SERVER-16184 repeated WriteBackListener error on out-of-order upgrade

1 files changed, 120 insertions, 0 deletions

diff --git a/src/mongo/db/commands/writeback_compatibility_shim.cpp b/src/mongo/db/commands/writeback_compatibility_shim.cpp
new file mode 100644
index 00000000000..e10daff425b
--- /dev/null
+++ b/src/mongo/db/commands/writeback_compatibility_shim.cpp
@@ -0,0 +1,120 @@
+/**
+ *    Copyright (C) 2014 10gen Inc.
+ *
+ *    This program is free software: you can redistribute it and/or  modify
+ *    it under the terms of the GNU Affero General Public License, version 3,
+ *    as published by the Free Software Foundation.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU Affero General Public License for more details.
+ *
+ *    You should have received a copy of the GNU Affero General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the GNU Affero General Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kCommand
+
+#include "mongo/platform/basic.h"
+
+#include <string>
+
+#include "mongo/base/init.h"
+#include "mongo/db/client.h"
+#include "mongo/db/commands.h"
+#include "mongo/db/commands/server_status.h"
+#include "mongo/db/operation_context.h"
+#include "mongo/util/log.h"
+#include "mongo/util/mongoutils/str.h"
+
+namespace mongo {
+
+    using std::string;
+    using mongoutils::str::stream;
+
+    /**
+     * This command is required in v2.8 mongod to prevent v2.6 mongos from entering a tight loop and
+     * spamming the server with invalid writebacklisten requests.  This command reports an error
+     * and pauses, which is safe because the original v2.6 WBL command was a long-poll (30s).
+     */
+    class WriteBackCommand : public Command {
+    public:
+        WriteBackCommand() : Command("writebacklisten") {}
+
+        void help(stringstream& helpOut) const {
+            helpOut << "v2.8 disallowed internal command, present for compatibility only";
+        }
+
+        virtual bool isWriteCommandForConfigServer() const { return false; }
+
+        //
+        // Same as v2.6 settings
+        //
+
+        virtual bool adminOnly() const { return true; }
+        virtual bool slaveOk() const { return true; }
+
+        virtual void addRequiredPrivileges(const std::string& dbname,
+                                           const BSONObj& cmdObj,
+                                           std::vector<Privilege>* out) {
+            ActionSet actions;
+            actions.addAction(ActionType::internal);
+            out->push_back(Privilege(ResourcePattern::forClusterResource(), actions));
+        }
+
+        virtual bool run(OperationContext* opCtx,
+                         const string&, BSONObj&, int, string&, BSONObjBuilder& result, bool) {
+
+            string errMsg = stream()
+                << "Writeback functionality is no longer present in v2.8 mongod, "
+                << "a v2.6 mongos may be running in the v2.8 cluster at "
+                << opCtx->getClient()->clientAddress(false);
+
+            error() << errMsg;
+
+            // Prevent v2.6 mongos from spamming writebacklisten retries
+            const int kSleepSecsBeforeMessage = 5;
+            sleep(kSleepSecsBeforeMessage);
+
+            return appendCommandStatus(result, Status(ErrorCodes::CommandNotFound, errMsg));
+        }
+    };
+
+    /**
+     * The "writeBacksQueued" field is required in ServerStatus output to avoid v2.6 mongos crashing
+     * confusingly when upgrading a cluster.
+     */
+    class WriteBacksQueuedSSM : public ServerStatusMetric {
+    public:
+        WriteBacksQueuedSSM() : ServerStatusMetric(".writeBacksQueued") {}
+
+        virtual void appendAtLeaf(BSONObjBuilder& b) const {
+            // always append false, we don't queue writebacks
+            b.appendBool(_leafName, false);
+        }
+    };
+
+    namespace {
+        MONGO_INITIALIZER(RegisterWriteBackShim)(InitializerContext* context) {
+            // Leaked intentionally: a Command registers itself when constructed.
+            new WriteBackCommand();
+            // Leaked intentionally: a SSM registers itself when constructed.
+            new WriteBacksQueuedSSM();
+            return Status::OK();
+        }
+    }
+
+} // namespace