- 1 year ago
outReceived from twisted ProcessProtocol merges messages if received too fast (buffering problem?)
Yes, the outReceived
method in Twisted's ProcessProtocol
can merge messages if they are received too quickly. This behavior is typically due to buffering.
When data is received from a subprocess, Twisted's ProcessProtocol
buffers the data until a newline character (\n
) is encountered. Once a newline is received, outReceived
is called and the buffered data is passed as a single string parameter. If the subprocess sends multiple lines of output without any newlines, the data will be buffered until a newline is received, and then outReceived
will be called with the concatenated string.
To handle this buffering issue and process individual lines of output, you can implement a custom buffering mechanism in your ProcessProtocol
subclass. Here's an example:
pythonfrom twisted.internet import protocol
class CustomProcessProtocol(protocol.ProcessProtocol):
def __init__(self):
self.buffer = ""
def outReceived(self, data):
# Append the received data to the buffer
self.buffer += data
# Process complete lines
while "\n" in self.buffer:
line, self.buffer = self.buffer.split("\n", 1)
self.processLine(line)
def processLine(self, line):
# Process the individual line of output
print("Received line:", line)
In this example, the CustomProcessProtocol
class maintains a buffer to store received data. The outReceived
method appends the received data to the buffer and then processes complete lines by splitting the buffer on newline characters. The processLine
method is called for each individual line of output.
By implementing this buffering mechanism, you can ensure that each line of output is processed separately, even if they are received too quickly and get buffered together.
Note: If you are using Twisted 21.2.0 or later, you can use the StdioConsumer
protocol instead of ProcessProtocol
. StdioConsumer
handles line buffering automatically, so you don't need to implement your own buffering mechanism.