SERVER-43985 Make mongos pre-cache the routing table on startup

5 files changed, 74 insertions, 0 deletions

diff --git a/buildscripts/resmokeconfig/suites/sharding_last_stable_mongos_and_mixed_shards.yml b/buildscripts/resmokeconfig/suites/sharding_last_stable_mongos_and_mixed_shards.yml
index 0e4f771557f..d4b370f0704 100644
--- a/buildscripts/resmokeconfig/suites/sharding_last_stable_mongos_and_mixed_shards.yml
+++ b/buildscripts/resmokeconfig/suites/sharding_last_stable_mongos_and_mixed_shards.yml
@@ -180,6 +180,7 @@ selector:
   - jstests/sharding/time_zone_info_mongos.js
   # Remove if/once SERVER-50547 is backported to 4.0.
   - jstests/sharding/pipeline_length_limit.js
+  - jstests/sharding/mongos_precache_routing_info.js
   - jstests/sharding/warm_up_connection_pool.js
 
 executor:
diff --git a/jstests/sharding/mongos_precache_routing_info.js b/jstests/sharding/mongos_precache_routing_info.js
new file mode 100644
index 00000000000..3471f208e99
--- /dev/null
+++ b/jstests/sharding/mongos_precache_routing_info.js
@@ -0,0 +1,35 @@
+(function() {
+'use strict';
+
+// create
+var s = new ShardingTest({shards: 2});
+var db = s.getDB("test");
+var ss = db.serverStatus();
+
+const shardCommand = {
+    shardcollection: "test.foo",
+    key: {num: 1}
+};
+
+// shard
+assert.commandWorked(s.s0.adminCommand({enablesharding: "test"}));
+assert.commandWorked(s.s0.adminCommand(shardCommand));
+
+// split numSplits times
+const numSplits = 2;
+var i;
+for (i = 0; i < numSplits; i++) {
+    var midKey = {num: i};
+    assert.commandWorked(s.s0.adminCommand({split: "test.foo", middle: midKey}));
+}
+
+// restart mongos
+s.restartMongos(0);
+db = s.getDB("test");
+
+// check for # refreshes started
+ss = db.serverStatus();
+assert.eq(1, ss.shardingStatistics.catalogCache.countFullRefreshesStarted);
+
+s.stop();
+})();
diff --git a/src/mongo/s/server.cpp b/src/mongo/s/server.cpp
index 3ac128f4794..15b2e0105a7 100644
--- a/src/mongo/s/server.cpp
+++ b/src/mongo/s/server.cpp
@@ -426,6 +426,11 @@ Status initializeSharding(OperationContext* opCtx) {
         return status;
     }
 
+    status = preCacheMongosRoutingInfo(opCtx);
+    if (!status.isOK()) {
+        return status;
+    }
+
     status = preWarmConnectionPool(opCtx);
     if (!status.isOK()) {
         return status;
diff --git a/src/mongo/s/sharding_initialization.cpp b/src/mongo/s/sharding_initialization.cpp
index 4dc7372960e..6f090bbb4ab 100644
--- a/src/mongo/s/sharding_initialization.cpp
+++ b/src/mongo/s/sharding_initialization.cpp
@@ -270,6 +270,33 @@ Status waitForShardRegistryReload(OperationContext* opCtx) {
     return {ErrorCodes::ShutdownInProgress, "aborting shard loading attempt"};
 }
 
+Status preCacheMongosRoutingInfo(OperationContext* opCtx) {
+    if (serverGlobalParams.clusterRole == ClusterRole::ConfigServer) {
+        return Status::OK();
+    }
+    auto grid = Grid::get(opCtx);
+
+    auto shardingCatalogClient = grid->catalogClient();
+    auto result =
+        shardingCatalogClient->getAllDBs(opCtx, repl::ReadConcernLevel::kMajorityReadConcern);
+
+    if (!result.isOK()) {
+        return result.getStatus();
+    }
+
+    auto cache = grid->catalogCache();
+    for (auto& db : result.getValue().value) {
+        for (auto& coll : shardingCatalogClient->getAllShardedCollectionsForDb(
+                 opCtx, db.getName(), repl::ReadConcernLevel::kMajorityReadConcern)) {
+            auto resp = cache->getShardedCollectionRoutingInfoWithRefresh(opCtx, coll);
+            if (!resp.isOK()) {
+                return resp.getStatus();
+            }
+        }
+    }
+    return Status::OK();
+}
+
 Status preWarmConnectionPool(OperationContext* opCtx) {
     if (!gWarmMinConnectionsInShardingTaskExecutorPoolOnStartup) {
         return Status::OK();
diff --git a/src/mongo/s/sharding_initialization.h b/src/mongo/s/sharding_initialization.h
index 56c5f652ddd..5af0cc6f265 100644
--- a/src/mongo/s/sharding_initialization.h
+++ b/src/mongo/s/sharding_initialization.h
@@ -90,6 +90,12 @@ Status initializeGlobalShardingState(OperationContext* opCtx,
 Status waitForShardRegistryReload(OperationContext* opCtx);
 
 /**
+ * Pre-caches mongod routing info for the calling process.
+ */
+
+Status preCacheMongosRoutingInfo(OperationContext* opCtx);
+
+/**
  * Warms up connections to shards with best effort strategy.
  */