@dotcom-reliability-kit/serialize-request

A utility function to serialize a request object (Express or IncomingMessage) in a way that's friendly to loggers, view engines, and converting to JSON. This module is part of FT.com Reliability Kit.

• Usage
  • serializeRequest
  • configuration options
    • includeHeaders
  • SerializedRequest type
    • SerializedRequest.id
    • SerializedRequest.method
    • SerializedRequest.url
    • SerializedRequest.headers
    • SerializedRequest.route
• Migrating
• Contributing
• License

Usage

Install @dotcom-reliability-kit/serialize-request as a dependency:

npm install --save @dotcom-reliability-kit/serialize-request

Include in your code:

import serializeRequest from '@dotcom-reliability-kit/serialize-request';

[!TIP] If you're using this package with TypeScript, we recommend using the following settings in your tsconfig.json file to avoid type errors:

{
    "esModuleInterop": true,
    "module": "nodenext",
    "moduleResolution": "nodenext"
}

serializeRequest

The serializeRequest function accepts a request-like object (e.g. an instance of Express.Request or an object with method and url properties) and returns a plain JavaScript object (conforming to the SerializedRequest type) which contains the relevant properties. The example below assumes that app is an Express application:

app.get('/fruit/:fruitId', (request, response, next) => {
    console.log(serializeRequest(request));
    next();
});
// {
//     id: 'request137',
//     method: 'GET',
//     url: '/fruit/feijoa',
//     headers: {
//         accept: '*/*'
//     },
//     route: {
//         path: '/fruit/:fruitId',
//         params: { fruitId: 'feijoa' }
//     }
// }

You can also pass in a plain object if you already have one that looks like a request:

serializeRequest({
    method: 'get',
    url: '/hello'
});

Configuration options

Config options can be passed into the serializeRequest function as a second argument. It expects an object with any of the keys below.

serializeRequest(request, {
    // Config options go here
});

options.includeHeaders

An array of request headers to include in the serialized request object. This must be an Array of Strings, with each string being a header name. It's important that you do not include headers which include personally-identifiable-information, API keys, or other privileged information.

This option defaults to:

[
    'accept',
    'accept-encoding',
    'accept-language',
    'content-type',
    'referer',
    'user-agent'
]

Example of usage:

serializeRequest(request, {
    includeHeaders: [
        'accept',
        'content-length',
        'content-type',
        'user-agent'
    ]
});

The default set of headers is also available to use, so that you don't need to repeat them if you want to add new included headers. It can be accessed as DEFAULT_INCLUDED_HEADERS:

import serializeRequest, { DEFAULT_INCLUDED_HEADERS } from '@dotcom-reliability-kit/serialize-request';

serializeRequest(request, {
    includeHeaders: [
        ...DEFAULT_INCLUDED_HEADERS,
        'my-custom-header'
    ]
});

SerializedRequest type

The SerializedRequest type documents the return value of the serializeRequest function. It will have the following properties, extracting them from a given request object.

SerializedRequest.id

This is extracted from the request.headers['x-request-id'] property and is always cast to a String. It defaults to null.

SerializedRequest.method

This is extracted from the request.method property and is always cast to a String and switched to uppercase. It defaults to "-".

SerializedRequest.url

This is extracted from the request.url property and is always cast to a String. It defaults to "/".

SerializedRequest.headers

This is extracted from the request.headers property and is filtered to only include the headers specified in the includeHeaders option. It defaults to an empty object.

SerializedRequest.route

This is an object extracted from request.route.path (string) and request.params (object) if they are present and conform to the same properties on an Express Request object. It defaults to undefined.

Migrating

Consult the Migration Guide if you're trying to migrate to a later major version of this package.

Contributing

See the central contributing guide for Reliability Kit.

License

Licensed under the MIT license.
Copyright © 2022, The Financial Times Ltd.