SERVER-21596 Check if output collection is sharded when doing mapReduce

1 files changed, 6 insertions, 0 deletions

diff --git a/src/mongo/s/commands/cluster_map_reduce_cmd.cpp b/src/mongo/s/commands/cluster_map_reduce_cmd.cpp
index 42272057bb9..ec4d6a4fef6 100644
--- a/src/mongo/s/commands/cluster_map_reduce_cmd.cpp
+++ b/src/mongo/s/commands/cluster_map_reduce_cmd.cpp
@@ -514,6 +514,12 @@ public:
 
             // Do the splitting round
             ChunkManagerPtr cm = confOut->getChunkManagerIfExists(txn, finalColLong);
+
+            uassert(34359,
+                    str::stream() << "Failed to write mapreduce output to " << finalColLong
+                                  << "; expected that collection to be sharded, but it was not",
+                    cm);
+
             for (const auto& chunkSize : chunkSizes) {
                 BSONObj key = chunkSize.first;
                 const int size = chunkSize.second;