We observe the error if occurs should occur at the first snap but what is shown in pipeline statistics it is appearing in after 1st snap. The errors occurring on REST snap is shown on MAPPER and vice versa. Please see the screenshots.
Several parts of the pipeline can run at once, so it is possible that they may show you errors simultaneously. If one fails fatally, it will stop others, and they may then fail if they were in the middle of something.
Obviously, the behavior of the effects of these errors could seem to be random, based on the data and the speed of the various processes.
What COULD have happened above is that payload wasn’t returned, which caused that payload error, and it may have stopped the rest call just as it was trying to connect, and you got that error. Other snaps may have finished, or didn’t start, or flushed their caches, etc… and just say they were aborted.
Not worried about the other snap’s behavior but the error message here is irrelevant.
Mapper snap can not get REST API 503 error
REST SNAP can not give error for mapper.
The sequence is mapper->rest get
so if mapper fails due to $payload is undefined that error can not go to rest get.
Also the above screenshots are from different execution cycle due to same error, so both behavior is expected to be same.