Proposal for new wildcards for topic filtering

[Stefan Hupe]

Hi!

I have played around with topic filtering for a while and I think, that it would be really helpful, if we could add some new wildcards for topic filtering on broker side:

WILDCARDS: 

+, #, *, -

1. WILDCARD + (filter single section of a topic)

Just used. Example

Topics:

/a/b/c/d

/a/x/c/d

/a/x/y/d

/a/e/f/g

/a/h/f/i

client(id=123).subscribe.topic("/a/+/c/d")

Results:

/a/b/c/d

/a/x/c/d

client(id=123).subscribe.topic("/a/+/+/d")

Results:

/a/b/c/d

/a/x/c/d

/a/x/y/d

client(id=123).subscribe.topic("/a/+/f/+")

Results:

/a/e/f/g

/a/h/f/i

 

 2. WILDCARD # (for many sections at the end of a topic)

Just used. Example

client(id=123).subscribe.topic("/a/x/#")

Results:

/a/x/c/d

/a/x/y/d

 

3. WILDCARD # (for many sections IN a topic) 

Example:

Topics:

/a/b/c/d

/a/e/f/g 

/a/h/i/d

/a/k/l/m/d 

 

client(id=123).subscribe.topic("/a/#/d")

Results:

 

/a/b/c/d

/a/h/i/d
/a/k/l/m/d 

I have very often the use case, that I am interested in a special value, e.g. temperatures in a building, so I wanna subscribe to /house/#/temperature without the knowledge of alls the sections between /house and /temperature (because I the numbers of sections are different). 

 

4. WILDCARD * (single character in a topic section)

Example:

Topics:

/house/flat01/room01/temperature

/house/flat01/room02/temperature

/house/flat01/room13/temperature

/house/flat01/oven/temperature

client(id=123).subscribe.topic("/house/flat01/room0*/temperature")

Results:

 

/house/flat01/room01/temperature

/house/flat01/room02/temperature

 

 

5. WILDCARD + (many characters in topic section) 

 

client.(id=123).subscibe.topic("/house/flat01/room+/temperature") 

 

Results:

/house/flat01/room01/temperature

/house/flat01/room02/temperature

/house/flat01/room13/temperature

 

6. "WILDCARD" - (get messages without payload)

 I wanna get some information like

• Is there currently a message for a specific topic in the queue of the broker?
• How many messages for a specific topic are in the queue of the broker? (Should I download them now or later?)
• What kind of topics are currently in the queue of the broker (like topic discovery)?

Example:

client(id=123).subscribe.topic("/house/#/-")

As a results I will get empty messages for those topics without any payload:

/house/flat01/room01/temperature

/house/flat01/room02/temperature

/house/flat01/room13/temperature

/house/flat01/oven/temperature

That I know, that currently messages for these topics are available and I can chosse, which topic I wanna subscribe to (discovery). 

client(id=123).subscibe.topic("/house/flat01/room04/temperature/-")

Result:

UNKNOWN TOPIC

client(id=123).subscribe.topic("/house/float01/room01/temperature/-")

Results:

 /house/flat01/room01/temperature

message 1

message 2

message 3

message 4 

So I know, that there are messages for this topics and that there are four messages. (E.g. I could decide to start the subscription later if there are enough messages in the queue.)

Why I don't use the filter with payload? I wanna let the messages in the queue. And I don't want to have all the network traffic for downloading large payloads I am not interested in, because I am only interested to know, what kind of topics exists and after that choose those one I wanna really subscribe to.

Any feedback?

Best

Stefan 

 

 

 

 

[Stefan Hupe]

/-

will deliver all messages in the queue without payload

/--

will deliver only one message for each topic without payload