* Submodules sync.

* Update

* Use ids query method instead of get method for metrics persistence.

#2933

* Query by alias name.

* #2943

Change the statement column type from Keyword to Text.

This reverts commit db8c4546.

* Use ids query method instead of get method for metrics persistence.

#2933

* Query by alias name.

* Support bootstrap class enhance and fix OOM by empty stack of exception.

* Agent document update

* Remove a word.

* Fix wrong cause exception search.

* Fix the condition

* Revert bootstrap class loader enhance.

* Remove import.

* no message

Change go2sky repo. Tetrate.io donated it to SkyAPM

* Remove login permanently.

* Sync UI change.

* Delete `org.apache.skywalking.apm.webapp.security`

* Delete tests.

* Create install_agent_on_websphere.md

* Update README.md

* Check disallowed imports in agent instrumentation classes

* Remove check script

* Remove script

* Add config to control tracing sql parameters

受leader要求，移除公司名单。

* Update powered-by.md

* Update powered-by.md

Change order and format

添加恒天财富投资管理股份有限公司支持信息

* Update powered-by.md

* Update powered-by.md

Chang order

* Update ES-Server-FAQ.md

[Thread Pool](https://www.elastic.co/guide/en/elasticsearch/reference/6.3/modules-threadpool.html?nsukey=W48pJFXgvLgtyfM%2FXI%2FQ8BhcPYE0WjNFGwKD%2Bv0cjUkocQhh1FCPQwklwVBOec541GcUkX899f%2FQv5ikjA8ckqdcrlVHpjATTKbJarNA1Gr%2BltpTiDJe%2FMuqrZGa0CAkbLfIGrYqMyc0s%2BlkxFr%2BzEo2hmWsgMaPZvK9K6f9Xugz0k0v1Wb2nfeex8ZQn0Y9SFEHwRaYV5uzw8rnH9I%2BGg%3D%3D)

From this document, we can find that the bulk thread pool setting is deleted.

write
For single-document index/delete/update and bulk requests. Thread pool type is fixed with a size of # of available processors, queue_size of 200. The maximum size for this pool is 1 + # of available processors.

* Update ES-Server-FAQ.md

* configration-zookeeper

Nacos standalone mode don't use in-memory storage therefore we don't
need mysql

* restore solrj-plugin

* restore solrj-plugin

* TracingContext optimize

* fix checkstyle

#2886

* Add cluster-etcd-plugin

* Provide Apollo dynamic configuration center implementation. fixes #2825

Add CI scripts for plugin import check.

Typical test benchmark for performance improvement. Check PR for more detail.

