There is a few steps to check whether taskserver functions properly.
1] Check whether java program is running using "ps -ef | grep java" command
Example output
splunk 8371 8123 0 01:11 ? 00:05:20 /opt/splunk/jdk1.8.0_181/bin/java -Ddw.server.applicationConnectors[0].port=9998 -jar /opt/splunk/HF2/etc/apps/splunk_app_db_connect/linux_x86_64/bin/../../jars/server.jar
2] If java process with server.jar is not up and running, check whether java path is configured properly in $SPLUNK_HOME/splunk_app_db_connect/your_platform/bin/customized.java.path and then correct java path in your system if it points to the wrong path.
Example of customized.java.path in /opt/splunk/HF2/etc/apps/splunk_app_db_connect/linux_x86_64/bin
/opt/splunk/jdk1.8.0_181/bin/java
3] If Java process is running with server.jar, check the connectivity to task server using CURL command after login to the Splunk server where DB Connect app is installed
Example
curl -k -u admin:password https://localhost:<mgmt_port>/servicesNS/nobody/splunk_app_db_connect/db_connect/dbxproxy/taskserver
curl -k http://localhost:9998/api/taskserver
curl --noproxy localhost -k http://localhost:9998/api/taskserver
Example output
{"status":"**RUNNING**","schedulerStatus":0,"message":"task server is running","info":{"ProcessName":"8371@kheolin05.sv.splunk.com","Uptime":"57931358","javaVMName":"Java HotSpot(TM) Server VM","javaVersion":"1.8.0_181","TotalMemory":"357302272","javaVendor":"Oracle Corporation","javaSpecificationVersion":"1.8","MaxMemory":"954466304","FreeMemory":"92405888"},"serverId":"16df13b1-549c-4d42-9a79-1e0ae5d163fd"}[/opt/splunk/HF2/etc/apps/splunk_app_db_connect/linux_x86_64/bin:HF2]$
** If curl command only works with "--noproxy localhost" option, check whether http_proxy is configured in your system environment variable and then configure no_proxy environment variable for localhost and restart Splunk instance
Example
no_proxy=localhost,127.0.0.1
** Here tcp port# 9998 is default port for taskserver, port for taskserver can be found in step#1 above in port=9998
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