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globalsign / mgo

The MongoDB driver for Go
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wrong tag for field ExpireAfter in struct indexSpec in session.go #242

Closed yangwangxing closed 6 years ago

yangwangxing commented 6 years ago

in session.go

type indexSpec struct { ... ExpireAfter int bson:"expireAfterSeconds,omitempty"
... }

should remove omitempty in ExpireAfter's tag description, otherwise TTL index ExpireAfter will be ignored

https://docs.mongodb.com/manual/tutorial/expire-data/#expire-documents-at-a-specific-clock-time

eminano commented 6 years ago

Hi @KinOSurvival ,

Could you provide the scenario you're facing for this to be an issue?

Thanks! Esther

yangwangxing commented 6 years ago

expiresAtIndex := mgo.Index{ Key: []string{"expires_at"}, Unique: false, Name: "session_expires_at_index", Background: false, //mgo has a bug, ExpireAfter set as 0 will be ignored, so set it to 1 second ExpireAfter: time.Duration(1) * time.Second, }

    err := collection.EnsureIndex(expiresAtIndex)

after executing this, index created, but without expireAfterSeconds settings

domodwyer commented 6 years ago

Hi @KinOSurvival

If the omitempty tag is removed, all records would have a TTL of value of 0 seconds, and they would be removed in the next TTL sweep. It's a quirk of the Go "zero value" which is a little tricky in this corner-case.

As the records are typically swept every 60 seconds within MongoDB, try using a TTL of 1 second - it's makes little practical difference due to the periodic sweep. This works for us :)

I'm closing this as there's a reasonable solution, feel free to reply if there's a problem though!

Dom

jinq0123 commented 5 years ago

Please add a comment to mgo.Index.ExpireAfter. It took me some time to find out the reason.