SERVER-30993 Always remove UUIDs when setting featureCompatibilityVersion to 3.4

1 files changed, 150 insertions, 0 deletions

diff --git a/jstests/multiVersion/incomplete_upgrade_downgrade.js b/jstests/multiVersion/incomplete_upgrade_downgrade.js
new file mode 100644
index 00000000000..5c1367b3e49
--- /dev/null
+++ b/jstests/multiVersion/incomplete_upgrade_downgrade.js
@@ -0,0 +1,150 @@
+/**
+ * This test verifies that if mongod exits after setting the FCV document to 3.4 before the
+ * collection UUIDs are removed, that re-running the downgrade to 3.4 is possible.
+ */
+(function() {
+    "use strict";
+
+    let checkFCV = function(adminDB, version) {
+        let res = adminDB.runCommand({getParameter: 1, featureCompatibilityVersion: 1});
+        assert.commandWorked(res);
+        assert.eq(res.featureCompatibilityVersion, version);
+        assert.eq(adminDB.system.version.findOne({_id: "featureCompatibilityVersion"}).version,
+                  version);
+    };
+
+    let setFCV = function(adminDB, version) {
+        assert.commandWorked(adminDB.runCommand({setFeatureCompatibilityVersion: version}));
+    };
+
+    // Inserts test data
+    let insertDataForConn = function(conn, dbs) {
+        for (let i = 0; i < 20; i++) {
+            let doc = {id: i, a: "foo", conn: conn.name};
+            for (let j in dbs) {
+                assert.writeOK(conn.getDB(dbs[j]).foo.insert(doc));
+            }
+        }
+    };
+
+    // Verifies that UUIDs exist when uuidsExpected is true, and that UUIDs do not exist when
+    // uuidsExpected is false.
+    let checkCollectionUUIDs = function(adminDB, uuidsExpected, excludeLocal = true) {
+        let databaseList = adminDB.runCommand({"listDatabases": 1}).databases;
+
+        databaseList.forEach(function(database) {
+            if (excludeLocal && database.name == "local") {
+                jsTest.log("Skipping local");
+                return;
+            }
+            let currentDatabase = adminDB.getSiblingDB(database.name);
+            let collectionInfos = currentDatabase.getCollectionInfos();
+            for (let i = 0; i < collectionInfos.length; i++) {
+                // Always skip system.indexes due to SERVER-30500.
+                if (collectionInfos[i].name == "system.indexes") {
+                    continue;
+                }
+                // Exclude checking all collections in local until SERVER-30131 is fixed.
+                if (!uuidsExpected) {
+                    assert(!collectionInfos[i].info.uuid,
+                           "Unexpected uuid for collection: " + tojson(collectionInfos[i]));
+                } else {
+                    assert(collectionInfos[i].info.uuid,
+                           "Expect uuid for collection: " + tojson(collectionInfos[i]));
+                }
+            }
+        });
+    };
+
+    jsTest.log("Testing Incomeplete Downgrade");
+
+    let dbpath = MongoRunner.dataPath + "incomplete_downgrade";
+    resetDbpath(dbpath);
+
+    let conn = MongoRunner.runMongod({dbpath: dbpath});
+    assert.neq(null, conn, "mongod was unable to start up");
+    let adminDB = conn.getDB("admin");
+
+    // Insert test data.
+    insertDataForConn(conn, ["admin", "local", "test"]);
+
+    // Ensure featureCompatibilityVersion is 3.6 and collections have UUIDs.
+    checkFCV(adminDB, "3.6");
+    checkCollectionUUIDs(adminDB, true);
+
+    // Set failure point to exit after setting featureCompatibilityVersion document before removing
+    // UUIDs from collections.
+    assert.commandWorked(
+        conn.adminCommand({configureFailPoint: "featureCompatibilityDowngrade", mode: "alwaysOn"}));
+
+    // Downgrade, which should trigger a shutdown, so don't check for result.
+    // Mongod should stop responding.
+    assert.soon(function() {
+        try {
+            adminDB.runCommand({setFeatureCompatibilityVersion: "3.4"});
+        } catch (e) {
+            return true;
+        }
+    }, "Mongod should stop responding", 10 * 1000);
+
+    // Check for clean exit.
+    MongoRunner.validateCollectionsCallback = function() {};
+    MongoRunner.stopMongod(conn);
+
+    // Start mongod again with the same dbpath
+    conn = MongoRunner.runMongod({dbpath: dbpath, noCleanData: true});
+    assert.neq(null, conn, "mongod was unable to start up");
+    adminDB = conn.getDB("admin");
+
+    // FeatureCompatibility document should be 3.4.
+    checkFCV(adminDB, "3.4");
+
+    // Check that collections still have UUIDs.
+    checkCollectionUUIDs(adminDB, /* uuidsExpected */ true);
+
+    // Now that failpoint is not set, resume downgrade.
+    setFCV(adminDB, "3.4");
+
+    // Verify no collections have UUIDS now.
+    checkCollectionUUIDs(adminDB, false);
+
+    jsTest.log("Testing Incomplete Upgrade");
+
+    // Set failure point to exit before setting featureCompatibilityVersion document and after
+    // creating UUIDs for collections.
+    assert.commandWorked(
+        conn.adminCommand({configureFailPoint: "featureCompatibilityUpgrade", mode: "alwaysOn"}));
+
+    // Try upgrade to 3.6, which triggers the failpoint to exit, immediately after creating UUIDs.
+    assert.soon(function() {
+        try {
+            adminDB.runCommand({setFeatureCompatibilityVersion: "3.6"});
+        } catch (e) {
+            return true;
+        }
+    }, "Mongod should stop responding", 10 * 1000);
+
+    // Verify mongod stopped cleanly
+    MongoRunner.stopMongod(conn);
+
+    // Start mongod again with the same dbpath
+    conn = MongoRunner.runMongod({dbpath: dbpath, noCleanData: true});
+    assert.neq(null, conn, "mongod was unable to start up");
+    adminDB = conn.getDB("admin");
+
+    // Check that collections have UUIDs.
+    checkCollectionUUIDs(adminDB, /* uuidsExpected */ true);
+
+    // The FCV document should not be updated yet.
+    checkFCV(adminDB, "3.4");
+
+    // Now that failpoint is not set, resume upgrade.
+    setFCV(adminDB, "3.6");
+
+    // Verify all collections still have UUIDS.
+    checkCollectionUUIDs(adminDB, true);
+
+    // Verify FCV.
+    checkFCV(adminDB, "3.6");
+
+})();