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Posted to notifications@shardingsphere.apache.org by GitBox <gi...@apache.org> on 2020/10/08 02:19:51 UTC
[GitHub] [shardingsphere-elasticjob] wwj-go opened a new issue #1546: Implement a new SPI mechanism to replace Java native SPI mechanism
wwj-go opened a new issue #1546:
URL: https://github.com/apache/shardingsphere-elasticjob/issues/1546
Java's native SPI mechanism has the following disadvantages:
1. Cannot be loaded on demand. Although `ServiceLoader `does lazy loading, it can basically only be obtained by traversal, that is, all the implementation classes of the interface have to be loaded and instantiated once. If you do not want to use certain implementation classes, or the instantiation of certain classes is time-consuming, java SPI is not a good choice.
2. The way to obtain a certain implementation class is not flexible enough, it can only be obtained in the form of Iterator, and the corresponding implementation class cannot be obtained according to a certain parameter. In order to realize the function, it is usually necessary to wrap a layer on it, such as `JobItemExecutorFactory`, `JobShardingStrategyFactory`, etc., which is easy to cause duplication of code.
3. It is not safe for multiple concurrent and multithreaded instances to use the `ServiceLoader `class.
Based on the above reasons, it is necessary to implement another SPI mechanism to work with elastic-job to solve these problems.
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[GitHub] [shardingsphere-elasticjob] wwj-go closed issue #1546: Implement a new SPI mechanism to replace Java native SPI mechanism
Posted by GitBox <gi...@apache.org>.
wwj-go closed issue #1546:
URL: https://github.com/apache/shardingsphere-elasticjob/issues/1546
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[GitHub] [shardingsphere-elasticjob] wwj-go edited a comment on issue #1546: Implement a new SPI mechanism to replace Java native SPI mechanism
Posted by GitBox <gi...@apache.org>.
wwj-go edited a comment on issue #1546:
URL: https://github.com/apache/shardingsphere-elasticjob/issues/1546#issuecomment-705395078
@TeslaCN hi，thanks for your reply. I have read the code you said in https://github.com/apache/shardingsphere , and I find that someone have merge it into this project named `ElasticJobServiceLoader`.
Personally, from a performance perspective，I think its not a good design.
1.` register(final Class<T> service)` just save the classes not instances，this is equivalent to saying that instantiation of java SPI is not necessary and is a waste.
2. Every time call `newServiceInstances(final Class<T> service)` will reinstantiate all implements and for the caller like `ElasticJobListenerFactory、 JobErrorHandlerFactory`， just use one implement and discard the rest , it is a serious waste.
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[GitHub] [shardingsphere-elasticjob] wwj-go commented on issue #1546: Implement a new SPI mechanism to replace Java native SPI mechanism
Posted by GitBox <gi...@apache.org>.
wwj-go commented on issue #1546:
URL: https://github.com/apache/shardingsphere-elasticjob/issues/1546#issuecomment-705896473
Thanks for your reply，I have got it.
> It is true of the disadvantages of SPI as you said, but there are still lots of advantages of SPI.
> I only want to discuss the main advantage, `SPI is the standard way of Java extension, developers do not need learn any extra knowledge to understand this way`.
> So I prefer use the standard way to do extension in ElasticJob.
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[GitHub] [shardingsphere-elasticjob] wwj-go edited a comment on issue #1546: Implement a new SPI mechanism to replace Java native SPI mechanism
Posted by GitBox <gi...@apache.org>.
wwj-go edited a comment on issue #1546:
URL: https://github.com/apache/shardingsphere-elasticjob/issues/1546#issuecomment-705395078
@TeslaCN hi，thanks for your reply. I have read the code you said in https://github.com/apache/shardingsphere , and I find that someone have merge it into this project named `ElasticJobServiceLoader`.
Personally, from a performance perspective，I think its not a good design.
1.` register(final Class<T> service)` just save the classes not instances，this is equivalent to saying that instantiation of java SPI is not necessary and is a waste.
2. Every time call `newServiceInstances(final Class<T> service)` will reinstantiate all implements and for the caller like `ElasticJobListenerFactory、 JobErrorHandlerFactory`， just use one implement and discard the rest , it is a serious waste.
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[GitHub] [shardingsphere-elasticjob] TeslaCN removed a comment on issue #1546: Implement a new SPI mechanism to replace Java native SPI mechanism
Posted by GitBox <gi...@apache.org>.
TeslaCN removed a comment on issue #1546:
URL: https://github.com/apache/shardingsphere-elasticjob/issues/1546#issuecomment-705407285
Please contact wechat ss_assistant_1 to join us.
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[GitHub] [shardingsphere-elasticjob] TeslaCN removed a comment on issue #1546: Implement a new SPI mechanism to replace Java native SPI mechanism
Posted by GitBox <gi...@apache.org>.
