Mongo Atlas Serverless issues

[gunsh]

I have just encountered an issue while trying to connect to an Mongo Atlas Serverless instance. I do not suppose Hangfire.Mongo has been tested against it. Please see part of the full stack trace below. This comes as a consequence of calling Hangfire.HangfireApplicationBuilderExtensions.UseHangfireDashboard().

As the limitations docs seem to imply the $out aggregation stage is unsupported and $merge is suggested as a replacement.

Perhaps adding serverless support is something you could consider.

Unhandled exception. MongoDB.Driver.MongoCommandException: Command aggregate failed: $out is not allowed or the syntax is incorrect, see the Atlas documentation for more information.
   at MongoDB.Driver.Core.WireProtocol.CommandUsingCommandMessageWireProtocol`1.ProcessResponse(ConnectionId connectionId, CommandMessage responseMessage)
   at MongoDB.Driver.Core.WireProtocol.CommandUsingCommandMessageWireProtocol`1.SendMessageAndProcessResponse(CommandRequestMessage message, Int32 responseTo, IConnection connection, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.WireProtocol.CommandUsingCommandMessageWireProtocol`1.Execute(IConnection connection, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.WireProtocol.CommandWireProtocol`1.Execute(IConnection connection, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Servers.Server.ServerChannel.ExecuteProtocol[TResult](IWireProtocol`1 protocol, ICoreSession session, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Servers.Server.ServerChannel.Command[TResult](ICoreSession session, ReadPreference readPreference, DatabaseNamespace databaseNamespace, BsonDocument command, IEnumerable`1 commandPayloads, IElementNameValidator commandValidator, BsonDocument additionalOptions, Action`1 postWriteAction, CommandResponseHandling responseHandling, IBsonSerializer`1 resultSerializer, MessageEncoderSettings messageEncoderSettings, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Operations.CommandOperationBase`1.ExecuteProtocol(IChannelHandle channel, ICoreSessionHandle session, ReadPreference readPreference, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Operations.ReadCommandOperation`1.ExecuteAttempt(RetryableReadContext context, Int32 attempt, Nullable`1 transactionNumber, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Operations.RetryableReadOperationExecutor.Execute[TResult](IRetryableReadOperation`1 operation, RetryableReadContext context, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Operations.ReadCommandOperation`1.Execute(RetryableReadContext context, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Operations.ReadCommandOperation`1.Execute(IReadBinding binding, CancellationToken cancellationToken)
   at MongoDB.Driver.OperationExecutor.ExecuteReadOperation[TResult](IReadBinding binding, IReadOperation`1 operation, CancellationToken cancellationToken)
   at MongoDB.Driver.MongoDatabase.ExecuteReadOperation[T](IClientSessionHandle session, IReadOperation`1 operation, ReadPreference readPreference, CancellationToken cancellationToken)
   at MongoDB.Driver.MongoDatabase.RunCommand[TResult](IClientSessionHandle session, Command`1 command, ReadPreference readPreference, CancellationToken cancellationToken)
   at MongoDB.Driver.MongoDatabase.<>c__DisplayClass49_0`1.<RunCommand>b__0(IClientSessionHandle session)
   at MongoDB.Driver.MongoDatabase.UsingImplicitSession[TResult](Func`2 func, CancellationToken cancellationToken)
   at MongoDB.Driver.MongoDatabase.RunCommand[TResult](Command`1 command, ReadPreference readPreference, CancellationToken cancellationToken)
   at Hangfire.Mongo.Migration.Strategies.Backup.CollectionMongoBackupStrategy.BackupCollection(IMongoDatabase database, String collectionName, String backupCollectionName)
   at Hangfire.Mongo.Migration.Strategies.Backup.CollectionMongoBackupStrategy.Backup(MongoStorageOptions storageOptions, IMongoDatabase database, MongoSchema fromSchema, MongoSchema toSchema)
   at Hangfire.Mongo.Migration.MongoMigrationManager.MigrateUp()
   at Hangfire.Mongo.MongoStorage..ctor(IMongoClient mongoClient, String databaseName, MongoStorageOptions storageOptions)
   at Hangfire.Mongo.MongoStorage..ctor(MongoClientSettings mongoClientSettings, String databaseName, MongoStorageOptions storageOptions)
   at Hangfire.Mongo.MongoBootstrapperConfigurationExtensions.UseMongoStorage(IGlobalConfiguration configuration, MongoClientSettings mongoClientSettings, String databaseName, MongoStorageOptions storageOptions)
   at Hangfire.Mongo.MongoBootstrapperConfigurationExtensions.UseMongoStorage(IGlobalConfiguration configuration, String connectionString, MongoStorageOptions storageOptions)

[gottscj]

@gunsh,

The $out operator is used for backing up collections before a migration. Consider using drop or none strategies instead. Let me know if it works out. :)

[gunsh]

Well, I did have MigrateMongoMigrationStrategy but the database used for Hangfire was completely empty, hence nothing to migrate. I tried DropMongoMigrationStrategy per your suggestions but now I got a different error: Command create failed: capped collections are not allowed for serverless.

[gottscj]

@gunsh,

You need to set the SupportsCappedCollection option to false in the MongoOptions object.

Br

[gunsh]

Okay, that finally did it. Thanks.

So far so good. In case it helps others, this is what I ended up using:

                    new MongoStorageOptions
                    {
                        SupportsCappedCollection = false,
                        MigrationOptions = new MongoMigrationOptions
                        {
                            MigrationStrategy = new DropMongoMigrationStrategy(),
                            BackupStrategy = new NoneMongoBackupStrategy(),
                        }
                    }

We'll see how it goes from here.

[gottscj]

@gunsh,

Thanks for sharing! ❤️