* Fix missing licenses in dist.

* Move all CoreRegisterLinker together into SharingReceiver.

* Setup receiver endpoint

* Revert "Provide create, delete, isExists template method by elastic client. (#2425)"

This reverts commit e6a7720f.

* Support endpoint group in mesh.

* Fix CI.

* Refactor for reduce string compare.

* Support endpoint naming rule in service level

* Support grpc exporter.

* Support scope(all) metric export and finish document.

* Close exporter even in local debug env. And fix CI.

* Remove the system.out

* Fix absent 4.

* Support subscription from remote.

* Add the doc

* Update application.yml

* Added elasticsearch warehouse certification support

* Add the elasticsearch service for Http Basic instructions

* Update backend-storage.md

Change document.

* The role of OAP server.
Mixed: Receive agent data, level 1 aggregate, level 2 aggregate
Receiver: Receive agent data, level 1 aggregate
Aggregator: level 2 aggregate

* Mistake, stadalone default.

* Update application.yml

* #2327

Add a new module for share receiver server or to be a bridge of core server.

* Rename the module name.

* Extend envoy metric service, scope and OAL lexer/parser.

* Finish metric extension and oal.

* Make test env works.

* Finish test of envoy connection and memory metric.

* Change document.

* Finish docker compose test.

[Performance Improvement]Backend streaming thread model improvement

* Zookeeper plugin

* The prototype of topN sql worker.

* Add scope and new manual dispatcher.

* no message

* Finish topN persistence codes. Not test yet. And query have not added.

* Finish the top n database statement persistent.

* Support different slow thresholds for different db types.

* Fix wrong db default threshold

* Finish new query protocol binding.

* Provide query empty implementation and sync ui.

* Finish all codes, hope it works :P
I will run the tests tonight.

* Fix

* Fix

* Fix a startup issue.

* Add time bucket to persistent.

* Fix wrong query result column name.

* Fix Database query.

* Fix checkstyle.

* Fix wrong order logic, and add a test case to verify, to fix https://github.com/apache/incubator-skywalking/pull/2239#discussion_r255948249

* Support lettuce plugin

* lettuce plugin bugfix

* lettuce plugin fix license issue

* lettuce plugin fix cluster and config issue

* plugin lettuce compatible with low 5.0.x version

* lettuce plugin support version accurately describes on Supported-list.md

* plugin lettuce compatible with low 5.0.2 version

* lettuce plugin fix wrong batch method intercept point

* move lettuce to optional plugins

* fix ci issue

* fix ci issue

* Modify the description file

* Pom code optimization

* Optimization operation name

* Optimization operation name2

* plugin support redisson

* Change a label name for  sw instance to avoid confict.

* Fix a wrong metric name.

* Fix too many counter instances.

* Set uptime to second.

* Fix format.

* Fix format

* Remove two unnecessary counter.

* Provide grafana dashboard settings and remove unnecessary metric.

* Provide a simple UI brief doc. Fix #2137

* Finish the basic codes of telemetry.

* Add many telemetry in oap.

* Fix a test case.

* Finish all telemetry metric.

* Fix format.

* Make telemetry works.

* Support JVM metrics.

* Add doc for telemetry.

* Fix typo.

* Fix #2135

* Finish the APIs of telemetry module.

* Add prometheus license.

* Active default telemetry provider.

* add ojdbc component id

* Support Gson plugin

* fix add Canal plugin

* fix add UnitTest

* fix   format pom.xml

* Delete CanalApplication.java

* fix support cluster url

* fix add Licensed

* fix bug

* fix

* Provide consul cluster plugin.

* Change log and application config file.

* Add consul's config item into the docker's application.yml.

* Fixed bug.

* Add consul description into  readme.

* Add okhttp component license.

* Fix support rabbitmq plugin

* fix Unit test rename sw3 to sw6

* Update pom.xml

* fix adjust rabbitmq Unit test

* fix add rabbitmq component in docker component-libraries.yml

* Update RabbitMQProducerInterceptor.java

* Update RabbitMQProducerInterceptor.java

2. Zookeeper implementation of the cluster module using name space to support using same zookeeper cluster by different OAP clusters.

* Support alarm in service instance and endpoint.

* Fix alarm default settings and document.

* Fix wrong default setting

* Make service instance and endpoint scopes available in alarm core.

* Fix alarm bug.

* Correct namespace description

* Support sampling trace at server side and keep metric right.

* Add a trace sampling document

* Fix wrong default value.

* Fix document issue.

* Fix assemble issue.

* Fix wrong settings and doc.

Also fixed several bugs in this merge.

* feat:Active System.env Config In Both Collector And agent.config.
1、moving related codes into apm-util module.
2、update Setting-override.md about how to use.

* resolve docs.

* typo

* finish test case.

* Update README.md

* support set config from system.envs.

* Close the clients which are unreachable.
Remote client manager test case and comments.

* Test the GRPCRemote client.

* 1. Catch the throwable for onComplete method cause of it will throw exception when connection lost.
2. Check the gRPC channel state, send message when state is ready, wait 5 second when state is not ready.

Notice: gRPC channel getState with true parameter will trigger reconnect operation.

* gRPC client will reconnect to the server when network recorvered.

* Recovery application.yml

* Recovery proto module commit id.

* no message

* Fixed compile error.

* Change some codes to make zipkin receiver works, not done yet.

* @adriancole Zipkin receiver is coming back again.

* Fix document and fix for Zipkin receiver.

* Fix some bugs.

* Fix register bug.

* Fix transfer bug for new backend core.

* OAP server testing module.

#1930

* #Missing delete code.