Docker-alpine: Alpine 3.8 causes error in AWS-SDK (cannot load such file -- webrick/httputil)

[cameck]

Backtrace:

Traceback (most recent call last):
    34: from ./bin/init:3:in `<main>'
    33: from /usr/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in `require'
    32: from /usr/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in `require'
    31: from /usr/app/lib/poller.rb:4:in `<top (required)>'
    30: from /usr/app/lib/poller.rb:4:in `new'
    29: from /usr/lib/ruby/gems/2.5.0/gems/aws-sdk-resources-2.6.18/lib/aws-sdk-resources/services/sqs/queue_poller.rb:210:in `initialize'
    28: from /usr/lib/ruby/gems/2.5.0/gems/aws-sdk-core-2.6.18/lib/seahorse/client/base.rb:101:in `new'
    27: from /usr/lib/ruby/gems/2.5.0/gems/aws-sdk-core-2.6.18/lib/seahorse/client/base.rb:213:in `build_plugins'
    26: from /usr/lib/ruby/gems/2.5.0/gems/aws-sdk-core-2.6.18/lib/seahorse/client/base.rb:170:in `plugins'
    25: from /usr/lib/ruby/gems/2.5.0/gems/aws-sdk-core-2.6.18/lib/seahorse/client/base.rb:170:in `Array'
    24: from /usr/lib/ruby/gems/2.5.0/gems/aws-sdk-core-2.6.18/lib/seahorse/client/base.rb:170:in `to_a'
    23: from /usr/lib/ruby/gems/2.5.0/gems/aws-sdk-core-2.6.18/lib/seahorse/client/plugin_list.rb:58:in `each'
    22: from /usr/lib/ruby/gems/2.5.0/gems/aws-sdk-core-2.6.18/lib/seahorse/client/plugin_list.rb:72:in `each_plugin'
    21: from /usr/lib/ruby/gems/2.5.0/gems/aws-sdk-core-2.6.18/lib/seahorse/client/plugin_list.rb:72:in `synchronize'
    20: from /usr/lib/ruby/gems/2.5.0/gems/aws-sdk-core-2.6.18/lib/seahorse/client/plugin_list.rb:73:in `block in each_plugin'
    19: from /usr/lib/ruby/2.5.0/set.rb:338:in `each'
    18: from /usr/lib/ruby/2.5.0/set.rb:338:in `each_key'
    17: from /usr/lib/ruby/gems/2.5.0/gems/aws-sdk-core-2.6.18/lib/seahorse/client/plugin_list.rb:59:in `block in each'
    16: from /usr/lib/ruby/gems/2.5.0/gems/aws-sdk-core-2.6.18/lib/seahorse/client/plugin_list.rb:103:in `plugin'
    15: from /usr/lib/ruby/gems/2.5.0/gems/aws-sdk-core-2.6.18/lib/seahorse/client/plugin_list.rb:133:in `require_plugin'
    14: from /usr/lib/ruby/gems/2.5.0/gems/aws-sdk-core-2.6.18/lib/seahorse/client/plugin_list.rb:133:in `each'
    13: from /usr/lib/ruby/gems/2.5.0/gems/aws-sdk-core-2.6.18/lib/seahorse/client/plugin_list.rb:134:in `block in require_plugin'
    12: from /usr/lib/ruby/gems/2.5.0/gems/aws-sdk-core-2.6.18/lib/seahorse/client/plugin_list.rb:134:in `const_get'
    11: from /usr/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in `require'
    10: from /usr/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in `require'
     9: from /usr/lib/ruby/gems/2.5.0/gems/aws-sdk-core-2.6.18/lib/aws-sdk-core/plugins/request_signer.rb:1:in `<top (required)>'
     8: from /usr/lib/ruby/gems/2.5.0/gems/aws-sdk-core-2.6.18/lib/aws-sdk-core/plugins/request_signer.rb:2:in `<module:Aws>'
     7: from /usr/lib/ruby/gems/2.5.0/gems/aws-sdk-core-2.6.18/lib/aws-sdk-core/plugins/request_signer.rb:26:in `<module:Plugins>'
     6: from /usr/lib/ruby/gems/2.5.0/gems/aws-sdk-core-2.6.18/lib/aws-sdk-core/plugins/request_signer.rb:61:in `<class:RequestSigner>'
     5: from /usr/lib/ruby/gems/2.5.0/gems/aws-sdk-core-2.6.18/lib/aws-sdk-core/plugins/request_signer.rb:67:in `<class:Handler>'
     4: from /usr/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in `require'
     3: from /usr/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in `require'
     2: from /usr/lib/ruby/gems/2.5.0/gems/aws-sdk-core-2.6.18/lib/aws-sdk-core/signers/s3.rb:4:in `<top (required)>'
     1: from /usr/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in `require'
/usr/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in `require': cannot load such file -- webrick/httputils (LoadError)

The code that sets the app into this failure is:

Aws::SQS::QueuePoller.new(QUEUE_URL)

Dockerfile:

FROM alpine:3.8

ENV BUILD_PACKAGES curl-dev ruby-dev build-base

# Update and install base packages
RUN apk update && apk upgrade && apk add $BUILD_PACKAGES

# Install ruby and ruby-bundler
RUN apk add ruby ruby-io-console ruby-bundler

RUN mkdir /usr/app
WORKDIR /usr/app

COPY Gemfile /usr/app/
COPY Gemfile.lock /usr/app/
RUN bundle install

COPY . /usr/app

# Clean APK cache
RUN rm -rf /var/cache/apk/*

ENTRYPOINT ["./bin/init"]

Gemfile:

source 'https://rubygems.org'

gem 'aws-sdk', '~> 2'
gem 'json'

Specifying FROM alpine:3.7 fixes the issue.

[btalbot]

Looks like Alpine linux 3.8 (using ruby 2.5) made the webrick gem an optional install. The gem is listed as a default gem which is supposed to be always available and cannot be uninstalled (https://stdgems.org/2.5.1/) but Alpine seems to have thought it should be optional.

apk add ruby-webrick

fixes the issue for me on alpine 3.8