fix: Remove thread pool executor logic until we get a better handle o…

…n what's causing thread pool hangs. refs graphiti-api#469

revert: "thread pool scope and mutex need to be global across all instances of Scope for it to be a global thread pool (graphiti-api#471)"
revert: "add thread pool and concurrency_max_threads configuration option (graphiti-api#470)"

This reverts commit 51fb51c.
This reverts commit 697d761.

lib/graphiti/configuration.rb

@@ -8,20 +8,6 @@ class Configuration
     #   Defaults to false OR if classes are cached (Rails-only)
     attr_accessor :concurrency
 
-    # This number must be considered in accordance with the database
-    # connection pool size configured in `database.yml`. The connection
-    # pool should be large enough to accommodate both the foreground
-    # threads (ie. web server or job worker threads) and background
-    # threads. For each process, Graphiti will create one global
-    # executor that uses this many threads to sideload resources
-    # asynchronously. Thus, the pool size should be at least
-    # `thread_count + concurrency_max_threads + 1`. For example, if your
-    # web server has a maximum of 3 threads, and
-    # `concurrency_max_threads` is set to 4, then your pool size should
-    # be at least 8.
-    # @return [Integer] Maximum number of threads to use when fetching sideloads concurrently
-    attr_accessor :concurrency_max_threads
-
     attr_accessor :respond_to
     attr_accessor :context_for_endpoint
     attr_accessor :links_on_demand
@@ -40,7 +26,6 @@ class Configuration
     def initialize
       @raise_on_missing_sideload = true
       @concurrency = false
-      @concurrency_max_threads = 4
       @respond_to = [:json, :jsonapi, :xml]
       @links_on_demand = false
       @pagination_links_on_demand = false

lib/graphiti/scope.rb

@@ -2,23 +2,6 @@ module Graphiti
   class Scope
     attr_accessor :object, :unpaginated_object
     attr_reader :pagination
-
-    @@thread_pool_executor_mutex = Mutex.new
-
-    def self.thread_pool_executor
-      return @thread_pool_executor if @thread_pool_executor
-
-      concurrency = Graphiti.config.concurrency_max_threads || 4
-      @@thread_pool_executor_mutex.synchronize do
-        @@thread_pool_executor ||= Concurrent::ThreadPoolExecutor.new(
-          min_threads: 0,
-          max_threads: concurrency,
-          max_queue: concurrency * 4,
-          fallback_policy: :caller_runs
-        )
-      end
-    end
-
     def initialize(object, resource, query, opts = {})
       @object = object
       @resource = resource
@@ -66,7 +49,7 @@ def resolve_sideloads(results)
           @resource.adapter.close if concurrent
         }
         if concurrent
-          promises << Concurrent::Promise.execute(executor: self.class.thread_pool_executor, &resolve_sideload)
+          promises << Concurrent::Promise.execute(&resolve_sideload)
         else
           resolve_sideload.call
         end

spec/configuration_spec.rb

@@ -150,21 +150,6 @@
     end
   end
 
-  describe "#concurrency_max_threads" do
-    include_context "with config", :concurrency_max_threads
-
-    it "defaults" do
-      expect(Graphiti.config.concurrency_max_threads).to eq(4)
-    end
-
-    it "is overridable" do
-      Graphiti.configure do |c|
-        c.concurrency_max_threads = 1
-      end
-      expect(Graphiti.config.concurrency_max_threads).to eq(1)
-    end
-  end
-
   describe "#raise_on_missing_sideload" do
     include_context "with config", :raise_on_missing_sideload