Flushing doesn't work with asynchronous transport

[sheerun]

• @sentry/node (5.0.5)

Sentry.flush() doesn't wait for events to be delivered by transport. This can result in dropped events in serverless environment like AWS lambda.

Reproduction:

const Sentry = require('@sentry/node')

function sleep(delay) {
  return new Promise(resolve => setTimeout(resolve, delay))
}

class FakeTransport extends Sentry.Transports.HTTPTransport {
  async sendEvent(event) {
    console.log('Started sending ' + event.event_id)
    await sleep(500)
    console.log('Finished sending ' + event.event_id)
    return { status: 200 }
  }
}

Sentry.init({
  dsn: 'https://fake@sentry.io/1234',
  transport: FakeTransport,
  beforeSend: (event) => {
    console.log('Before send ' + event.event_id)
    return event
  }
})

async function main() {
  Sentry.captureException(new Error('test 3'))
  console.log('Before')
  await Sentry.flush(2000)
  console.log('After')
  await sleep(3000)
}

main()

Before
Before send 3879a904216343bcb7999f116e336797
Started sending 3879a904216343bcb7999f116e336797
After
Finished sending 3879a904216343bcb7999f116e336797

[HazAT]

You need to add the request to the transport internal buffer so close is aware when requests are finished.

sentry-javascript/packages/node/src/transports/base.ts

Line 39 in f412f7b

protected readonly _buffer: PromiseBuffer<Response> = new PromiseBuffer(30);

sentry-javascript/packages/node/src/transports/base.ts

Line 78 in f412f7b

return this._buffer.add(

So if you implement your custom transport, you need to at least implement close which takes care of this.

[sheerun]

I don't want to implement custom transport. The issue is with default http / https transport. I've just provided you a way to reproduce this issue.

To reproduce this issue directly on upstream https implementation, please change in node_modules https transport sendEvent to:

    HTTPSTransport.prototype.sendEvent = function (event) {
        console.log('sending https')
        // ... rest
    };

and add console.log('resolved') near resolve() call in BaseTransport.prototype._sendWithModule of base transport.

The result are following logs:

Before
Before send 4f316abe03e94142bfa75e2c231b2ceb
sending https
After
Before send 5d6c78c88ea74e06ae721c9ace4cf04f
sending https
resolved
resolved

As you can see even default transports fails to fully send events after Sentry.flush() finishes.

Also: Why isn't promise returned from sendEvent automatically added to _buffer? It seems more sensitive than documenting internal _buffer thing.

Please reopen