[Docs] .hostname is not available in log templates

[olyashok]

Description

.hostname is mentioned as variable in several places in docs but actually is not resolveable by code

https://github.com/flyteorg/flyteplugins/blob/b0684d97a1cf240f1a44f310f4a79cc21844caa9/go/tasks/pluginmachinery/tasklog/template.go#L69

Are you sure this issue hasn't been raised already?

• [X] Yes

Have you read the Code of Conduct?

• [X] Yes

[dosubot[bot]]

🤖

Hey @olyashok! Good to see you back. Hope you're doing well!

Thank you for bringing this to our attention. Based on the code in the Flyte repository, the .hostname variable is indeed resolvable.

The initDefaultRegexes() function creates a regular expression for the hostname variable using the MustCreateRegex() function. This regular expression is then stored in the Hostname field of the templateRegexes struct.

Later, in the templateVarsForScheme() function, the Hostname regular expression is used to create a TemplateVar struct, which pairs the regular expression with the actual value of the hostname (input.HostName). This is done in the TemplateSchemePod case of the switch statement.

Finally, in the GetTaskLogs() function, the replaceAll() function is called, which replaces all instances of the hostname variable in the template string with the actual value of the hostname.

Here is the relevant code:

func initDefaultRegexes() templateRegexes {
	return templateRegexes{
		// ...
		MustCreateRegex("hostname"),
		// ...
	}
}

// ...

func (input Input) templateVarsForScheme(scheme TemplateScheme) TemplateVars {
	// ...
	case TemplateSchemePod:
		// ...
		vars = append(
			vars,
			TemplateVar{defaultRegexes.Hostname, input.HostName},
		)
		// ...
	}
	// ...
}

// ...

func (p TemplateLogPlugin) GetTaskLogs(input Input) (Output, error) {
	// ...
		Uri:           replaceAll(templateURI, templateVars),
	// ...
}

As for the discrepancy between the Flyte documentation and the actual implementation of the .hostname variable in the codebase, I wasn't able to find an answer within the repository. The same goes for any known issues or bugs related to the .hostname variable in the Flyte codebase.

If you have more specific information or examples that could help clarify the issue, it would be greatly appreciated.

Sources

• flyteplugins/go/tasks/pluginmachinery/tasklog/template.go

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[eapolinario]

good catch! Hostname is indeed not being handled right now, although it should be very easy to add. Before we add it, it's worth understanding how hostname is set in k8s, which is described here. We simply have to add hostname when instantiating taskLog.Input here.

[novahow]

I am interested in this issue.

[eapolinario]

@novahow , feel free to work on it. Tag me on the PR and I'll gladly review it.