No validations in otlphttpexporter

[anupamdalmia10]

Describe the bug
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Validate method does not evaluate the given config for the exporter.

opentelemetry-collector/exporter/otlphttpexporter/config.go

Line 42 in 04baaae

// Validate checks if the exporter configuration is valid

Steps to reproduce
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When collector is started with no value for endpoint in config.yaml for otlphttpexporter, collector crashes saying either endpoint or traces_endpoint (for traces pipeline) must be defined. Similar behaviour is observed for metrics and logs pipeline.

What did you expect to see?
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These checks should be performed in Validate method, instead they are being done in factory.go in composeSignalURL method.

opentelemetry-collector/exporter/otlphttpexporter/factory.go

Line 60 in 04baaae

func composeSignalURL(oCfg *Config, signalOverrideURL string, signalName string) (string, error) {

What did you see instead?
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What version did you use?
Version: (e.g., v0.4.0, 1eb551b, etc)

What config did you use?
Config: (e.g. the yaml config file)

Environment
OS: (e.g., "Ubuntu 20.04")
Compiler(if manually compiled): (e.g., "go 14.2")

Additional context
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[jpkrohling]

Good catch. The OTLP exporter was done before we had Validate and never changed to use it. Would you be open to send a PR doing this work?

[anupamdalmia10]

Sure, will raise a PR soon!

[josephwoodward]

@anupamdalmia10 I'm happy to take this one off your hands if you find you don't have the time?

[anupamdalmia10]

@josephwoodward, sure
I'll share my findings though, at the point where this Validate gets called, we do not have information about in which pipeline will be using this exporter.
So the only validation I could think of adding in this validation function is to check if everything(endpoint, traces_endpoint, metrics_endpoint, logs_endpoint) is blank. Not sure if we want to add this here. As this will also be evaluated when pipelines are being built.

@jpkrohling , comments?

[jpkrohling]

We can still validate that there is at least one endpoint being specified.

[anupamdalmia10]

Raised PR for this: #4860