db.killOp()

Kill Read Operations

The db.killOp() method can be run on a mongos and can kill queries (read operations) that are running on more than one shard in a cluster.

For example, to kill a query operation on a sharded cluster:

Kill Write Operations

Within a Session

MongoDB drivers associate all operations with a server session, with the exception of unacknowledged writes.

If the write operation is associated with a session, you can use the killSessions command on the mongos to kill the write operation across shards.

1. Run the aggregation pipeline $currentOp on the mongos to find the lsid (logical session id).

   use admin
   db.aggregate( [
      { $currentOp : { allUsers: true, localOps: true } },
      { $match : <filter condition> } // Optional.  Specify the condition to find the op.
                                      // e.g. { "op" : "update", "ns": "mydb.someCollection" }
   ] )

   1. Using the returned lsid information, issue the killSessions command on the mongos to kill the operation on the shards.

      db.adminCommand( { killSessions: [
         { "id" : UUID("80e48c5a-f7fb-4541-8ac0-9e3a1ed224a4"), "uid" : BinData(0,"47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU=") }
      ] } )

Without a Session

If the write operation is not associated with a session, you must find and kill the operation on all the shards associated with the write.

1. From a mongos, run the aggregation pipeline $currentOp to find the opid(s) of the query operation on the shards:

   use admin
   db.aggregate( [
      { $currentOp : { allUsers: true } },
      { $match : <filter condition> } // Optional.  Specify the condition to find the op.
   ] )

   When run on a mongos, $currentOp returns the opids in the format of "<shardName>:<opid on that shard>"; e.g.

   {
      "shard" : "shardB",
      ..
      "opid" : "shardB:79214",
      ...
   },
   {
      "shard" : "shardA",
      ..
      "opid" : "shardA:100913",
      ...
   },

2. Using the opid information, issue db.killOp() on the mongos to kill the operation on the shards.

   db.killOp("shardB:79014");
   db.killOp("shardA:100813");