Slow documentation generation

Describe the bug I have noticed that the generation is really slow. Then I have investigated thru VisualVM, and noticed that it is expending most of the time with HTTP requests. Why is that? What is it downloading?

Expected behaviour To be much faster. Do not download anything, since I’m generating a local documentation from local source code.

Screenshots

To Reproduce

git clone https://github.com/korlibs/korge.git
./gradlew dokkaHtmlMultiModule

Dokka configuration

Default configuration.

Installation

• Operating system: macOS
• Dokka version: 1.7.10

[soywiz]

In my case offline mode was a solution: https://github.com/korlibs/korge/blob/d296abdc2657cd3680efdaa573a3ae38eedb8ea3/build.gradle.kts#L165-L167

But indeed I have the feeling that it is downloading too many things, because it expends several minutes downloading, and now sure why.

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BTW also a performance thing (I can open another ticket):

The other thing I noticed is that in Chrome after a few navigations after some time, the performance starts degrading while navigating thru the documentation: https://dokka.korge.org/ It seems that the navigation is setting the html content of the toc everytime the page loads. It seems that Chrome is degenerating not sure why, because firefox and safari seems to handle it reasonably well.

Maybe at some point dokka could use the History API: https://developer.mozilla.org/en-US/docs/Web/API/History_API , when clicking internal links do not fully load the new page but only the content, so the Table of Contents is kept and only updated. In my case the TOC is really huge, so avoiding setting it everytime would be much better in terms of battery.

Alternatively the TOC could be constructed dynamically (it can load the toc html as it is, cache them in the local storage based on the contents hash, and put nodes on demand when opening sections). By profiling I noticed that the problem was when setting the html of the content, and then the browser re-rendering everything (tried to disabled setting the html of the table of contents and fixed the performance issue). Also chrome pseudo-hangs while closing the tab with the korlibs dokka documentation.

https://user-images.githubusercontent.com/570848/194839535-8e8e62ac-94f8-4efc-9682-2d157a832308.mov

[IgnatBeresnev]

The initial problem with slow network calls seems to have been resolved. I outlined this problem and possible solutions in new documentation, so it should hopefully clear things up.

If you set offlineMode to true, but still want Dokka to generate external links to types from the standard library or JDK (or some other dependency), you can try caching package-lists locally and provide them as file URLs:

import org.jetbrains.dokka.gradle.DokkaTask

tasks.withType<DokkaTask>().configureEach {
    dokkaSourceSets.configureEach {
        externalDocumentationLink {
            packageListUrl.set(
                rootProject.projectDir.resolve("serialization.package.list").toURL()
            )
        }
    }
}

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As for the rest of the slowness, I think it’s best to submit individual issues for specific problems. We already have #2699 and #2741 to begin with. So I’ll close this issue for the lack of Definition of Done, but do let us know if you encounter anything else!