SERVER-43719 Load RWC defaults from persisted values during startup

4 files changed, 87 insertions, 0 deletions

diff --git a/jstests/noPassthrough/read_write_concern_defaults_startup.js b/jstests/noPassthrough/read_write_concern_defaults_startup.js
new file mode 100644
index 00000000000..e63077fe1cd
--- /dev/null
+++ b/jstests/noPassthrough/read_write_concern_defaults_startup.js
@@ -0,0 +1,62 @@
+// Verifies read/write concern defaults are loaded at startup by a mongos and non-sharded replica
+// set node.
+//
+// This test restarts a replica set node, which requires persistence and journaling.
+// @tags: [requires_sharding, requires_persistence, requires_journaling]
+(function() {
+"use strict";
+
+function runTest(conn, failPointConn, restartFn) {
+    // Set a default rwc.
+    assert.commandWorked(
+        conn.adminCommand({setDefaultRWConcern: 1, defaultReadConcern: {level: "majority"}}));
+    let res = assert.commandWorked(conn.adminCommand({getDefaultRWConcern: 1}));
+    assert.eq(res.defaultReadConcern, {level: "majority"});
+
+    // Restart the node with disabled rwc refreshes.
+    restartFn();
+    reconnect(conn);
+    reconnect(failPointConn);
+
+    // Verify the server attempted to load the defaults at startup.
+    checkLog.contains(conn, "Failed to load read and write concern defaults at startup");
+    checkLog.contains(conn,
+                      "Failing read/write concern persisted defaults lookup because of fail point");
+
+    // Disable the fail point and verify the defaults can be returned.
+    assert.commandWorked(
+        failPointConn.adminCommand({configureFailPoint: "failRWCDefaultsLookup", mode: "off"}));
+    res = assert.commandWorked(conn.adminCommand({getDefaultRWConcern: 1}));
+    assert.eq(res.defaultReadConcern, {level: "majority"});
+}
+
+jsTestLog("Testing mongos...");
+{
+    // Use 1 node CSRS so the failpoint to disable rwc lookup only needs to be set on one node.
+    const st = new ShardingTest({shards: 1, config: 1});
+
+    runTest(st.s, st.configRS.getPrimary(), () => {
+        assert.commandWorked(st.configRS.getPrimary().adminCommand(
+            {configureFailPoint: "failRWCDefaultsLookup", mode: "alwaysOn"}));
+        st.restartMongos(0);
+    });
+
+    st.stop();
+}
+
+jsTestLog("Testing plain replica set node...");
+{
+    const rst = new ReplSetTest({nodes: 1});
+    rst.startSet();
+    rst.initiate();
+
+    const primary = rst.getPrimary();
+    runTest(primary, primary, () => {
+        rst.restart(
+            primary,
+            {setParameter: "failpoint.failRWCDefaultsLookup=" + tojson({mode: "alwaysOn"})});
+    });
+
+    rst.stopSet();
+}
+})();
diff --git a/src/mongo/db/db.cpp b/src/mongo/db/db.cpp
index 65fb74748a5..97f2580e389 100644
--- a/src/mongo/db/db.cpp
+++ b/src/mongo/db/db.cpp
@@ -525,6 +525,17 @@ ExitCode _initAndListen(int listenPort) {
         }
     }
 
+    try {
+        if (serverGlobalParams.clusterRole != ClusterRole::ShardServer &&
+            replSettings.usingReplSets()) {
+            ReadWriteConcernDefaults::get(startupOpCtx.get()->getServiceContext())
+                .refreshIfNecessary(startupOpCtx.get());
+        }
+    } catch (const DBException& ex) {
+        warning() << "Failed to load read and write concern defaults at startup"
+                  << causedBy(redact(ex.toStatus()));
+    }
+
     auto storageEngine = serviceContext->getStorageEngine();
     invariant(storageEngine);
     BackupCursorHooks::initialize(serviceContext, storageEngine);
diff --git a/src/mongo/db/read_write_concern_defaults_cache_lookup_mongod.cpp b/src/mongo/db/read_write_concern_defaults_cache_lookup_mongod.cpp
index 33a0cc3f22e..07dfc900c48 100644
--- a/src/mongo/db/read_write_concern_defaults_cache_lookup_mongod.cpp
+++ b/src/mongo/db/read_write_concern_defaults_cache_lookup_mongod.cpp
@@ -32,11 +32,18 @@
 #include "mongo/db/dbdirectclient.h"
 #include "mongo/db/namespace_string.h"
 #include "mongo/db/read_write_concern_defaults.h"
+#include "mongo/util/fail_point.h"
 
 namespace mongo {
 namespace {
 
+MONGO_FAIL_POINT_DEFINE(failRWCDefaultsLookup);
+
 BSONObj getPersistedDefaultRWConcernDocument(OperationContext* opCtx) {
+    uassert(51762,
+            "Failing read/write concern persisted defaults lookup because of fail point",
+            !MONGO_unlikely(failRWCDefaultsLookup.shouldFail()));
+
     DBDirectClient client(opCtx);
     return client.findOne(NamespaceString::kConfigSettingsNamespace.toString(),
                           QUERY("_id" << ReadWriteConcernDefaults::kPersistedDocumentId));
diff --git a/src/mongo/s/server.cpp b/src/mongo/s/server.cpp
index 2db78c6db78..faa5ccf183b 100644
--- a/src/mongo/s/server.cpp
+++ b/src/mongo/s/server.cpp
@@ -579,6 +579,13 @@ ExitCode runMongosServer(ServiceContext* serviceContext) {
             ->getBalancerConfiguration()
             ->refreshAndCheck(opCtx)
             .transitional_ignore();
+
+        try {
+            ReadWriteConcernDefaults::get(serviceContext).refreshIfNecessary(opCtx);
+        } catch (const DBException& ex) {
+            warning() << "Failed to load read and write concern defaults at startup"
+                      << causedBy(redact(ex.toStatus()));
+        }
     }
 
     startMongoSFTDC();