webhooks: Implement a send buffer for socket writes

This prevents ClientConnection.send() from blocking, removing the possibility that callers become reentrant.

Signed-off-by:  Eric Callahan <arksine.code@gmail.com>

klippy/webhooks.py

@@ -158,8 +158,8 @@ class ClientConnection:
         self.sock = sock
         self.fd_handle = self.reactor.register_fd(
             self.sock.fileno(), self.process_received)
-        self.partial_data = ""
-        self.mutex = self.reactor.mutex()
+        self.partial_data = self.send_buffer = ""
+        self.is_sending_data = False
         logging.info(
             "webhooks: New connection established")
 
@@ -222,12 +222,16 @@ class ClientConnection:
         self.send({'method': "response", 'params': result})
 
     def send(self, data):
-        with self.mutex:
+        self.send_buffer += json.dumps(data) + "\x03"
+        if not self.is_sending_data:
+            self.is_sending_data = True
+            self.reactor.register_callback(self._do_send)
+
+    def _do_send(self, eventtime):
         retries = 10
-            data = json.dumps(data) + "\x03"
-            while data:
+        while self.send_buffer:
             try:
-                    sent = self.sock.send(data)
+                sent = self.sock.send(self.send_buffer)
             except socket.error as e:
                 if e.errno == errno.EBADF or e.errno == errno.EPIPE \
                         or not retries:
@@ -239,13 +243,13 @@ class ClientConnection:
                     continue
             retries = 10
             if sent > 0:
-                    data = data[sent:]
+                self.send_buffer = self.send_buffer[sent:]
             else:
                 logging.info(
-                        "webhooks: Error sending server data,"
-                        " closing socket")
+                    "webhooks: Error sending server data,  closing socket")
                 self.close()
                 break
+        self.is_sending_data = False
 
 class WebHooks:
     def __init__(self, printer):