Pushing copy of App fails when including the sync directory: push failed: failed to deploy app: error initializing stores: failed to initialize stores: (AtlasError) cannot create a new collection -- already using 500 collections of 500

MongoDB Atlas App Services & Realm
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1

I am trying to automatically create a copy of an existing App in a CICD pipeline.
Following the instructions as described here: https://www.mongodb.com/docs/atlas/app-services/apps/copy/,

I get this error when trying to push the updated/copied configuration to the new app:

push failed: failed to deploy app: error initializing stores: failed to initialize stores: (AtlasError) cannot create a new collection -- already using 500 collections of 500

Which seems to be incorrect because I only have 13 collections in my database / cluster (it is a shared cluster; but I assume the 500 limit is meant per user, right?).

Furthermore, if, in addition to the root_config.json as mentioned in the article, I also remove the sync directory from the app I want to copy before I copy its contents, the push does succeed. And afterwards I can enable sync without problems from the UI, which results in the exact same configuration that I am trying to push in the first place… but doing this through the UI does not meet my CI/CD needs.

Does anyone has any idea what could be going wrong here / suggestions how to fix this issue?

Note: Pushing a copy of the app as described in the article, including its sync directory, did succeed the first few times. It was only after a while that I started to get this error.

Any suggestions much appreciated!

2

Hi, if you provide your application id we can take a look behind the scenes, but Device Sync creates a lot of metadata collections (something on the order of 10 + the number of collections you are syncing). These collections are hidden from the Data Explorer / Compass, but you can see them if you use the shell and they will be prefixed by __realm_sync. I tell you think just so you can confirm they are there though, removing them will break sync for the application.

Therefore, I suspect that you have several (dozens or so) applications enabling sync on this shared cluster. The short answer is that you can/should move to a dedicated tier cluster which has no limitations on data stored, number of collections, or operations per second.

Best,
Tyler

3

Hi Tyler,

Thank you for your quick reply.
The id of the app I’m trying to copy is: 657cb67429738cbcd4dc60ee

I have 4 apps running on that cluster/project (all copies of the same app, successfully copied as described above). I used the mongosh listDatabases command and see 17 instances starting with ‘__realm_sync*’, which would lead me to believe there should be max 17 * 13 = 221 collections there if I understand you correctly.

I feel like something goes wrong specifically when I use the cli to push a copy of an app. As said, I can create a copy without sync enabled through the cli, and then manually enable sync through the UI without getting there error - giving me another reason to believe the 500 limit has not been reached yet.

I believe I have been able to create about 20 copies of the initial app through the cli before the error first appeared. I now deleted most of those copies and only have 4 running still. So I don’t understand why I would not be able to create at least another 16 again. I just used the appservices app delete command to delete the copies, and I can confirm from the UI that they are no longer running. But maybe I need to something else to fully clean the effect they have had on the cluster?

All the copies I made solely differ w.r.t to their root_config.json (they use(d) the same cluster/database/schemas). So I initially reasoned the copies would not increase the number of collections at all, because they share the same collections.

I’m planning to move to a dedicated cluster in a few weeks, but feel like the current size/stage of development of the app should not mandate that yet, and would prefer to save on the associated costs for now.

Thanks in advance for your time / any other suggestions!

Best Julius

4

Hi, it does seem possible that some part of your experience has led to metadata being left around (though we should be cleaning it up) . Can you post the result of listing all the databases in your cluster? I can provide you with the ones you can likely drop to clear up some capacity for collections.

5

Hey Tyler, thanks again for your quick response.

Below is a list of all my databases in the cluster;
The “fiber-dev” database is the only one I knowingly use in my config files / the one with data in it that I’d like to keep for development purposes.

If you could provide the reasoning deciding which ones I can delete that’d be great; then I know how to solve this problem in the future might it pop up again…

Thanks in advance!

