Add FAQ for ElasticSearch server side setting (#2859)

* Create ES-Server-FAQ.md

* Update README.md

* Update ES-Server-FAQ.md

docs/en/FAQ/ES-Server-FAQ.md

+# ElasticSearch 
+Some new user may face the following error in ElasticSearch storage. ERROR CODE 429. Or ElasticSearch performance is not as good as expected.
+```
+    Suppressed: org.elasticsearch.client.ResponseException: method [POST], host [http://127.0.0.1:9200], URI [/service_instance_inventory/type/6_tcc-app-gateway-77b98ff6ff-crblx.cards_0_0/_update?refresh=true&timeout=1m], status line [HTTP/1.1 429 Too Many Requests]
+{"error":{"root_cause":[{"type":"remote_transport_exception","reason":"[elasticsearch-0][10.16.9.130:9300][indices:data/write/update[s]]"}],"type":"es_rejected_execution_exception","reason":"rejected execution of org.elasticsearch.transport.TransportService$7@19a5cf02 on EsThreadPoolExecutor[name = elasticsearch-0/write, queue capacity = 200, org.elasticsearch.common.util.concurrent.EsThreadPoolExecutor@389297ad[Running, pool size = 2, active threads = 2, queued tasks = 200, completed tasks = 147611]]"},"status":429}
+        at org.elasticsearch.client.RestClient$SyncResponseListener.get(RestClient.java:705) ~[elasticsearch-rest-client-6.3.2.jar:6.3.2]
+        at org.elasticsearch.client.RestClient.performRequest(RestClient.java:235) ~[elasticsearch-rest-client-6.3.2.jar:6.3.2]
+        at org.elasticsearch.client.RestClient.performRequest(RestClient.java:198) ~[elasticsearch-rest-client-6.3.2.jar:6.3.2]
+        at org.elasticsearch.client.RestHighLevelClient.performRequest(RestHighLevelClient.java:522) ~[elasticsearch
+```
+
+You could add following config to `elasticsearch.yml`, set the value based on your env.
+```yml
+# In tracing scenario, consider to set more than this at least.
+thread_pool.bulk.queue_size: 1000
+
+thread_pool.bulk.size: 16
+thread_pool.index.queue_size: 500
+thread_pool.write.queuq_size: 500
+
+# When you face query error at trace page, remember to check this.
+index.max_result_window: 1000000
+```

docs/en/FAQ/README.md

@@ -10,4 +10,5 @@ These are known and common FAQs. We welcome you to contribute yours.
 * [Too many GRPC logs in the console](Too-many-gRPC-logs.md)
 * [The trace doesn't continue in kafka consumer side](kafka-plugin.md)
 * [Agent or collector version upgrade](Upgrade.md)
-* [EnhanceRequireObjectCache class cast exception](EnhanceRequireObjectCache-Cast-Exception.md)
\ No newline at end of file
+* [EnhanceRequireObjectCache class cast exception](EnhanceRequireObjectCache-Cast-Exception.md)
+* [ElasticSearch server performance FAQ, including ERROR CODE:429](ES-Server-FAQ.md)