#gocd

Hi all. I'm trying to write a Go CD SCM plugin; currently I exported a simple plugin, and it appears in the Admin > Plugins section. However it doesn't appear in the list when I try to choose a source for a material.

I should say, I'm using Kotlin instead of Java, not sure if that would be a problem.

I'm handling the "scm-configuration" request and sending back basically the same stuff I found in the SCM example, that I found through the Go CD docs.

Still, it doesn't appear in that list. Any ideas?

Anyone here?

butts_butts: Did you see any error in the plugins page? Any logs in the log dir?

arvindsv: there were no errors in the plugins page, no. I'll check the logs now.

arvindsv: so there are a bunch of ERROR logs, related to plugins, with messages like "Failed to fetch Plugin Settings metadata for plugin : cd.go.authentication.passwordfile java.lang.RuntimeException: Interaction with plugin with id 'cd.go.authentication.passwordfile' implementing 'authorization' extension failed while requesting for 'go.plugin-settings.get-configuration'. Reason: [The plugin sent a response that could not be understood by Go. Plugin

But none that mention my plugin.

Ok. Where did you check that it does not show up? I wonder if this bug could be affecting you too: https://github.com/gocd/gocd/issues/2947

Maybe check while editing a pipeline to add a material?

Ah. Actually I was always looking in the list via editing an existing pipeline. I just tried adding a new pipeline to see if it worked that way, but it also doesn't show up there.

So, both places.

Is the code available somewhere? Or is it going to be private?

Also, maybe starting from another SCM plugin's code might help. Like this one: https://github.com/gocd/go-plugins/blob/master/...

Private I'm afraid.

Yeah, this is the example I've been working from.

I was wondering, does the plugin need to have correct responses for *all* of the messages listed on this page: https://developer.gocd.org/16.3.0/writing_go_pl...

Or if I only support, for example, the "scm-configuration" request with a correct response, is that enough for it to appear as a material in Go?

And more generally, how can I debug the plugin, is there a way I can make print statements?

Hmm. Usually, the reason it won't show is because it is not recognized as an SCM plugin. Do you respond to this: https://github.com/gocd/go-plugins/blob/2c0cc22...

With the argument: "scm"?

Yes, once the plugin is loaded and works, you can use log statements wherever you want.

The problem, in this case, is that it is not loaded/recognized as an SCM plugin.

I think.

Yup, I respond to `pluginIdentifier`

This is part of the infra, which you'll have no control over - from a plugin perspective.

You respond with: "scm", ["1.0"]?

Yup.

It's Kotlin, but:

override fun pluginIdentifier(): GoPluginIdentifier { return GoPluginIdentifier(EXTENSION_NAME, listOf("1.0")) }

Where EXTENSION_NAME is:

val EXTENSION_NAME = "scm";

Hmm.

Ok.

In your equivalent of this line: https://github.com/gocd/go-plugins/blob/2c0cc22..., maybe put in a throw or print out something to a file.

So that we can see if it's coming there.

You could also debug it, in IntelliJ, if you attach to the server process.

To your earlier question, usually, you need to respond to all the messages there.

But, if you don't, I'd expect something to fail/throw.

So, I'm suspecting it is not loaded.

It's possible that the JAR is not exported properly from your build and it's not finding it.

I suppose you have the annotation: https://github.com/gocd/go-plugins/blob/2c0cc22...

That's what it uses to figure out which class to send the message to (and create an instance of).

Yup, I have the @Extension annotation.

I think it is getting loaded by Go, because I see it in Admin > Plugins.

Also, if I don't implement `pluginIdentifier`, an error shows up in the Admin > Plugins section for my plugin.

I'll try throwing in the handle function.

- I should mention, I'm primarily a c++ programmer; this is the first time I've dabbled in the Java world

Quite possible I'm building the jar incorrectly or something. In IntelliJ IDEA, I'm using build artifact.

:) That's ok. You're doing well so far. This is not your fault. GoCD should be telling you what's going on.

:)

Yeah, throw in the handle function and let's see.

When I setup the build artifact stuff in IDEA, it wouldn't let me choose my the entry point file, unless that file had a main function inside it, so I added an empty one. Not sure if that can cause any issues?

No, that should be ok.

Ok, throwing an IllegalArugumentException in that function; loading now.

Interaction with plugin with id 'TestMaterial' implementing 'scm' extension failed while requesting for 'scm-configuration'. Reason: [null]

Ok, I guess that's something.

It's calling the function.

Ok, that should be happening from around here: https://github.com/gocd/gocd/blob/be1ff52e07d80...

