SERVER-29452 Handle missing featureCompatibilityVersion document

2 files changed, 163 insertions, 0 deletions

diff --git a/jstests/multiVersion/major_version_upgrade.js b/jstests/multiVersion/major_version_upgrade.js
index 1365fac361c..07966eba73a 100644
--- a/jstests/multiVersion/major_version_upgrade.js
+++ b/jstests/multiVersion/major_version_upgrade.js
@@ -174,6 +174,14 @@
             // We're on the latest version, check bad indexes are still readable.
             validateBadIndexesStandalone(testDB);
         }
+
+        // Make sure a featureCompatibilityVersion document exists during the version.binVersion
+        // === 3.4 iteration and all remaining iterations of "version".
+        if (version.binVersion === "3.4") {
+            let adminDB = conn.getDB("admin");
+            assert.commandWorked(adminDB.runCommand({"setFeatureCompatibilityVersion": "3.4"}));
+        }
+
         // Shutdown the current mongod.
         MongoRunner.stopMongod(conn);
 
@@ -282,6 +290,15 @@
                 GetIndexHelpers.findByKeyPattern(testDB[oldVersionCollection].getIndexes(), {b: 1}),
                 `index from ${oldVersionCollection} should be available; nodes: ${tojson(nodes)}`);
         }
+
+        // Make sure a featureCompatibilityVersion document exists during the version.binVersion
+        // === 3.4 iteration and all remaining iterations of "version".
+        if (version.binVersion === "3.4") {
+            let primaryAdminDB = primary.getDB("admin");
+            assert.commandWorked(
+                primaryAdminDB.runCommand({setFeatureCompatibilityVersion: "3.4"}));
+            rst.awaitReplication();
+        }
     }
 
     // Stop the replica set.
diff --git a/jstests/multiVersion/set_feature_compatibility_version.js b/jstests/multiVersion/set_feature_compatibility_version.js
index a9829dcc393..32125a9d4d2 100644
--- a/jstests/multiVersion/set_feature_compatibility_version.js
+++ b/jstests/multiVersion/set_feature_compatibility_version.js
@@ -26,6 +26,85 @@
     const latest = "latest";
     const downgrade = "3.4";
 
+    let recoverMMapJournal = function(isMMAPv1, conn, dbpath) {
+        // If we're using mmapv1, recover the journal files from the unclean shutdown before
+        // attempting to run with --repair.
+        if (isMMAPv1) {
+            let returnCode = runMongoProgram("mongod",
+                                             "--port",
+                                             conn.port,
+                                             "--journalOptions",
+                                             /*MMAPV1Options::JournalRecoverOnly*/ 4,
+                                             "--dbpath",
+                                             dbpath);
+            assert.eq(returnCode, /*EXIT_NET_ERROR*/ 48);
+        }
+    };
+
+    let doStartupFailTests = function(withUUIDs, dbpath) {
+        // Fail to start up if no admin database is present but other non-local databases are
+        // present.
+        if (withUUIDs) {
+            setupMissingAdminDB(latest, dbpath);
+        } else {
+            setupMissingAdminDB(downgrade, dbpath);
+        }
+        conn = MongoRunner.runMongod({dbpath: dbpath, binVersion: latest, noCleanData: true});
+        assert.eq(
+            null,
+            conn,
+            "expected mongod to fail when data files are present and no admin database is found.");
+
+        // Fail to start up if no featureCompatibilityVersion document is present and non-local
+        // databases are present.
+        if (withUUIDs) {
+            setupMissingFCVDoc(latest, dbpath);
+        } else {
+            setupMissingFCVDoc(downgrade, dbpath);
+        }
+        conn = MongoRunner.runMongod({dbpath: dbpath, binVersion: latest, noCleanData: true});
+        assert.eq(
+            null,
+            conn,
+            "expected mongod to fail when data files are present and no featureCompatibilityVersion document is found.");
+    };
+
+    let setupMissingFCVDoc = function(version, dbpath) {
+        let conn = MongoRunner.runMongod({dbpath: dbpath, binVersion: version});
+        assert.neq(null,
+                   conn,
+                   "mongod was unable to start up with version=" + version + " and no data files");
+        adminDB = conn.getDB("admin");
+        if (version === latest) {
+            assert.eq(
+                adminDB.system.version.findOne({_id: "featureCompatibilityVersion"}).version,
+                "3.6",
+                "expected 3.6 mongod with no data files to start up with featureCompatibilityVersion 3.6");
+        } else {
+            assert.eq(
+                adminDB.system.version.findOne({_id: "featureCompatibilityVersion"}).version,
+                "3.4",
+                "expected 3.4 mongod with no data files to start up with featureCompatibilityVersion 3.4");
+        }
+        assert.writeOK(adminDB.system.version.remove({_id: "featureCompatibilityVersion"}));
+        MongoRunner.stopMongod(conn);
+        return conn;
+    };
+
+    let setupMissingAdminDB = function(version, dbpath) {
+        conn = MongoRunner.runMongod({dbpath: dbpath, binVersion: version});
+        assert.neq(null,
+                   conn,
+                   "mongod was unable to start up with version=" + version + " and no data files");
+        let testDB = conn.getDB("test");
+        assert.commandWorked(testDB.createCollection("testcoll"));
+        adminDB = conn.getDB("admin");
+        assert.commandWorked(adminDB.runCommand({dropDatabase: 1}),
+                             "expected drop of admin database to be successful");
+        MongoRunner.stopMongod(conn);
+        return conn;
+    };
+
     //
     // Standalone tests.
     //
@@ -105,6 +184,73 @@
     checkFCV(adminDB, "3.4");
     MongoRunner.stopMongod(conn);
 
