def parseNodeNum(self, cmd):
# Make sure the command even has enough arguments for there to be a
# node number argument present!
if not len(cmd.cmdArgs) >= 1:
logger.error(
"CommandHandler.parseNodeNum(): I expected this command to have at least one argument, a node number. It doesn't."
)
return None
# Try parsing the first argument as a node number. If this fails,
# log an error and use the invalid node number '-1'.
try:
cmd.nodeNum = int(cmd.cmdArgs[0])
except ValueError:
logger.error(
"CommandHandler.parseNodeNum(): I expected the first argument to this command to be a node number, an integer. It isn't. Using -1 instead."
)
cmd.nodeNum = -1 # Invalid value.
return # No point in setting the component or skipping the arg.
# Change the component name in this thread's logging context to the
# name of the node that sent this command. When we finish processing
# the command later, we can switch the component back to "server"
logmaster.setComponent("node#%d" % cmd.nodeNum)
# Now that we've parsed the node number into its own attribute,
# it doesn't need to be in the arg list any more. Strip it off arg list.
cmd.cmdArgs = cmd.cmdArgs[1:]
return cmd.nodeNum
def parseNodeNum(self, cmd):
# Make sure the command even has enough arguments for there to be a
# node number argument present!
if not len(cmd.cmdArgs) >= 1:
logger.error(
"CommandHandler.parseNodeNum(): I expected this command to have at least one argument, a node number. It doesn't."
)
return None
# Try parsing the first argument as a node number. If this fails,
# log an error and use the invalid node number '-1'.
try:
cmd.nodeNum = int(cmd.cmdArgs[0])
except ValueError:
logger.error(
"CommandHandler.parseNodeNum(): I expected the first argument to this command to be a node number, an integer. It isn't. Using -1 instead."
)
cmd.nodeNum = -1 # Invalid value.
return # No point in setting the component or skipping the arg.
# Change the component name in this thread's logging context to the
# name of the node that sent this command. When we finish processing
# the command later, we can switch the component back to "server"
logmaster.setComponent("node#%d" % cmd.nodeNum)
# Now that we've parsed the node number into its own attribute,
# it doesn't need to be in the arg list any more. Strip it off arg list.
cmd.cmdArgs = cmd.cmdArgs[1:]
return cmd.nodeNum
def process(this, msg: communicator.Message):
# If we're not already in the CommandHandler worker thread, then
# do the work in that thread, in the background.
if threading.current_thread(
) != this: # Ensure we're in worker thread.
this(lambda: this.process(msg))
return
self = this # Our thready self is this very object that we are operating on.
# logger.debug("CommandHandler.process(): Processing the message: [%s]..." % msg.data.strip())
try:
cmd = Command(msg) # Parse message into command/argument words.
except EmptyCommand:
logger.info(
"CommandHandler.process(): Ignoring empty command [%s]." %
msg.data)
return
# For the moment, we are assuming that all commands are originating
# from sensor nodes, and that the first argument to every command
# is the node's ID (0,1,2,3). However, this is really an unnecessary
# convention for all but the POWERED_ON message, because all subsequent
# messages from a given node will be received on a Connection that is
# already associated with that node. So, consider changing this. It
# would require some extensive rewriting though. Also, even if we don't
# do that, really, we should check for the node number only if this is a
# command that isn't coming from the user (operator of server app), as
# opposed to coming from a remote node. Should Messages be marked
# with their source? Or should we just be more flexible in our parsing?
# Some commands may not make sense to associate with nodes at all, e.g.
# a server shutdown command. Need to think this through properly, and
# figure out what's really the right way to handle things.
nodenum = self.parseNodeNum(
cmd) # Extract node number from command line.
#\_ Also updates component in log context.
