Adds the possibility to vary the template of tablet debug urls.

[mpawliszyn]

Sometimes the way you get to a tablet from a webpage is different from how a machine does it from within the same part of the network fabric.

[michael-berlin]

Change looks good to me after my comment is addressed.

Do you actually need to customize the whole path? A prefix would not be good enough?

[michael-berlin]

This is not good because you would crash the vtgate at runtime.

Instead, you could make the template a global variable and set it during init().

Also, please use Exitf instead of Fatalf: https://godoc.org/github.com/golang/glog#Exitf

[mpawliszyn]

Yeah thanks for the tip. It's been fixed I think. I'm clearly still green behind the ears.

[mpawliszyn]

@michael-berlin I think all that I'm customizing is the prefix, or that the prefix is all that is included in the link. If you have any recommended improvements with that context then I'd happily do them.

[demmer]

We (at Slack) have a similar issue and have never put the time into addressing it so thanks for this feature.

However I'd like to be able to format an URL based on just the hostname without the port. From my brief understanding of the code it seems like I could do this with "http://{{.GetHostNameLevel 0}}.some.domain" -- if so that would be perfect, but if not then it'd be great to enable this as part of this change.

[mpawliszyn]

GetHostNameLevel is there to help divide up the hostname into it's components. If you want the whole thing I think http://{{.Tablet.Hostname}} should work.

[mpawliszyn]

I actually just tested this out and it indeed works.

[michael-berlin]

I feel like this is a non-trivial feature. How about leaving a pointer in this help text for interested users?

e.g. add: "See the Go code for getTabletDebugURL() how to customize this."

And then you can document the feature and tricks like {{.Tablet.Hostname}} there.

[michael-berlin]

Having a full fledged template here seems to be preferred over adding a simple prefix. That works for me.

Can you please address my comments? After that I can merge it. Thank you :)

[michael-berlin]

This is currently unused. I assume you want to use it in your custom templates?

Please document how to use this and why it must be kept in the code.

Also, please add a test for this method. This will better demonstrate the intended use and also make sure that this functionality won't be broken.

[mpawliszyn]

Ok done.

[michael-berlin]

I feel like this is a non-trivial feature. How about leaving a pointer in this help text for interested users?

e.g. add: "See the Go code for getTabletDebugURL() how to customize this."

And then you can document the feature and tricks like {{.Tablet.Hostname}} there.

[michael-berlin]

nit: missing period

See: https://github.com/golang/go/wiki/CodeReviewComments#comment-sentences

[michael-berlin]

nit: missing period

See: https://github.com/golang/go/wiki/CodeReviewComments#comment-sentences

[michael-berlin]

Can you please move this to the first group of imports?

[mpawliszyn]

@michael-berlin I think I've addressed all of your comments now.

[michael-berlin]

Thank you for addressing all the comments and the test :) The documentation of the feature looks very good now :)

I've rebased the code and fixed some minor nitpicks from my side (see the additional commits).

I'll merge this as soon as tests have passed.