Is Oplog required for meteor apps Even if there is No replication?

help
1

Hello,

I have high CPU usage and few users for my meteor app.
I was told Oplog not working is the cause of high CPU usage.
So, Is Oplog required for meteor apps Even if there is No replication?

Thanks

2

Yes, because Meteor doesn’t assume that it’s the only one accessing the database (so if you for example manually make a change in mongo, you will instantly see it reflected in Meteor). So you will actually have to set up a Mongo replica set with just one member in it.

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3

If I manually make a change in a mongo collection (insert, update, delete) and I see it reflected in meteor app, that means OpLog is working, right?

4

No, because the fallback Meteor has if it doesn’t find a working Oplog is to spam the database checking for changes, hence the massive performance problems. And the default installation of Mongo does not come with a replica set and oplog.

But if you test many times, and every time you make a change you see it reflected in Meteor within a fraction of a second, then I believe the Oplog should be working :stuck_out_tongue:
Kadira is still up btw, so you could try installing that.

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5

Thanks for the info.
When I execute the app with meteor run --settings staging/settings.json locally
meteor uses OpLog or spams the database?

6

The development installation of Meteor installs MongoDB with oplog enabled.

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