From d4ddb5cfd2c7188ed8e9d4fe21037d5254015376 Mon Sep 17 00:00:00 2001
From: joshemb <josh@elixxir.io>
Date: Thu, 29 Sep 2022 10:40:39 -0700
Subject: [PATCH] Add prose worthy comments explaining the bug fix
---
fileTransfer/send.go | 26 +++++++++++++++++++-------
1 file changed, 19 insertions(+), 7 deletions(-)
diff --git a/fileTransfer/send.go b/fileTransfer/send.go
index 37457e613..fd736280c 100644
--- a/fileTransfer/send.go
+++ b/fileTransfer/send.go
@@ -74,32 +74,44 @@ func (m *manager) sendingThread(stop *stoppable.Single) {
healthChanID := m.cmix.AddHealthCallback(func(b bool) { healthChan <- b })
for {
select {
+ // A quit signal has been sent by the user. Typically, this is a result
+ // of a user-level shutdown of the client.
case <-stop.Quit():
jww.DEBUG.Printf("[FT] Stopping file part sending thread (%s): "+
"stoppable triggered.", stop.Name())
m.cmix.RemoveHealthCallback(healthChanID)
stop.ToStopped()
return
+
+ // If the network becomes unhealthy, we will cease sending files until
+ // it is resolved.
case healthy := <-healthChan:
+ // There exists an edge case where an unhealthy signal is received
+ // due to a user-level shutdown, meaning the health tracker has
+ // ceased operation. If the health tracker is shutdown, a healthy
+ // signal will never be received, and this for loop will run
+ // infinitely. If we are caught in this loop, the stop's Quit()
+ // signal will never be received in case statement above, and this
+ // sender thread will run indefinitely. To avoid lingering threads
+ // in the case of a shutdown, we must actively listen for either the
+ // Quit() signal or a network health update here.
for !healthy {
select {
case <-stop.Quit():
- // It's possible during shutdown that the health tracker gets
- // shutdown before the quit signal is received by the case
- // statement listening for stop.Quit() above. As a result, we
- // must listen for the quit signal here, to avoid waiting
- // for a healthy signal that will never come.
+ // Listen for a quit signal if the network becomes unhealthy
+ // before a user-level shutdown.
jww.DEBUG.Printf("[FT] Stopping file part sending "+
"thread (%s): stoppable triggered.", stop.Name())
m.cmix.RemoveHealthCallback(healthChanID)
stop.ToStopped()
return
- // If a quit signal is not received, we must wait until the
- // network is healthy before we can continue sending files.
+ // Wait for a healthy signal before continuing to send files.
case healthy = <-healthChan:
}
}
+ // A file part has been sent through the queue and must be sent by
+ // this thread.
case packet := <-m.sendQueue:
m.sendCmix(packet)
}
--
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