autohost-canary

autohost-canary

Adds an end-point for tracking in-depth status of a service. Services determine what gets reported as status via API.

Installation & Setup

npm install autohost-canary -S

var autohost = require( "autohost" );
var host;
var hyped = require( "hyped" )();
var fount = require( "fount" );
var postal = require( "postal" );
// create the channel used to communicate between
// various components and the status tracker
var channel = postal.channel( "ahcanary" );
 
fount.register( "ahcanary", channel );
host = hyped.createHost( autohost, {
    port: config.nonstop.host.port,
    modules: [
        "autohost-canary"
    ],
    fount: fount
}, function() {
    host.start();
} );
 
// by publishing a status to a topic, the status tracker will update its state
// where topic is the key and the message will be the value. This is a very simple
// way to get a quick glimpse into what's happening. See status messages for more
// details on how to control status.
 
// this example demonstrates tracking rabbit connectivity:
rabbit.on( "connected", function( msg ) {
    channel.publish( "rabbit", { value: "connected" } );
} );
 
rabbit.on( "closed", function( msg ) {
    channel.publish( "rabbit", { value: "closed" } );
} );
 
rabbit.on( "failed", function( msg ) {
    channel.publish( "rabbit", { value: "connection failed" } );
} );

HTTP API

The only thing you can do is get the status:

GET /api/ah/status

If you're using hyped then you can access the same endpoint via status:self. The names and routes were chosen to make the chance of collision extremely low.

The result will be a JSON object with your keys/values and a few bonus items:

{
    // your stuff here ...
    "memory": { a hash containing memory usage details },
    "uptime": "a human readable duration",
    "version": "a version specifier from your package.json OR nonstop-info"
}

Status Messages

You get a little more control on what status is reported based on how you format your message.

Default

You can publish a message with default to tell canary that if the key is removed or reset to still display the key with the default value.

channel.publish( "database", { default: "pending" } );

Reset

Publishing this message will cause the key to revert to undefined or a previously provided default value.

channel.publish( "key", { reset: true } );

Value

Updates the current status for the topic to the value provided.

channel.publish( "usersConnected", x );

Time to live (milliseconds)

Some values are only good for a period of time or don't have a compensating event to tell you when the value has changed. To address this, you can put a ttl property on the message body which will cause the value to be removed from status or revert to a previously assigned default.

channel.publish( "processingMessages", value: true, ttl: 100 )