graphQL/stoptimes call returns 500, when using a GTFS file with frequencies

[jaimeventura]

We realized that after adding a new gtfs file to our OTP instance, with trips with frequencies (besides scheduled times), the calls to graphQL "stoptimes" were returning 500.
To be sure of this, we removed the frequencies.txt file and the issue disappeared (of course we didn’t had results for the period where frequencies were applied).

We tried this on both “prod” and “latest” docker images.

Another thing we noticed, whilst using the file with frequencies, was that:

• When using OTP builtin webinterface, we were able to see results
• When using digitransit (whose requests go through graphql) we were not

With further debug, it was found that the call to get stoptimes would work only with scheduledTimetable:

@@ -1800,9 +1804,30 @@
                         .name("stoptimes")
                         .description("List of times when this trip arrives to or departs from a stop")
                         .type(new GraphQLList(stoptimeType))
                        .dataFetcher(environment -> TripTimeShort.fromTripTimes(
                                index.patternForTrip.get((Trip) environment.getSource()).scheduledTimetable,  # HERE!
                                environment.getSource()))

In this situation, OTP throws the following:

otp_1          | 18:40:40.356 WARN (ExecutionStrategy.java:70) Exception while fetching data
otp_1          | java.lang.ArrayIndexOutOfBoundsException: null
otp_1          | 18:40:40.357 WARN (FieldErrorInstrumentation.java:174) Exception while fetching field
otp_1          | java.lang.ArrayIndexOutOfBoundsException: null
otp_1          | 18:40:40.409 WARN (ExecutionStrategy.java:70) Exception while fetching data
otp_1          | java.lang.ArrayIndexOutOfBoundsException: null
otp_1          | 18:40:40.411 WARN (FieldErrorInstrumentation.java:174) Exception while fetching field
otp_1          | java.lang.ArrayIndexOutOfBoundsException: null
otp_1          | 18:40:40.429 WARN (FieldErrorInstrumentation.java:133) Errors executing query

That's because the Trip didn't had a "scheduledTimetable".
So we've implement a fix. Its been working for some time an we believe its ok:

                         .name("stoptimes")
                         .description("List of times when this trip arrives to or departs from a stop")
                         .type(new GraphQLList(stoptimeType))
                        .dataFetcher(environment ->{
                                Timetable timetable = index.patternForTrip.get((Trip) environment.getSource()).scheduledTimetable;

                                // If the Trip is frequency-based, there are no scheduled tripTimes (they must com from <FrequencyEntry>.tripTimes)
                                if (timetable.tripTimes.isEmpty()) {

                                        // This should probably be encapsulated into a function named TripTimeShort.fromFrequencyTripTimes,
                                        // since it does the same as existing function TripTimeShort.fromTripTimes, but for Frequency.
                                        // Or, it could also be moved into TripTimeShort.fromTripTimes.

                                        List<TripTimeShort> out = Lists.newArrayList();

                                        for (FrequencyEntry freq : timetable.frequencyEntries) {
                                              TripTimes times = freq.tripTimes;
                                               for (int i = 0; i < times.getNumStops(); ++i) {
                                                         out.add(new TripTimeShort(times, i, timetable.pattern.getStop(i), null));
                                               }
                                        }
                                       return out;
                               } else {
                                       return TripTimeShort.fromTripTimes(timetable, environment.getSource());
                               }
                        })
                         .build())
```

We're grad to share it via patch or pull request.

[optionsome]

Thank you for the information. Go ahead and create a pull request. We will take a better look at the fix then.

[jaimeventura]

Hey @optionsome, i believe the commit in this PR is not perfect for merge, but i would kindly appreciate some comments on the PR itself or the issue.
Cheers