TTL indexes are not created

[ItalyPaleAle]

With Mongoose 3.8.19 and MongoDB 2.6.5, Mongoose is not creating TTL indexes ("expireAfterSeconds"), in no way.

See this SO question: http://stackoverflow.com/questions/26892660/mongoose-doesnt-create-ttl-indexes

[shrayolacrayon]

You can create the index in this sort of manner -

exampleSchema = {field1 : {type : Date, index: {expires : 50}}, field2: String}

[ItalyPaleAle]

Thanks Shraya.
As I wrote on SO, I've tried that too (and also expires with the final s). None of those work, hence I suspect a bug in Mongoose.

[shrayolacrayon]

So this may be a workaround, but after creating the schema with the defined indexes and the model, can you try using ModelName.ensureIndexes?
See http://mongoosejs.com/docs/api.html#model_Model.ensureIndexes.

You will be able to get the same functionality as the ensureIndexes() command in the mongo shell.
Let me know if that works.

[ItalyPaleAle]

It's still not working:

'use strict';

var mongoose = require('mongoose')
var Schema = mongoose.Schema

var sessionSchema = new Schema({
    _id: { type: String, required: true, index: { unique: true } },
    user: { type: Schema.Types.ObjectId },
    expire: { type: Date, index: { expireAfterSeconds: 21600 } }
})

module.exports = mongoose.model('Session', sessionSchema)

// Fix for Mongoose not creating the TTL indexes (see https://github.com/LearnBoost/mongoose/issues/2459#issuecomment-62802096 )
mongoose.model('Session').ensureIndexes(function(err) {
    console.log('ensure index', err)
})

On the console I get:

MongoError: Index with name: _id_ already exists with different options

(Note I had deleted the collection prior restarting the Node app)

[shrayolacrayon]

Okay, so it seems that your real problem is not with the TTL index, but with the _id index, which is created automatically, and in turn is failing at the start of creating the indexes.
I'll look into a potential solution regarding non-default _ids in Mongoose.

[ItalyPaleAle]

Ok, I'm not on my work computer now so I can't test this assumption... But given that (a) the index on _id is created (I can see it in the database, even if it doesn't look like it's set as "unique", as I specified) and that (b) ensureIndex with Mongoose is failing; I assume that something is creating an index by default on the custom _id. Is that MongoDB or Mongoose? If it's Mongoose, why is it doing that?

[shrayolacrayon]

MongoDB by default creates a unique index on _id so you need not create an index on it. You also do not need to include the ensureIndex call. Your schema should work just fine if you take out the index field in _id.

[ItalyPaleAle]

Ok, I removed the index on the _id field and it's now working.
Thanks for your help.

PS: Maybe you should consider specifying it in the docs?

[arimus]

This was fun to track down. However, I was indeed simply able to remove the unique:true from two of the_id fields in my schema definitions. Then there was no error and the rest of my indexes were created fine.

Having this error logged in the console (at very least in debug mode), since it is a severe error in that indexes will not be generated, would seem to be a good enhancement. It's good to know when expected behavior is failing & what the problem is.

[vkarpov15]

Models have an "index" event that's emitted when index builds are done, or when an index fails to build. See http://stackoverflow.com/questions/14333603/how-should-mongooses-model-onindex-be-used

[dman777]

Would it be the same thing here with my index: true? I can't get expires to work:

var CpuSchema = new Schema({
    createdAt: { type: Date, expires: '24h' },
    timestamp : { type : Date, index: true },

[vkarpov15]

Do schema.index({ createdAt: 1 }, { expireAfterSeconds: 3600 });. http://docs.mongodb.org/manual/core/index-ttl/

[dman777]

Isn't mongoose supposed to take care of this? I would like to know if my timestamp : { type : Date, index: true } is interfering with mongoose creating the ttl index.

[vkarpov15]

Try listening to the Model.on('index', function(error) {}); event to see if there are any issues building indexes.

Also, is mongoose supposed to take care of what exactly?

[revstage]

this schema configuration works for me on Mongoose 5.7.0 and MongoDB v4.2.0

expireAt: {
  type: Date,
  default: Date.now,
  index: { expires: '1d' }
}