Improve error handling for TCP connections
In the abstract DNSService's _dns_handle_tcp method, error handling is broken in a way that stops the main loop for handling TCP connections. Because socket.timeout is a subclass of socket.error, the error handling block for socket.timeout is never reached. Because of this, error handling of a TCP timeout is sent to the socket.error block. Due to the way eventlet hijacks these errors, the errorcode is not available and a KeyError is raised. This KeyError interferes with the main loop because it is not caught. Further improvement may include ensuring that these main loops can never die due to unexpected exceptions. Many thanks to Erik Andersson for pointing out the issue, which was seemingly innocuous but ended up being the cause of our problems. Closes-bug: 1549980 Change-Id: I47e1260a0818cc42cbd56e4d296e083f8fcbbae5
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@ -263,6 +263,14 @@ class DNSService(object):
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break
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payload += data
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# NOTE: Any uncaught exceptions will result in the main loop
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# ending unexpectedly. Ensure proper ordering of blocks, and
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# ensure no exceptions are generated from within.
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except socket.timeout:
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client.close()
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LOG.warning(_LW("TCP Timeout from: %(host)s:%(port)d") %
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{'host': addr[0], 'port': addr[1]})
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except socket.error as e:
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client.close()
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errname = errno.errorcode[e.args[0]]
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@ -270,11 +278,6 @@ class DNSService(object):
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_LW("Socket error %(err)s from: %(host)s:%(port)d") %
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{'host': addr[0], 'port': addr[1], 'err': errname})
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except socket.timeout:
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client.close()
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LOG.warning(_LW("TCP Timeout from: %(host)s:%(port)d") %
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{'host': addr[0], 'port': addr[1]})
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except struct.error:
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client.close()
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LOG.warning(_LW("Invalid packet from: %(host)s:%(port)d") %
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