move prefetch qos to WorkerChannel

This way the log collecter can use a channel with prefetching while the
other workers still consume items one by one.

ofborg/src/bin/evaluation-filter.rs

@@ -56,7 +56,7 @@ fn main() -> Result<(), Box<dyn Error>> {
         no_wait: false,
     })?;
 
-    let handle = chan.consume(
+    let handle = easylapin::WorkerChannel(chan).consume(
         tasks::evaluationfilter::EvaluationFilterWorker::new(cfg.acl()),
         easyamqp::ConsumeConfig {
             queue: queue_name.clone(),

ofborg/src/bin/github-comment-filter.rs

@@ -57,7 +57,7 @@ fn main() -> Result<(), Box<dyn Error>> {
         no_wait: false,
     })?;
 
-    let handle = chan.consume(
+    let handle = easylapin::WorkerChannel(chan).consume(
         tasks::githubcommentfilter::GitHubCommentWorker::new(cfg.acl(), cfg.github()),
         easyamqp::ConsumeConfig {
             queue: "build-inputs".to_owned(),

ofborg/src/bin/github-comment-poster.rs

@@ -46,7 +46,7 @@ fn main() -> Result<(), Box<dyn Error>> {
         no_wait: false,
     })?;
 
-    let handle = chan.consume(
+    let handle = easylapin::WorkerChannel(chan).consume(
         tasks::githubcommentposter::GitHubCommentPoster::new(cfg.github_app_vendingmachine()),
         easyamqp::ConsumeConfig {
             queue: "build-results".to_owned(),

ofborg/src/bin/log-message-collector.rs

@@ -48,6 +48,7 @@ fn main() -> Result<(), Box<dyn Error>> {
         no_wait: false,
     })?;
 
+    // Regular channel, we want prefetching here.
     let handle = chan.consume(
         tasks::log_message_collector::LogMessageCollector::new(
             PathBuf::from(cfg.log_storage.clone().unwrap().path),

ofborg/src/bin/mass-rebuilder.rs

@@ -53,7 +53,7 @@ fn main() -> Result<(), Box<dyn Error>> {
         no_wait: false,
     })?;
 
-    let handle = chan.consume(
+    let handle = easylapin::WorkerChannel(chan).consume(
         tasks::evaluate::EvaluationWorker::new(
             cloner,
             &nix,

ofborg/src/easylapin.rs

@@ -86,8 +86,6 @@ impl<'a, W: SimpleWorker + 'a> ConsumerExt<'a, W> for CloseOnDrop<Channel> {
     type Handle = Pin<Box<dyn Future<Output = ()> + 'a>>;
 
     fn consume(self, mut worker: W, config: ConsumeConfig) -> Result<Self::Handle, Self::Error> {
-        task::block_on(self.basic_qos(1, BasicQosOptions::default()))?;
-
         let mut consumer = task::block_on(self.basic_consume(
             &config.queue,
             &config.consumer_tag,
@@ -117,6 +115,20 @@ impl<'a, W: SimpleWorker + 'a> ConsumerExt<'a, W> for CloseOnDrop<Channel> {
     }
 }
 
+// Same as a regular channel, but without prefetching,
+// used for services with multiple instances.
+pub struct WorkerChannel(pub CloseOnDrop<Channel>);
+
+impl<'a, W: SimpleWorker + 'a> ConsumerExt<'a, W> for WorkerChannel {
+    type Error = lapin::Error;
+    type Handle = Pin<Box<dyn Future<Output = ()> + 'a>>;
+
+    fn consume(self, worker: W, config: ConsumeConfig) -> Result<Self::Handle, Self::Error> {
+        task::block_on(self.0.basic_qos(1, BasicQosOptions::default()))?;
+        self.0.consume(worker, config)
+    }
+}
+
 struct ChannelNotificationReceiver<'a> {
     channel: &'a mut CloseOnDrop<lapin::Channel>,
     deliver: &'a Delivery,