Merge changes I2ddef3ec,I70db2336 into stable-3.1
* changes:
Explain how to set index.numStripedLocks
Document last index update timestamp storage
diff --git a/src/main/resources/Documentation/about.md b/src/main/resources/Documentation/about.md
index fd0b56e..83d3862 100644
--- a/src/main/resources/Documentation/about.md
+++ b/src/main/resources/Documentation/about.md
@@ -103,3 +103,17 @@
For further information and supported options, refer to [config](config.md)
documentation.
+
+### Last index update timestamp storage
+
+The plugin keeps track of the timestamp when it lastly updated an index.
+When the [`autoReindex.enabled` option](config.md) is set to `true`, the timestamp
+is used to determine which changes to reindex when a node is temporarily out of
+sync with the primary, for example, after a node being offline for a long time.
+
+The HA plugin keeps the last update timestamp for each index in the following files:
+* `<gerrit_home>/data/high-availability/group`
+* `<gerrit_home>/data/high-availability/account`
+* `<gerrit_home>/data/high-availability/change`
+
+The timestamp is stored in this format `yyyy-mm-ddTHH:MM:SS.ss`, i.e.: `2020-12-18T12:17:53.25`.
diff --git a/src/main/resources/Documentation/config.md b/src/main/resources/Documentation/config.md
index 68fa8eb..482d301 100644
--- a/src/main/resources/Documentation/config.md
+++ b/src/main/resources/Documentation/config.md
@@ -180,7 +180,11 @@
Defaults to true.
```index.numStripedLocks```
-: Number of striped locks to use during reindexing.
+: Number of striped locks to use during reindexing. Should be of the same order
+ of magnitude of the open changes. I.e.: if one has 5000 changes, one might want
+ to have at least 1000 striped locks. The value has to be tuned empirically
+ by checking the number of failures in acquiring the locking. Checking the
+ `consider increasing the number of shards` warnings should help.
Defaults to 10.
```index.synchronize```
