SERVER-21414 serverStatus storageEngine.persistent

Under the server status statistics, "storageEngine.persistent" is either 0 or 1
to indicate if the storage engine persists data to disk.

(cherry picked from commit 76cc3b37b1912c35c80084b859efcdc93b104637)

4 files changed, 13 insertions, 1 deletions

diff --git a/src/mongo/db/storage/mmap_v1/mmap_v1_engine.cpp b/src/mongo/db/storage/mmap_v1/mmap_v1_engine.cpp
index 160c268c6fa..71913e7b389 100644
--- a/src/mongo/db/storage/mmap_v1/mmap_v1_engine.cpp
+++ b/src/mongo/db/storage/mmap_v1/mmap_v1_engine.cpp
@@ -337,6 +337,10 @@ bool MMAPV1Engine::isDurable() const {
     return getDur().isDurable();
 }
 
+bool MMAPV1Engine::isEphemeral() const {
+    return false;
+}
+
 RecordAccessTracker& MMAPV1Engine::getRecordAccessTracker() {
     return _recordAccessTracker;
 }
diff --git a/src/mongo/db/storage/mmap_v1/mmap_v1_engine.h b/src/mongo/db/storage/mmap_v1/mmap_v1_engine.h
index 4fac787b4b0..7488a6592ff 100644
--- a/src/mongo/db/storage/mmap_v1/mmap_v1_engine.h
+++ b/src/mongo/db/storage/mmap_v1/mmap_v1_engine.h
@@ -66,6 +66,8 @@ public:
 
     virtual bool isDurable() const;
 
+    virtual bool isEphemeral() const;
+
     virtual Status closeDatabase(OperationContext* txn, StringData db);
 
     virtual Status dropDatabase(OperationContext* txn, StringData db);
diff --git a/src/mongo/db/storage/storage_engine.h b/src/mongo/db/storage/storage_engine.h
index 73330798d1c..7fcee4cfa10 100644
--- a/src/mongo/db/storage/storage_engine.h
+++ b/src/mongo/db/storage/storage_engine.h
@@ -171,6 +171,11 @@ public:
     virtual bool isDurable() const = 0;
 
     /**
+     * Returns true if the engine does not persist data to disk; false otherwise.
+     */
+    virtual bool isEphemeral() const = 0;
+
+    /**
      * Only MMAPv1 should override this and return true to trigger MMAPv1-specific behavior.
      */
     virtual bool isMmapV1() const {
diff --git a/src/mongo/db/storage/storage_init.cpp b/src/mongo/db/storage/storage_init.cpp
index a90ddecfe25..365369e6855 100644
--- a/src/mongo/db/storage/storage_init.cpp
+++ b/src/mongo/db/storage/storage_init.cpp
@@ -55,7 +55,8 @@ public:
     virtual BSONObj generateSection(OperationContext* txn, const BSONElement& configElement) const {
         auto engine = txn->getClient()->getServiceContext()->getGlobalStorageEngine();
         return BSON("name" << storageGlobalParams.engine << "supportsCommittedReads"
-                           << bool(engine->getSnapshotManager()));
+                           << bool(engine->getSnapshotManager()) << "persistent"
+                           << !engine->isEphemeral());
     }
 
 } storageSSS;