On-Demand Queries

Each Event Stream Processor instance has a single Command and Control server thread that handles requests for information (metadata) or instructions to perform tasks such as quiesce or shutdown.

The esp_query On-Demand SQL Query utility uses this process to send requests for information to Event Stream Processor.

The esp_cnc and esp_client utilities send directives to Event Stream Processor via this process. See the Command and Control Executables topic for more details.

• SQL Syntax in Event Stream Processor
  The ESP On-Demand Query interface allows you to query active windows in a running ESP project using the esp_query tool.
• esp_query
  Executes an SQL statement, supplied by standard input or the -Q option, on the server and prints the results to the standard output.