MB-35938: Add support for "unselect bucket"

Clients may go back to the no bucket by selecting
"@no bucket@" (which is an invalid bucket name so
it may never be a conflict with a real bucket)

Change-Id: Id83d8a7bb1968cdc9684b64b5088542c64133db5
Reviewed-on: http://review.couchbase.org/114670
Tested-by: Build Bot <[email protected]>
Reviewed-by: Jim Walker <[email protected]>

Author: trondn

daemon/memcached.cc

@@ -225,7 +225,6 @@ bool associate_bucket(Connection& connection, const char* name) {
     disassociate_bucket(connection);
 
     /* Try to associate with the named bucket */
-    /* @todo add auth checks!!! */
     for (size_t ii = 1; ii < all_buckets.size() && !found; ++ii) {
         Bucket &b = all_buckets.at(ii);
         std::lock_guard<std::mutex> guard(b.mutex);

daemon/protocol/mcbp/select_bucket_executor.cc

@@ -52,19 +52,6 @@ ENGINE_ERROR_CODE select_bucket(Cookie& cookie, const std::string& bucketname) {
         return ENGINE_ENOTSUP;
     }
 
-    // We can't switch bucket if we've got multiple commands in flight
-    if (connection.getNumberOfCookies() > 1) {
-        LOG_INFO(
-                "{}: select_bucket failed - multiple commands in flight. "
-                R"({{"cid":"{}/{:x}","connection":"{}","bucket":"{}"}})",
-                connection.getId(),
-                connection.getConnectionId().data(),
-                ntohl(cookie.getRequest().getOpaque()),
-                connection.getDescription(),
-                bucketname);
-        return ENGINE_ENOTSUP;
-    }
-
     auto oldIndex = connection.getBucketIndex();
 
     try {
@@ -117,7 +104,28 @@ void select_bucket_executor(Cookie& cookie) {
 
     auto& connection = cookie.getConnection();
     cookie.logCommand();
-    auto ret = connection.remapErrorCode(select_bucket(cookie, bucketname));
+
+    ENGINE_ERROR_CODE code = ENGINE_SUCCESS;
+
+    // We can't switch bucket if we've got multiple commands in flight
+    if (connection.getNumberOfCookies() > 1) {
+        LOG_INFO(
+                "{}: select_bucket failed - multiple commands in flight. "
+                R"({{"cid":"{}/{:x}","connection":"{}","bucket":"{}"}})",
+                connection.getId(),
+                connection.getConnectionId().data(),
+                ntohl(cookie.getRequest().getOpaque()),
+                connection.getDescription(),
+                bucketname);
+        code = ENGINE_ENOTSUP;
+    } else if (bucketname == "@no bucket@") {
+        // unselect bucket!
+        associate_bucket(connection, "");
+    } else {
+        code = select_bucket(cookie, bucketname);
+    }
+
+    auto ret = connection.remapErrorCode(code);
     cookie.logResponse(ret);
     if (ret == ENGINE_DISCONNECT) {
         connection.setState(StateMachine::State::closing);

tests/testapp/testapp_bucket.cc

@@ -662,3 +662,15 @@ TEST_P(BucketTest, TestMemcachedBucketBigObjects)
     connection.get(name, Vbid(0));
     connection.deleteBucket("mybucket_000");
 }
+
+TEST_P(BucketTest, SelectNoBucket) {
+    auto& connection = getAdminConnection();
+    connection.selectBucket("default");
+    connection.selectBucket("@no bucket@");
+    try {
+        connection.get("foo", Vbid(0));
+        FAIL() << "We should get " + to_string(cb::mcbp::Status::NoBucket);
+    } catch (const ConnectionError& error) {
+        EXPECT_EQ(cb::mcbp::Status::NoBucket, error.getReason());
+    }
+}