Limit the overall amount of connections in one configuration

[balhar-jakub]

As a System Programmer, I can limit the connections for all services across the API Mediation Layer for given time frame e.g. requests per minute.

Notes

• This story reflects the limits only for a specific Gateway instance.
• The implementation goes only in V3.

Acceptance Criteria:

• There is no default limitation on connection to specific services.
• There is a configuration that allows the limitation on connection documented in https://docs.zowe.org/stable/user-guide/api-mediation/configuration-routing and documented in example-zowe.yaml and schema
• When the configuration has a value that is non zero positive integer, limit the amount of concurrent connection passed on to every specific service to the specified number.
  • When there is no space for further connection to the service, let the connection wait in queue
  • If there is new available space for further connection to the specific service, take the first in the queue
• When the limit of connections is approached, log information that this happened with new code and Info as the log level
  • On the debug level, notify that the connection is waiting with info about what service it is waiting for.

Demonstration

• Show 10 parallel connections to the same service with long-running operation
• Change the configuration to 2 and show that only the first two connections are being processed while the rest waits in queue, Show the info message about the queue
• For the third connection, show that the debug message appears.