CHANGELOG: update for PR11946

Also update helper message to include the new flag.

CHANGELOG-3.4.md

@@ -9,6 +9,23 @@ The minimum recommended etcd versions to run in **production** are 3.2.28+, 3.3.
 <hr>
 
 
+## [v3.4.10](https://github.com/etcd-io/etcd/releases/tag/v3.4.10) (TBD)
+
+See [code changes](https://github.com/etcd-io/etcd/compare/v3.4.9...v3.4.10) and [v3.4 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_4.md) for any breaking changes.
+
+### Package `etcd server`
+
+- Add [`--unsafe-no-fsync`](https://github.com/etcd-io/etcd/pull/11946) flag.
+  - Setting the flag disables all uses of fsync, which is unsafe and will cause data loss. This flag makes it possible to run an etcd node for testing and development without placing lots of load on the file system.
+
+### Go
+
+- Compile with [*Go 1.12.17*](https://golang.org/doc/devel/release.html#go1.12).
+
+
+<hr>
+
+
 ## [v3.4.9](https://github.com/etcd-io/etcd/releases/tag/v3.4.9) (2020-05-20)
 
 See [code changes](https://github.com/etcd-io/etcd/compare/v3.4.8...v3.4.9) and [v3.4 upgrade guide](https://github.com/etcd-io/etcd/blob/master/Documentation/upgrades/upgrade_3_4.md) for any breaking changes.

CHANGELOG-3.5.md

@@ -126,6 +126,8 @@ Note that any `etcd_debugging_*` metrics are experimental and subject to change.
 - Improve logging around snapshot send and receive.
 - [Push down RangeOptions.limit argv into index tree to reduce memory overhead](https://github.com/etcd-io/etcd/pull/11990).
 - Add [reason field for /health response](https://github.com/etcd-io/etcd/pull/11983).
+- Add [`--unsafe-no-fsync`](https://github.com/etcd-io/etcd/pull/11946) flag.
+  - Setting the flag disables all uses of fsync, which is unsafe and will cause data loss. This flag makes it possible to run an etcd node for testing and development without placing lots of load on the file system.
 
 ### Package `embed`
 

etcdmain/help.go

@@ -212,6 +212,8 @@ Experimental feature:
 Unsafe feature:
   --force-new-cluster 'false'
     Force to create a new one-member cluster.
+  --unsafe-no-fsync 'false'
+    Disables fsync, unsafe, will cause data loss.
 
 CAUTIOUS with unsafe flag! It may break the guarantees given by the consensus protocol!
 `