Re: [mosquitto-dev] Is there a function in the broker to "delete" a topi

[Andrew Thomas <andrew.thomas@xxxxxxxxxxx>]

Hi Roger,

Apologies for the delay in responding.  All my mosquitto messages were being filtered into a folder I never look at.

I eventually solved this by creating a new function:

int retain__clear_retained_message(char* topic)
{
	int rc = 0;
	char* local_sub;
	char** split_topics;
	struct mosquitto_msg_store stored;

	assert(topic);

	rc = sub__topic_tokenise(topic, &local_sub, &split_topics, NULL);
	if (rc) return rc;

	// If stored.payloadlen is 0, retain__store will remove the retained message
	memset(&stored, 0, sizeof(struct mosquitto_msg_store));
	set_retained(topic, &stored, split_topics);

	mosquitto__free(local_sub);
	mosquitto__free(split_topics);

	return 0;
}

Regards,
	Andrew


-----Original Message-----
From: mosquitto-dev <mosquitto-dev-bounces@xxxxxxxxxxx> On Behalf Of Roger Light via mosquitto-dev
Sent: Friday, April 5, 2024 6:25 PM
To: General development discussions for the mosquitto project <mosquitto-dev@xxxxxxxxxxx>
Cc: Roger Light <roger@xxxxxxxxxx>
Subject: Re: [mosquitto-dev] Is there a function in the broker to "delete" a topic

Hi Andrew,

There's not a straightforward way to do this in the broker. You could do what Nick suggested, then have a plugin deny access to outgoing messages with zero length, if your clients can't cope with zero length messages.

Regards,

Roger

On Fri, 5 Apr 2024 at 12:12, Andrew Thomas via mosquitto-dev <mosquitto-dev@xxxxxxxxxxx> wrote:
>
> Hello all,
>
>
>
> I am customizing the mosquitto broker, and I would like to be able to “delete” a topic.  As I understand it, that really just means removing retained messages for that topic.  I realize that the topic will re-appear if a client sends a new message to it, but this would still be very useful for my application.
>
>
>
> Are there functions in the broker code that:
>
> Remove the retained message for a topic, and Remove the retained 
> messages for a topic and all its descendants?
>
>
>
> Thanks,
>
>                 Andrew
>
>
>
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