notify when db is ready about node-red-nodes HOT 9 OPEN

Hi

I think there is something to explore here.

I'm away from my laptop, so can't readily dig up examples, but some of our config nodes tackle this in different ways.

Some just provide shared config properties, with no functional code. It is left to the individual nodes to make use of the properties in whatever way makes sense.

Some represent a connection to an external system, and provide connection pooling. They also wrap the api such that it can always be called, regardless of the connection state. The async nature of node-red means messages can be flowing without everything connected etc. The MQTT connection, for example, allows subscriptions to be made even if not connected; they get buffered for when the connection is available.

Adding a node event would be another way if tackling it. But I want to think how this could be more widely applied. I'd rather a standard set of events over having node-specific events.

from node-red-nodes.

I did experiment to see if events.on("nodes-started"){} might work but unfortunately not.

from node-red-nodes.

as node.db only gets assigned within that same function can you not just check if it exists ? (I know it's not the node.js event style but... until we have a better plan)

from node-red-nodes.

thanks for your comment. do you have an example of how this would work? essentially i want to be able to make a db request during our node's init - at least prior to having this.on('input',...) invoked.

from node-red-nodes.

maybe something like...

        var i = 0;
        var chk = function() {
            if (!node.levelConfig.db) {
                i += 1;
                if (i >= 20) {
                    node.error("Database didn't connect"); // report some lack of database error after 10 secs
                }
                setTimeout( function() {
                    chk();
                }, 500); // check every 0.5 secs
            }
            else {
                // do something when we see database
            }
        }
        chk();

from node-red-nodes.

yes, this would work. to be honest i liked my suggestion better ...
thanks for the example.

from node-red-nodes.

Yes, an event based solution is much cleaner than having to poll. But at
least you can poll today until we get to doing this properly.

On Mon, 19 Jan 2015 18:58 Andrew McClure [email protected] wrote:

yes, this would work. to be honest i liked my suggestion better ...
thanks for the example.

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#90 (comment)
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from node-red-nodes.

actually that code need to break out of the loop once it gets the timeout error... :-)

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This adds backwards and hopefully forwards compatibility :)

    int i =0;
    this.dbChk = function() { // node <=> this
        if (!node.levelConfig.db) {
            i += 1;
            if (i >= 20) {
                node.error("Database didn't connect"); // report some lack of database error after 10 secs
                return;
            }
            setTimeout( function() {
                node.dbChk();
            }, 500); // check every 0.5 secs
        }
        else {
            node.levelConfig.emit('connect'); // Use existing handler.
        }
    }

    events.on("nodes-started",function(){
        node.dbChk();
    });

from node-red-nodes.