* 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

* fix gRPCHost

* fix gRPCHost

* 1. Sleep 500 milliseconds after a batch re-call finish.
2. Re-create register lock index when the system property named debug is setting.
3. Get the register inventory before lock to avoid increment the sequence but not use.
4. Return the exchange flag after all the references and spans in one segment parsed to reduce the number of segment parse.
5. Put the not exchanged segment into a collection then try to exchange no more than 10 times because of the exchange is asynchronous.
6. Cache the segment object to avoid repeated deserialization.

#2185

* #2185
1. Sleep 500 milliseconds after a batch re-call finish.
2. Re-create register lock index when the system property named debug is setting.
3. Get the register inventory before lock to avoid increment the sequence but not use.

* fix no language attr value in mesh (#2182)

* Fixed the inventory register lock invalid bug. (#2184)

* #2183

Merge commit into master.

* Make the h2 register lock same as mysql.

* Fix #2186

* #2183

Merge commit into master.

* Make the h2 register lock same as mysql.

* [maven-release-plugin] prepare release v6.0.0-GA

* [maven-release-plugin] prepare for next development iteration

correct spelling error.

* Update trace-mode-grafana.json

Update heatmap expression

* Update trace-mode-grafana.json

* Update mesh-mode-grafana.json

fix bugs for more than one instance

* Update mesh-mode-grafana.json

Fix heatmap

* fixed  the index name to format name in logs

* modify the log level from info to debug

* Update ReferenceIdExchanger.java

Change comments of codes.

* 🎉 PHP agent

* Update powered-by.md

Change user list order

* Refactor service instance inventory to properties based entity.

* Fix a bug and refactor properties update.

* support overview-cn.md translation

* update overview-cn.md translation

* update fix error statement problem

* update fix error statement

* plugin support redisson

* Add properties for service inventory

* Fix code bugs

* Provide develop doc for inventory extension.

Add 5 new users based on #443

* remove duplicate config in docker.

* Revert "remove duplicate config in docker."

This reverts commit eb774035

* update content.

* 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