Discussion points KW5

Owned by ise (Unlicensed)
Jan 27, 2015

Agenda for the needed discussions on the server-side instrumentation topic:

Work done

  • ASM
    • Intern Strings on the class parsing for saving the memory (costs more time)
    • Instrumentation
      • Reads all instrumentation points from the class type and enhanced exception sensor setting
      • Uses method Id from the RSC to instrument method
      • Logic divided in MethodInstrumenter and ConstructorInstrumenter
      • Possibility to create string constants for the descriptors to even speed up more
      • Need IHookDispatcher in the Commons for testing (we can have only on agent if we do testing on Agent and use string constants for the descriptors)
  • Configuration creator - two main features:
    1. Environment to AgentConfiguration
      • read environment and registers sensors
      • register platform ID, maybe this is not right place, but we need agent Id to be saved in the agent configuration
      • basically uses the old Agent's sensor type config classes and copies data from the Environment, no reusing of the object here on purpose
    2. Check for instrumentation points
      • runs class and method filter on the assignments in the Environment
      • for passed methods we create RSC, register method ident, connect all needed sensor Ids and copy needed settings for the Agent (like property path, settings, etc..)
      • here also no interaction between Ci classes and RSC/sensor configs, they don't know about each other
      • RSC
        • only saves sensor ids nothing else and minimum of data need for the 
  • Agent service
    • Combines all components together
    • Instrumentation result sent back to the agent containing byte code and set of RSCs  
  • Agent
    • IdManager
      • On start tries to connect to the CMR and get the AgentConfiguration
      • Saves the platform id and feeds the Configuration storage (which also now has much less)
    • Byte-code analyzer
      • Creates hash (256hex) and calls CMR for the Instrumentation result
      • If something is returned adds RSCs to the IHookMapper and returns instrumented byte-code
    • HookDispatcher
      • Changes based on the new RSC way
      • IHookMapper changed to not differentiate between mapping methods and constructors - all the same
    • HookSupplier new stuff
      • supplies hooks and sensor configs if needed

General problems/proposals

  • Agent service
    • How to deal with the Environments and Configurations, we want to skip configuration creation if the one is already created for the agent and did not change.
    • Is there a way to pre-create Configuration for Environment
  • Configuration creator
    • MethodType can not be "merged" if method changes, we always need a new one, because otherwise we can not instrument correctly
    • Save patterns in the CI classes already, easier and faster to access later in the filters (they don't have to be persisted, use @AfterDeserialize or smth)
    • Is meaningful capturing missing
    • Filters and assignments, we can maybe have a better solution here (closely related to CI):
      • split assignment in kind of a set of filters (ex. method name filter, annotation filter, etc)
      • each filter know if it's applied on class or method
      • if it is wild-card or not
      • each has priority for usage in searching against the class cache (for example no wild-card annotation filter has advantage over wild-card class name filter)
  • Registration is bottle neck for the complete thing at the moment:
    • 90% of time spent here, we need some ideas or smth
  • Agent
    • IdManager
      • do we need registration thread now
      • what do we do when we cannot connect to the CMR?
    • ByteCode analyzer
      • how to deal with the class pools, inserting and removing class paths, etc (everything we had until now)
    • JavaAgent
      • when IHookDispatcher is only in Commons I get class not def. exception when executing the hooks.. so now'it in both Commons and Agent

Work in future

  • agent clean-up
    • remove unused stuff
    • fix tests
  • management of the class cache
    • persisting, loading, etc
  • saving byte code to disk
  • deal with configuration updates
    • know when saved byte code is not anymore valid
  • updating of the class byte-code during run-time
  • asynchronous agent service
    • don't wait for the byte code to get come back, rather continue using original byte code until it's returned then apply