MongoDB 2.6: maxTimeMS on an instance/database level

Question

MongoDB 2.6 introduced the .maxTimeMS() cursor method, which allows you to specify a max running time for each query. This is awesome for ad-hoc queries, but I wondered if there was a way to set this value on a per-instance or per-database (or even per-collection) level, to try and prevent locking in general.

And if so, could that value then be OVERWRITTEN on a per-query basis? I would love to set an instance level timeout of 3000ms or thereabouts (since that would be a pretty extreme running time for queries issued by my application), but then be able to ignore it if I had a report to run.

Here's the documentation from mongodb.org, for reference: http://docs.mongodb.org/manual/reference/method/cursor.maxTimeMS/#behaviors

Answer 1

Jason,

Currently MongoDB does not support a global / universal "maxTimeMS". At the moment this option is applicable to the individual operations only. If you wish to have such a global setting available in MongoDB, I would suggest raising a SERVER ticket at https://jira.mongodb.org/browse/SERVER along with use-cases that can take advantage of such setting.

Answer 2

I know this is old but came here with a similar question and decided to post my findings, The timeout, as a global parameter, is supported by the drivers as part of the connection string, which makes sense because it's the driver the one that can control this global parameters, here you can find documentation about this: https://docs.mongodb.com/manual/reference/connection-string/, but each driver can handle this slightly different (c# for example uses Mongo Settings parameter for this, python has it as parameters in the init constructor, etc)

To test this you can start a test server using mtools like this:

mlaunch --replicaset --name testrepl --nodes 3 --port 27000

Then an example in python will be like:

from pymongo import MongoClient

c =  MongoClient(host="mongodb://localhost:27000,localhost:27001,localhost:27002/?replicaSet=testrepl&wtimeoutMS=2000&w=3")
c.test_database.col.insert({ "name": "test" })

I'm using the URI method so this can be used in other drivers, but Python also supports the parameters w and wtimeout, in this example all the write operations will be defaulted to 2 segs and 3 nodes have to be confirmed before returning, if you restart the database and use the wtimeout of 1 (meaning 1 ms) you will see an exception because the replication will take a bit longer to initialize the first time you execute the python script.

Hope this helps others coming with the same question.