SERVER-24939 Pull read concern extract, check and wait to separate utility

1 files changed, 133 insertions, 0 deletions

diff --git a/src/mongo/db/read_concern.cpp b/src/mongo/db/read_concern.cpp
new file mode 100644
index 00000000000..f4baada6218
--- /dev/null
+++ b/src/mongo/db/read_concern.cpp
@@ -0,0 +1,133 @@
+/**
+ *    Copyright (C) 2016 MongoDB 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 "mongo/db/read_concern.h"
+
+#include "mongo/base/status.h"
+#include "mongo/base/status_with.h"
+#include "mongo/db/commands.h"
+#include "mongo/db/curop.h"
+#include "mongo/db/operation_context.h"
+#include "mongo/db/repl/read_concern_args.h"
+#include "mongo/db/repl/replication_coordinator.h"
+#include "mongo/db/server_options.h"
+#include "mongo/db/server_parameters.h"
+#include "mongo/util/log.h"
+
+namespace mongo {
+namespace {
+
+// This is a special flag that allows for testing of snapshot behavior by skipping the replication
+// related checks and isolating the storage/query side of snapshotting.
+bool testingSnapshotBehaviorInIsolation = false;
+ExportedServerParameter<bool, ServerParameterType::kStartupOnly> TestingSnapshotBehaviorInIsolation(
+    ServerParameterSet::getGlobal(),
+    "testingSnapshotBehaviorInIsolation",
+    &testingSnapshotBehaviorInIsolation);
+
+}  // namespace
+
+StatusWith<repl::ReadConcernArgs> extractReadConcern(OperationContext* txn,
+                                                     const BSONObj& cmdObj,
+                                                     bool supportsReadConcern) {
+    repl::ReadConcernArgs readConcernArgs;
+
+    auto readConcernParseStatus = readConcernArgs.initialize(cmdObj);
+    if (!readConcernParseStatus.isOK()) {
+        return readConcernParseStatus;
+    }
+
+    if (!supportsReadConcern && !readConcernArgs.isEmpty()) {
+        return {ErrorCodes::InvalidOptions,
+                str::stream() << "Command does not support read concern"};
+    }
+
+    return readConcernArgs;
+}
+
+Status waitForReadConcern(OperationContext* txn, const repl::ReadConcernArgs& readConcernArgs) {
+    repl::ReplicationCoordinator* const replCoord = repl::ReplicationCoordinator::get(txn);
+
+    // Skip waiting for the OpTime when testing snapshot behavior
+    if (!testingSnapshotBehaviorInIsolation && !readConcernArgs.isEmpty()) {
+        Status status = replCoord->waitUntilOpTimeForRead(txn, readConcernArgs);
+        if (!status.isOK()) {
+            return status;
+        }
+    }
+
+    if ((replCoord->getReplicationMode() == repl::ReplicationCoordinator::Mode::modeReplSet ||
+         testingSnapshotBehaviorInIsolation) &&
+        (readConcernArgs.getLevel() == repl::ReadConcernLevel::kMajorityReadConcern ||
+         readConcernArgs.getLevel() == repl::ReadConcernLevel::kLinearizableReadConcern)) {
+        // ReadConcern Majority is not supported in ProtocolVersion 0.
+        if (!testingSnapshotBehaviorInIsolation && !replCoord->isV1ElectionProtocol()) {
+            return {ErrorCodes::ReadConcernMajorityNotEnabled,
+                    str::stream() << "Replica sets running protocol version 0 do not support "
+                                     "readConcern: majority"};
+        }
+
+        const int debugLevel = serverGlobalParams.clusterRole == ClusterRole::ConfigServer ? 1 : 2;
+
+        LOG(debugLevel) << "Waiting for 'committed' snapshot to be available for reading: "
+                        << readConcernArgs;
+
+        Status status = txn->recoveryUnit()->setReadFromMajorityCommittedSnapshot();
+
+        // Wait until a snapshot is available.
+        while (status == ErrorCodes::ReadConcernMajorityNotAvailableYet) {
+            LOG(debugLevel) << "Snapshot not available yet.";
+            replCoord->waitUntilSnapshotCommitted(txn, SnapshotName::min());
+            status = txn->recoveryUnit()->setReadFromMajorityCommittedSnapshot();
+        }
+
+        if (!status.isOK()) {
+            return status;
+        }
+
+        LOG(debugLevel) << "Using 'committed' snapshot: " << CurOp::get(txn)->query();
+    }
+
+    if (readConcernArgs.getLevel() == repl::ReadConcernLevel::kLinearizableReadConcern) {
+        if (!readConcernArgs.getOpTime().isNull())
+            return {ErrorCodes::FailedToParse,
+                    "afterOpTime not compatible with linearizable read concern"};
+
+        if (!replCoord->getMemberState().primary())
+            return {ErrorCodes::NotMaster,
+                    "cannot satisfy linearizable read concern on non-primary node"};
+    }
+
+    return Status::OK();
+}
+
+}  // namespace mongo