Amplify Datastore sync stops

[millarm]

Describe the bug
Symptoms:

Amplify react native application that's is working reliably under test conditions, but when I use it for real it stops syncing.

It's an application that's for tracking location data, so testing requires getting up, and away from a desk!

Symptoms are:

App is working fine locally on device, but there is no sync to the backend from DataStore, so other clients don't get updated. No errors are logged, and there doesn't seem to be any API to force DataStore to sync.

First question is:

1. What's the best way to debug this sort of sync issue? As an amplify developer where should I look for logging/data?

(Seems to be: Amplify.Logger.LOG_LEVEL = 'DEBUG'; which outputs debug logging. Can one enable logging for just DataStore?)

This is my schema:

type Journey
  @model
  @auth(
    rules: [
      {
        allow: owner
      }
    ]
  ) {
  id: ID!
  timestamp: AWSDateTime!
  appVersion: String!
  buildVersion: String!
  bundleIdentifer: String!
  device: String!
  active: Boolean
  segments: [Segment] @connection(keyName: "bySegment", fields: ["id"])
  owner: String
}

type Segment
  @model
  @key(name: "bySegment", fields: ["journeyID"])
  @auth(
    rules: [
      {
        allow: owner
      }
    ]
  ) {
  id: ID!
  journeyID: ID!
  startTime: AWSDateTime!
  startPosition: AWSJSON!
  endTime: AWSDateTime
  endPosition: AWSJSON
  sensorData: String
  locations: AWSJSON!
  owner: String
}

With debug logging on it seems the error is caused by:

Util - attempt #9 with this vars: ["query operation($limit: Int, $nextToken: String, $lastSync: AWSTimestamp){\n\t\tsyncSegments(limit: $limit, nextToken: $nextToken, lastSync: $lastSync){\n\t\t\titems {\n\t\t\t\t\t\t\tid\njourneyID\nstartTime\nstartPosition\nendTime\nendPosition\nsensorData\nlocations\nowner\n_version\n_lastChangedAt\n_deleted\n\t\t\t\t\t\t}\n\t\t\t\t\t\tnextToken\n\t\t\t\t\t\tstartedAt\n\t\t}\n\t}",{"limit":1000,"nextToken":null,"lastSync":0}]

I get an error logged (only with debug logging on)

errors: Array(1)
0:
data: null
errorInfo: null
errorType: "MappingTemplate"
locations: [{…}]
message: "Transformation too large"
path: Array(1)
0: "syncSegments"
length: 1

So... how do I go about establishing what's causing this, and fixing the issue?

[millarm]

More details - the root cause here appears to be the Segment model, and, at a wild guess... the JSON object in locations

This is... an array of locations, so is of variable size.

GraphQL request

{
	"query": "query operation($limit: Int, $nextToken: String, $lastSync: AWSTimestamp) {\n  syncSegments(limit: $limit, nextToken: $nextToken, lastSync: $lastSync) {\n    items {\n      id\n      journeyID\n      startTime\n      startPosition\n      endTime\n      endPosition\n      sensorData\n      locations\n      owner\n      _version\n      _lastChangedAt\n      _deleted\n    }\n    nextToken\n    startedAt\n  }\n}\n",
	"variables": {
		"limit": 1000,
		"nextToken": null,
		"lastSync": 0
	}
}

Response

{
	"data": {
		"syncSegments": null
	},
	"errors": [{
		"path": ["syncSegments"],
		"data": null,
		"errorType": "MappingTemplate",
		"errorInfo": null,
		"locations": [{
			"line": 2,
			"column": 3,
			"sourceName": null
		}],
		"message": "Transformation too large"
	}]
}

[millarm]

Notes: the locations array is likely to be around 60 objects -> but could go as high as 150 objects. It's dependent on how fast you are travelling. :-)

[millarm]

And... Seem to have fixed this issue by following instructions here:

#5181

Adding this:

DataStore.configure({
  syncPageSize: 100,

})

Seems to have worked around the current issue

[Amplifiyer]

thanks @millarm for confirming. Closing this since the issue is resolved for you.

[github-actions]

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