Handle IndexError when reading msg files (#671)

Don't close queues if only msg file size is incorrect

CHANGELOG.md

@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 - lavinmqctl didn't recognize 201/204 response codes from set_permissions, set_user_tags and add_vhost
+- Queues will no longer be closed if file size is incorrect. Fixes [#669](https://github.com/cloudamqp/lavinmq/issues/669)
 
 ### Changed
 

spec/storage_spec.cr

@@ -98,6 +98,36 @@ describe LavinMQ::DurableQueue do
       queue.message_count.should eq 2
     end
   end
+
+  it "handles files with few extra bytes" do
+    queue_name = Random::Secure.hex(10)
+    with_amqp_server do |s|
+      vhost = s.vhosts.create("test_vhost")
+      with_channel(s, vhost: vhost.name) do |ch|
+        q = ch.queue(queue_name)
+        queue = vhost.queues[queue_name].as(LavinMQ::DurableQueue)
+        mfile = queue.@msg_store.@segments.first_value
+
+        # fill up one segment
+        message_size = 41
+        while mfile.size < (LavinMQ::Config.instance.segment_size - message_size*2)
+          q.publish_confirm "a"
+        end
+        remaining_size = LavinMQ::Config.instance.segment_size - mfile.size - message_size
+        q.publish_confirm "a" * remaining_size
+
+        # publish one more message to create a new segment
+        q.publish_confirm "a"
+
+        # resize first segment to LavinMQ::Config.instance.segment_size
+        mfile.resize(LavinMQ::Config.instance.segment_size)
+
+        # read messages, should not raise any error
+        q.subscribe(tag: "tag", no_ack: false, &.ack)
+        should_eventually(be_true) { queue.empty? }
+      end
+    end
+  end
 end
 
 describe LavinMQ::VHost do

src/lavinmq/queue/message_store.cr

@@ -129,6 +129,11 @@ module LavinMQ
           @size -= 1
           notify_empty(true) if @size.zero?
           return Envelope.new(sp, msg, redelivered: false)
+        rescue ex : IndexError
+          Log.warn { "Msg file size does not match expected value, moving on to next segment" }
+          select_next_read_segment && next
+          return if @size.zero?
+          raise Error.new(@rfile, cause: ex)
         rescue ex
           raise Error.new(@rfile, cause: ex)
         end