Re: [mosquitto-dev] Order of "topic" rules in bridge definitions

[Roger Light <roger@xxxxxxxxxx>]

Hi Jos,

Yes, it's exactly as Ian says.

We haven't explicitly guaranteed this behaviour, but I see no reason
why it would change.

Cheers,

Roger


On Wed, Jan 21, 2015 at 1:58 PM, Ian Craggs
<icraggs@xxxxxxxxxxxxxxxxxxxxxxx> wrote:
> Hi Jos,
>
> if it's anything like when I "designed" this in RSMB, then the ordering
> should be significant, for two reasons:
>
> 1) it's simpler to implement
> 2) it provides predictable behaviour -- the first topic item in the list
> takes precedence
>
> Not sophisticated, but it's meant for low footprint servers.
>
> Ian
>
>
> On 01/21/2015 11:56 AM, Jos Vos wrote:
>>
>> Hi,
>>
>> I'm doing some experiments with bridging.  When doing this, one question
>> remained unanswered from the documentation: how are multiple topic rules
>> in a bridge definition interpreted if their patterns are not mutually
>> exclusive?
>>
>> What I have: 3 mosquitto servers, think of them as the left, middle
>> and right server, and the middle server is setting up a bridge to
>> both the left and right server.  I first tried this:
>>
>>    connection leftbridge
>>    address 127.0.0.1:1883
>>    cleansession true
>>    topic # in 0 bridged/fromleft/ ""
>>    topic # out 0 "" bridged/frommiddle/
>>
>>    connection rightbridge
>>    address 127.0.0.1:9883
>>    cleansession true
>>    topic # in 0 bridged/fromright/ ""
>>    topic # out 0 "" bridged/frommiddle/
>>
>> This works, that is, all messages appear on all servers and are
>> prefixed by every bridge path they have passed.  So, left messages
>> in "tst" arrive at the right as "bridged/frommiddle/bridged/fromleft/tst".
>>
>> Now I wanted to avoid the double prefixes and, after some attempts, I
>> ended up with this config:
>>
>>    connection leftbridge
>>    address 127.0.0.1:1883
>>    cleansession true
>>    topic # in 0 bridged/fromleft/ ""
>>    topic # out 0 bridged/fromright/ bridged/fromright/
>>    topic # out 0 "" bridged/frommiddle/
>>
>>    connection rightbridge
>>    address 127.0.0.1:9883
>>    cleansession true
>>    topic # in 0 bridged/fromright/ ""
>>    topic # out 0 bridged/fromleft/ bridged/fromleft/
>>    topic # out 0 "" bridged/frommiddle/
>>
>> Now this seems to work, but as soon as I exchange the "out" rules in
>> each bridge, I see the old behavior, so the order does matter.
>>
>> My question is: can I rely on the matching order for topics (the
>> first match determines the policy) and in this way safely list
>> exceptions *before* the generic "" rule?
>>
>> Thx,
>>
>> --
>> --    Jos Vos <jos@xxxxxx>
>> --    X/OS Experts in Open Systems BV   |   Phone: +31 20 6938364
>> --    Amsterdam, The Netherlands        |     Fax: +31 20 6948204
>> _______________________________________________
>> mosquitto-dev mailing list
>> mosquitto-dev@xxxxxxxxxxx
>> To change your delivery options, retrieve your password, or unsubscribe
>> from this list, visit
>> https://dev.eclipse.org/mailman/listinfo/mosquitto-dev
>
>
> --
> Ian Craggs
> icraggs@xxxxxxxxxx                 IBM United Kingdom
> Paho Project Lead; Committer on Mosquitto
>
>
> _______________________________________________
> mosquitto-dev mailing list
> mosquitto-dev@xxxxxxxxxxx
> To change your delivery options, retrieve your password, or unsubscribe from
> this list, visit
> https://dev.eclipse.org/mailman/listinfo/mosquitto-dev