a new exporter without a location returns an error about setting default location

[odeke-em]

Given code that used to work in the past

        projectID := "odeke-sandbox"
        sde, err := stackdriver.NewExporter(stackdriver.Options{
                ProjectID: projectID,
        })
        if err != nil {
                log.Fatalf("Failed to start Stackdriver OpenCensus exporter: %v", err)
        }
        defer sde.Flush()
        trace.RegisterExporter(sde)

I get back an unexpected error

$ GOOGLE_APPLICATION_CREDENTIALS=odeke-sandbox.json go run main.go 
2019/06/24 17:40:06 Setting Stackdriver default location failed: Get \
http://169.254.169.254/computeMetadata/v1/instance/zone: dial tcp 169.254.169.254:80: \
i/o timeout

I believe we should only be trying to find a default location if we are on GCE and in the past we've been able to run this exporter on local computers or even on other clouds.

[DazWilkin]

I just noticed this too.

I am using the Agent to export to Stackdriver and, when I saw the error, reconfigured my client to use the Stackdriver exporter directly. Since the agent uses the same code, it's unsurprising that both fail.

Curiously, I do have some measurements recorded to Stackdriver so, somehow -- and I don't understand how -- I had this working albeit briefly.

[DazWilkin]

What's curious is that it's looking for /instance/zone in the metadata.

When I deployed the agent to a GCE VM, it incorrectly (because it's using this metadata link) binds to the VM's zone:

2019/06/26 16:47:06 Setting Stackdriver default location to "us-west1-c"

So, it's both ignoring my specified project value and it's choosing to reference ./instance/zone when I assume it should be looking for:

curl \
--header "Metadata-Flavor: Google" \
http://169.254.169.254/computeMetadata/v1/project/project-id

See comment below: the error is confusing but accurate. It is setting the default location to the correct zone. I just don't know why it's doing this. I need to determine whether there's another reason why I'm not getting measurements (consistently) to Stackdriver.

[DazWilkin]

Hmmm:
https://github.com/census-ecosystem/opencensus-go-exporter-stackdriver/blame/master/stackdriver.go#L293

Adding Location to the Stackdriver Exporter avoids the error:

sd, err := stackdriver.NewExporter(stackdriver.Options{
		ProjectID:    "...",
		Location:     "us-west1-c",
	})

But:

1. Why is the Location necessary?
2. The OpenCensus Agent does not currently provide a mechanism to define Location

[odeke-em]

Kindly paging @fabxc @rghetia from #84

[rghetia]

It is misleading to print that message when it is not running on GCE. @odeke-em , @DazWilkin it should still continue to export the metrics/traces without location. Does it not?

Agent does not inject resource labels but it simply forwards those it receives from the client.

[DazWilkin]

I think so.

Confirming now.

I think this was a red-herring error for another issue that my client has.

[DazWilkin]

Yes, measurements are being reported by Stackdriver.