# Now that we know the node number that this command claims to be coming
# from, we take this at face value, and assume that the entire connection
# on which we received that message is the main connection associated with
# that node number, and change the connection window's title accordingly.
# Please observe that this is a very brittle thing to do, because it only
# really makes sense for node-specific commands received over a MainServer
# connection. See the comment above the previous line of code. So, for
# example, if the user tries to type a command on the console, the following
# line will at present cause the command-handler thread to raise an exception
# and exit, effectively crippling the server.
if hasattr(
msg.conn, 'term'
): # Is the connection this message came from even associated with a terminal widget?
msg.conn.term.set_title("Node #%d Main Server Connection #%d" %
(nodenum, msg.conn.cid))
# Finally, we are ready to try dispatching the command for execution.
try:
# Note to self, the "msg" above, a Communicator message,
# does not have exactly the same fields as the original
# Message class objects defined in this file. This may
# cause problems. Need to fix them. - Obsolete comment?
self.dispatch_command(cmd)
except Exception as e:
logger.error(
"CommandHandler.process(): Caught an exception [%s] while dispatching command [%s]. Ignoring."
% (str(e), cmd.cmdString))
finally:
# Most command handlers will temporarily change the "component"
# field in this thread's logging context to the name of whatever
# node sent the command, to facilitate debugging. Here, we change
# it back to "server" to avoid confusion when debugging the command
# parse-and-dispatch process.
logmaster.setComponent("server")
def process(this, msg: communicator.Message):
# If we're not already in the CommandHandler worker thread, then
# do the work in that thread, in the background.
if threading.current_thread() != this: # Ensure we're in worker thread.
this(lambda: this.process(msg))
return
self = this # Our thready self is this very object that we are operating on.
# logger.debug("CommandHandler.process(): Processing the message: [%s]..." % msg.data.strip())
try:
cmd = Command(msg) # Parse message into command/argument words.
except EmptyCommand:
logger.info("CommandHandler.process(): Ignoring empty command [%s]." % msg.data)
return
# For the moment, we are assuming that all commands are originating
# from sensor nodes, and that the first argument to every command
# is the node's ID (0,1,2,3). However, this is really an unnecessary
# convention for all but the POWERED_ON message, because all subsequent
# messages from a given node will be received on a Connection that is
# already associated with that node. So, consider changing this. It
# would require some extensive rewriting though. Also, even if we don't
# do that, really, we should check for the node number only if this is a
# command that isn't coming from the user (operator of server app), as
# opposed to coming from a remote node. Should Messages be marked
# with their source? Or should we just be more flexible in our parsing?
# Some commands may not make sense to associate with nodes at all, e.g.
# a server shutdown command. Need to think this through properly, and
# figure out what's really the right way to handle things.
nodenum = self.parseNodeNum(cmd) # Extract node number from command line.
# \_ Also updates component in log context.
# Now that we know the node number that this command claims to be coming
# from, we take this at face value, and assume that the entire connection
# on which we received that message is the main connection associated with
# that node number, and change the connection window's title accordingly.
# Please observe that this is a very brittle thing to do, because it only
# really makes sense for node-specific commands received over a MainServer
# connection. See the comment above the previous line of code. So, for
# example, if the user tries to type a command on the console, the following
# line will at present cause the command-handler thread to raise an exception
# and exit, effectively crippling the server.
if hasattr(
msg.conn, "term"
): # Is the connection this message came from even associated with a terminal widget?
msg.conn.term.set_title("Node #%d Main Server Connection #%d" % (nodenum, msg.conn.cid))
# Finally, we are ready to try dispatching the command for execution.
try:
# Note to self, the "msg" above, a Communicator message,
# does not have exactly the same fields as the original
# Message class objects defined in this file. This may
# cause problems. Need to fix them. - Obsolete comment?
self.dispatch_command(cmd)
except Exception as e:
logger.error(
"CommandHandler.process(): Caught an exception [%s] while dispatching command [%s]. Ignoring."
% (str(e), cmd.cmdString)
)
finally:
# Most command handlers will temporarily change the "component"
# field in this thread's logging context to the name of whatever
# node sent the command, to facilitate debugging. Here, we change
# it back to "server" to avoid confusion when debugging the command
# parse-and-dispatch process.
logmaster.setComponent("server")
