Auto merge of #5278 - bundler:seg-worker-thread-creation-failure, r=indirect

[Worker] Fail gracefully when creating threads fails

3 files changed, 50 insertions, 5 deletions

diff --git a/lib/bundler/errors.rb b/lib/bundler/errors.rb
index be72a9ee47..ecd9260ea0 100644
--- a/lib/bundler/errors.rb
+++ b/lib/bundler/errors.rb
@@ -53,6 +53,7 @@ module Bundler
   class GemfileLockNotFound < BundlerError; status_code(22); end
   class PluginError < BundlerError; status_code(29); end
   class SudoNotPermittedError < BundlerError; status_code(30); end
+  class ThreadCreationError < BundlerError; status_code(33); end
   class GemfileEvalError < GemfileError; end
   class MarshalError < StandardError; end
 
diff --git a/lib/bundler/worker.rb b/lib/bundler/worker.rb
index 3ef5addcee..62d93e285e 100644
--- a/lib/bundler/worker.rb
+++ b/lib/bundler/worker.rb
@@ -25,11 +25,8 @@ module Bundler
       @request_queue = Queue.new
       @response_queue = Queue.new
       @func = func
-      @threads = Array.new(size) do |i|
-        Thread.start { process_queue(i) }.tap do |thread|
-          thread.name = "#{name} Worker ##{i}" if thread.respond_to?(:name=)
-        end
-      end
+      @size = size
+      @threads = nil
       trap("INT") { abort_threads }
     end
 
@@ -37,6 +34,7 @@ module Bundler
     #
     # @param obj [String] mostly it is name of spec that should be downloaded
     def enq(obj)
+      create_threads unless @threads
       @request_queue.enq obj
     end
 
@@ -70,13 +68,37 @@ module Bundler
     # Stop the worker threads by sending a poison object down the request queue
     # so as worker threads after retrieving it, shut themselves down
     def stop_threads
+      return unless @threads
       @threads.each { @request_queue.enq POISON }
       @threads.each(&:join)
+      @threads = nil
     end
 
     def abort_threads
+      return unless @threads
       @threads.each(&:exit)
       exit 1
     end
+
+    def create_threads
+      creation_errors = []
+
+      @threads = Array.new(@size) do |i|
+        begin
+          Thread.start { process_queue(i) }.tap do |thread|
+            thread.name = "#{name} Worker ##{i}" if thread.respond_to?(:name=)
+          end
+        rescue ThreadError => e
+          creation_errors << e
+          nil
+        end
+      end.compact
+
+      return if creation_errors.empty?
+
+      message = "Failed to create threads for the #{name} worker: #{creation_errors.map(&:to_s).uniq.join(", ")}"
+      raise ThreadCreationError, message if @threads.empty?
+      Bundler.ui.info message
+    end
   end
 end
diff --git a/spec/bundler/worker_spec.rb b/spec/bundler/worker_spec.rb
new file mode 100644
index 0000000000..786778b08f
--- /dev/null
+++ b/spec/bundler/worker_spec.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+require "spec_helper"
+require "bundler/worker"
+
+describe Bundler::Worker do
+  let(:size) { 5 }
+  let(:name) { "Spec Worker" }
+  let(:function) { proc {|object, worker_number| [object, worker_number] } }
+  subject { described_class.new(size, name, function) }
+
+  after { subject.stop }
+
+  describe "#initialize" do
+    context "when Thread.start raises ThreadError" do
+      it "raises when no threads can be created" do
+        allow(Thread).to receive(:start).and_raise(ThreadError, "error creating thread")
+
+        expect { subject.enq "a" }.to raise_error(Bundler::ThreadCreationError, "Failed to create threads for the Spec Worker worker: error creating thread")
+      end
+    end
+  end
+end