I’m trying to add ex_cldr_collation as a dependency to a standard phoenix application. I’m having an issue with the docker build.

I understood that the libicu-dev package is required for building, which got me one step further (at first compilation failed, but now the application at least compiles).

When the image starts the phoenix application, I get this error:

  crasher:
    initial call: application_master:init/4
    pid: <0.2044.0>
    registered_name: []
    exception exit: {{shutdown,
                      {failed_to_start_child,kernel_safe_sup,
                       {on_load_function_failed,'Elixir.Cldr.Collation',
                        {{badmatch,
                          {error,
                           {load_failed,
                            "Failed to load NIF library: '/app/lib/ex_cldr_collation-0.7.0/priv/ucol.so: undefined symbol: ucol_strcollIter_67'"}}},
                         [{'Elixir.Cldr.Collation',init,0,
                           [{file,"lib/cldr_collation.ex"},{line,20}]},
                          {init,'-run_on_load_handlers/2-fun-0-',1,[]}]}}}},
                     {kernel,start,[normal,[]]}}
      in function  application_master:init/4 (application_master.erl, line 142)
  ...

As far as I understand, the runner image also has to have an icu dependency although that’s not mentioned explicitly in the documentation of ex_cldr_collation. But I’m failing to understand which packages exactly would provide these undefined symbols (ucol_strcollIter_67). I’ve tried adding libicu-dev, just like in the builder image, but that didn’t work. The package libicu67 also didn’t resolve the problem.

There was some recent activity on the issue tracker of ex_cldr_collation, but that seems to be more related to ubuntu and alpine images. Moreover, there is no mention of packages required at runtime in the docs, only a mention of what’s required to build, which confuses me a bit.

Suggestions appreciated!