Add annotations and metadata to segments with the X-Ray SDK for Node.js

You can record additional information about requests, the environment, or your application with annotations and metadata. You can add annotations and metadata to the segments that the X-Ray SDK creates, or to custom subsegments that you create.

Annotations are key-value pairs with string, number, or Boolean values. Annotations are indexed for use with filter expressions. Use annotations to record data that you want to use to group traces in the console, or when calling the GetTraceSummaries API.

Metadata are key-value pairs that can have values of any type, including objects and lists, but are not indexed for use with filter expressions. Use metadata to record additional data that you want stored in the trace but don't need to use with search.

In addition to annotations and metadata, you can also record user ID strings on segments. User IDs are recorded in a separate field on segments and are indexed for use with search.

Recording annotations with the X-Ray SDK for Node.js

Use annotations to record information on segments or subsegments that you want indexed for search.

Annotation Requirements

• Keys – Up to 500 alphanumeric characters. No spaces or symbols except underscores.

• Values – Up to 1,000 Unicode characters.

• Entries – Up to 50 annotations per trace.

To record annotations

1. Get a reference to the current segment or subsegment.

   var AWSXRay = require('aws-xray-sdk');
   ...
   var document = AWSXRay.getSegment();

2. Call addAnnotation with a String key, and a Boolean, Number, or String value.

   document.addAnnotation("mykey", "my value");

The SDK records annotations as key-value pairs in an annotations object in the segment document. Calling addAnnotation twice with the same key overwrites previously recorded values on the same segment or subsegment.

To find traces that have annotations with specific values, use the annotations.key keyword in a filter expression.

Example app.js - annotations

var AWS = require('aws-sdk');
var AWSXRay = require('aws-xray-sdk');
var ddb = AWSXRay.captureAWSClient(new AWS.DynamoDB());
...
app.post('/signup', function(req, res) {
    var item = {
        'email': {'S': req.body.email},
        'name': {'S': req.body.name},
        'preview': {'S': req.body.previewAccess},
        'theme': {'S': req.body.theme}
    };

    var seg = AWSXRay.getSegment();
    seg.addAnnotation('theme', req.body.theme);
  
    ddb.putItem({
      'TableName': ddbTable,
      'Item': item,
      'Expected': { email: { Exists: false } }
  }, function(err, data) {
...

Recording metadata with the X-Ray SDK for Node.js

Use metadata to record information on segments or subsegments that you don't need indexed for search. Metadata values can be strings, numbers, Booleans, or any other object that can be serialized into a JSON object or array.

To record metadata

1. Get a reference to the current segment or subsegment.

   var AWSXRay = require('aws-xray-sdk');
   ...
   var document = AWSXRay.getSegment();

2. Call addMetadata with a string key, a Boolean, number, string, or object value, and a string namespace.

   document.addMetadata("my key", "my value", "my namespace");

   or

   Call addMetadata with just a key and value.

   document.addMetadata("my key", "my value");

If you don't specify a namespace, the SDK uses default. Calling addMetadata twice with the same key overwrites previously recorded values on the same segment or subsegment.

Recording user IDs with the X-Ray SDK for Node.js

Record user IDs on request segments to identify the user who sent the request. This operation isn’t compatible with AWS Lambda functions because segments in Lambda environments are immutable. The setUser call can be applied only to segments, not subsegments.

To record user IDs

1. Get a reference to the current segment or subsegment.

   var AWSXRay = require('aws-xray-sdk');
   ...
   var document = AWSXRay.getSegment();

2. Call setUser() with a string ID of the user who sent the request.

   var user = 'john123';
   
   AWSXRay.getSegment().setUser(user);

You can call setUser to record the user ID as soon as your express application starts processing a request. If you will use the segment only to set the user ID, you can chain the calls in a single line.

Example app.js - user ID

var AWS = require('aws-sdk');
var AWSXRay = require('aws-xray-sdk');
var uuidv4 = require('uuid/v4');
var ddb = AWSXRay.captureAWSClient(new AWS.DynamoDB());
...
    app.post('/signup', function(req, res) {
    var userId = uuidv4();
    var item = {
        'userId': {'S': userId},
        'email': {'S': req.body.email},
        'name': {'S': req.body.name}
    };

    var seg = AWSXRay.getSegment().setUser(userId);
  
    ddb.putItem({
      'TableName': ddbTable,
      'Item': item,
      'Expected': { email: { Exists: false } }
  }, function(err, data) {
...

To find traces for a user ID, use the user keyword in a filter expression.