Fetch AWS config from ec2metadata if on an ec2 instance #5
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Fetch AWS config from ec2metadata if on an ec2 instance
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@doodlesbykumbi Any chance you'd have some time to look over this PR? |
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@jepperson2 Any idea what happens if there is no IMO, this provider should support as many configurations as possible. At the moment the envvar |
Updated provisioner to fall back to region from ec2metadata
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@doodlesbykumbi If there is no ec2metadata it silently fails and keeps going. No effect if not running on an ec2 instance With the latest commit, this now supports the expected precedence relationship: envvars -> shared config -> ec2metadata region. |
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@doodlesbykumbi Any chance you could review this again? Would love to see this merged and reflected in a release I could use. |
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Is there anything else this PR needs before it can be merged? |
main.go
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| // If the region could not be found in an environment variable or a shared config file, | ||
| // create metaSession to fetch the ec2 instance region and pass to the regular Session. | ||
| if *sess.Config.Region == "" { | ||
| metaSession, _ := session.NewSession() |
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Throwing away the error returned here and below (by Region) seems like it could make problems harder to diagnose. Is there any reason not to call printAndExit if error is non-nil?
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Failing silently here causes a more helpful error to be thrown later.
If I printAndExit here or after fetching the region, it throws: RequestError: send request failed caused by: Get http://169.254.169.254/latest/meta-data/placement/availability-zone: dial tcp 169.254.169.254:80: connect: host is down as opposed to MissingRegion: could not find region configuration when I don't catch this error.
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You are correct that it would be harder to diagnose a problem in the case that I am on an ec2 instance but this lookup fails for some reason.
If I'm not on an ec2 instance, however, and my config isn't set anywhere, failing silently here provides the MissingRegion:... error.
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As an alternative, looks like you can use EC2Metadata.Available to determine whether you're on an EC2 instance. So, you could do this, instead:
if *sess.Config.Region == "" {
metaSession, err := session.NewSession()
if err != nil {
printAndExit(err)
}
metaClient := ec2metadata.New(metaSession)
if metaClient.Available() {
if region, err := metaClient.Region(); err == nil {
sess.Config.Region = aws.String(region)
} else {
printAndExit(err)
}
}
}
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That's a great suggestion! Thanks, @apotterri! My latest commit reflects these changes
Don't ignore errors
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Looks great! Thanks very much for doing this. |
Not the prettiest solution, but there doesn't appear to be native support for fetching the region from the ec2 instance it's running on.
Relevant feature request in aws-go-sdk: aws/aws-sdk-go#1103