Remove unnecessary checks from MetricsHub extensions

[CherfaElyes]

Specification

Since the ExtensionManager is responsible of finding an extension that matches the configuration and the sources as follows:

public Optional<IProtocolExtension> findSourceExtension(
	final Source source,
	final TelemetryManager telemetryManager
	) {
	final List<IProtocolExtension> sourceExtensions = protocolExtensions
		.stream()
		.filter(extension ->
			telemetryManager
				.getHostConfiguration()
				.getConfigurations()
				.values()
				.stream()
				.anyMatch(extension::isValidConfiguration)
		)
		.filter(extension -> extension.getSupportedSources().contains(source.getClass()))
		.toList();

	return filterWithBusinessLogic(telemetryManager, sourceExtensions);
}

We are sure that within the extension, both the configuration and the source cannot be null. Consequently, there is no need to test if they are null within each extension.

Example - Check Source

The following check is not necessary within the WmiSourceProcessor since the call to this processor is only made after checking that Source instanceof WmiSource, which ensures that Source is not null.

if (wmiSource == null) {
	log.warn("Hostname {} - Malformed WMI source {}. Returning an empty table.", hostname, wmiSource);
	return SourceTable.empty();
}

Example - Check Configuration

This check is not relevant as we already know that the configuration cannot be null.

if (winConfiguration == null) {
	log.warn(
		"Hostname {} - The Windows protocol credentials are not configured. Cannot process Windows IPMI source.",
		telemetryManager.getHostname()
	);
	return SourceTable.empty();
}

This kind of checks needs to be removed from all the extensions and the source and criterion processors. Unit tests that fail after the refactoring need to be fixed as well.

Milestone

• HTTP
• IPMI
• OsCommand
• SNMP
• SNMPv3
• Wbem
• WMI
• WinRm