Hi Sourav, Thanks a lot for the mail and the screenshot. That said, usually, when we ask for a capture, we mean a pcap file, not a png one :) It's fine, I have the information I need.
I also used this documentation: http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Toc398718037 Please note that the MQTT messages are carried on top of TCP. Also, as > mentioned in previous mail, I am trying to load balance the traffic based > on the topic mentioned in the MQTT message( 3rd line from end ) which means > that all the traffic corresponding to a particular topic should be > forwarded to a specific server only. > That's doable only in the following condition: - the client speaks first (no server banner) - the information is available in first session buffer - the information is available always at the same place It seems MQTT meet the 3 rules above, so we may be able to do something. So considering above requirement, I have the following questions : > > 1. Is MQTT already supported as an out of box feature? > No, MQTT is not supported out of the box. > 2. Is there a configurable hook/plugin through which above can be achieved? > You might be able to code a MQTT protocol parser in Lua. You could even do MQTT routing to a specific farm based on the topic, but load-balancing is an other story. > 3. If no configuration/plugins are available, how easy it would be to add > the feature/code in order to retrieve payload information from TCP packets > and parse it as par MQTT? > Very complicated, I'm afraid... > 4. What are main modules which I should look into in order to implement > the same in case not yet implemented? > > Well, as I mentionned above, there might be some stuff we can do. Please check http://cbonte.github.io/haproxy-dconv/configuration-1.5.html#req.payload_lv Following your capture, this fetch can be used to retrieve the whole topic: req.payload_lv(1,1) => it fetch content in the TCP payload buffer whose size is specified at byte 1 for 1 byte and data is stored right after the size. This fetch has the corresponding ACL to match against static patterns. Imagine 3 topics: topic1, topic2, topic3, then you could do: frontend mqtt [...] use_backend bk_topic1 if { req.payload_lv(1,1),lower topic1 } use_backend bk_topic2 if { req.payload_lv(1,1),lower topic2 } use_backend bk_topic3 if { req.payload_lv(1,1),lower topic3 } backend bk_topic1 [...] backend bk_topic2 [...] backend bk_topic3 [...] The same could be applied in a single backend, using the use-server statement. I hope this help and this is enough. Be aware that once the TCP session has been forwarded to a server, then all subsequent messages are going to be forwarded to this server, regardless of the next topics set over the same connection. To be routed again, a client must send next PUBLISH message over a new TCP connection. Baptiste On Thu, Sep 10, 2015 at 7:58 PM, Baptiste <[email protected]> wrote: > On Thu, Sep 10, 2015 at 4:05 PM, Sourav Das <[email protected]> > wrote: > > Hi, > > > > I have been going through the HAProxy documentation for my work which > deals > > with scaling and load balancing for MQTT Brokers. > > > > However, I could not find any configuration regarding the Client Affinity > > where the routing of the MQTT traffic is done based on the topic present > in > > the MQTT message. As MQTT is also carried over TCP, is it possible to > use a > > pre-configured hook in HAProxy so that the traffic can be routed to the > > appropriate server based on the MQTT topic. > > > > At present I am not able to find out any hook which enables this to be > done. > > I am a bit curious to know whether the support of MQTT is planned in > future > > releases of HAProxy. > > > > > > Please let me know if this makes sense. > > > > Regards, > > Sourav > > > Hi Sourav, > > This would be doable only if the information can be retrived from the > payload of the first request sent by the client. > could you provide more information about how MQTT protocol works? Is > there any server banner? > A simple TCP dump containing an example of the message you want to > route would be appreciated and allow us to deliver you an accurate > answer. > > Baptiste > >
