vsan-health service not starting : "An error occurred while starting service 'vsan-health'"

  Symptoms

• vsan-health service not starting : "An error occurred while starting service 'vsan-health'"
• vSAN related logs will not capture the actual error.
• vMon log will also give any hint on the failure. 
• Checking vmware-vsan-health-runtime.log.stderr gives the following trace

Starting service process with pid: 542.
Traceback (most recent call last):
  File "/usr/lib/vmware-vpx/vsan-health/VsanMgmtServer.py", line 382, in <module>
    SetupLogging(gCmdOptions, logdir)
  File "/usr/lib/vmware-vpx/vsan-health/VsanMgmtServer.py", line 194, in SetupLogging
    Logger.InitLogging(logDir)
  File "/usr/lib/vmware-vpx/vsan-health/logger/Logger.py", line 295, in InitLogging
    SetupLoggers(loggerConfFile, logDir)
  File "/usr/lib/vmware-vpx/vsan-health/logger/Logger.py", line 273, in SetupLoggers
    configInFile = UpdateFormatterHandlerPath(f)
  File "/usr/lib/vmware-vpx/vsan-health/logger/Logger.py", line 231, in UpdateFormatterHandlerPath
    config = json.load(configFile)
  File "/usr/lib/python3.5/json/__init__.py", line 268, in load
    parse_constant=parse_constant, object_pairs_hook=object_pairs_hook, **kw)
  File "/usr/lib/python3.5/json/__init__.py", line 319, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python3.5/json/decoder.py", line 339, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib/python3.5/json/decoder.py", line 357, in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

Cause

This issue can happen if the logger.conf is corrupted

Impact / Risks

• VAMI based backups will fail since the service is stopped.
• vSAN monitoring information would not be available.

Resolution

To resolve the issue.

1. Change Directory: cd /etc/vmware-vsan-health
2. Move the file logger.conf to another location.

mv logger.conf /var/tmp/logger.conf

3. Once done, try restarting the service : 

vmon-cli -r vsan-health