Hangs when a "Long Stack Trace" gets returned with GraphQLNonNull

[jsonmaur]

Okay, so this is a super weird issue that took forever to debug. I'm still not totally sure what's happening, but here it is.

I'm using Knex to query a Postgres database in my resolver. When I have a non-null object type and the resolver returns no rows (undefined) from the database, it should return an error message of "Cannot return null for non-nullable field RootQueryType.user.", but instead GraphQL will completely hang. But if the db returns a row, everything works fine. When the object type allows null, it won't hang and instead just return null.

This only happens when NODE_ENV === 'development'. I dug into this and found out it's coming from Bluebird, the promise library behind Knex. According to this, when NODE_ENV is set to development, they return "long stack traces". These can be disabled with BLUEBIRD_LONG_STACK_TRACES=0, and with that environment variable set, GraphQL will no longer hang when an undefined result comes back from the database.

So why would GraphQL hang when a long stack trace is returned from Knex/Bluebird? You can reproduce this issue with the code in this repo. Let me know if you need any more details.

[robzhu]

Hey @jsonmaur are you still hitting this issue? Have you found a workaround?

[jsonmaur]

I haven't had a chance to test it with the latest graphql version yet. I worked around it by setting the environment variable BLUEBIRD_LONG_STACK_TRACES=0 in my server. If I get some time next week I'll see if it's still an issue.

Any idea what it could be?

[robzhu]

Not sure based on the information you've provided, but it sounds like this is a relatively unique case and you have a workaround to unblock you. Closing the issue, but please re-open if you hit it again and I'll help investigate.