soft lock on down

lib/actions/down.js

@@ -18,6 +18,12 @@ module.exports = async (db, client) => {
     throw new Error("Could not migrate down, a lock is in place.");
   }
 
+  try {
+    await lock.activate(db);
+  } catch(err) {
+    throw new Error(`Could not create a lock: ${err.message}`);
+  }
+
   if (lastAppliedItem) {
     try {
       const migration = await migrationsDir.loadMigration(lastAppliedItem.fileName);
@@ -31,6 +37,7 @@ module.exports = async (db, client) => {
       }
 
     } catch (err) {
+      await lock.clear(db);
       throw new Error(
         `Could not migrate down ${lastAppliedItem.fileName}: ${err.message}`
       );
@@ -45,5 +52,6 @@ module.exports = async (db, client) => {
     }
   }
 
+  await lock.clear(db);
   return downgraded;
 };

test/actions/down.test.js

@@ -81,8 +81,10 @@ describe("down", () => {
     }
 
     return {
+      insertOne: sinon.stub().returns(Promise.resolve()),
       createIndex: sinon.stub().returns(Promise.resolve()),
       find: sinon.stub().returns(findStub),
+      deleteMany: sinon.stub().returns(Promise.resolve()),
     }
   }
 
@@ -209,6 +211,14 @@ describe("down", () => {
     expect(items).to.deep.equal(["20160609113225-last_migration.js"]);
   });
 
+  it("should lock if feature is enabled", async() => {
+    await down(db);
+    expect(changelogLockCollection.createIndex.called).to.equal(true);
+    expect(changelogLockCollection.find.called).to.equal(true);
+    expect(changelogLockCollection.insertOne.called).to.equal(true);
+    expect(changelogLockCollection.deleteMany.called).to.equal(true);
+  });
+
   it("should ignore lock if feature is disabled", async() => {
     config.read = sinon.stub().returns({
       changelogCollectionName: "changelog",
@@ -227,6 +237,19 @@ describe("down", () => {
     expect(changelogLockCollection.find.called).to.equal(false);
   });
 
+  it("should yield an error when unable to create a lock", async() => {
+    changelogLockCollection.insertOne.returns(Promise.reject(new Error("Kernel panic")));
+
+    try {
+      await down(db);
+      expect.fail("Error was not thrown");
+    } catch (err) {
+      expect(err.message).to.deep.equal(
+        "Could not create a lock: Kernel panic"
+      );
+    }
+  });
+
   it("should yield an error when changelog is locked", async() => {
     const findStub = {
       toArray: () => {