Draft: Fix Thread Exhaustion and ES Connection Reliability Improvements

Fix for Issue: #240 (closed), #205

Implemented Fixes

1. Replaced Elasticsearch client cache with concurrent hash map
2. Added Connection Pool Limits
3. Added Client Cleanup Methods/cleanup of stale or unhealthy connections
4. Implemented retry mechanism to handle ES connection interrupts
5. Execute query with health checks
6. Moving configuration of ES connection settings to application.properties
7. Added unit tests

Testing

Pod resource usage after indexing 100k+ records:

Executing top (resouce usage):

  PID  PPID USER     STAT   VSZ %VSZ CPU %CPU COMMAND
    7     1 appuser  S    3108m   2%  29   0% java -Xms1000M -Xmx1000M --add-opens java.base/java.lang=ALL-UNNAMED --add-opens java.base/java.lang.reflect=ALL-UNNAMED -jar /app.jar
 1262     0 appuser  S     2984   0%  25   0% bash
    1     0 appuser  S     1712   0%  21   0% /bin/sh -c . /entrypoint.sh
 1280  1262 appuser  R     1700   0%  24   0% top

Executing ps -lfT | wc -l (thread count):

160