SERVER-29131 Support resumeAfter option to control where to start returning notifications from, which always errors if no entry with the given resumeToken exists

1 files changed, 80 insertions, 0 deletions

diff --git a/src/mongo/db/pipeline/document_source_check_resume_token.cpp b/src/mongo/db/pipeline/document_source_check_resume_token.cpp
new file mode 100644
index 00000000000..beaa8844dcb
--- /dev/null
+++ b/src/mongo/db/pipeline/document_source_check_resume_token.cpp
@@ -0,0 +1,80 @@
+/**
+ * Copyright (C) 2017 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.
+ */
+
+#include "mongo/platform/basic.h"
+
+#include "mongo/db/pipeline/document_source_check_resume_token.h"
+
+using boost::intrusive_ptr;
+namespace mongo {
+const char* DocumentSourceCheckResumeToken::getSourceName() const {
+    return "$_checkResumeToken";
+}
+
+Value DocumentSourceCheckResumeToken::serialize(
+    boost::optional<ExplainOptions::Verbosity> explain) const {
+    // This stage is created by the DocumentSourceChangeNotification stage, so serializing it here
+    // would result in it being created twice.
+    return Value();
+}
+
+intrusive_ptr<DocumentSourceCheckResumeToken> DocumentSourceCheckResumeToken::create(
+    const intrusive_ptr<ExpressionContext>& expCtx, DocumentSourceCheckResumeTokenSpec spec) {
+    return new DocumentSourceCheckResumeToken(expCtx, std::move(spec));
+}
+
+DocumentSourceCheckResumeToken::DocumentSourceCheckResumeToken(
+    const intrusive_ptr<ExpressionContext>& expCtx, DocumentSourceCheckResumeTokenSpec spec)
+    : DocumentSource(expCtx), _token(spec.getResumeToken()), _seenDoc(false) {}
+
+DocumentSource::GetNextResult DocumentSourceCheckResumeToken::getNext() {
+    pExpCtx->checkForInterrupt();
+
+    auto nextInput = pSource->getNext();
+    uassert(40584,
+            "resume of change notification was not possible, as no change data was found. ",
+            _seenDoc || !nextInput.isEOF());
+
+    if (_seenDoc || !nextInput.isAdvanced())
+        return nextInput;
+
+    _seenDoc = true;
+    auto doc = nextInput.getDocument();
+
+    ResumeToken receivedToken(doc["_id"]);
+    uassert(
+        40585,
+        str::stream()
+            << "resume of change notification was not possible, as the resume token was not found. "
+            << receivedToken.toDocument().toString(),
+        receivedToken == _token);
+    // Don't return the document which has the token; the user has already seen it.
+    return pSource->getNext();
+}
+
+}  // namespace mongo