auth storage panic on server lease revoke routine with JWT token](https://github.com/etcd-io/etcd/issues/9695).
- Fix [`mvcc` server panic from restore operation](https://github.com/etcd-io/etcd/pull/9775).
- Let's assume that a watcher had been requested with a future revision X and sent to node A that became network-partitioned thereafter. Meanwhile, cluster makes progress. Then when the partition gets removed, the leader sends a snapshot to node A. Previously if the snapshot's latest revision is still lower than the watch revision X, **etcd server panicked** during snapshot restore operation.
See [code changes](https://github.com/etcd-io/etcd/compare/v3.3.4...v3.3.5) and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md) for any breaking changes. **Again, before running upgrades from any previous release, please make sure to read change logs below and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md).**
See [code changes](https://github.com/etcd-io/etcd/compare/v3.3.3...v3.3.4) and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md) for any breaking changes. **Again, before running upgrades from any previous release, please make sure to read change logs below and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md).**
- Fix [TLS reload](https://github.com/etcd-io/etcd/pull/9570) when [certificate SAN field only includes IP addresses but no domain names](https://github.com/etcd-io/etcd/issues/9541).
- In Go, server calls `(*tls.Config).GetCertificate` for TLS reload if and only if server's `(*tls.Config).Certificates` field is not empty, or `(*tls.ClientHelloInfo).ServerName` is not empty with a valid SNI from the client. Previously, etcd always populates `(*tls.Config).Certificates` on the initial client TLS handshake, as non-empty. Thus, client was always expected to supply a matching SNI in order to pass the TLS verification and to trigger `(*tls.Config).GetCertificate` to reload TLS assets.
- However, a certificate whose SAN field does [not include any domain names but only IP addresses](https://github.com/etcd-io/etcd/issues/9541) would request `*tls.ClientHelloInfo` with an empty `ServerName` field, thus failing to trigger the TLS reload on initial TLS handshake; this becomes a problem when expired certificates need to be replaced online.
- Now, `(*tls.Config).Certificates` is created empty on initial TLS client handshake, first to trigger `(*tls.Config).GetCertificate`, and then to populate rest of the certificates on every new TLS connection, even when client SNI is empty (e.g. cert only includes IPs).
- By default, `etcd --initial-election-tick-advance=true`, then local member fast-forwards election ticks to speed up "initial" leader election trigger.
- This benefits the case of larger election ticks. For instance, cross datacenter deployment may require longer election timeout of 10-second. If true, local node does not need wait up to 10-second. Instead, forwards its election ticks to 8-second, and have only 2-second left before leader election.
- Major assumptions are that: cluster has no active leader thus advancing ticks enables faster leader election. Or cluster already has an established leader, and rejoining follower is likely to receive heartbeats from the leader after tick advance and before election timeout.
- However, when network from leader to rejoining follower is congested, and the follower does not receive leader heartbeat within left election ticks, disruptive election has to happen thus affecting cluster availabilities.
- Now, this can be disabled by setting `--initial-election-tick-advance=false`.
- Disabling this would slow down initial bootstrap process for cross datacenter deployments. Make tradeoffs by configuring `etcd --initial-election-tick-advance` at the cost of slow initial bootstrap.
See [code changes](https://github.com/etcd-io/etcd/compare/v3.3.2...v3.3.3) and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md) for any breaking changes. **Again, before running upgrades from any previous release, please make sure to read change logs below and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md).**
- Adjust [election timeout on server restart](https://github.com/etcd-io/etcd/pull/9415) to reduce [disruptive rejoining servers](https://github.com/etcd-io/etcd/issues/9333).
- 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.
- e.g. `etcd --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, `etcd --auto-compaction-mode=periodic --auto-compaction-retention=72h` automatically `Compact` with 72-hour retention windown for every 7.2-hour. **Now, `Compact` happens, for every 1-hour but still with 72-hour retention window.**
- e.g. Previously, `etcd --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 but still with 30-minute retention window.**
- 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 `etcd --auto-compaction-mode=periodic --auto-compaction-retention=24h`).
- For instance, when hourly writes are 100 and `etcd --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 `etcd --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.
