1434895 - Continuation token error message should not be a generic 500 ISE

Status: RESOLVED DUPLICATE of bug 1434921

(Taskcluster :: Services, enhancement)

Description

[John Ford [:jhford] CET/CEST Berlin Time]

When making a request to the listNamespaces, Franziskus was getting an error:

method:     listNamespaces
errorCode:  InternalServerError
statusCode: 500
time:       2018-02-01T13:25:22.172Z
tasks error: Error: Internal Server Error, incidentId: 81ba6ca5-3ceb-4d40-9b66-5ce14616cad5

I looked up the incidentId and found this error:

Feb 01 14:25:22 taskcluster-index app/web.2: Thu, 01 Feb 2018 13:25:22 GMT base:api Error occurred handling: /namespaces/docker.images.v1.nss, err: AssertionError [ERR_ASSERTION]: Expected an encoded continuation token with a single tilde as separator, as JSON: {"generatedMessage":false,"name":"AssertionError [ERR_ASSERTION]","code":"ERR_ASSERTION","actual":false,"expected":true,"operator":"=="}, incidentId: fc6582ee-e06a-402c-a6d9-6b8e26ef5d80 AssertionError [ERR_ASSERTION]: Expected an encoded continuation token with a single tilde as separator

We determined the root cause to be that Franziskus was putting a continuation token in the first call, and that continuation token wasn't valid.

The bug report here is that we should give a more useful error message to the user than a 500 ISE.  Since we know that a single tilde is part of a continuation token, we could search for a ~ in the value and give a 400 with an error message "invalid continuation token".