optimize memory issues (#767)

* optimize memory issues

1. introduce jemalloc support, which can dump current memory usage
2. reduce the GlobalEvent broadcaster memory usage.
3. reduce tcp & udp tunnel memory usage

TODO: if peer conn tunnel hangs, the unbounded channel of peer rpc
may consume lots of memory, which should be improved.

* select a port from 15888+ when port is 0

easytier/src/common/global_ctx.rs

@@ -97,7 +97,7 @@ impl GlobalCtx {
         let net_ns = NetNS::new(config_fs.get_netns());
         let hostname = config_fs.get_hostname();
 
-        let (event_bus, _) = tokio::sync::broadcast::channel(1024);
+        let (event_bus, _) = tokio::sync::broadcast::channel(8);
 
         let stun_info_collection = Arc::new(StunInfoCollector::new_with_default_servers());
 
@@ -141,10 +141,13 @@ impl GlobalCtx {
     }
 
     pub fn issue_event(&self, event: GlobalCtxEvent) {
-        if self.event_bus.receiver_count() != 0 {
-            self.event_bus.send(event).unwrap();
-        } else {
-            tracing::warn!("No subscriber for event: {:?}", event);
+        if let Err(e) = self.event_bus.send(event.clone()) {
+            tracing::warn!(
+                "Failed to send event: {:?}, error: {:?}, receiver count: {}",
+                event,
+                e,
+                self.event_bus.receiver_count()
+            );
         }
     }