How do you treat consistency issues?
Right after updating a thing attribute I performed a search request, but miss that value. How can this happen?
The Bosch IoT Things service provides a search functionality which is highly dedicated in updating its internal index as fast as possible. However, while working on highly distributed systems/networks, the search functionality is provided according to “eventual consistency” paradigms. In order to scale accordingly, it guarantees to reach a consistent state at some point in time - but not immediately.
The example you could run into, reports a pretty similar situation: the update was successfully applied in the Things persistence, however at the time of resolving the search request, a older information was used to execute your search request. The consistency should recover within some time.
If it is important to know when exactly a twin modification is reflected in the search index,
request the search-persisted acknowledgement in the corresponding
command. Doing so delays the command response until search index update completes. There is no guarantee
that search index update completes before the duration given by the
timeout parameter; applications should be ready
to handle error statuses such as
408 Request Timeout if only
search-persisted is requested,
424 Dependency Failed if other acknowledgement labels are also requested.
Requesting the search-persisted adds significant latency
to command processing and incurs higher costs. Do not request
search-persisted unless it is really necessary.
Further reading: Amazon