MongoDB get size of Capped collection

Question

Is it possible to get max size of capped collection in MongoDB, the same size you have specified during creation?

Check [this](https://groups.google.com/forum/#!topic/mongodb-user/-3fmsKwb4GA) — Deepak Biswal, Oct 09 '14 at 06:57

score 3 · Accepted Answer · answered Oct 09 '14 at 07:20

Before V2.6, you can get it by

db.system.namespaces.findOne({name : namespace}).options.size;
// namesapce : <db>.<collection>

For V2.6+ (I test on V2.6.4), you can only get integral multiples of EXTENT_SIZE.

returnSize = Math.ceil(specifiedSize / EXTENT_SIZE) * EXTENT_SIZE
// for example, returnsize = Math.ceil(1 / 4096) * 4096 = 4096

score 3 · Answer 2 · answered Sep 26 '17 at 10:22

db.collectioname.stats()

will give you the max size. It will always be in multiple of 256

> db.createCollection( "log_cap2", { capped: true, size: 7500 } )

{ "ok" : 1 } >

db.log_cap2.stats() { "ns" : "test.log_cap2", "size" : 0, "count" : 0, "storageSize" : 4096, "capped" : true, "max" : -1, "maxSize" : 7680,

Even thou I gave size as 7500 it will allocate in multiples of 256

256*29 = 7424 256*30=7680

2 Answers2