The Linkbox API is fronted by bot protection which under load
intermittently returns an HTML challenge page with a 200 status
instead of JSON. This surfaced as a fatal JSON decode error, and the
web API path misread the empty decoded result as an expired token,
hammering the login endpoint with requests which also failed to
decode and keeping the bot protection triggered.
Treat responses which fail to decode as retryable errors so the pacer
backs off until the block lifts, and only refresh the token when the
response actually parsed as JSON and reported an error.
Nick Craig-Wood
d6190dc4f2