dd-trace-meteor-methods

tracing.js

// Datadog tracer must initialize before other imports to enable auto-instrumentation.
const tracer = require("dd-trace").init({
    // Configure via env vars (DD_SERVICE, DD_ENV, DD_VERSION, DD_TRACE_ENABLED, etc.)
});

const { Meteor } = require("meteor/meteor");

const METHOD_SPAN_NAME = "meteor.method";
const MAX_ARGS_LENGTH = 1024;

function safeStringify(args) {
    try {
        const str = JSON.stringify(args);
        return str.length > MAX_ARGS_LENGTH
            ? str.slice(0, MAX_ARGS_LENGTH) + "...[truncated]"
            : str;
    } catch (_e) {
        return "[unserializable]";
    }
}

/**
 * Before-all hook: start a Datadog span for every Meteor method invocation.
 * The span is stored on `this._ddSpan` so the after hook can finish it.
 */
Meteor.beforeAllMethods(function (...args) {
    const methodName = this._methodName;
    const connectionId = this && this.connection && this.connection.id;
    const userId = this && this.userId;
    const methodId =
        (this && (this._methodId || this.methodId)) ||
        (this && this._message && this._message.id) ||
        (this && this._ddpMessage && this._ddpMessage.id);

    const parentSpan = tracer.scope().active();

    const span = tracer.startSpan(METHOD_SPAN_NAME, {
        resource: methodName,
        childOf: parentSpan || undefined,
        tags: {
            "meteor.method": methodName,
            component: "meteor",
            ...(connectionId ? { "meteor.connection_id": connectionId } : {}),
            ...(userId ? { "meteor.user_id": userId } : {}),
            ...(methodId ? { "meteor.method_id": methodId } : {}),
            "meteor.method_args": safeStringify(args),
        },
    });

    this._ddSpan = span;

    // Activate this span as the current scope so nested Meteor.call()
    // invocations automatically become child spans.
    this._scopeActivate = (fn) => tracer.scope().activate(span, fn);

    console.log(`[method-hooks] BEFORE >> ${methodName} | userId: ${userId || 'none'} | connectionId: ${connectionId || 'none'} | methodId: ${methodId || 'none'} | parentSpan: ${parentSpan ? 'yes' : 'none'}`);
});

/**
 * After-all hook: finish the Datadog span, tagging any errors.
 */
Meteor.afterAllMethods(function () {
    const span = this._ddSpan;
    if (!span) return;

    if (this.error) {
        span.setTag("error", this.error);
    }

    console.log(`[method-hooks] AFTER  >> ${this._methodName} | result: ${this.error ? 'ERROR' : 'OK'}`);
    span.finish();
});