Metrics

Moleculer has a built-in metrics feature. You can enable it within the broker options with metrics: true option.
If it is enabled, the broker emits metrics events at every requests. You can subsribe to these events in your services and transfer them to your Tracer system (ZipKin, OpenTracing…etc).

Context params & meta

You can customize that the broker puts some ctx.meta and ctx.params fields to the metrics events.

Define it in the action definition:

module.exports = {
    name: "test",
    actions: {
        import: {
            cache: true,
            metrics: {
                // Don't add `ctx.params` to metrics payload. Default: false
                params: false,
                // Add `ctx.meta` to metrics payload. Default: true
                meta: true
            },
            handler(ctx) {
                // ...
            }
        }
    }
}

If the value is true, it adds all fields. If Array, it adds only the specified fields. If Function, it calls with params or metaand you need to return an Object.

Examples

All fields

// Action definition
{
    metrics: { params: true }
}

// Request params
broker.call("user.create", { name: "John", lastname: "Doe" });

// Metrics payload
{
    params: { name: "John", lastname: "Doe" }
}

Only selected fields

// Action definition
{
    metrics: { 
        params: ["name"],
        meta: ["user"]
    }
}

// Request params
broker.call("user.create", { name: "John", lastname: "Doe" }, { meta: { user } });

// Metrics payload
{
    params: { name: "John" },
    meta: {
        user: {
            // ...
        }
    }
}

Custom mapping function

// Action definition
{
    metrics: { 
        params: p => {
            return { 
                name: p.name + ' ' + p.lastname
            };
        }
    }
}

// Request params
broker.call("user.create", { name: "John", lastname: "Doe" });

// Metrics payload
{
  params: { name: "John Doe" }
}

Request started event

The broker emits an metrics.trace.span.start event when a new request is started.
The payload looks like the following:

{
    // Context ID
    id: '4563b09f-04cf-4891-bc2c-f26f80c3f91e',
    // Request ID
    requestID: null,
    // Level of call
    level: 1,
    // Start time
    startTime: 1493903164726,
    // Is it a remote call
    remoteCall: false,
    // Called action
    action: {
        name: 'users.get'
    }
    // Params
    params: {
        id: 5
    }
    // Meta
    meta: {}
    // Node ID
    nodeID: "node-1",
    // Caller nodeID if it's requested from a remote node
    callerNodeID: "node-2",
    // Parent context ID if it is a sub-call
    parentID: '123456'
}

Request finished event

The broker emits an metrics.trace.span.finish event when the call/request is finished.
The payload looks like the following:

{
    // Context ID
    id: '4563b09f-04cf-4891-bc2c-f26f80c3f91e',
    // Request ID
    requestID: null,
    // Level of call
    level: 1,
    // Start time
    startTime: 1493903164726,
    // End time
    endTime: 1493903164731.3684,
    // Duration of request
    duration: 5.368304,
    // Is it a remote call
    remoteCall: false,
    // Is it resolved from cache
    fromCache: false,
    // Called action
    action: {
        name: 'users.get'
    }
    // Params
    params: {
        id: 5
    }
    // Meta
    meta: {}
   
    // Node ID
    nodeID: "node-1",
    // Caller nodeID if it's a remote call
    callerNodeID: "node-2",
    // Parent context ID if it is a sub-call
    parentID: '123456'

    // Error if the call returned with error
    error: {
        name: "ValidationError",
        message: "Invalid incoming parameters"
    }
}

Circuit-breaker events

metrics.circuit-breaker.opened

The broker sends this event when the circuit breaker module changed its state to open.

Payload

Name	Type	Description
nodeID	String	Node ID
action	String	Action name
failures	Number	Count of failures

metrics.circuit-breaker.half-opened

The broker sends this event when the circuit breaker module changed its state to half-open.

Payload

Name	Type	Description
nodeID	String	Node ID
action	String	Action name

metrics.circuit-breaker.closed

The broker sends this event when the circuit breaker module changed its state to closed.

Payload

Name	Type	Description
nodeID	String	Node ID
action	String	Action name