* Support dynamically configure alarm settings

* Update documentation

* Provide Consul dynamic configuration center implementation

* Add more unit tests

* Fix unit test

* Add more unit tests and remove unused file

* Remove redundant doc

* Upgrade guava version to support higher JDK version

* Adjust license version

* Update doc

Modify `hot` to `host`

* Add pulsar apm plugin.

* Fix check style

* Fix pulsar consumer component define.

* Add pulsar to component-libraries.yml

* Fix error interceptor class.

* Add pulsar to agent support list.

* Add Pulsar to ComponentsDefine and component-libraries.yml

* Move create entry span log of consumer from after method to before method

* Fix send callback issue when exception cause.

* Fix test issues

* Move pulsar plugin to optional plugins

* Add none messages tests for interceptor of producer and consumer.

* Remove unused comments.

* Move pulsar plugin back to the apm-sdk-plugin

* Fix comments

* remove set startTime for entry span(default is set by System.currentTimeMillis)

* Fix comments

* Support timeout configuration in agent and backend.

* Fix CI

* no message

* Add feature to control the maximum history agent log files.

* Add Light4J 1.6.x plug-in

* Add unit test for Light4J plug-in

* Add missing id to server-starter

* Remove mentions of version 1.6.x

Some local testing showed that the plugin successfully generated traces for a light4j project built with light-codegen v2.x. Therefore, there is no need for a separate plugin for v2.x and no distinction needs to be made with light4j v1.6.x.

* Update supported light4j versions

* Use ContextSnapshot to maintain trace

In a typical Light4j project, the ExceptionHandler#handleRequest is the asynchronous execution point. The flow is ExceptionHandler#handleRequest -> HttpServerExchange#dispatch -> ... -> ExceptionHandler#handleRequest. This means that handleRequest is being intercepted twice and each time a LocalSpan is created. Without handling thread propagation, the trace segment gets split up.

By saving a ContextSnapshot into the enhanced object (ExceptionHandler), we can determine if it is necessary to continue the segment.

* Update logic for span creation in trace

By default, the Light4J plugin now overrides the Undertow plugin's entry span with its own. This new entry span is created just before execution of the ExceptionHandler#handleRequest in the I/O thread. The entry span is generated here because it is considered the starting point of the Light4J handler chain.

There is now also the option to enable detailed span creation when tracing requests through Light4J. These local spans mark which middleware and business handlers are involved with handling the HTTP request to a Light4J service.

* Update skywalking version

* Update light4j version

* Fix LightInstrumentation javadoc

* Remove import violating checkstyle

This import was added from the link reference in the javadoc. The javadoc has now been changed to just reference the method name.

* Move light4j agent config property

* Sync UI

* agent support custom properties.

* Update als_setting.md

* Update als_setting.md

* add cassandra java driver 3.x plugin

* Add TTL E2E test

* Add to Jenkins stage and minor bugfix

* Upgrade e2e container version

* Polish and minor fix

* Polish

* support es https ssl config.

* update

* update docs.

* refactoring var name.

* fix

* update docs.

* add config in es section.

* fix logical.

* Add envoy metrics sending example
Signed-off-by: NDhi Aurrahman <dio@tetrate.io>

* Newline
Signed-off-by: NDhi Aurrahman <dio@tetrate.io>

* Fix
Signed-off-by: NDhi Aurrahman <dio@tetrate.io>

* Tear down note
Signed-off-by: NDhi Aurrahman <dio@tetrate.io>

* Typo
Signed-off-by: NDhi Aurrahman <dio@tetrate.io>

* Update document.

* Enable ALS document

* Support Gateway without agent

* add logstash logback plugin

* add logstash logback plugin, set pom provided, refine logback doc

* refine logstash logback doc

* refine the comment

* remove the app_id that not related to SkyWalking

* remove tag @date for CI error: unknown tag: date

* add description for iLoggingEvent for ci warning: no description for @param

* Fix the zookeeper plugin has many nodes in the cluster case

* support version

* Support play 2.x 

* ADD: add operationName length threshold

* MOD:move operationName threshold to Config, simplified code

* MOD:update agent set-up document, clean code

* MOD:add agent.operation_name_threshold conf prefix

* Support op group name in agent config core.

* Provide core API for operation name grouping, rest template plugin update, and doc update.

* Fix doc

* Fix test case.

* Fix missing changes.

* add shuyun to powered-by.md (#3341)

* add shuyun to powered-by.md

* update powered-by.md

* Remove static method.

* Log4j2 support AsyncRoot print tid
Support AsyncRoot print tid of all versions of log4j2 2.1+

* support ACL

* support digest only

* Add pattern logger to replace the easy logger.
* Doc update
* Support console log 

change `agent.span_limit_per_segment` default value to match the default value of `SPAN_LIMIT_PER_SEGMENT` in https://github.com/apache/skywalking/blob/master/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/conf/Config.java

* improve auto connect

* add config

* use int instread of atomic

* update format

* update doc

* update var name and doc

* fix

* support elasticsearch address configuration with http scheme.

* update logical.

* Update backend-storage.md

* Update backend-storage.md

* Update ES-Server-FAQ.md

* add http

* update plugin

* Add StaticMethodsAroundInterceptor to be injected.

* move to options plugin

* move folder

* update pom

* support https

* add witness class

* Make JDK9-11 available for bootstrap instrumentation

* Remove temp folder of old bootstrap instrumentation requirement.

* remove witness ,work for jdk6,7,8,9,10,11

* Make JDK 12 works.

* move jdk-http-plugin to bootstrap-plugins folder

* add httpsclient

* update README.md

* Support upgrade backend w/o rebooting agents

* Make JDK9-11 available for bootstrap instrumentation

* Remove temp folder of old bootstrap instrumentation requirement.

* correct 3rd default alarm rule description

* unit change: 1000ms -> 1s

* Remove javassist dependency

*   Finish the PR.

* Change doc title level.

* Remove the duplicated codes.

* POC: Intercept successfully.

* Refactor codes

* Build the new core

* Setup the new core.

* Push the javassist version to 3.23.2-GA, as it is the last version supports JDK 1.6 compile, according to https://github.com/jboss-javassist/javassist/blob/rel_3_23_2_ga/pom.xml#L149-L160

* Finish the all codes.

* Document updated for bootstrap instrumentation.

* Add a notice to document.

* Remove unexpected file.

* Set javassist version right. Add judge in core interceptors

* Fixe no log bridge implementation