Change systemd unit files to create /var/log/mosquitto

This happens before starting the broker.

Also don't quit with an error if opening the log file isn't possible.

Closes #821.

ChangeLog.txt

@@ -2,6 +2,10 @@ Broker:
 - Fix usage message only mentioning v3.1.1. Closes #1713.
 - Fix broker refusing to start if only websockets listeners were defined.
   Closes #1740.
+- Change systemd unit files to create /var/log/mosquitto before starting.
+  Closes #821.
+- Don't quit with an error if opening the log file isn't possible.
+  Closes #821.
 
 Client library:
 - Improved documentation around connect callback return codes. Close #1730.

service/systemd/mosquitto.service.notify

@@ -1,5 +1,5 @@
 [Unit]
-Description=Mosquitto MQTT v3.1/v3.1.1 Broker
+Description=Mosquitto MQTT Broker
 Documentation=man:mosquitto.conf(5) man:mosquitto(8)
 After=network.target
 Wants=network.target
@@ -10,6 +10,8 @@ NotifyAccess=main
 ExecStart=/usr/sbin/mosquitto -c /etc/mosquitto/mosquitto.conf
 ExecReload=/bin/kill -HUP $MAINPID
 Restart=on-failure
+ExecStartPre=/bin/mkdir -m 740 -p /var/log/mosquitto
+ExecStartPre=/bin/chown mosquitto: /var/log/mosquitto
 
 [Install]
 WantedBy=multi-user.target

service/systemd/mosquitto.service.simple

@@ -1,5 +1,5 @@
 [Unit]
-Description=Mosquitto MQTT v3.1/v3.1.1 Broker
+Description=Mosquitto MQTT Broker
 Documentation=man:mosquitto.conf(5) man:mosquitto(8)
 After=network.target
 Wants=network.target
@@ -8,6 +8,8 @@ Wants=network.target
 ExecStart=/usr/sbin/mosquitto -c /etc/mosquitto/mosquitto.conf
 ExecReload=/bin/kill -HUP $MAINPID
 Restart=on-failure
+ExecStartPre=/bin/mkdir -m 740 -p /var/log/mosquitto
+ExecStartPre=/bin/chown mosquitto: /var/log/mosquitto
 
 [Install]
 WantedBy=multi-user.target

src/logging.c

@@ -114,7 +114,6 @@ int log__init(struct mosquitto__config *config)
 			log_destinations = MQTT3_LOG_STDERR;
 			log_priorities = MOSQ_LOG_ERR;
 			log__printf(NULL, MOSQ_LOG_ERR, "Error: Unable to open log file %s for writing.", config->log_file);
-			return MOSQ_ERR_INVAL;
 		}
 		restore_privileges();
 	}