DS_QM
Process Template used to service real-time querying and subscription calls from Delta Dashboards onto the Delta Stream platform. The Query Manager process protects both the backend Delta Stream platform processes from multiple Delta Dashboard queries and subscription requests and the Delta Dashboard frontends from high volume, high velocity updates.
Query manager (Subscription mode)
Applies throttling, conflation and fan-out algorithms to real-time streaming data produced by a Stream Tickerplant in order to push the data to large numbers of consumers with minimal latency.
Query manager (Managed polling mode)
Applies throttling and caching against user queries to optimize the end-to-end system load when supporting large numbers of users.
Parameters
The below table details the DS_QM template parameters.
| name | type | default value | description |
|---|---|---|---|
| initialStateFunct | Analytic | dxEmptyFunctionNull | Sets the analytic to run on start up |
| logQuery | Boolean | True | Sets whether or not to log query information |
Query manager
The Query Manager (QM) process handles polling and real-time subscriptions. Located between clients (e.g. Dashboards/Delta Servers) and the underlying databases/tickerplants Responsible for:
- Managing clusters of connections to the clients
- Managing multiple, possibly overlapping, polling subscriptions from the clients
- Managing connections to a number of distinct, possibly password-protected, databases
- Querying databases periodically, according to subscribed parameters and polling intervals
- Publishing query results to the corresponding clients
- Managing multiple, possibly overlapping, real-time subscriptions from the clients
- Managing connections to a number of distinct, possibly password-protected, tickerplants
- Aggregating real-time subscriptions into the smallest possible single subscription
- Subscribing to tickerplants
- Caching real-time updates from tickerplants
- Periodically sending batched updates, at a fixed interval (fixed per instance of QM)
- Filtering updates by record (i.e. by sym)
- Option to filter updates by field (column)
- Option to aggregate results to return only the last records, defined by a set of key fields
- Managing session IDs to define collections of subscriptions as sessions
- Bundling real-time results into a single message per session