[change] Stop sending data on repeated 404 responses #105

The openwisp-monitoring agent will exit (killing both the
processes for collecting and sending data) if the device
has been deleted from OpenWISP Controller.

The delete is determined by checking if the openwisp-config agent
agent is running, which exits on repeated 404 response
for checksum response.

Closes #105

openwisp-monitoring/files/monitoring.agent

@@ -190,6 +190,20 @@ send_data() {
 					[ "$VERBOSE_MODE" -eq "1" ] && logger -s "Data not sent successfully. Retrying in $timeout seconds." \
 						-p daemon.warn
 					failures=$((failures + 1))
+					if [ "$response_code" = "404" ]; then
+						# If we get a HTTP 404 response, it could mean that the device has been deleted from OpenWISP
+						# Controller. We check if openwisp-config agent is running to determine if the device has been
+						# deleted. If openwisp-config agent is not running, the monitoring agent will also exit.
+						if ! pgrep -x "openwisp_config" >/dev/null; then
+							logger -s "Giving up and shutting down: the device may have been deleted from OpenWISP Controller" \
+								-t openwisp-monitoring \
+								-p daemon.err
+							# get process id of the process collecting data
+							pid=$(pgrep -f "openwisp-monitoring.*--mode collect")
+							kill -SIGKILL "$pid"
+							exit 2
+						fi
+					fi
 					sleep "$timeout"
 				fi
 			done