ENOMEM with MQTT Subscription List

[kingston]

I have a working MQTT subscription list, when I add a new topic for subscription my subscribe fails with ENOMEM error -12.

If I remove another topic, I can add new topics successfully so I know its not syntax or an issue with the topic.  I have increased the stack and heap and still see the error.  Is there any way to dig deeper into what is causing the subscribe error?

[Didrik Rokhaug]

Hi,

How do you add the new topics?

Do you increase the list_count correspondingly?

Best regards,

Didrik

[kingston]

All the topics are statically assigned at compile time into a struct mqtt_topic subscribe_topic. 

After the topic struct is created it is passed to the subscription function with

const struct mqtt_subscription_list subscription_list = {
.list = subscribe_topic,
.list_count = ARRAY_SIZE(subscribe_topic),
.message_id = 1234
};

return mqtt_subscribe(&client, &subscription_list);
}

[kingston]

My current memory settings are:

# Memory
CONFIG_MAIN_STACK_SIZE=20480
CONFIG_HEAP_MEM_POOL_SIZE=16384
CONFIG_NRF_MODEM_LIB_SENDMSG_BUF_SIZE=2048
CONFIG_NRF_MODEM_LIB_HEAP_SIZE=4096
CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=8192
CONFIG_THREAD_NAME=y
CONFIG_LOG_STRDUP_MAX_STRING=100

[Didrik Rokhaug]

The .list field in the mqtt_subscription_list struct should be an array, not a single struct.

This works for me:

	struct mqtt_topic subscribe_topics[] = {
		{
			.topic = {
				.utf8 = CONFIG_MQTT_SUB_TOPIC,
				.size = strlen(CONFIG_MQTT_SUB_TOPIC)
			},
			.qos = MQTT_QOS_1_AT_LEAST_ONCE
		},
		{
			.topic = {
				.utf8 = "foo",
				.size = strlen("foo")
			},
			.qos = MQTT_QOS_1_AT_LEAST_ONCE
		}
	};

	const struct mqtt_subscription_list subscription_list = {
		.list = subscribe_topics,
		.list_count = ARRAY_SIZE(subscribe_topics),
		.message_id = 1234
	};

[kingston]

Thanks I was defining the list as an array, it was just a paste error into Devzone.  It appears that the error is solved after increasing the message and payload buffer size with CONFIG_MQTT_MESSAGE_BUFFER_SIZE=256
CONFIG_MQTT_PAYLOAD_BUFFER_SIZE=256

Without this addition, any time I had more than 7 topics I received the ENOMEM during subscription.