See [code changes](https://github.com/etcd-io/etcd/compare/v3.3.1...v3.3.2) and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md) for any breaking changes. **Again, before running upgrades from any previous release, please make sure to read change logs below and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md).**
See [code changes](https://github.com/etcd-io/etcd/compare/v3.3.0...v3.3.1) and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md) for any breaking changes. **Again, before running upgrades from any previous release, please make sure to read change logs below and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md).**
- A node gets network partitioned with a watcher on a future revision, and falls behind receiving a leader snapshot after partition gets removed. When applying this snapshot, etcd watch storage moves current synced watchers to unsynced since sync watchers might have become stale during network partition. And reset synced watcher group to restart watcher routines. Previously, there was a bug when moving from synced watcher group to unsynced, thus client would miss events when the watcher was requested to the network-partitioned node.
See [code changes](https://github.com/etcd-io/etcd/compare/v3.2.0...v3.3.0) and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md) for any breaking changes. **Again, before running upgrades from any previous release, please make sure to read change logs below and [v3.3 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md).**
- Fix [etcd database size grows until `mvcc: database space exceeded`](https://github.com/etcd-io/etcd/issues/8009).
- [Support database size larger than 8GiB](https://github.com/etcd-io/etcd/pull/7525) (8GiB is now a suggested maximum size for normal environments)
- [Reduce memory allocation](https://github.com/etcd-io/etcd/pull/8428) on [Range operations](https://github.com/etcd-io/etcd/pull/8475).
- [Rate limit](https://github.com/etcd-io/etcd/pull/8099) and [randomize](https://github.com/etcd-io/etcd/pull/8101) lease revoke on restart or leader elections.
- Prevent [spikes in Raft proposal rate](https://github.com/etcd-io/etcd/issues/8096).
- Support `clientv3` balancer failover under [network faults/partitions](https://github.com/etcd-io/etcd/issues/8711).
- Better warning on [mismatched `etcd --initial-cluster`](https://github.com/etcd-io/etcd/pull/8083) flag.
- If resolved IP addresses of `etcd --initial-advertise-peer-urls` and `etcd --initial-cluster` do not match (e.g. [due to DNS error](https://github.com/etcd-io/etcd/pull/9210)), etcd will exit with errors.
- v3.3 error: `failed to resolve https://s1.test:2380 to match --initial-cluster=s1=https://s1.test:2380 (failed to resolve "https://s1.test:2380" (error ...))`.
- Deprecate `grpclog.Logger`, upgrade to [`grpclog.LoggerV2`](https://github.com/etcd-io/etcd/pull/8533).
- Deprecate [`grpc.ErrClientConnTimeout`](https://github.com/etcd-io/etcd/pull/8505) errors in `clientv3`.
- Use [`MaxRecvMsgSize` and `MaxSendMsgSize`](https://github.com/etcd-io/etcd/pull/8437) to limit message size, in etcd server.
- Translate [gRPC status error in v3 client `Snapshot` API](https://github.com/etcd-io/etcd/pull/9038).
- v3 `etcdctl` [`lease timetolive LEASE_ID`](https://github.com/etcd-io/etcd/issues/9028) on expired lease now prints [`"lease LEASE_ID already expired"`](https://github.com/etcd-io/etcd/pull/9047).
- In v3.3, `curl -L http://localhost:2379/v3alpha/kv/put -X POST -d '{"key": "Zm9v", "value": "YmFy"}'` still works as a fallback to `curl -L http://localhost:2379/v3beta/kv/put -X POST -d '{"key": "Zm9v", "value": "YmFy"}'`, but `curl -L http://localhost:2379/v3alpha/kv/put -X POST -d '{"key": "Zm9v", "value": "YmFy"}'` won't work in v3.4. Use `curl -L http://localhost:2379/v3beta/kv/put -X POST -d '{"key": "Zm9v", "value": "YmFy"}'` instead.
- Change `etcd --auto-compaction-retention` flag to [accept string values](https://github.com/etcd-io/etcd/pull/8563) with [finer granularity](https://github.com/etcd-io/etcd/issues/8503).
- Now that `etcd --auto-compaction-retention` accepts string values, etcd configuration YAML file `auto-compaction-retention` field must be changed to `string` type.
- Previously, `--config-file etcd.config.yaml` can have `auto-compaction-retention: 24` field, now must be `auto-compaction-retention: "24"` or `auto-compaction-retention: "24h"`.
- If configured as `etcd --auto-compaction-mode periodic --auto-compaction-retention "24h"`, the time duration value for `etcd --auto-compaction-retention` flag must be valid for [`time.ParseDuration`](https://golang.org/pkg/time/#ParseDuration) function in Go.
- Upgrade [`boltdb/bolt`](https://github.com/boltdb/bolt#project-status) from [**`v1.3.0`**](https://github.com/boltdb/bolt/releases/tag/v1.3.0) to [`coreos/bbolt`](https://github.com/coreos/bbolt/releases) [**`v1.3.1-coreos.6`**](https://github.com/coreos/bbolt/releases/tag/v1.3.1-coreos.6).