TeslaCN removed a comment on issue #1546:
URL: https://github.com/apache/shardingsphere-elasticjob/issues/1546#issuecomment-705407285
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[GitHub] [shardingsphere-elasticjob] wwj-go commented on issue #1546: Implement a new SPI mechanism to replace Java native SPI mechanism
Posted by GitBox <gi...@apache.org>.
wwj-go commented on issue #1546:
URL: https://github.com/apache/shardingsphere-elasticjob/issues/1546#issuecomment-705395078
@TeslaCN hi，thanks for your reply. I have read the code you said in https://github.com/apache/shardingsphere , and I find that someone have merge it into this project named `ElasticJobServiceLoader`.
Personally, from a performance perspective，I think its not a good design.
1.` register(final Class<T> service)` just save the classes not instances，this is equivalent to saying that instantiation of java SPI is not necessary and is a waste.
2. Every time call `newServiceInstances(final Class<T> service)` will reinstantiate all implements and for the caller like `ElasticJobListenerFactory、 JobErrorHandlerFactory`， just use the first implement and discard the rest , it is a serious waste.
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[GitHub] [shardingsphere-elasticjob] wwj-go commented on issue #1546: Implement a new SPI mechanism to replace Java native SPI mechanism
Posted by GitBox <gi...@apache.org>.
wwj-go commented on issue #1546:
URL: https://github.com/apache/shardingsphere-elasticjob/issues/1546#issuecomment-705294312
hi @Technoboy- , I have implemented an SPI loading mechanism to adapt to elastic-job, can you assign this task to me?
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[GitHub] [shardingsphere-elasticjob] wwj-go commented on issue #1546: Implement a new SPI mechanism to replace Java native SPI mechanism
Posted by GitBox <gi...@apache.org>.
wwj-go commented on issue #1546:
URL: https://github.com/apache/shardingsphere-elasticjob/issues/1546#issuecomment-705395078
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[GitHub] [shardingsphere-elasticjob] TeslaCN commented on issue #1546: Implement a new SPI mechanism to replace Java native SPI mechanism
Posted by GitBox <gi...@apache.org>.
TeslaCN commented on issue #1546:
URL: https://github.com/apache/shardingsphere-elasticjob/issues/1546#issuecomment-705345807
Personally I think that:
1. Those implementations of interfaces are highly modular (such as 'elasticjob-error-handler-email'). Users just introduce the dependencies as needed.
2. A certain implementation can be distinguished by a string based type defined in 'TypedSPI'. Iterator is acceptable because factory methods are invoke less frequently.
3. The current factories using static block to institate instances.
You may consider referencing the SPI registry in https://github.com/apache/shardingsphere.
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[GitHub] [shardingsphere-elasticjob] TeslaCN commented on issue #1546: Implement a new SPI mechanism to replace Java native SPI mechanism
Posted by GitBox <gi...@apache.org>.
TeslaCN commented on issue #1546:
URL: https://github.com/apache/shardingsphere-elasticjob/issues/1546#issuecomment-705345807
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[GitHub] [shardingsphere-elasticjob] terrymanu commented on issue #1546: Implement a new SPI mechanism to replace Java native SPI mechanism
Posted by GitBox <gi...@apache.org>.
terrymanu commented on issue #1546:
URL: https://github.com/apache/shardingsphere-elasticjob/issues/1546#issuecomment-705472224
It is true of the disadvantages of SPI as you said, but there are still lots of advantages of SPI.
I only want to discuss the main advantage, `SPI is the standard way of Java extension, developers do not need learn any extra knowledge to understand this way`.
So I prefer use the standard way to do extension in ElasticJob.
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[GitHub] [shardingsphere-elasticjob] terrymanu commented on issue #1546: Implement a new SPI mechanism to replace Java native SPI mechanism
Posted by GitBox <gi...@apache.org>.
terrymanu commented on issue #1546:
URL: https://github.com/apache/shardingsphere-elasticjob/issues/1546#issuecomment-705472224
It is true of the disadvantages of SPI as you said, but there are still lots of advantages of SPI.
I only want to discuss the main advantage, `SPI is the standard way of Java extension, developers do not need learn any extra knowledge to understand this way`.
So I prefer use the standard way to do extension in ElasticJob.
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[GitHub] [shardingsphere-elasticjob] TeslaCN commented on issue #1546: Implement a new SPI mechanism to replace Java native SPI mechanism
Posted by GitBox <gi...@apache.org>.
TeslaCN commented on issue #1546:
URL: https://github.com/apache/shardingsphere-elasticjob/issues/1546#issuecomment-705407285
Please contact wechat ss_assistant_1 to join us.
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[GitHub] [shardingsphere-elasticjob] wwj-go closed issue #1546: Implement a new SPI mechanism to replace Java native SPI mechanism
Posted by GitBox <gi...@apache.org>.
wwj-go closed issue #1546:
URL: https://github.com/apache/shardingsphere-elasticjob/issues/1546
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