Bugfix: DLX doesn't update timestamp on republish (#583)

When a message was dead letter the timestamp wasn't updated. This caused TTL to misbehave if a message was dead lettered to another queue with TTL:

    Declare queue q1 with x-message-ttl = 100 and x-dead-letter-routing-key = q2
    Declare queue q2 with x-message-ttl = 100 and x-dead-letter-routing-key = q3
    Publish message to q1.

After 100ms the message is dead lettered to q2 (via default exchange). Because the message timestamp isn't updated the message will expire immediately in q2 and dead lettered to q3.

This will fix this by setting a new timestamp on the message when it's published by the dead lettering.

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - A bug in delay exchanges caused messages to be routed to x-dead-letter-exchange instead of bound queues. It also ruined any dead lettering headers.
 - A bug that prevented headers exchange to match on table in message headers.
 - Purging a queue with a lot of messages blocked LavinMQ from other operations.
+- Message timestamps not being updated when dead lettered breaking TTL.
 
 ## [1.2.4] - 2023-09-26
 

spec/dlx_spec.cr

@@ -1,5 +1,6 @@
 require "./spec_helper"
 require "./../src/lavinmq/queue"
+require "./../src/lavinmq/rough_time"
 
 describe "Dead lettering" do
   q_name = "ttl"
@@ -29,4 +30,32 @@ describe "Dead lettering" do
       x_death[1].as(AMQ::Protocol::Table)["queue"].should eq q_delayed_2.name
     end
   end
+
+  it "should update message timestamp on publish" do
+    v = Server.vhosts.create("test")
+    q_args = AMQ::Protocol::Table.new({
+      "x-message-ttl"             => 200,
+      "x-dead-letter-exchange"    => "",
+      "x-dead-letter-routing-key" => "q2",
+    })
+    v.declare_queue("q", true, false, q_args)
+    v.declare_queue("q2", true, false, AMQ::Protocol::Table.new)
+
+    ts = RoughTime.unix_ms
+    msg = LavinMQ::Message.new(ts, "", "q", AMQ::Protocol::Properties.new, 0, IO::Memory.new)
+
+    v.publish msg
+
+    select
+    when v.queues["q2"].empty_change.receive
+    when timeout(1.second)
+      fail "timeout: message not dead lettered?"
+    end
+
+    v.queues["q2"].basic_get(no_ack: true) do |env|
+      msg = env.message
+    end
+
+    msg.timestamp.should be > ts
+  end
 end

src/lavinmq/queue/queue.cr

@@ -639,7 +639,7 @@ module LavinMQ
 
     private def dead_letter_msg(msg : BytesMessage, props, dlx, dlrk)
       @log.debug { "Dead lettering ex=#{dlx} rk=#{dlrk} body_size=#{msg.bodysize} props=#{props}" }
-      @vhost.publish Message.new(msg.timestamp, dlx.to_s, dlrk.to_s,
+      @vhost.publish Message.new(RoughTime.unix_ms, dlx.to_s, dlrk.to_s,
         props, msg.bodysize, IO::Memory.new(msg.body))
     end