- Upgrade [`google.golang.org/grpc`](https://github.com/grpc/grpc-go/releases) from [**`v1.2.1`**](https://github.com/grpc/grpc-go/releases/tag/v1.2.1) to [**`v1.7.5`**](https://github.com/grpc/grpc-go/releases/tag/v1.7.5).
- Upgrade [`github.com/ugorji/go/codec`](https://github.com/ugorji/go) to [**`v1.1`**](https://github.com/ugorji/go/releases/tag/v1.1), and [regenerate v2 `client`](https://github.com/etcd-io/etcd/pull/8721).
- Upgrade [`github.com/ugorji/go/codec`](https://github.com/ugorji/go) to [**`ugorji/go@54210f4e0`**](https://github.com/ugorji/go/commit/54210f4e076c57f351166f0ed60e67d3fca57a36), and [regenerate v2 `client`](https://github.com/etcd-io/etcd/pull/8574).
- Upgrade [`github.com/grpc-ecosystem/grpc-gateway`](https://github.com/grpc-ecosystem/grpc-gateway/releases) from [**`v1.2.2`**](https://github.com/grpc-ecosystem/grpc-gateway/releases/tag/v1.2.2) to [**`v1.3.0`**](https://github.com/grpc-ecosystem/grpc-gateway/releases/tag/v1.3.0).
- Upgrade [`golang.org/x/crypto/bcrypt`](https://github.com/golang/crypto) to [**`golang/crypto@6c586e17d`**](https://github.com/golang/crypto/commit/6c586e17d90a7d08bbbc4069984180dce3b04117).
- Add [CRL based connection rejection](https://github.com/etcd-io/etcd/pull/8124) to manage [revoked certs](https://github.com/etcd-io/etcd/issues/4034).
- [Server accepts connections if IP matches, without checking DNS entries](https://github.com/etcd-io/etcd/pull/8223). For instance, if peer cert contains IP addresses and DNS names in Subject Alternative Name (SAN) field, and the remote IP address matches one of those IP addresses, server just accepts connection without further checking the DNS names.
- [Server supports reverse-lookup on wildcard DNS `SAN`](https://github.com/etcd-io/etcd/pull/8281). For instance, if peer cert contains only DNS names (no IP addresses) in Subject Alternative Name (SAN) field, server first reverse-lookups the remote IP address to get a list of names mapping to that address (e.g. `nslookup IPADDR`). Then accepts the connection if those names have a matching name with peer cert's DNS names (either by exact or wildcard match). If none is matched, server forward-lookups each DNS entry in peer cert (e.g. look up `example.default.svc` when the entry is `*.example.default.svc`), and accepts connection only when the host's resolved addresses have the matching IP address with the peer's remote IP address.
- Add [`etcd --experimental-initial-corrupt-check`](https://github.com/etcd-io/etcd/pull/8554) flag to [check cluster database hashes before serving client/peer traffic](https://github.com/etcd-io/etcd/issues/8313).
- Add [`etcd --experimental-corrupt-check-time`](https://github.com/etcd-io/etcd/pull/8420) flag to [raise corrupt alarm monitoring](https://github.com/etcd-io/etcd/issues/7125).
- Add [`etcd --experimental-enable-v2v3`](https://github.com/etcd-io/etcd/pull/8407) flag to [emulate v2 API with v3](https://github.com/etcd-io/etcd/issues/6925).
- Add [`etcd --max-txn-ops`](https://github.com/etcd-io/etcd/pull/7976) flag to [configure maximum number operations in transaction](https://github.com/etcd-io/etcd/issues/7826).
- Add [`etcd --max-request-bytes`](https://github.com/etcd-io/etcd/pull/7968) flag to [configure maximum client request size](https://github.com/etcd-io/etcd/issues/7923).
- Add [`etcd --client-crl-file`, `--peer-crl-file`](https://github.com/etcd-io/etcd/pull/8124) flags for [Certificate revocation list](https://github.com/etcd-io/etcd/issues/4034).
- Add [`etcd --peer-cert-allowed-cn`](https://github.com/etcd-io/etcd/pull/8616) flag to support [CN-based auth for inter-peer connection](https://github.com/etcd-io/etcd/issues/8262).
- Add [`etcd --listen-metrics-urls`](https://github.com/etcd-io/etcd/pull/8242) flag for additional `/metrics` and `/health` endpoints.
