Add property filter to broker signal subscription

[fvacek]

.app/broker/currentClient:subscribe() can have two params currently

• path
• method

I suggest to provide third optional parameter property, which will behave like additional subscription filter. Notificaton is currently delivered to client if:

1. signal method equals method subscribed
2. signal path starts with path subscribed

Proposed change is to add third option:

1. signal path ends with property subscribed

This change enables client to subscribe not only method but also method of some property.

Use-case:

We wand to subscribe chng signal of all alarms in shv tree but not other properties changes. Only way how to achieve this currently is to call subscribe for every alarm node. With this change implemented, one can call subscribe only once.

Before:

• .app/broker/currentClient:subscribe({"path": "foo/bar1/alarm", "method": "chng"})
• .app/broker/currentClient:subscribe({"path": "foo/bar2/alarm", "method": "chng"})
• .app/broker/currentClient:subscribe({"path": "foo/bar/baz/alarm", "method": "chng"})

After:

• .app/broker/currentClient:subscribe({"path": "foo", "method": "chng", "property": "alarm"})

[fvacek]

@Cynerd

[fvacek]

Version 2

We keep path parameter unchanged.

A new pattern parameter will be added, when pattern is specified, then the path parameter is ignored. pattern parameter can hold glob pattern plus globstar (**). Signals with paths matching pattern will be subscribed.

Sub-broker note

When subscription with pattern is requested, then broker must split pattern to local and sub-broker path. One possible implementation is:

1. foreach subrokers mountpoint
   1. remove last part of the pattern after slash, until it matches moutpoint
   2. matching part of pattern is local pattern, rest of pattern must be subscribed in subbroker
   3. if local part ends with **, then ** must be prepended also to subbroker pattern

• https://man7.org/linux/man-pages/man7/glob.7.html
• https://man7.org/linux/man-pages/man3/fnmatch.3.html
• https://en.wikipedia.org/wiki/Glob_(programming)