Do you now see a message in the logs? "Failed to fetch SCM metadata for plugin ..."

In the server los.

logs*

Will check

Yup!

Ok.

So it's definitely getting into there.

Ok, good. Can you check the logs to see if you had any messages earlier about this?

Yup

Well, if you mean before I put in the exception? This definitely wasn't in the logs then

I searched for some keywords that didn't appear then, that are there now

I see. And, were you handling the 'scm-view' call too, earlier?

The displayValue in the response to 'scm-view' is what is supposed to show up in the dropdown.

I guess you have. Otherwise, you'd see the message: "Failed to fetch SCM metadata for plugin"

I was handling "scm-view" earlier, like a few days ago. Then I removed everything except for "scm-configuration" to try and nail down what was failing.

So currently no, I'm not handling scm-view. I assumed that scm-view was the Angular view that would show up if you added the material to a pipeline; the UI that you would enter the repository location, etc?

Right. But, the 'displayValue' in that response to scm-view is important. It's needed for the dropdown.

Ah, ok

I'll re-activate that then

You can also use the logger like this: https://github.com/gocd/go-plugins/blob/2c0cc22...

And it'll log to a plugin-specific log file.

Maybe you can log the requests and your responses.

I usually just do something like this: https://github.com/gocd-contrib/gocd_auth_plugi...

That way, I have a running log of what is going on.

Ah, nice. I'll do that next, maybe I'm returning some garbage JSON.

I don't think so. If the JSON was invalid, you'd still see a message in the logs.

I'm now curious what's going on.

Tell me when you find out. :)

Will do

No doubt it's something small that I've forgotten!

I tried to throw inside the function I'm calling for scm-configuration and scm-view (instead of inside handle() )

And now I see no errors

So it seems they're not called, but the handle() function is called.

Ok. So, you're not dispatching to your functions inside the plugin?

I wonder if this is a problem with the Kotlin when(..) { .. } syntax that I'm using to replace the if-else chain in the Java examples

I am doing, but using this when syntax.

Kotlin does compile down to Java.

So, I'd be surprised if it fails there.

But perhaps I'm using the syntax incorrectly

Will check with a simple if

Possibly.

You could also add the default condition (I don't know Kotlin) to see if it's falling through.

As I said this is all new to me, so I (perhaps foolishly!) decided to try Kotlin instead of Java.

when ... else.

:)

Hey, what's fun about sticking to what we know.

I'm sure you can make it work with Kotlin.

Hope so! Kotlin seems like quite a nice language, lots of syntactic sugar.

Ok, some progress

I'm now getting "Failed to fetch Plugin Settings metadata for plugin"

I'm handling only scm-view and scm-configuration, and from looking a bit at the Go source, I guess this error is because I'm not handling one of the other messages.

Ok, so the problem was

In my `handle` function, I was returning a response with the not-found code (404), if one of the messages wasn't handled.

I did that because Kotlin wouldn't let me return `null`, and the fix for this is adding ? to the return type for the `handle` function, so that I can return null.

Now, returning null for unimplemented requests, I get errors in the log.

Now I'll test to see if the Kotlin `when` syntax will work.

Yup, when syntax works.

Now I'll add back the implementations of the other requests... and hopefully....

Ok good!

This "Plugin Settings metadata" error, is that about the response to validate-scm-configuration?

What else does it say?

It's about either the config or the view messages.

Not about validate.

"2017-06-26 17:18:31,543 ERROR [Thread-75] PluginSettingsMetadataLoader:77 - Failed to fetch Plugin Settings metadata for plugin : TestPlugin java.lang.RuntimeException: Interaction with plugin with id 'TestPlugin' implementing 'scm' extension failed while requesting for 'go.plugin-settings.get-configuration'. Reason: [The plugin sent a null response]"

It's saying I sent a null response to one of the requests, view or config?

Are you handling the go.plugin-settings.get-configuration message?

That's what it is sending.

And, it's saying you returned false.

null, sorry.

I think I know what's going on.

It's documented wrong.

I thought we moved it out of that place, but it's not.

I'll look at it in a few mins.

And fix it.

I'll need to go see when it changed.

Oh? The request name or what?

The problem is that there are two pieces of configuration.

One is the response to: go.plugin-settings.get-configuration

That is what shows up in the plugin settings.

A little gear next to the name of the plugin in Admin -> Plugins.

Second is for scm plugin config itself: https://developer.gocd.org/current/writing_go_p...

This: https://developer.gocd.org/current/writing_go_p...

Can you handle this and return empty ({}), please?