Proceedings of the Focus Group on Patterns for Resource Management and Optimization

EuroPLoP 2002, July 3-7, Kloster Irsee, Germany

Participants

Michael Kircher, Prashant Jain, Markus Völter, Peter Sommerlad, Dietmar Schütz,
Ansgar Radermacher, Reinhard Maier, Titos Saridakis, Amir Raveh

Workshop goals:

Get Feedback on Resource Management
Collect views about Resource Management
Resource Management versus Performance, Reliability and Security
Definition of a "Resource"
Definition of "Resource Management"
Categorization of Resources
What are common resources?

Example Resources

Type	Example
Not reusable	Sheet of Paper in the Printer, Piece of Cake, CPU cycles
Sharable by time-slice	I/O Ports, Book in a Library, User Focus of a GUI, Printer, Chair, Keyboard during Pair Programming, Passage through a narrow corridor, TLS-key
Sharable by space-partitioning	Network Switch, DSP, Bandwidth, Multi-user Computer System, Floor Space, Screen Space, Memory
Sharable, but no time-slice or space-partitioning	Read-only Objects, TV-Set
Not covered	Monitor, Process, Thread, Mutex, Transactions (because they are synchronization primitives themselves)
Unclear	Queue, Socket (because it is unclear how they can be categorized)
Unknown (to be categorized)	Objects, Service, Interrupt Channel, Remote Objects, Component Instances, I/O Channel

Definition: What is a Resource?

Entity that is available only in a limited supply
There exists a requestor that needs the entity to perform a function
There exists a mechanism that provides the entity on request

Definition: What is Resource Management?

It is a strategy to supply resources to requestors.
Requestor and Resource Manager conform to a contract that is compliant to the strategy.
Differentiate between the illusion of unlimited resources and making the requestor take full responsibility of request, release, and synchronization of resources.

Challenges in Resource Management

Acquisition
LifeCycle
Release
Coordination
Access
Tracking/Monitor/Profile
Conflict Resolution and Prevention

Resource Properties & their implications

not reusable => not sharable (time & space)
can be partitioned => sharable (space)
can get synchronized => sharable (time)
no exclusive access => sharable

Derived Resource Management implications

reusability influences release strategy
when you need to share, first partition, then time-slice (& synchronize)
resource usage influences how it is to be managed

Non-functional Requirements of Resource Management

Performance
Security
Reliability
Simplicity
Scalability
Flexibility (Strategy, Configuration)
Robustness
Availability (time between request and actual acquisition)
Usability (ease of use for the requestor)

Conflicts:

Performance vs. Security,
Performance vs. Scalability,
Security vs. Availability,
Security vs. Usability,
Flexibility vs. Robustness,
Reliability vs. Availability

Table of resouce types

Resource Categories:

Not reusable : acquire access, no synchronization on access, can be acquired only once, synchronization on acquistion (e.g. piece of cake)
Partitioning: partition synchronously before allowing acquisition, no synchronization on access, support release (e.g. floor space)
Time slicing :
a) Acquire for exclusive access, release (e.g. shopping cart)
b) Acquire as one of many users, synchronize access, release (e.g. )
Non-exclusive access : nothing to do, but eventually acquire it and access it, no synchronization required, multiple users possible (e.g. cinema screen)

Things to check out

2 additional patterns by Markus Völter (Leasing & Sponsor, Transaction Pattern)
Stream&Callback versus Partial Access
Swapping versus Caching
Relationship to Manager pattern