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Re: [paho-dev] Persistence (C Language)
- From: Ian Craggs <icraggs@xxxxxxxxxxxxxxxxxxxxxxx>
- Date: Fri, 6 Jan 2017 16:13:38 +0000
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when you use the MQTTCLIENT_PERSISTENCE_DEFAULT persistence option, the persistence_context should be set to a directory to use. That's it. The persistence capability is all done for you, you don't need to make any calls to the persistence layer yourself.
The MQTTCLIENT_PERSISTENCE_USER option is provided if you want to use another persistence library. Here is an example of using Redis (https://bugs.eclipse.org/bugs/show_bug.cgi?id=410419). In that case, you would implement the persistence interface, but you still wouldn't make the actual calls yourself, that would still be done by the Paho library.
I hope that is a good explanation.
On 12/30/2016 10:29 AM, Jaspar LÃchte wrote:
I donât know, if this is the ârightâ place to get help for using MQTT Paho.
I am doing some research on persistent messaging with MQTT. I use the open source Mosquitto Broker in combination with MQTT-Paho for C language.
I just set up a publisher (able to publish various messages on a topic) and a subscriber (to receive them).
Now I wanted to get persistence mode. I tried to figure out how to use the functions from the MQTTClientPersistence.h Header.
There is no example for using persistence header. I thought I need to use the client, then I thought about a void pointer.
The other thing I am not sure about is, what to use as a persistence type?
If I use MQTTCLIENT_PERSISTENCE_DEFAULT the paho script is doing everything for me and I dont need to open an own PersistenceClient? And for MQTTCLIENT_PERSISTENCE_USER I need to set up everything on my own? (with opening, and saving messages and all the stuff?)
What ever I try, I get SIGSEGV in the Persistence_open function.
MQTTClient_create(&client, config->host, config->cid, MQTTCLIENT_PERSISTENCE_DEFAULT, dir);
// some connection options â
//persist.popen((void**)&handle, config->cid, config->host, dir);
persist.popen(&client, config->cid, config->host, dir);
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Paho Project Lead; Committer on Mosquitto