[SERVER-21095] Using tailable cursor on capped collection memory leak - MongoDB Jira

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Operating System:
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Steps To Reproduce:

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Create capped collection.
Insert one record - save id,
Create tailable cursor with query id > saved id.
tyr to get next record in a loop.
Every loop ther is an amount of memory leaked in the server.

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Create capped collection. Insert one record - save id, Create tailable cursor with query id > saved id. tyr to get next record in a loop. Every loop ther is an amount of memory leaked in the server.

Using a tailable cursor on a capped collection leads to memory leak in the server if the first cursor MoveNext does not get a record.

BsonValue lastId = collection.FindAll().SetSortOrder(SortBy.Descending("_id")).SetLimit(1).First()["_id"];

cursor = collection.Find(Query.GT("_id", lastId))

              .SetFlags(QueryFlags.AwaitData | QueryFlags.TailableCursor | QueryFlags.NoCursorTimeout);

using (var enumerator = new MongoCursorEnumerator<BsonDocument>(cursor))

	while (triggerThread.IsAlive)

		if (enumerator.MoveNext())

			var document = enumerator.Current;

			if (document != null)

				HandleNextData(document);

		else

			if (enumerator.IsDead)

				break;

			if (!enumerator.IsServerAwaitCapable)

				Thread.Sleep(TimeSpan.FromMilliseconds(100));

If the cursor query is changed to "GTE"

cursor = collection.Find(Query.GTE("_id", lastId))

so as the first result the last record is returned all works fine.

Participants:: Daniel Pasette, Frank Pfattheicher, Kelsey Schubert, Ramon Fernandez Marina, Robert Stam, Scott Hernandez