- Support [additional (non) TLS `/metrics` endpoints for a TLS-enabled cluster](https://github.com/etcd-io/etcd/pull/8282).
- e.g. `etcd --listen-metrics-urls=https://localhost:2378,http://localhost:9379` to serve `/metrics` and `/health` on secure port 2378 and insecure port 9379.
- Useful for [bypassing critical APIs when monitoring etcd](https://github.com/etcd-io/etcd/issues/8060).
- Add [`etcd --auto-compaction-mode`](https://github.com/etcd-io/etcd/pull/8123) flag to [support revision-based compaction](https://github.com/etcd-io/etcd/issues/8098).
- Change `etcd --auto-compaction-retention` flag to [accept string values](https://github.com/etcd-io/etcd/pull/8563) with [finer granularity](https://github.com/etcd-io/etcd/issues/8503).
- Now that `etcd --auto-compaction-retention` accepts string values, etcd configuration YAML file `auto-compaction-retention` field must be changed to `string` type.
- Previously, `etcd --config-file etcd.config.yaml` can have `auto-compaction-retention: 24` field, now must be `auto-compaction-retention: "24"` or `auto-compaction-retention: "24h"`.
- If configured as `--auto-compaction-mode periodic --auto-compaction-retention "24h"`, the time duration value for `etcd --auto-compaction-retention` flag must be valid for [`time.ParseDuration`](https://golang.org/pkg/time/#ParseDuration) function in Go.
- e.g. `etcd --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. `etcd --auto-compaction-mode=periodic --auto-compaction-retention=72h` automatically `Compact` with 72-hour retention windown, for every 7.2-hour.
- e.g. `etcd --auto-compaction-mode=periodic --auto-compaction-retention=30m` automatically `Compact` with 30-minute retention windown, for every 3-minute.
- Periodic compactor continues to record latest revisions for every 1/10 of given compaction period (e.g. 1-hour when `etcd --auto-compaction-mode=periodic --auto-compaction-retention=10h`).
- For instance, when hourly writes are 100 and `--auto-compaction-retention=10`, v3.1 compacts revision 1000, 2000, and 3000 for every 10-hour, while v3.2.x, v3.3.0, v3.3.1, and v3.3.2 compact revision 1000, 1100, and 1200 for every 1-hour. Futhermore, when writes per minute are 1000, v3.3.0, v3.3.1, and v3.3.2 with `--auto-compaction-mode=periodic --auto-compaction-retention=30m` compact revision 30000, 33000, and 36000, for every 3-minute with more finer granularity.
- Whether compaction succeeds or not, this process repeats for every 1/10 of given compaction period. If compaction succeeds, it just removes compacted revision from historical revision records.
- Serve [`/health` endpoint as unhealthy](https://github.com/etcd-io/etcd/pull/8272) when [alarm (e.g. `NOSPACE`) is raised or there's no leader](https://github.com/etcd-io/etcd/issues/8207).
- [Remove `"errors"` field](https://github.com/etcd-io/etcd/pull/9162) since `v3.3.0-rc.3` (did exist only in `v3.3.0-rc.0`, `v3.3.0-rc.1`, `v3.3.0-rc.2`).
- Move [logging setup to embed package](https://github.com/etcd-io/etcd/pull/8810)
- Support [ranges in transaction comparisons](https://github.com/etcd-io/etcd/pull/8025) for [disconnected linearized reads](https://github.com/etcd-io/etcd/issues/7924).
- Add [nested transactions](https://github.com/etcd-io/etcd/pull/8102) to extend [proxy use cases](https://github.com/etcd-io/etcd/issues/7857).
- Add [lease comparison target in transaction](https://github.com/etcd-io/etcd/pull/8324).
- Add [hash by revision](https://github.com/etcd-io/etcd/pull/8263) for [better corruption checking against boltdb](https://github.com/etcd-io/etcd/issues/8016).
- Add [health balancer](https://github.com/etcd-io/etcd/pull/8545) to fix [watch API hangs](https://github.com/etcd-io/etcd/issues/7247), improve [endpoint switch under network faults](https://github.com/etcd-io/etcd/issues/7941).
- [Refactor balancer](https://github.com/etcd-io/etcd/pull/8840) and add [client-side keepalive pings](https://github.com/etcd-io/etcd/pull/8199) to handle [network partitions](https://github.com/etcd-io/etcd/issues/8711).
- Add [`MaxCallSendMsgSize` and `MaxCallRecvMsgSize`](https://github.com/etcd-io/etcd/pull/9047) fields to [`clientv3.Config`](https://godoc.org/github.com/coreos/etcd/clientv3#Config).
