* Add `@Spi` annotation as the general annotation for SPI definition.
* Add isDefault in @Spi, add loadDefaultInstance and improve loadFirstInstanceOrDefault method, improve test cases
* Add SpiLoaderException class for thrown when something goes wrong while loading Provider
* Rearrange packages of base SPI mechanism

NOTE: this PR contains breaking changes regarding API.

* Fix issue of memory leak in metric.js

Apply to both simple-http and netty-http modules.

1. Added ARM64 architecture in .travis.yml
2. Updated 'embedded-consul' version to 2.2.0, 'consul-api' version to 1.4.5 for ARM64 support.
3. Updated grpc.version for 'io.grpc:protoc-gen-grpc-java' to 1.30.2, for ARM64 support.

Signed-off-by: odidev <odidev@puresoftware.com>

- convert BlockException to a simple RuntimeException (with necessary message)

Signed-off-by: Jason Joo <hblzxsj@163.com>

- doc: Fix a typo in description of booting options for sentinel-dashboard
- Fix mismatched name of parameter to its comment for VersionUtils.parseVersion()

* Optimize logging statements using placeholder to avoid unnecessary concatenation (issue #1735)

Signed-off-by: yunfeiyanggzq <yunfeiyang@buaa.edu.cn>

Signed-off-by: yunfeiyanggzq <yunfeiyang@buaa.edu.cn>

Signed-off-by: yunfeiyanggzq <yunfeiyang@buaa.edu.cn>

Signed-off-by: yunfeiyanggzq <yunfeiyang@buaa.edu.cn>

Fix issue #1705.

- Use CAS to make it thread safe and limited in the declared range.

Signed-off-by: cj <power4j@outlook.com>

Use `getRequestURI` instead of `getServletPath` to get URI of current request(Both in prefix and regex matching).

Signed-off-by: yunfeiyanggzq <yunfeiyang@buaa.edu.cn>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

- Fix NPE bug in consumer filter (when non-biz error occurred)
- Improve default fallback in Dubbo 2.7.x adapter: convert the BlockException to a simple RuntimeException (with necessary message)
- Polish code and comments

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

If entry already exists in request just skip creation.

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

* Support customized origin parser in Apache Dubbo 2.7.x adapter
* Unify Dubbo callback registry (for fallback and origin parser) into DubboAdapterGlobalConfig
* Polish default fallback implementation (wrap exception with RpcResult rather than directly throw it out)

- Unify the extended interface as a few event handlers: onPass, onBlocked, onComplete and onError
- Polish related code

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

* Unify Dubbo callback registry (for fallback and origin parser) into DubboAdapterGlobalConfig
* Polish default fallback implementation (wrap exception with RpcResult rather than directly throw it out)

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

- Add EntryType args to all hook methods

- Rename: whenComplete -> whenTerminate
- Execute the exit handler directly after the onExit hook of all slots

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

- Only carry context in tryPass/onComplete method (this might be generic in upcoming versions)

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

* Refactor the workflow to fix the bug that circuit breaker may remain half-open state forever when the request is blocked by upcoming rules: revert the state change in exit handler (as a temporary workaround)
* Add exit handler in Entry as a per-invocation hook.

Signed-off-by: cj <power4j@outlook.com>