fix(message-dequeuer): ability to disable batching

app/lib/message_dequeuer/initial_processor.rb

@@ -17,7 +17,7 @@ module MessageDequeuer
             # Process the original message and then all of those
             # found for batching.
             process_message(@queued_message)
-            @other_messages.each { |message| process_message(message) }
+            @other_messages&.each { |message| process_message(message) }
           end
         ensure
           @state.finished
@@ -45,6 +45,8 @@ module MessageDequeuer
     end
 
     def find_other_messages_for_batch
+      return unless Postal::Config.postal.batch_queued_messages?
+
       @other_messages = @queued_message.batchable_messages(100)
       log "found #{@other_messages.size} associated messages to process at the same time", batch_key: @queued_message.batch_key
     rescue StandardError

doc/config/environment-variables.md

@@ -19,6 +19,7 @@ This document contains all the environment variables which are available for thi
 | `POSTAL_SMTP_RELAYS` | Array of strings | An array of SMTP relays in the format of smtp://host:port | [] |
 | `POSTAL_TRUSTED_PROXIES` | Array of strings | An array of IP addresses to trust for proxying requests to Postal (in addition to localhost addresses) | [] |
 | `POSTAL_QUEUED_MESSAGE_LOCK_STALE_DAYS` | Integer | The number of days after which to consider a lock as stale. Messages with stale locks will be removed and not retried. | 1 |
+| `POSTAL_BATCH_QUEUED_MESSAGES` | Boolean | When enabled queued messages will be de-queued in batches based on their destination | true |
 | `WEB_SERVER_DEFAULT_PORT` | Integer | The default port the web server should listen on unless overriden by the PORT environment variable | 5000 |
 | `WEB_SERVER_DEFAULT_BIND_ADDRESS` | String | The default bind address the web server should listen on unless overriden by the BIND_ADDRESS environment variable | 127.0.0.1 |
 | `WEB_SERVER_MAX_THREADS` | Integer | The maximum number of threads which can be used by the web server | 5 |

doc/config/yaml.yml

@@ -31,6 +31,8 @@ postal:
   trusted_proxies: []
   # The number of days after which to consider a lock as stale. Messages with stale locks will be removed and not retried.
   queued_message_lock_stale_days: 1
+  # When enabled queued messages will be de-queued in batches based on their destination
+  batch_queued_messages: true
 
 web_server:
   # The default port the web server should listen on unless overriden by the PORT environment variable

lib/postal/config_schema.rb

@@ -96,6 +96,11 @@ module Postal
         description "The number of days after which to consider a lock as stale. Messages with stale locks will be removed and not retried."
         default 1
       end
+
+      boolean :batch_queued_messages do
+        description "When enabled queued messages will be de-queued in batches based on their destination"
+        default true
+      end
     end
 
     group :web_server do

spec/lib/message_dequeuer/initial_message_processor_spec.rb

@@ -62,6 +62,7 @@ module MessageDequeuer
         @queued_message3 = create(:queued_message, message: @message3)
       end
 
+      context "when postal.batch_queued_messages is enabled" do
         it "calls the single message process for the initial message and all batchable messages" do
           [queued_message, @queued_message2, @queued_message3].each do |msg|
             expect(SingleMessageProcessor).to receive(:process).with(msg,
@@ -72,6 +73,20 @@ module MessageDequeuer
         end
       end
 
+      context "when postal.batch_queued_messages is disabled" do
+        before do
+          allow(Postal::Config.postal).to receive(:batch_queued_messages?) { false }
+        end
+
+        it "does not call the single message process more than once" do
+          expect(SingleMessageProcessor).to receive(:process).once.with(queued_message,
+                                                                        logger: logger,
+                                                                        state: processor.state)
+          processor.process
+        end
+      end
+    end
+
     context "when an error occurs while finding batchable messages" do
       before do
         allow(queued_message).to receive(:batchable_messages) { 1 / 0 }