asciidoctor: ERROR: <stdin>: line 123: Failed to generate image: 301 "Moved Permanently"

[anoff]

I am a bit unsure where to file this issue. But trying to figure out what is going wrong I found out that the error only occurs with asciidoctor-diagram 2.0.2

I have a docker container that I use to build asciidoctor with inline plantUML diagrams using Hugo. The setup is in place for 1.5 years now. Recently I started seeing errors in my pipeline and the rendered HTML page in the form of:

ERROR 2020/07/19 10:55:15 code/2019-10-autoscaling-ci-agent-with-azure-kubernetes.adoc: asciidoctor: ERROR: <stdin>: line 160: Failed to generate image: 301 "Moved Permanently"

I tried looking at the current documentation of asciidoctor/-diagram but couldn't find anything that seemed to have changed. So I started debugging various versions that have changed since it last worked.

Long story short; this error occurs if I use asciidoctor-diagram -v 2.0.2 but does not occur if I use v2.0.1, 2.0.0, 1.5.19.

Would appreciate any hints as to what might cause this behavior with the latest version.

[pepijnve]

No idea right away what might be causing the issue. Based on your investigation I think this is probably due to the particular version of PlantUML that's included in 2.0.2. Why that would cause a 301 return code is a mystery to me too.

Could you provide a sample document that reliably triggers the error for you?

[anoff]

Trying to get a minimal example I found out a few other things:

• only happens if I use hugo to compile, can't reproduce with a plain asciidoctor call
• seems to have something to do with :plantuml-server-url:
• I used to set it to http://plantuml.com/plantuml which returns a 301 Moved header if you curl it
• using http://www.plantuml.com/plantuml does not give an error and produces images correctly
• not really reproducable (maybe due to caches)

So without 💯 % understanding what is going on here, it seems that the latest version minds that there is a redirect on the render server, whereas older ones do not.

I got my solution (setting the server URL differently) for now :)

Thanks Pepijn

[pepijnve]

Ah, the server-url bit explains it. The code that's handling the http request does not support redirects yet. That should be easy enough to add.

[pepijnve]

@anoff 7b12aab adds built-in support for HTTP redirects. With that change http://plantuml.com/plantuml will work as well.

[anoff]

Oh wow, awesome :) Thanks alot!