Fix arangorestore API to create _rev on shard leader [BTS-1232]. (#18191)

neunhoef · KVS85 · web-flow · commit b5a5a5149fbb · 2023-03-02T13:57:22.000+03:00
* Backport from devel.

* Update CHANGELOG

---------

Co-authored-by: Vadim &lt;vadim@arangodb.com&gt;
diff --git a/CHANGELOG b/CHANGELOG
@@ -1,6 +1,12 @@
 v3.8.9 (XXXX-XX-XX)
 -------------------
 
+* Fixed a bug in the API used by `arangorestore`: On restore, a new _rev value
+  is generated for each imported document to avoid clashes with previously
+  present data. This must be created on the shard leader rather than the
+  coordinator. The bug happened, when two coordinators were creating the same
+  _rev value for two different documents concurrently.
+
 * Updated ArangoDB Starter to 0.15.7.
 
 * Updated OpenSSL to 1.1.1t and OpenLDAP to 2.6.4.
diff --git a/arangod/RestHandler/RestReplicationHandler.cpp b/arangod/RestHandler/RestReplicationHandler.cpp
@@ -1531,11 +1531,14 @@ Result RestReplicationHandler::parseBatch(transaction::Methods& trx,
             // prevent checking for _rev twice in the same document
             checkRev = false;
 
-            char ridBuffer[arangodb::basics::maxUInt64StringSize];
-            RevisionId newRid = physical->newRevisionId();
-            
-            documentsToInsert.add(it.key);
-            documentsToInsert.add(newRid.toValuePair(ridBuffer));
+            // We simply get rid of the `_rev` attribute here on the
+            // coordinator. We need to create a new value but it has to be
+            // unique in the shard, therefore the shard leader must create the
+            // value. If multiple coordinators would create a timestamp based
+            // _rev value concurrently, we could get a duplicate, which would
+            // lead to a clash on the actual shard leader and can lead to
+            // RocksDB conflicts or even data corruption between primary index
+            // and data in the documents column family.
           } else {
             // copy key/value verbatim
             documentsToInsert.add(it.key);
