Is there a limitation on GetAllSnapshotsAsync in FirestoreDb API?

[vdsouza]

I am trying to retrieve a large amount of data from production using this method but getting the following error: (Dot Net Core application)  I also found a related report made in 2021 but it is closed with unknown resolution.

Grpc.Core.RpcException: Status(StatusCode="Internal", Detail="Error reading next message. InvalidDataException: Unexpected end of content while reading the message content.", DebugException="System.IO.InvalidDataException: Unexpected end of content while reading the message content.")
---> System.IO.InvalidDataException: Unexpected end of content while reading the message content.
at Grpc.Net.Client.Internal.StreamExtensions.ReadMessageContentAsync(Stream responseStream, Memory`1 messageData, Int32 length, CancellationToken cancellationToken)
at Grpc.Net.Client.Internal.StreamExtensions.ReadMessageAsync[TResponse](Stream responseStream, GrpcCall call, Func`2 deserializer, String grpcEncoding, Boolean singleMessage, CancellationToken cancellationToken)
at Grpc.Net.Client.Internal.GrpcCall`2.ReadMessageAsync(Stream responseStream, String grpcEncoding, Boolean singleMessage, CancellationToken cancellationToken)
at Grpc.Net.Client.Internal.HttpContentClientStreamReader`2.MoveNextCore(CancellationToken cancellationToken)
--- End of inner exception stack trace ---
at Grpc.Net.Client.Internal.HttpContentClientStreamReader`2.MoveNextCore(CancellationToken cancellationToken)
at Google.Cloud.Firestore.FirestoreDb.<GetDocumentSnapshotsAsync>b__38_0(BatchGetDocumentsRequest req, CallSettings settings)
at Google.Cloud.Firestore.RetryHelper.Retry[TRequest,TResponse](RetrySettings retrySettings, Func`3 fn, TRequest request, CallSettings callSettings, IClock clock, IScheduler scheduler)
at Google.Cloud.Firestore.FirestoreDb.GetDocumentSnapshotsAsync(IEnumerable`1 documents, ByteString transactionId, FieldMask fieldMask, CancellationToken cancellationToken)
at Google.Cloud.Firestore.FirestoreDb.GetAllSnapshotsAsync(IEnumerable`1 documents, ByteString transactionId, FieldMask fieldMask, CancellationToken cancellationToken)

based on the nature of this error, I strongly feel like it is fetching part of the data for whatever reason and that is why I see "Error reading next message. InvalidDataException: Unexpected end of content while reading the message content."  Seems like either Firestore timeout or this API can pull only certain number records during debugging?  Anyone has any clue?  It has no problems when deployed to GCP and everything works just fine but only while debugging is the issue.

The referencing code that produces above error is this:

var documentReferences = await firestoreDb.Collection(COLLECTIONNAME).ListDocumentsAsync().ToListAsync();
var fieldMask = new FieldMask("test");

var documentSnapshot = await firestoreDb.GetAllSnapshotsAsync(documentReferences, fieldMask);  -- it is failing right here

Another incident:  In another case, I know one of our collections had way over 4k documents but while debugging it only fetches less than half of the data resulting in my filters do not find the data I am looking for.  

The referencing code for this incident is:

CollectionReference colRef = firestoreDb.Collection(collectionName).Document(sortDate)
.Collection(COLLECTIONNAME).Document(document).Collection(COLLECTIONNAME1);

var snapshot = colRef.GetSnapshotAsync().GetAwaiter().GetResult();  - This does not throw any error but returns only partial data while debugging resulting in unable to find the root cause of the issue(s) reported by the end users while debugging.  However, in GCP all the data is returning as expected when we look at the logs.  For example: Pointing to Production from local machine and debugging only returns 1866 records but in GCP log we see more than 4k records/documents returned.  That said, is there any limitation on FirestoreDb API while debugging?  If so, how can we over come with this issue so that we can troubleshoot efficiently?

[ms4446 · Accepted solution]

The "Unexpected end of content" error often points to network instability, request timeouts, or data size limits. These issues are more likely to arise during debugging, as your local network might not be as robust as Google Cloud Platform's (GCP) production environment.

I'd recommend a combination of these approaches:

1. Batching: Break down your document retrieval into smaller batches. This can mitigate timeout issues and network congestion. The code example you provided is a great starting point.

int batchSize = 100; // Adjust as needed
var documentReferences = await firestoreDb.Collection(COLLECTIONNAME).ListDocumentsAsync().ToListAsync();
var fieldMask = new FieldMask("test");
List<DocumentSnapshot> allSnapshots = new List<DocumentSnapshot>();

for (int i = 0; i < documentReferences.Count; i += batchSize)
{
    var batch = documentReferences.Skip(i).Take(batchSize);
    var batchSnapshots = await firestoreDb.GetAllSnapshotsAsync(batch, fieldMask);
    allSnapshots.AddRange(batchSnapshots);
}

// Now 'allSnapshots' contains all the documents fetched in batches 

2. Pagination: If batching isn't ideal, use Firestore's built-in pagination features to fetch documents in manageable chunks.

3. Check Your Network: Ensure a stable connection with sufficient bandwidth during debugging. If possible, try debugging from a location with a more reliable network setup.

4. Timeout Adjustments: Increase the request timeout settings in your CallSettings. Be mindful not to set it too high, as this could lead to unnecessarily long-running requests.

5. Local Emulator Configuration: If you're using the Firestore emulator, review its documentation for potential data size or request/response limitations. You might be able to adjust these limits in the emulator's configuration.

Additional Debugging Tips:

• Log Everything: Keep track of how many documents are fetched in each batch/page to pinpoint where issues might be occurring.
• Double-Check Data Size: Verify that your individual documents and overall request sizes comply with Firestore's limits.
• Emulator vs. Production: Remember that the emulator might not perfectly replicate the behavior of the production Firestore environment.

The optimal approach will depend on the specific nature and size of your data, as well as your local debugging setup. It might take some experimentation to find the perfect balance.

[vdsouza]

@ms4446 Thank you for your prompt response.  I tried the Batch approach and it works without any issues.  However, what I do not understand is there is absolutely no network issues because I am wired with 100/100mbs bandwidth as shown below.  

Furthermore, my colleagues do not have that problem both in office or on VPN.  The only difference there might be is, I always keep update on everything on my laptop.  Things like Visual Studio updates, Nuget package updates etc.

Also, do you have any example on pagination and increasing the connection timeouts?  I googled it but did not find any useful results.