trouble debugging daemon=TRUE

[cboettig]

I cannot get my site to load when I use daemon=TRUE and I'm not sure how to debug this one. If I omit that option, everything works just swanky.

If I include daemon=TRUE, the site still builds as before, I get the identical terminal output plus the additional line:

To stop the server, run servr::daemon_stop("35325888") or restart your R session

and of course I get my command prompt back, but as far as I can tell the server isn't running. Am I missing something or is daemon=TRUE not compatible with servr::jekyll? fwiw, my site source is here https://github.com/cboettig/2015.

[yihui]

I tested my own minimal Jekyll repo, and it worked. I tried to build your site, but it requires a few additional ruby gems that do not seem to be straightforward for me to install...

[cboettig]

okay, I can replicate the same problem with your minimal site; I guess a few more details are pertinent.

I'm running inside docker, though not clear why that should cause daemon=TRUE to break when everything else works. You should at least be able to reproduce what I get if you're up for running docker.

The gems are already installed on my image, so inside the repo for your minimal image you can run:

docker run  -v $(pwd):/data -p 8787:8787 -p 4000:4000 -d -u 0 cboettig/labnotebook supervisord

This sets up RStudio on port 8787 and an open port on 4000. It links the current working dir to /data on the container. (-u 0 and supervisord are things to launch rstudio, I should handle these as defaults instead).

I then go into RStudio via http://localhost:8787 (login = rstudio:rstudio). Switch to the /data working dir and everything is dapper when I run:

jeykll::serve(host='0.0.0.0', port=4000)

and your site builds and displays on localhost:4000 as expected. yay. (Note that docker now requires we use that 0.0.0.0 for the external port to work). Try

jeykll::serve(host='0.0.0.0', port=4000, daemon=TRUE)

and the site builds but doesn't display. Weird, eh? Same problem occurs if we try this just on a bash shell on the container (e.g. take RStudio out of the mix). Works fine unless we have daemon=TRUE.

[cboettig]

(minor edit to the above: I meant to write that when using daemon=TRUE the site does build as before, but doesn't display on the port, even though no errors appear. Just edited my comment above.)

[yihui]

If you are using docker, then I'm out of ideas. One thing you need to be careful is not to close the R session: daemon = TRUE relies on the R session; once the R session is closed, the daemonized server will be shut down. I do not quite see what the advantage is to use daemon = TRUE in your case.

[cboettig]

Yeah, I realize that; I'm not closing the R session.

My idea is that a user should be able to just open RStudio, render the site by running jekyll() at the RStudio prompt, and then still have a usable RStudio session where they can continue to edit & test the Rmd. This is the advantage of daemon=TRUE. Otherwise one needs to run the jekyll() function from somewhere other than the RStudio instance (e.g. from the terminal). Does that make any sense?

I do this with docker, since as you noted dependencies aren't always a trivial thing, particularly with ruby in the mix.

Guess I'll have to dig deeper into what you're doing with daemon=TRUE; but your source-code looks a bit over my head. Is it possible that daemon=TRUE isn't respecting the host=0.0.0.0 or the port somehow? It looks like the non-daemon approach is doing the same thing as jekyll serve (but maybe I'm wrong), but can't wrap my head around what the daemon approach is doing.

[yihui]

You can first check if the following minimal httpuv example works:

httpuv::startDaemonizedServer("0.0.0.0", 4000, app = list(
  call = function(req) list(
      status = 200L,
      headers = list(
        'Content-Type' = 'text/html'
      ),
      body = 'Hello World!'
  )
))

If it does not, I guess I won't be able to help.

[cboettig]

Ah, thanks for the minimal example, that's helpful. With that I can see that the problem only occurs when run from RStudio, and works just fine outside of RStudio. Since this shows my problem is just related to whatever httpuv is doing and not anything that servr is doing, so I will close this issue and follow up in a more appropriate place. Thanks again for your help debugging and sorry for the trouble!

[yihui]

No worries. I guess even if you report to the httpuv repo, Joe is unlikely to investigate it soon. The hep page of httpuv::startDaemonizedServer has stated that this function is experimental.