/**
     * # JMH version: 1.21
     * # VM version: JDK 1.8.0_111, Java HotSpot(TM) 64-Bit Server VM, 25.111-b14
     * # VM invoker: /Library/Java/JavaVirtualMachines/jdk1.8.0_111.jdk/Contents/Home/jre/bin/java
     * # VM options: -Dfile.encoding=UTF-8
     * # Warmup: 3 iterations, 10 s each
     * # Measurement: 5 iterations, 1000 ms each, 1000 calls per op
     * # Timeout: 10 min per iteration
     * # Threads: 1024 threads, ***WARNING: Synchronize iterations are disabled!***
     * # Benchmark mode: Throughput, ops/time
     * # Benchmark: org.apache.skywalking.apm.commons.datacarrier.common.AtomicRangeIntegerTest.testNewGetAndIncrementPerformance
     *
     * # Run progress: 0.00% complete, ETA 00:01:10
     * # Fork: 1 of 1
     * # Warmup Iteration   1: 2078993549.108 ops/s
     * # Warmup Iteration   2: 6408026002.297 ops/s
     * # Warmup Iteration   3: 5455960135.636 ops/s
     * Iteration   1: 165330.972 ops/s
     * Iteration   2: 95420.526 ops/s
     * Iteration   3: 173340.089 ops/s
     * Iteration   4: 94214.669 ops/s
     * Iteration   5: 261606.088 ops/s
     *
     *
     * Result "org.apache.skywalking.apm.commons.datacarrier.common.AtomicRangeIntegerTest.testNewGetAndIncrementPerformance":
     *   157982.469 ±(99.9%) 265443.465 ops/s [Average]
     *   (min, avg, max) = (94214.669, 157982.469, 261606.088), stdev = 68934.825
     *   CI (99.9%): [≈ 0, 423425.934] (assumes normal distribution)
     *
     *
     * # JMH version: 1.21
     * # VM version: JDK 1.8.0_111, Java HotSpot(TM) 64-Bit Server VM, 25.111-b14
     * # VM invoker: /Library/Java/JavaVirtualMachines/jdk1.8.0_111.jdk/Contents/Home/jre/bin/java
     * # VM options: -Dfile.encoding=UTF-8
     * # Warmup: 3 iterations, 10 s each
     * # Measurement: 5 iterations, 1000 ms each, 1000 calls per op
     * # Timeout: 10 min per iteration
     * # Threads: 1024 threads, ***WARNING: Synchronize iterations are disabled!***
     * # Benchmark mode: Throughput, ops/time
     * # Benchmark: org.apache.skywalking.apm.commons.datacarrier.common.AtomicRangeIntegerTest.testOriGetAndIncrementPerformance
     *
     * # Run progress: 50.00% complete, ETA 00:00:43
     * # Fork: 1 of 1
     * # Warmup Iteration   1: 3345520433.355 ops/s
     * # Warmup Iteration   2: 4823749249.799 ops/s
     * # Warmup Iteration   3: 6676209367.819 ops/s
     * Iteration   1: 34885.954 ops/s
     * Iteration   2: 33128.147 ops/s
     * Iteration   3: 31300.865 ops/s
     * Iteration   4: 19188.602 ops/s
     * Iteration   5: 34664.282 ops/s
     *
     *
     * Result "org.apache.skywalking.apm.commons.datacarrier.common.AtomicRangeIntegerTest.testOriGetAndIncrementPerformance":
     *   30633.570 ±(99.9%) 25249.253 ops/s [Average]
     *   (min, avg, max) = (19188.602, 30633.570, 34885.954), stdev = 6557.151
     *   CI (99.9%): [5384.317, 55882.822] (assumes normal distribution)
     *
     *
     * # Run complete. Total time: 00:01:26
     *
     * REMEMBER: The numbers below are just data. To gain reusable insights, you need to follow up on
     * why the numbers are the way they are. Use profilers (see -prof, -lprof), design factorial
     * experiments, perform baseline and negative tests that provide experimental control, make sure
     * the benchmarking environment is safe on JVM/OS/HW level, ask for reviews from the domain experts.
     * Do not assume the numbers tell you what you want them to tell.
     *
     * Benchmark                                                  Mode  Cnt       Score        Error  Units
     * AtomicRangeIntegerTest.testNewGetAndIncrementPerformance  thrpt    5  157982.469 ± 265443.465  ops/s
     * AtomicRangeIntegerTest.testOriGetAndIncrementPerformance  thrpt    5   30633.570 ±  25249.253  ops/s
     */

* Update backend-alarm.md

* Update backend-alarm.md

* Fix no stream register.

* Make sure list order.

* Refactor codes.

* Fix wrong revert.

* Revert SolrJ plugin.

* Remove an unexpected test case.

* Revert "Remove an unexpected test case."

This reverts commit 359990e18b0c0ae1a6e1005ff985bf237ec05619.

* Clear context.

* Fix a leak.

* Adjust pom plugin position and add docs

* Polishing

* Update as requested

* fix potential NullPointerException

* Revert "fix potential NullPointerException"

This reverts commit 8393656

* fix potential NullPointerException
the static paramater is best to use the class to reference