db.adminCommand(
...    {
...      listDatabases: 1
...    }
... )
{
  databases: [
    {
      name: '__realm_sync_64f43c7dc45369bc2280cbaa',
      sizeOnDisk: Long('7938048'),
      empty: false
    },
    {
      name: '__realm_sync_657c9f1ecb5abd78027cad2f',
      sizeOnDisk: Long('6922240'),
      empty: false
    },
    {
      name: '__realm_sync_657cb27b29738cbcd4d573de',
      sizeOnDisk: Long('3948544'),
      empty: false
    },
    {
      name: '__realm_sync_657cb4236e644de4be53d077',
      sizeOnDisk: Long('3928064'),
      empty: false
    },
    {
      name: '__realm_sync_657cb67429738cbcd4dc60ee',
      sizeOnDisk: Long('3756032'),
      empty: false
    },
    {
      name: '__realm_sync_657cb6efcb5abd7802a8acce',
      sizeOnDisk: Long('4747264'),
      empty: false
    },
    {
      name: '__realm_sync_657cb72420f53848adc95f37',
      sizeOnDisk: Long('4567040'),
      empty: false
    },
    {
      name: '__realm_sync_657da0cb6e644de4becaa677',
      sizeOnDisk: Long('4554752'),
      empty: false
    },
    {
      name: '__realm_sync_657da119cb5abd78021befab',
      sizeOnDisk: Long('6115328'),
      empty: false
    },
    {
      name: '__realm_sync_657da1f6f09cceef34d5aa95',
      sizeOnDisk: Long('5070848'),
      empty: false
    },
    {
      name: '__realm_sync_657da35429738cbcd4532a80',
      sizeOnDisk: Long('5840896'),
      empty: false
    },
    {
      name: '__realm_sync_657da3accb5abd78022170ea',
      sizeOnDisk: Long('3985408'),
      empty: false
    },
    {
      name: '__realm_sync_657ec5ecf09cceef3460ec07',
      sizeOnDisk: Long('3788800'),
      empty: false
    },
    {
      name: '__realm_sync_657eca44ba243ca50ab83d12',
      sizeOnDisk: Long('5677056'),
      empty: false
    },
    {
      name: '__realm_sync_657ecd62afad6ecd1122012d',
      sizeOnDisk: Long('139264'),
      empty: false
    },
    {
      name: '__realm_sync_657ed52dab43cf9b04d30aad',
      sizeOnDisk: Long('40960'),
      empty: false
    },
    {
      name: '__realm_sync_657ed9e5cb5abd7802ee4885',
      sizeOnDisk: Long('40960'),
      empty: false
    },
    { name: 'fiber-dev', sizeOnDisk: Long('3170304'), empty: false },
    { name: 'admin', sizeOnDisk: Long('344064'), empty: false },
    { name: 'local', sizeOnDisk: Long('1132654592'), empty: false }
  ],
  totalSize: Long('1207230464'),
  totalSizeMb: Long('1151'),
  ok: 1,
  '$clusterTime': {
    clusterTime: Timestamp({ t: 1702901336, i: 26 }),
    signature: {
      hash: Binary.createFromBase64('8MMel1IIbzlf6+5lcvA0Ss18rDY=', 0),
      keyId: Long('7263176850183028738')
    }
  },
  operationTime: Timestamp({ t: 1702901336, i: 26 })
}
6

So each sync database is suffixed with the application_id in the URL https://realm.mongodb.com/groups/GROUP_ID/apps/APP_ID/dashboard ). Looking at your group, you have the following applications that exist

658035b3846edb77f4d77e6b
657f5375cb5abd7802819b03
657cb67429738cbcd4dc60ee
657cb6efcb5abd7802a8acce
64f43c7dc45369bc2280cbaa

Therefore, you should be able to delete the _realm_sync{app_id} databases for applications not in this list.

On my end, I will take a look at why these were not cleaned up for these applications (since we should be doing that on termination of sync and/or deletion of the application).

Best,
Tyler

1 Like
7

Thank you Tyler, that solved it!

Quick overview for future reference:

Problem

Deleting realm apps (through the cli) seems to not always remove the corresponding databases correctly when using Realm/Atlas Sync. This may unexpectedly lead you to reach the 500 collection limit on a shared cluster with only a few apps actually running.

Solution

  1. Identify the id’s of the applications that are currently running by inspecting the _id column of the output of:
$ appservices app list
  1. Connect to your cluster:
$ mongosh "mongodb+srv://YOUR_CLUSTER_NAME.YOUR_HASH.mongodb.net/" --apiVersion YOUR_API_VERSION --username YOUR_USERNAME
  1. Identify the database names that have are suffixed with id’s of non-existing apps:
db.adminCommand( { listDatabases: 1 } )
  1. Delete each of the databases that have no associated running app (for each of those databases, do):
use DATABASE_NAME

db.dropDatabase()

This last step could probably be done in a much cleaner / safer way by iterating over the list of identified database names. But I’m new to the Mongosh tool so I did it step by step in a manual fashion.

8

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