Error: Failed to load Cairo backend

[Aaron Mackey]

I'm sorry this isn't very reproducible, except that two different users have approached me about a shiny server-driven web app that works fine when I freshly start (or restart) shiny-server, but after a few days (or longer) they encounter this Cairo error, as if some piece of the backend machinery has quietly disappeared.  I'm stumped where to begin looking; is shiny-server doing anything special to hibernate between requests?

Thanks for any other clues,

-Aaron

[win...@rstudio.com]

Shiny does check to see if you have the Cairo package installed when renderPlot() is called. I have no idea why it should start throwing that error, though -- I haven't seen it before. Are they using Cairo directly in their apps, or are they just using renderPlot?

In 0.4.1, it was in renderPlot:

https://github.com/rstudio/shiny/blob/v/0/4/1/R/shinywrappers.R#L86

In 0.5.0, it was moved to a separate function plotPNG, which gets called from renderPlot:

https://github.com/rstudio/shiny/blob/master/R/imageutils.R#L33

-Winston

[Aaron Mackey]

I'm using CairoSVG to return SVG from a reactiveText() call (shiny 0.3.1, shiny-server 0.3.0); server.R calls library(Cairo) at startup.

Thanks,

-Aaron

--
Aaron J. Mackey, PhD
Assistant Professor
Center for Public Health Genomics
University of Virginia
ama...@virginia.edu
http://www.cphg.virginia.edu/mackey

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