marathon-event-bus-client
v0.1.7
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Listen to Marathon's Event Bus, and send events to event handler implementations
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marathon-event-bus-client
A generic client to listen to Marathon's (Server Sent) Event Bus.
Usage
Install as a dependency like this:
npm install marathon-event-bus-client --save
Events
Known Marathon events
As of the Marathon sources there are currently the following events:
pod_created_event
pod_updated_event
pod_deleted_event
scheduler_registered_event
scheduler_reregistered_event
scheduler_disconnected_event
subscribe_event
unsubscribe_event
event_stream_attached
event_stream_detached
add_health_check_event
remove_health_check_event
failed_health_check_event
health_status_changed_event
unhealthy_task_kill_event
group_change_success
group_change_failed
deployment_info
deployment_success
deployment_failed
deployment_step_success
deployment_step_failure
app_terminated_event
status_update_event
instance_changed_event
unknown_instance_terminated_event
instance_health_changed_event
framework_message_event
Internal events
The Marathon Event Bus Client itself emits the following events:
subscribed
: Is emitted after a successful subscription to the Marathon Event Bus.unsubscribed
: Is emitted afterunsubscribe()
is called.error
: Is emitted in case of internal or upstream errors.
Using the client
Options
You can specify the following properties when instantiating the Marathon Event Bus Client:
marathonHost
: The Marathon base URL. Default ismaster.mesos
.marathonPort
: The Marathon port. Default is8080
.marathonProtocol
: The Marathon protocol (http
orhttps
). Default ishttp
.marathonUri
: The relative path where the Marathon Event Bus endpoint can be found. Default is/v2/events
.marathonHeaders
: A dict of http headers which should be added to Marathon's API requests , mainly for authentication/authorization (bothAuthorization
andContent-Type
are allowed). See the Marathon docs or the DC/OS docs for further info. Not used by default.eventTypes
: Anarray
of event types emitted by Marathon (see above for a list). Default is["deployment_info", "deployment_success", "deployment_failed"]
.handlers
: A map object consisting of handler functions for the individual Marathon events. See below for an explanation. No defaults.
Methods
The Marathon Event Bus Client only exposes the subscribe()
and the unsubscribe()
methods. You can catch all above events via on(<eventType>, function (data) { ... }
.
Handler functions
The custom event handler functions can be configured by setting a map object as handlers
property during the instantiation. Each map object's property represents a event handling function. The property name needs to match on of the Marathon event types from the list of known Marathon events.
This is an example handlers
map object:
{ // Specify the custom event handlers
"deployment_info": function (name, data) {
console.log("We have a new deployment info!");
},
"deployment_success": function (name, data) {
console.log("Our deployment was successful!");
}
}
The function arguments are:
name
: The name of the emitted eventdata
: The emitted data for the event
Example code
For a complete example, have a look at examples/example.js. Also, for a "real-life example", you can refer to marathon-slack.
// Use the MarathonEventBusClient
const MarathonEventBusClient = require("marathon-event-bus-client");
// Define relevant event types
const eventTypes = ["deployment_info", "deployment_success", "deployment_failed"];
// Create MarathonEventBusClient instance
const mebc = new MarathonEventBusClient({
marathonHost: "localhost", // Use SSE test server
eventTypes: eventTypes,
marathonHeaders: { // When using the Marathon Event Bus outside the cluster, otherwise just omit the marathonHeaders.
"Authorization": "token=<authentication-token>" // Replace <authentication-token> with a real authentication token
},
handlers: { // Specify the custom event handlers
"deployment_info": function (name, data) {
console.log("Custom handler for " + name);
// Send information of the "deployment_info" event to an external service (here: Just an echo service)
request("https://echo.getpostman.com/get?name=" + name + "&startTime=" + data.timestamp, function (error, response, body) {
body = JSON.parse(body);
if (!error && response.statusCode == 200) {
console.log("Here's the data we have just sent to the echo service:");
console.log("--------------------");
console.log(JSON.stringify(body.args)); // Show the sent data
console.log("--------------------");
}
});
},
"deployment_success": function (name, data) {
console.log("Custom handler for " + name);
}
}
});
// Wait for "connected" event
mebc.on("connected", function () {
console.log("Subscribed to the Marathon Event Bus");
// For example purposes: Log all events we receive
// In real-world usage, you should define what needs to be done when
// receiving specific events in the `handlers` property for each event type
eventTypes.forEach(function (eventType) {
mebc.on(eventType, function (data) {
console.log("Caught '" + eventType + "' event!");
});
});
// Shutdown after 30 seconds
setTimeout(function () {
console.log("Shutting down");
// Unsubscribe from Event Bus
mebc.unsubscribe();
}, 30000);
});
// Wait for "unsubscribed" event
mebc.on("unsubscribed", function () {
console.log("Unsubscribed from the Marathon Event Bus");
});
// Catch error events
mebc.on("error", function (errorObj) {
console.log("Got an error on " + errorObj.timestamp + ":");
console.log(JSON.stringify(errorObj.error));
});
// Subscribe to Marathon Event Bus
mebc.subscribe();