Middleware queues

This picture schematically depicts three DB-Adapters: ZKM, CIANT and Montevideo Middleware have two dedicated fronts for each DBA – one for search requests (SEARCH) and second for requests of attribute value loading (LOAD).

The amount of asynchronous The configuration constant ASYNC_KEEP_ALIVE_TIMEOUT which determines how long an asynchronous operation will wait before termination, in case of an empty front, exists in order to lower the load caused by starting up and quitting the asynchronous operations.

Request lifecycle

The user enquiry has two phases - SEARCH and LOAD. The picture Fig 6.7 shows that the search condition is the input to the SEARCH phase, while its outcome is a list of matching origin_id source identifiers which comply with the condition. The LOAD phase comes after the SEARCH phase has been ended successfully. The input is REQID, position in the list (offset+count), identifier of the attribute according to which the results will be sorted and a list of attribute identifiers, whose values are to be opened. The outcomes are the values of the attributes which match these parameters.

The life span of an enquiry is defined by the configuration constant REQUEST_LIFE_SPAN.

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