* Check license header strictly

* Ignore header template

* Include more files to check list

* support elasticsearch address configuration with http scheme.

* update logical.

* Support etcd configuration.

* First commit

* Fix e2e test and some nits

* Documenting so11y and setting default values of it in dev env

* Feature of database session

* Make it configurable.

* Make the OAP server can't startup.

* Improve OAP server performance.

* configration-zookeeper

* Add cluster-etcd-plugin

* Provide Apollo dynamic configuration center implementation. fixes #2825

* Provide Nacos dynamic configuration center implementation. fixes #2816

* Add unit tests

* Sync

* Replace pull-mode with watch-mode

* Fix ci

* Unify dependency management

* Add integration tests

* Revert unexpected changes

* Add more test cases

* Revert unexpected changes

* Suppress IDE warning

* Correctify volumes position

* Add license header

* Remove Chinese comments

* Sync

* Sync

* Sync

* Sync

* Revert unexpected changes

* Rebase on refactored code and add missing config to docker

* Fix unit test

* Revert unnecessary changes

* Implement the base of config API module.

* Finish configuration module codebases w/o tests, revert some changes.

* Finish mock tests.

* Add new gRPC service for configuration.

* Make gRPC configuration sync provider works.

* Add database slow statement dynamic setting.

* Finish the dynamic configuration service.

* Fix version.

* The new feature of Elasticsearch storage with the time series implementation.

* Time bucket util improve.

* Fixed some Gramma error.

* Update ttl.md

Polish English a little.

* Update ttl.md

Add more explicit description of TTL

* Update ttl.md

* Update StorageModuleElasticsearchConfig.java

Set otherMetricsDataTTL = 0 as default, make user more clear.

* Rename the timeSeriesAble to capableOfTimeSeries

* Fixed a test case failure.

* Add ALS proto and receiver in envoy

* Fix #2546

* Change the stackdepth type

* Fix bug

* Fix CI failed

* fix #2599

* fix ci

* add license

* add ActiveTag error methods

* fix

* fix

* nacos

* nacos

* nacos

* nacos

* fix ci

* support nacos cluster

* fix yml

* fix license

* fix ci

* remove optional

* update license

* update license and doc

* fix

* Rename metric to metrics.

* Fixed test case execute failure issues.

* support es query span max size.

* refactoring segmentQueryMaxSize.

* fix

* fix

* fix default MetadataQuery Max size.

* revert mysql

* Make Jaeger receiver works in 12450 as default.

* Finish compile and codebase.

* Make codes runnable.

* Finish Jaeger query tests.

* Add document for jaeger receiver.

* Add readme.

* Fix a break link.

* Finish doc.

* 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 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

* 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

* 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.

* 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.

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

* 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.

* 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.