* Update user wall.

* Add a missing website.

- Set WORKDIR to skywalking
 - Change base image to openjdk:8u181-jdk-stretch which contains java tool-chains

* Refactor for cluster mode.

* Make send to L2 in certain cycle.

ADD China Eastern Airlines .Thanks

* Try adjustment.

* Remove heartbeat.

* Make heartbeat back to work. And default threadpool size more sense.

* Make L2 to less than before.

* Make instance heartbeat works.

* Try L1 aggregation thread = core * 2 * 2.

* Correct trace id.

* Fix match.

* Add cover token to retry.

* Retry new test plugin.

* Reset to jacoco.

* Update jacoco version.

* Update powered-by.md

* Update powered-by.md

Change list order.

[Performance Improvement]Backend streaming thread model improvement

* Zookeeper plugin

* Extend consume pool to data carrier.

* Change indicator aggregate worker and persistent worker to use default consumer pool.

* Fix CI.

* Support to register different host/port at cluster coordinator. Only for Zookeeper and Consul

* Provide document for internalComHost and internalComPort

* Reset port to default.

* fix no language attr value in mesh

* Fixed docker issues

* 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

* Make sure all document images ref from our Apache website.

* Change the statement.

* Update README.md

* Update powered-by.md

* Fixed an error that took a non-protocol uri string as a java.net.URL construct parameter.

* Fixed an error that took a non-protocol uri string as a java.net.URL construct parameter.

* Fixed checkstyle error.

* Set dist bin tar with -bin in the final name.

* Change dockerfile and makefile

* Update powered-by.md

* Update powered-by.md

* Update powered-by.md

fixed CPU UsagePercent Error
The cpu usage storage longitude should be one percent, not one in ten thousand. When the storage unit is one ten thousandth, as long as the usage rate does not exceed 100%. Stored values are less than one. When the current query is forced to be converted to a long type, it will always be 0. This is not correct.

* Add Database source

* Add DatabaseSource source and database_* script for oal

* Enable Database_Indicator

* Add file license

* Rename DatabaseService to ClientDatabase. In the future, we may have real database server monitoring.

* Add query database from H2

* refactor

* update submodule

* refactor

* Fix style

* Fix: unknown tag error

* fix checkstyle

* 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

* Optimize the grpc channel management.

* Rename old version concepts

* Notify when rebuild connection.

* Remove notify in new channel created.

* Remove println.

* Refactor register and reduce the lock time.

* Refactor es id generation mechanism.

* Wrong commit place.

for issue#2196