Generate the metric file name from the service name.

FileLockSuffix represents the suffix of the lock file.

FilePidPrefix represents the pid flag of filename.

MetricFileNameSuffix represents the suffix of the metric file.

MetricIdxSuffix represents the suffix of the metric index file.

MetricLogWriter writes and flushes metric items to current metric log.

MetricSearcher searches metric items from the metric log file under given condition.