Herald should be able to fail a computation if necessary. about cross-media-measurement HOT 7 CLOSED

It should be possible to update the Kingdom using the ComputationLogEntries service. Adding a log entry with an error type of PERMANENT should put the parent Computation into the FAILED state.

See computation_log_entry.proto.

from cross-media-measurement.

I would prefer to add another method in the ComputationsService.

It is a little weird to call one service to set computation result, and call another one to fail a computation. Using ComputationLogEntriesService to fail a computation is like a side effect of logging an error.

from cross-media-measurement.

I don't think another method is needed, given the following two properties:

1. If there's a ComputationLogEntry indicating a permanent failure, the Computation should be in the FAILED state. Otherwise, the state is inconsistent.
2. If the Computation has failed due to an unexpected error from a Duchy, there should be a corresponding ComputationLogEntry.

An alternative is to drop the error type from ComputationLogEntry and instead have failure information represented in the ComputationParticipant. This would be closer to how Requisition refusal works, where the Requisition has refusal details and refusing a Requisition fails the parent Computation/Measurement.

from cross-media-measurement.

I like the idea of moving the permanent failure to ComputationParticipant.

from cross-media-measurement.

CC @efoxepstein who initially added report log entries.

from cross-media-measurement.

I feel like we want to track error types in ComputationLogEntry too to make it easier to correlate log entries with what went wrong. That said, we could keep the source of truth for the current state at the ComputationParticipant level.

from cross-media-measurement.

FYI, currently all logging rpcs from the duchy to the kingdom are try-and-ignore-failure style. In other words, if a CreateComputationLogEntry rpc fails, the mill won't revert local changes and retry again later.

When we use the ComputationParticipant to fail a computation, we need to make sure the rpc succeeds.

from cross-media-measurement.