Simulate slow query in mongodb?

Question

Does MongoDb have anything like MySql's SELECT SLEEP(5); ?

I can see some internal sleep function that would pause the whole server, but I need to pause just the current query.

Disclaimer: just for testing purposes

I don't think such a thing exists atm, at least I have never heard of it. I suppose you could use a `$where` with some sneaky coding to make the JS thread sleep, but only for testing of course. However this will induce a sleep or `timeout()` per doc iteration of the find. — Sammaye, Oct 16 '12 at 07:38

score 8 · Accepted Answer · answered May 31 '13 at 00:59

8

You can use the $where operator to call sleep(). This should work in any language or ORM/ODM. For example, in Mongoid you could do:

Model.where( :$where => "sleep(100) || true" ).count

Tune the sleep value for the number of documents in the collection (it will delay on each one). This will do fairly horrible things to the DB server, so only use it for testing, and never (ever!) on a production server.

answered May 31 '13 at 00:59

code_monkey_steve

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in my question I mentioned that _sleep_ will pause the whole server, not just a single query – Oleg Mikheev May 31 '13 at 04:42
This doesn't pause the whole server (other queries will still run in between the calls to sleep on each document) but it does make it slower. – code_monkey_steve Jun 04 '13 at 18:36
what's the unit of 100 ? is it 100 seconds or 100 milliseconds? – carton.swing Apr 11 '19 at 10:07
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@carton.swing 100ms. https://docs.mongodb.com/manual/reference/method/sleep/index.html – Yetti Apr 03 '20 at 16:58

score 3 · Answer 2 · edited May 23 '17 at 11:50

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You can use the $where operator as code_monkey_steve says, but be sure you do with mongo version >= 2.4. Before that version no javascript can be run on parallel on the same server. The sleep command is javascript, so it would apparently block other javascript queries you could be making.

edited May 23 '17 at 11:50

Community

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answered Sep 15 '13 at 19:40

RubenCaro

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score 2 · Answer 3 · answered May 17 '21 at 07:24

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from mongo Shell you can run :

db.collection_name.find( { $where: function() { return sleep(100) || true }}).pretty();

tested and working.

answered May 17 '21 at 07:24

Atique Firoz

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please do not run this in production, only for testing purpose in dev environment – Atique Firoz May 17 '21 at 07:25

score 1 · Answer 4 · answered Oct 16 '12 at 07:45

From the mongo shell you can do sleep( ms ), eg sleep for 5 seconds before running a query:

> sleep(5000); db.collection.find(..);

This doesn't pause the current query, but does pause execution on that connection for the specific number of milliseconds before continuing with the next statement (which is equivalent to a select sleep(5) in MySQL).

Simulate slow query in mongodb?

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