CODEWITHSUNDEEP
pythonmongodbmongoenginerobo3t
Shay Nehmad
Shay Nehmad

Reputation: 1161

MongoDB TTL index doesn't delete expired documents

I'm trying to create a collection named ttl, and using a TTL index, make the documents in that collection expire after 30 seconds.

I've created the collection using mongoengine, like so: 

class Ttl(Document):
    meta = {
        'indexes': [
            {
                'name': 'TTL_index',
                'fields': ['expire_at'],
                'expireAfterSeconds': 0
            }
        ]
    }

    expire_at = DateTimeField()

The index has been created and Robo3T shows it's as expected.

The actual documents are inserted to the collection using mongoengine as well:

current_ttl = models.monkey.Ttl(expire_at=datetime.now() + timedelta(seconds=30))
current_ttl.save()

The save is successful (the document is inserted into the DB), but it never expires!

How can I make the documents expire?

I'm adding the collection's contents here as well in case I'm saving them wrong. These are the results of running db.getCollection('ttl').find({}): 

/* 1 */
{
    "_id" : ObjectId("5ccf0f5a4bdc6edcd3773cd6"),
    "created_at" : ISODate("2019-05-05T19:31:10.715Z")
}

/* 2 */
{
    "_id" : ObjectId("5ccf121c0b792dae8f55cc80"),
    "expire_at" : ISODate("2019-05-05T19:41:08.220Z")
}

/* 3 */
{
    "_id" : ObjectId("5ccf127d6729084a24772fad"),
    "expire_at" : ISODate("2019-05-05T19:42:47.522Z")
}

/* 4 */
{
    "_id" : ObjectId("5ccf15bab124a97322da28de"),
    "expire_at" : ISODate("2019-05-05T19:56:56.359Z")
}

The indexes themselves, as per the results of db.getCollection('ttl').getIndexes(), are:

/* 1 */
[
    {
        "v" : 2,
        "key" : {
            "_id" : 1
        },
        "name" : "_id_",
        "ns" : "monkeyisland.ttl"
    },
    {
        "v" : 2,
        "key" : {
            "expire_at" : 1
        },
        "name" : "TTL_index",
        "ns" : "monkeyisland.ttl",
        "background" : false,
        "expireAfterSeconds" : 0
    }
]

My db.version() is 4.0.8 and it's running on Ubuntu 18.04.

Upvotes: 4

Views: 1488

Answers (1)

Rony Fragin
Rony Fragin

Reputation: 126

The issue is with:

current_ttl = models.monkey.Ttl(expire_at=datetime.now() + timedelta(seconds=30))

that should be

current_ttl = models.monkey.Ttl(expire_at=datetime.utcnow() + timedelta(seconds=30))

Upvotes: 2

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