dd-trace/packages/datadog-plugin-ws/src/util.js

Datadog APM tracing client for JavaScript

'use strict'

const DatadogSpanContext = require('../../dd-trace/src/opentracing/span_context')

const TRACE_ID_UPPER_TAG = '_dd.p.tid'

// WeakMap to store message counters per socket without mutating the socket object
const socketCounters = new WeakMap()

/**
 * Creates a minimal span context for span links without retaining the full trace.
 * @param {DatadogSpanContext} spanContext
 * @returns {DatadogSpanContext | undefined}
 */
function createWebSocketSpanContext (spanContext) {
  if (!spanContext) return

  const traceIdUpper = spanContext._trace?.tags?.[TRACE_ID_UPPER_TAG]
  const trace = traceIdUpper
    ? { started: [], finished: [], tags: { [TRACE_ID_UPPER_TAG]: traceIdUpper } }
    : undefined

  return new DatadogSpanContext({
    traceId: spanContext._traceId,
    spanId: spanContext._spanId,
    parentId: spanContext._parentId,
    sampling: spanContext._sampling,
    traceparent: spanContext._traceparent,
    tracestate: spanContext._tracestate,
    isRemote: spanContext._isRemote,
    trace,
  })
}

/**
 * Returns whether distributed trace headers are present.
 * @param {Record<string, string | string[] | undefined>} headers
 * @returns {boolean}
 */
function hasTraceHeaders (headers) {
  return !!(headers && (headers['x-datadog-trace-id'] || headers.traceparent))
}

/**
 * Initializes WebSocket message counters for a socket.
 * @param {object} socket - The WebSocket socket object
 */
function initWebSocketMessageCounters (socket) {
  if (!socketCounters.has(socket)) {
    socketCounters.set(socket, {
      receiveCounter: 0,
      sendCounter: 0,
    })
  }
}

/**
 * Increments and returns the WebSocket message counter.
 * @param {object} socket - The WebSocket socket object
 * @param {string} counterType - Either 'receiveCounter' or 'sendCounter'
 * @returns {number} The incremented counter value
 */
function incrementWebSocketCounter (socket, counterType) {
  if (!socketCounters.has(socket)) {
    initWebSocketMessageCounters(socket)
  }
  const counters = socketCounters.get(socket)
  counters[counterType]++
  return counters[counterType]
}

/**
 * Builds a WebSocket span pointer hash.
 *
 * Format: <prefix><128 bit hex trace id><64 bit hex span id><32 bit hex counter>
 * Prefix: 'S' for server outgoing or client incoming, 'C' for server incoming or client outgoing
 *
 * @param {bigint} handshakeTraceId - The trace ID from the handshake span (as a BigInt)
 * @param {bigint} handshakeSpanId - The span ID from the handshake span (as a BigInt)
 * @param {number} counter - The message counter
 * @param {boolean} isServer - Whether this is a server (true) or client (false)
 * @param {boolean} isIncoming - Whether this is an incoming message (true) or outgoing (false)
 * @returns {string} The span pointer hash
 */
function buildWebSocketSpanPointerHash (handshakeTraceId, handshakeSpanId, counter, isServer, isIncoming) {
  // Determine prefix based on server/client and incoming/outgoing
  // Server outgoing or client incoming: 'S'
  // Server incoming or client outgoing: 'C'
  const prefix = (isServer && !isIncoming) || (!isServer && isIncoming) ? 'S' : 'C'

  // Pad trace ID to 32 hex chars (128 bits)
  const traceIdHex = handshakeTraceId.toString(16).padStart(32, '0')

  // Pad span ID to 16 hex chars (64 bits)
  const spanIdHex = handshakeSpanId.toString(16).padStart(16, '0')

  // Pad counter to 8 hex chars (32 bits)
  const counterHex = counter.toString(16).padStart(8, '0')

  return `${prefix}${traceIdHex}${spanIdHex}${counterHex}`
}

/**
 * Checks if the handshake span has extracted distributed tracing context.
 * A websocket server must not set the span pointer if the handshake has not extracted a context.
 *
 * A span has distributed tracing context if it has a parent context that was
 * extracted from headers (remote parent).
 *
 * @param {DatadogSpanContext} spanContext - The handshake span context
 * @param {{ hasTraceHeaders?: boolean } | undefined} socket - The WebSocket socket object
 * @returns {boolean} True if the span has distributed tracing context
 */
function hasDistributedTracingContext (spanContext, socket) {
  if (!spanContext) return false

  // Check if this span has a parent. If the parent was extracted from remote headers,
  // then this span is part of a distributed trace.
  // We check if the span has a parent by looking at _parentId.
  // In the JavaScript tracer, when a context is extracted from headers and a child span
  // is created, the child will have _parentId set to the extracted parent's span ID.
  //
  // For testing purposes, we also check if Datadog trace headers are present in the socket's
  // upgrade request, which indicates distributed tracing context was sent by the client.
  if (spanContext._parentId !== null) {
    return true
  }

  return !!socket?.hasTraceHeaders
}

module.exports = {
  createWebSocketSpanContext,
  hasTraceHeaders,
  initWebSocketMessageCounters,
  incrementWebSocketCounter,
  buildWebSocketSpanPointerHash,
  hasDistributedTracingContext,
}