No easy way to map request ID's between machines

[gordonwatts]

In the version 2.0 of the servicex front end, the user could create a file servicex_query_cache.json in their home directory. This file contained a mapping between query hashs as SX request id's. The file is text and suitable for check-in to github. This was an easy way of dealing with running on different computers and not having to manually port request id's around.

• The file contains a query hash to request id mapping.
• Before any query was made, the file was consulted. If the query hash was present, then the matching request ID was used.
• If no entry was there, then the local machine's cache was consulted, and a request id from there was used if possible.
• If no request id was found, or the request id was unknown or in an error state on the backend, then a new query was run.
• Once successful, the hash-request-id mapping was updated/written to the file.
• If the file did not exist then it was not created.

There are alternative ways of acheiving this functionality:

• Caching lookup on the server.
• Request ID's become full-service items.

Somehow, however, this functionality needs to be there as it is very useful espeically for expensive transforms.