Web Service Handler
• Additive functionality to Web Services.• Incrementally adds new capability to Web Service
endpoint.• Supports more modular architecture; separation
of tasks.• Processes SOAP header and body.• Called as either handler or filter.• Many handlers can get together to build a chain.
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Motivations I
• Web Services become fat because of utilizing many handlers.
• A handler may cause a convoy effect.• Requirements for distributing handlers.• Requirements for efficient handler
orchestration.
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Motivations II
• Reusability– A handler may be utilized by many Web Services.
• Modularity– Clean separation of the tasks improves
modularity.
• Loosely coupling – Messaging decouples the computing nodes ,
handlers and endpoints.
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Research Issues I
• Scalability.– Adding new handlers should not degrade the system
performance.
• Performance.– What are the benefits and costs of the distributed handler
structure?
• Flexibility– A new handler should be easily deployed and removed.
• Orchestration of the Distributed Handlers.– Efficient and effective handler workflow structure
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Research Issues II
• Messaging for the distributed handlers. –What are advantages and disadvantages ?
• Parallel execution of the handlers.–What are advantages and disadvantages ?
• Architectural principles for the distributed handlers.–Conditions for the distribution of a handler.
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Motivating Scenario I-A
• A typical handler execution scenario is sequential execution.
• The cost of the sequential handler execution : Tlogger+ Tmonitor + Tconverter millisecond
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Motivating Scenario I-B
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• The cost of the concurrent handler execution : MAX(Tlogger, Tmonitor, Tconverter)+Toverhead millisecond
Motivating Scenario II
• A CPU bound handler, having convoy effect on the execution, is deployed to a faster machine.
• Handler A9
gf10 3638 millisecond
everest 696 millisecond
Difference 2942 millisecond
Distributed Handler Architecture (DHArch)
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Gateway• An Interface between DHArch and A Web Service Container.• Provides flexibility to deploy DHArch for different SOAP processing engines.•Necessary to be written for each native system.
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The advantages of using NB in DHArch
• Queuing regulates message flow.• Provides guaranteed message delivery.• Efficient.• Scale vey well; tree structure. – Many handlers can be addressable.
• Asynchronous messaging.
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Messaging Format
• XML document.• Consists of three main
parts:– ID
• UUID generated key.
– Properties• Carries the necessary
properties to the handler.
– Payload• Carries the message.• SOAP message.
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<context><id>123456789</id><properties>
<oneway>true</oneway></properties><payload>
The message</payload>
</context>
Communication Manager
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Highlights of the Execution• DHArch utilizes two context objects:– Native container context – Distributed Handler Message Context
• Two level orchestration prevents the orchestration engine to become too complex.
• Queues are leveraged to regulate the message flow.
• Caching idea is utilized to expedite the message processing by decreasing the access time.
• The execution queue can be prioritized.
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Distributed Handler Message Context
• Keeps necessary information about a message to carry out the execution.• Every message has its own context.• Flow structure is kept inside of the context.• Basically, stores
• The message• Orchestration structures• Handler related parameters• Stage related parameters.
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Two level Orchestration
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• Separation of the flow description and the execution
• Four constructs in description level:• Sequential• Parallel• Looping• Conditional
• Engine utilizes only two execution types:– Sequential– Parallel
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Orchestration Schema
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Execution
Message Journey between two stages• A message travels from stage to stage• Stages has the ability to execute handlers in parallel manner.• A message can not exit from a stage without completing the execution of its handlers•Every stage contains at least one handler.•Every flow execution contains at least one stage.
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Test I- Performance I
4.
5.
6.
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Handler A CPU Bound
Handler B CPU Bound
Handler C IO Bound
Handler D CPU/IO
Handler E IO Bound
1. Axis in-memory2. Handlers are sequential in DHArch 3. Handler are parallel in DHArch
Stage 1 A, C
Stage 2 E
Stage 3 B,D
Stage 1 A, B
Stage 2 E
Stage 3 C,D
Stage 1 A,B,C,D
Stage 2 E
• Results are gathered in four environments:• Multicore• Multiprocessor• Local Area Network• Single processor
• Five handlers are utilized.• Six configurations are created.
Test I- Performance II
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Test I- Performance III
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Test II- Scalability I
• Results are collected in four environments:• Multicore• Multiprocessor• Local Area Network• Single processor
• The elapsed time of the service is measured while the number of the handlers is increasing.
• The same handler is utilized.• The handlers are running sequentially.• Single broker is leveraged.
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Test II- Scalability II
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Test II- Scalability III
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Test III-Cost I• Results are collected in four environments:
• Multicore• Multiprocessor• Local Area Network• Single processor
• We measured the overhead of adding a single handler.• We executed the same number of handlers both in
typical Axis handler mechanism and in DHArch . • The formula is :
– Difference = elapsed time in DHArch – elapsed time in regular Axis deployment
– Overhead = Difference/ the number of handlers
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Test III-Cost II
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Test III-Cost III
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Principles for distributing a handler
• Performance wise, a handler should provide enough contribution to be distributed.– Tgain ≥ Toverhead
• Some handlers cannot be separated from the Service Endpoint because of their nature. – i.e. Reliability
• Some handlers may not be efficiently distributed for every environment.– i.e. Security in WAN requires additional security.
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Contributions• A generic architecture for the efficient distributed
handler execution.• Leveraging queuing system for the handler
distribution.• Ability to utilize distributed resources for handler
execution.• Ability to update the handler chain during
execution.• Two level handler orchestration .• Parallel handler execution.• Detailed performance evaluation of Distributed
Handler Architecture.31
Questions and Comments ?
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