I/O Forwarding

• managing stdin/stdout/stderr from agents
  • Create a special stream to handle I/O.
  • Stdin can be delivered to a specific agent, or multicast to some agents.
  • Allow customizations/annotations of the filters
  • Having the capability to have a line based stream or a byte based one.
  • Handle I/O for a combined agent/user application on a case-by-case basis

• I/O from the application is the agents responsibility

Notes from Dec 3-5 meeting:

• I/O forwarding is a service provided by STCI
• Components
  • Service agents
  • Service junctions
  • Service stream
• Service Agent
  • Runs on the compute node and "reads" stdio and stderr from the process or agents
  • Forwards these along the Service Stream
• Service Junctions receive I/O from Service Agents and forward them down the stream, applying any filters specified

• Adding new (user) agents
  • When new (user) agents are added
    • A new Service Agent is created for each new (user) agent
    • A new Service Stream is created to forward I/O
      • because the new Service Agent can't be added to an existing Service Stream
  • This will results in the FE having many I/O streams
  • These streams can be periodically merged into a single stream to keep the number of streams manageable
    • E.g., after 100 I/O streams have been created in this way
  • Merging streams may require flushing the old streams before switching to using the new (merged) stream, so the merging operations should not be done frequently