Cut down the attempt times of ES (#3550)

### What problem does this PR solve?

#3541
### Type of change


- [x] Refactoring
- [x] Performance Improvement

rag/utils/es_conn.py

     FusionExpr
 from rag.nlp import is_english, rag_tokenizer
 
+ATTEMPT_TIME = 2
+
 
 @singleton
 class ESConnection(DocStoreConnection):
     def __init__(self):
         self.info = {}
         logging.info(f"Use Elasticsearch {settings.ES['hosts']} as the doc engine.")
-        for _ in range(24):
+        for _ in range(ATTEMPT_TIME):
             try:
                 self.es = Elasticsearch(
                     settings.ES["hosts"].split(","),
 
     def indexExist(self, indexName: str, knowledgebaseId: str) -> bool:
         s = Index(indexName, self.es)
-        for i in range(3):
+        for i in range(ATTEMPT_TIME):
             try:
                 return s.exists()
             except Exception as e:
                 if "minimum_should_match" in m.extra_options:
                     minimum_should_match = str(int(m.extra_options["minimum_should_match"] * 100)) + "%"
                 bqry.must.append(Q("query_string", fields=m.fields,
-                                type="best_fields", query=m.matching_text,
-                                minimum_should_match=minimum_should_match,
-                                boost=1))
+                                   type="best_fields", query=m.matching_text,
+                                   minimum_should_match=minimum_should_match,
+                                   boost=1))
                 bqry.boost = 1.0 - vector_similarity_weight
 
             elif isinstance(m, MatchDenseExpr):
         q = s.to_dict()
         logging.debug(f"ESConnection.search {str(indexNames)} query: " + json.dumps(q))
 
-        for i in range(3):
+        for i in range(ATTEMPT_TIME):
             try:
                 res = self.es.search(index=indexNames,
                                      body=q,
         raise Exception("ESConnection.search timeout.")
 
     def get(self, chunkId: str, indexName: str, knowledgebaseIds: list[str]) -> dict | None:
-        for i in range(3):
+        for i in range(ATTEMPT_TIME):
             try:
                 res = self.es.get(index=(indexName),
                                   id=chunkId, source=True, )
             operations.append(d_copy)
 
         res = []
-        for _ in range(100):
+        for _ in range(ATTEMPT_TIME):
             try:
                 r = self.es.bulk(index=(indexName), operations=operations,
                                  refresh=False, timeout="600s")
         if "id" in condition and isinstance(condition["id"], str):
             # update specific single document
             chunkId = condition["id"]
-            for i in range(3):
+            for i in range(ATTEMPT_TIME):
                 try:
                     self.es.update(index=indexName, id=chunkId, doc=doc)
                     return True
                 else:
                     raise Exception("Condition value must be int, str or list.")
         logging.debug("ESConnection.delete query: " + json.dumps(qry.to_dict()))
-        for _ in range(10):
+        for _ in range(ATTEMPT_TIME):
             try:
                 res = self.es.delete_by_query(
                     index=indexName,
             sql = sql.replace(p, r, 1)
         logging.debug(f"ESConnection.sql to es: {sql}")
 
-        for i in range(3):
+        for i in range(ATTEMPT_TIME):
             try:
                 res = self.es.sql.query(body={"query": sql, "fetch_size": fetch_size}, format=format,
                                         request_timeout="2s")