Resolving queries over data services¶

This diagram illustrates the request flow triggered by a user query.

The user makes the query site=AAA. DAS resolves it into several requests, by looking at the daskeys map for each available data service, which indicates that two services understand an input key site, which is transformed into queries for each of those services with parameter se and site_name.

DAS then makes the API calls (assuming the data isn’t already available).

• http://a.b.com/se=AAA
• http://c.com/site_name=AAA

and retrieves the results, which are re-mapped into DAS records according to the notation map for each of those services.

Query processing steps¶

DAS workflow consists of the following steps:

• parse input query
  • look-up for a superset of query conditions in DAS merge cache (ie, have we recently handled a query guaranteed to have returned the data being requested now)
    • if unavailable
      • query raw cache
        • query services, to get the records that aren’t available
        • write new records to raw cache
      • perform aggregation
        • write aggregation results to merged cache
    • get results from merged cache
• present DAS records in Web UI (converting records if necessary)