CHANGELOG-3.4: highlight new metrics, histogram upper bound changes

Signed-off-by: Gyuho Lee <gyuhox@gmail.com>

CHANGELOG-3.4.md

@@ -118,9 +118,16 @@ See [code changes](https://github.com/coreos/etcd/compare/v3.3.0...v3.4.0) and [
 
 ### Metrics, Monitoring
 
+- Increase [`etcd_network_peer_round_trip_time_seconds`](https://github.com/coreos/etcd/pull/9762) Prometheus metric histogram upper-bound.
+  - Previously, highest bucket only collects requests taking 0.8192 seconds or more.
+  - Now, highest buckets collect 0.8192 seconds, 1.6384 seconds, and 3.2768 seconds or more.
+- Increase [`etcd_debugging_mvcc_index_compaction_pause_duration_milliseconds`](https://github.com/coreos/etcd/pull/9762) Prometheus metric histogram upper-bound.
+  - Previously, highest bucket only collects requests taking 1.024 seconds or more.
+  - Now, highest buckets collect 1.024 seconds, 2.048 seconds, and 4.096 seconds or more.
 - Add [`etcd_server_is_leader`](https://github.com/coreos/etcd/pull/9587) Prometheus metric.
 - Add [`etcd_server_heartbeat_send_failures_total`](https://github.com/coreos/etcd/pull/9761) Prometheus metric.
 - Add [`etcd_server_slow_apply_total`](https://github.com/coreos/etcd/pull/9761) Prometheus metric.
+- Add [`etcd_snap_fsync_duration_seconds`](https://github.com/coreos/etcd/pull/9762) Prometheus metric.
 - Add [`etcd_disk_backend_defrag_duration_seconds`](https://github.com/coreos/etcd/pull/9761) Prometheus metric.
 - Add [`etcd_mvcc_hash_duration_seconds`](https://github.com/coreos/etcd/pull/9761) Prometheus metric.
 - Add [`etcd_mvcc_hash_rev_duration_seconds`](https://github.com/coreos/etcd/pull/9761) Prometheus metric.