Merge pull request #585 from heroku/retry-failed-downloads

Retry failed downlads for untar

lib/language_pack/fetcher.rb

@@ -21,7 +21,9 @@ def fetch(path)
 
     def fetch_untar(path, files_to_extract = nil)
       curl = curl_command("#{@host_url.join(path)} -s -o")
-      run!("#{curl} - | tar zxf - #{files_to_extract}", error_class: FetchError)
+      run! "#{curl} - | tar zxf - #{files_to_extract}",
+        error_class: FetchError,
+        max_attempts: 3
     end
 
     def fetch_bunzip2(path, files_to_extract = nil)

lib/language_pack/shell_helpers.rb

@@ -41,14 +41,25 @@ def self.initialize_env(path)
       end
     end
 
+    # run a shell command (deferring to #run), and raise an error if it fails
+    # @param [String] command to be run
+    # @return [String] result of #run
+    # @option options [Error] :error_class Class of error to raise, defaults to Standard Error
+    # @option options [Integer] :max_attempts Number of times to attempt command before raising
     def run!(command, options = {})
-      result      = run(command, options)
-      error_class = options.delete(:error_class) || StandardError
-      unless $?.success?
-        message = "Command: '#{command}' failed unexpectedly:\n#{result}"
-        raise error_class, message
+      max_attempts = options[:max_attempts] || 1
+      error_class = options[:error_class] || StandardError
+      max_attempts.times do |attempt_number|
+        result = run(command, options)
+        if $?.success?
+          return result
+        end
+        if attempt_number == max_attempts - 1
+          raise error_class, "Command: '#{command}' failed unexpectedly:\n#{result}"
+        else
+          puts "Command: '#{command}' failed on attempt #{attempt_number + 1} of #{max_attempts}."
+        end
       end
-      return result
     end
 
     # doesn't do any special piping. stderr won't be redirected.

spec/helpers/shell_spec.rb

@@ -1,23 +1,44 @@
 require 'spec_helper'
 
+describe "ShellHelpers" do
+  module RecordPuts
+    attr_reader :puts_calls
+    def puts(*args)
+      @puts_calls ||= []
+      @puts_calls << args
+    end
+  end
 
-class FakeShell
-  include LanguagePack::ShellHelpers
-end
+  class FakeShell
+    include RecordPuts
+    include LanguagePack::ShellHelpers
+  end
 
+  describe "#command_options_to_string" do
+    it "formats ugly keys correctly" do
+      env      = {%Q{ un"matched } => "bad key"}
+      result   = FakeShell.new.command_options_to_string("bundle install", env:  env)
+      expected = %r{env \\ un\\\"matched\\ =bad\\ key bash -c bundle\\ install 2>&1}
+      expect(result.strip).to match(expected)
+    end
 
-describe "ShellHelpers" do
-  it "format ugly keys correctly" do
-    env      = {%Q{ un"matched } => "bad key"}
-    result   = FakeShell.new.command_options_to_string("bundle install", env:  env)
-    expected = %r{env \\ un\\\"matched\\ =bad\\ key bash -c bundle\\ install 2>&1}
-    expect(result.strip).to match(expected)
+    it "formats ugly values correctly" do
+      env      = {"BAD VALUE"      => %Q{ )(*&^%$#'$'\n''@!~\'\ }}
+      result   = FakeShell.new.command_options_to_string("bundle install", env:  env)
+      expected = %r{env BAD\\ VALUE=\\ \\\)\\\(\\\*\\&\\\^\\%\\\$\\#\\'\\\$\\''\n'\\'\\'@\\!\\~\\'\\  bash -c bundle\\ install 2>&1}
+      expect(result.strip).to match(expected)
+    end
   end
 
-  it "formats ugly values correctly" do
-    env      = {"BAD VALUE"      => %Q{ )(*&^%$#'$'\n''@!~\'\ }}
-    result   = FakeShell.new.command_options_to_string("bundle install", env:  env)
-    expected = %r{env BAD\\ VALUE=\\ \\\)\\\(\\\*\\&\\\^\\%\\\$\\#\\'\\\$\\''\n'\\'\\'@\\!\\~\\'\\  bash -c bundle\\ install 2>&1}
-    expect(result.strip).to match(expected)
+  describe "#run!" do
+    it "retries failed commands when passed max_attempts: > 1" do
+      sh = FakeShell.new
+      expect { sh.run!("false", max_attempts: 3) }.to raise_error(StandardError)
+
+      expect(sh.puts_calls).to eq([
+        ["       Command: 'false' failed on attempt 1 of 3."],
+        ["       Command: 'false' failed on attempt 2 of 3."],
+      ])
+    end
   end
 end