- Fix [exceeded response size limit error in client-side](https://github.com/etcd-io/etcd/issues/9043).
- Accept [`Compare_LEASE`](https://github.com/etcd-io/etcd/pull/8324) in [`clientv3.Compare`](https://godoc.org/github.com/coreos/etcd/clientv3#Compare).
- Add [`LeaseValue` helper](https://github.com/etcd-io/etcd/pull/8488) to `Cmp``LeaseID` values in `Txn`.
- Add [`MoveLeader`](https://github.com/etcd-io/etcd/pull/8153) to `Maintenance`.
- Add [`HashKV`](https://github.com/etcd-io/etcd/pull/8351) to `Maintenance`.
- Add [`Leases`](https://github.com/etcd-io/etcd/pull/8358) to `Lease`.
- Add [`clientv3/ordering`](https://github.com/etcd-io/etcd/pull/8092) for enforce [ordering in serialized requests](https://github.com/etcd-io/etcd/issues/7623).
- Support [`etcdctl watch [key] [range_end] -- [exec-command…]`](https://github.com/etcd-io/etcd/pull/8919), equivalent to [v2 `etcdctl exec-watch`](https://github.com/etcd-io/etcd/issues/8814).
- Make `etcdctl watch -- [exec-command]` set environmental variables [`ETCD_WATCH_REVISION`, `ETCD_WATCH_EVENT_TYPE`, `ETCD_WATCH_KEY`, `ETCD_WATCH_VALUE`](https://github.com/etcd-io/etcd/pull/9142) for each event.
- Support [`etcdctl watch` with environmental variables `ETCDCTL_WATCH_KEY` and `ETCDCTL_WATCH_RANGE_END`](https://github.com/etcd-io/etcd/pull/9142).
- Enable [`clientv3.WithRequireLeader(context.Context)` for `watch`](https://github.com/etcd-io/etcd/pull/8672) command.
- Print [`"del"` instead of `"delete"`](https://github.com/etcd-io/etcd/pull/8297) in `txn` interactive mode.
- Print [`ETCD_INITIAL_ADVERTISE_PEER_URLS` in `member add`](https://github.com/etcd-io/etcd/pull/8332).
- Add [`grpc-proxy start --max-send-bytes`](https://github.com/etcd-io/etcd/pull/9250) flag to [configure maximum client request size](https://github.com/etcd-io/etcd/issues/7923).
- Add [`grpc-proxy start --max-recv-bytes`](https://github.com/etcd-io/etcd/pull/9250) flag to [configure maximum client request size](https://github.com/etcd-io/etcd/issues/7923).
- In v3.3, `curl -L http://localhost:2379/v3alpha/kv/put -X POST -d '{"key": "Zm9v", "value": "YmFy"}'` still works as a fallback to `curl -L http://localhost:2379/v3beta/kv/put -X POST -d '{"key": "Zm9v", "value": "YmFy"}'`, but `curl -L http://localhost:2379/v3alpha/kv/put -X POST -d '{"key": "Zm9v", "value": "YmFy"}'` won't work in v3.4. Use `curl -L http://localhost:2379/v3beta/kv/put -X POST -d '{"key": "Zm9v", "value": "YmFy"}'` instead.
- Fix [backend database in-memory index corruption](https://github.com/etcd-io/etcd/pull/8127) issue on restore (only 3.2.0 is affected).
- Fix [watch restore from snapshot](https://github.com/etcd-io/etcd/pull/8427).
- Fix [`mvcc/backend.defragdb` nil-pointer dereference on create bucket failure](https://github.com/etcd-io/etcd/pull/9119).
- Fix [server crash](https://github.com/etcd-io/etcd/pull/8010) on [invalid transaction request from gRPC gateway](https://github.com/etcd-io/etcd/issues/7889).
- Prevent [server panic from member update/add](https://github.com/etcd-io/etcd/pull/9174) with [wrong scheme URLs](https://github.com/etcd-io/etcd/issues/9173).
- Make [peer dial timeout longer](https://github.com/etcd-io/etcd/pull/8599).
- Make server [wait up to request time-out](https://github.com/etcd-io/etcd/pull/8267) with [pending RPCs](https://github.com/etcd-io/etcd/issues/8224).
- Fix [`grpc.Server` panic on `GracefulStop`](https://github.com/etcd-io/etcd/pull/8987) with [TLS-enabled server](https://github.com/etcd-io/etcd/issues/8916).