+    const isMMAPv1 = jsTest.options().storageEngine === "mmapv1";
+    // Fail to start up if no featureCompatibilityVersion is present.
+    doStartupFailTests(/*withUUIDs*/ true, dbpath);
+
+    // Fail to start up if no featureCompatibilityVersion is present and no collections have UUIDs.
+    doStartupFailTests(/*withUUIDs*/ false, dbpath);
+
+    // --repair can be used to restore a missing admin database and featureCompatibilityVersion
+    // document if at least some collections have UUIDs.
+    conn = setupMissingAdminDB(latest, dbpath);
+    recoverMMapJournal(isMMAPv1, conn, dbpath);
+    let returnCode = runMongoProgram("mongod", "--port", conn.port, "--repair", "--dbpath", dbpath);
+    assert.eq(
+        returnCode,
+        0,
+        "expected mongod --repair to execute successfully when restoring a missing admin database.");
+    conn = MongoRunner.runMongod({dbpath: dbpath, binVersion: latest, noCleanData: true});
+    assert.neq(null,
+               conn,
+               "mongod was unable to start up with version=" + latest + " and existing data files");
+    // featureCompatibilityVersion is 3.4 and targetVersion is 3.6 because the admin.system.version
+    // collection was restored without a UUID.
+    adminDB = conn.getDB("admin");
+    assert.eq(adminDB.system.version.findOne({_id: "featureCompatibilityVersion"}).version, "3.4");
+    assert.eq(adminDB.system.version.findOne({_id: "featureCompatibilityVersion"}).targetVersion,
+              "3.6");
+    let adminInfos = adminDB.getCollectionInfos();
+    assert(!adminInfos[0].uuid,
+           "Expected collection with infos " + tojson(adminInfos) + " to not have a UUID.");
+    MongoRunner.stopMongod(conn);
+
+    // --repair can be used to restore a missing featureCompatibilityVersion document to an
+    // existing admin database if at least some collections have UUIDs.
+    conn = setupMissingFCVDoc(latest, dbpath);
+    recoverMMapJournal(isMMAPv1, conn, dbpath);
+    returnCode = runMongoProgram("mongod", "--port", conn.port, "--repair", "--dbpath", dbpath);
+    assert.eq(
+        returnCode,
+        0,
+        "expected mongod --repair to execute successfully when restoring a missing featureCompatibilityVersion document.");
+    conn = MongoRunner.runMongod({dbpath: dbpath, binVersion: latest, noCleanData: true});
+    assert.neq(null,
+               conn,
+               "mongod was unable to start up with version=" + latest + " and existing data files");
+    // featureCompatibilityVersion is 3.6 because all collections were left intact with UUIDs.
+    adminDB = conn.getDB("admin");
+    assert.eq(adminDB.system.version.findOne({_id: "featureCompatibilityVersion"}).version, "3.6");
+    MongoRunner.stopMongod(conn);
+
+    // --repair cannot be used to restore a missing featureCompatibilityVersion document if there
+    // are no collections with UUIDs.
+    conn = setupMissingFCVDoc(downgrade, dbpath);
+    recoverMMapJournal(isMMAPv1, conn, dbpath);
+    returnCode = runMongoProgram("mongod", "--port", conn.port, "--repair", "--dbpath", dbpath);
+    assert.neq(returnCode, 0, "expected mongod --repair to fail if no collections have UUIDs.");
+
+    // If the featureCompatibilityVersion document is present but there are no collection UUIDs,
+    // --repair should not attempt to restore the document and thus not fassert.
+    conn = MongoRunner.runMongod({dbpath: dbpath, binVersion: downgrade});
+    assert.neq(null,
+               conn,
+               "mongod was unable to start up with version=" + downgrade + " and no data files");
+    MongoRunner.stopMongod(conn);
+    recoverMMapJournal(isMMAPv1, conn, dbpath);
+    returnCode = runMongoProgram("mongod", "--port", conn.port, "--repair", "--dbpath", dbpath);
+    assert.eq(returnCode, 0);
+
     //
     // Replica set tests.
     //