fix: retry pending report_status instead of forcing re-download

When report_status fails due to a transient server error (e.g., HTTP
502 during server maintenance), the agent previously deleted its local
checksums, forcing a full re-download and re-apply on the next cycle.
This is wasteful since the configuration was already applied
successfully.

Instead, save the pending status to a marker file and retry
report_status on the next polling cycle without re-downloading.
This ensures the controller receives the status update as soon as the
server recovers, without unnecessary network traffic or config
re-application.

Backward compatible: older controllers will simply receive the
delayed report_status and update their status accordingly.

Author: MichaelUray

openwisp-config/files/openwisp.agent

@@ -200,6 +200,7 @@ REGISTRATION_PARAMETERS="$WORKING_DIR/registration_parameters"
 TEST_CHECKSUM="$WORKING_DIR/test_checksum"
 UPDATE_INFO="$WORKING_DIR/update_info"
 STATUS_REPORT="$WORKING_DIR/status_report"
+PENDING_REPORT="$WORKING_DIR/pending_report"
 APPLYING_CONF="$WORKING_DIR/applying_conf"
 UPDATE_CONFIG_LOG="$WORKING_DIR/update-config.log"
 BOOTUP="$WORKING_DIR/bootup"
@@ -825,6 +826,7 @@ update_configuration() {
 		result=$?
 	fi
 
+	local status_to_report
 	if [ "$result" -eq "0" ]; then
 		logger "Configuration applied successfully" \
 			-t openwisp \
@@ -833,14 +835,22 @@ update_configuration() {
 		env -i ACTION="config-applied" /sbin/hotplug-call openwisp
 		# store the new checksum as last known checksum
 		cp "$CONFIGURATION_CHECKSUM" "$PERSISTENT_CHECKSUM"
+		status_to_report="applied"
 		retry_with_backoff report_status "applied"
 	else
+		status_to_report="error"
 		retry_with_backoff report_status "error"
 	fi
-	# if reporting of the status fails, let it retry in the next cycle
+	# if reporting of the status fails, save the pending status for retry
+	# in the next cycle without forcing a full re-download
 	# shellcheck disable=SC2181
 	if [ "$?" -ne "0" ]; then
-		rm -f $CONFIGURATION_CHECKSUM $PERSISTENT_CHECKSUM
+		echo "$status_to_report" >"$PENDING_REPORT"
+		logger -s "report_status failed, will retry in the next cycle" \
+			-t openwisp \
+			-p daemon.warning
+	else
+		rm -f "$PENDING_REPORT"
 	fi
 
 	rm $APPLYING_CONF
@@ -987,6 +997,19 @@ while true; do
 
 	if [ "$?" -eq "1" ]; then
 		update_configuration
+	elif [ -f "$PENDING_REPORT" ]; then
+		# Retry a previously failed report_status without re-downloading.
+		# This handles the case where the config was applied successfully
+		# but report_status failed due to a transient server error.
+		local pending_status
+		pending_status=$(cat "$PENDING_REPORT")
+		logger "Retrying pending report_status: $pending_status" \
+			-t openwisp \
+			-p daemon.info
+		retry_with_backoff report_status "$pending_status"
+		if [ "$?" -eq "0" ]; then
+			rm -f "$PENDING_REPORT"
+		fi
 	fi
 	env -i ACTION="end-of-cycle" /sbin/hotplug-call openwisp