@ableron/ableron

JavaScript Library for Ableron Server Side UI Composition.

Installation

npm i @ableron/ableron

Usage

Normally, you do not want to use ableron-js directly, because intercepting and modifying the response body within your service may be tricky. Instead, you may want to use an existing framework integration, which uses ableron-js under the hood, e.g.

• ableron-express
• ableron-fastify

To use ableron-js directly, do something like this:

import { Ableron } from '@ableron/ableron';

const ableron = new Ableron(
  /* optional configuration */
  {
    statsAppendToContent: true
    // ...
  },
  // optional logger
  pinoWinstonMorganOrWhateverYouMayHave() || console
);
const rawResponseBody = buildRawResponseBody();
const req = yourNodeJsRequestObject();
const res = yourNodeJsResponseObject();

try {
  ableron
    .resolveIncludes(rawResponseBody, req.headers)
    .then((transclusionResult) => {
      transclusionResult
        .getResponseHeadersToPass()
        .forEach((headerValue, headerName) => res.setHeader(headerName, headerValue));
      res.setHeader(
        'Cache-Control',
        transclusionResult.calculateCacheControlHeaderValueByResponseHeaders(res.getHeaders())
      );
      res.setHeader('Content-Length', Buffer.byteLength(transclusionResult.getContent()));
      res.status(transclusionResult.getStatusCodeOverride() || res.statusCode);
      setFinalResponseBody(transclusionResult.getContent());
    })
    .catch((e) => {
      logger.error(`[Ableron] Unable to perform UI composition: ${e.stack || e.message}`);
    });
} catch (e) {
  logger.error(`[Ableron] Unable to perform UI composition: ${e.stack || e.message}`);
}

Configuration

enabled

Default: true

Whether UI composition is enabled.

fragmentRequestTimeoutMillis

Default: 3000

Timeout in milliseconds for requesting fragments.

fragmentRequestHeadersToPass

Default:

[
  'Accept-Language',
  'Correlation-ID',
  'Forwarded',
  'Referer',
  'User-Agent',
  'X-Correlation-ID',
  'X-Forwarded-For',
  'X-Forwarded-Proto',
  'X-Forwarded-Host',
  'X-Real-IP',
  'X-Request-ID'
];

Request headers that are passed to fragment requests, if present.

fragmentAdditionalRequestHeadersToPass

Default: []

Extends fragmentRequestHeadersToPass. Use this property to pass all headers defined in fragmentRequestHeadersToPass plus the additional headers defined here. This prevents the need to duplicate fragmentRequestHeadersToPass if the only use case is to add additional headers instead of modifying the default ones.

primaryFragmentResponseHeadersToPass

Default: ['Content-Language', 'Location', 'Refresh']

Response headers of primary fragments to pass to the page response, if present.

cacheMaxItems

Default: 10000

Maximum number of items, the fragment cache may hold.

cacheVaryByRequestHeaders

Default: []

Fragment request headers which influence the requested fragment aside from its URL. Used to create fragment cache keys. Must be a subset of fragmentRequestHeadersToPass. Common example are headers used for steering A/B-tests.

cacheAutoRefreshEnabled

Default: false

Whether to enable auto-refreshing of cached fragments, before they expire. If set to true, cached fragments are getting asynchronously refreshed before they expire. This reduces the cache miss rate and thus have a positive impact on latency. On the other hand, additional traffic is introduced, because the cached fragments are loaded again even before their actual expiration time. Fragments are tried to be refreshed when only 15% of their initial time to live remains. In case of failure, refresh is repeated three times with a static delay of one second.

cacheAutoRefreshMaxAttempts

Default: 3

Maximum number of attempts to refresh a cached fragment.

cacheAutoRefreshInactiveFragmentsMaxRefreshs

Default: 2

Maximum number of consecutive refreshs of inactive cached fragments. Fragments are considered inactive, if they have not been read from cache between writing to cache and a refresh attempt.

statsAppendToContent

Default: false

Whether to append UI composition stats as HTML comment to the content.

statsExposeFragmentUrl

Default: false

Whether to expose fragment URLs in the stats appended to the content.

Contributing

All contributions are greatly appreciated, be it pull requests, feature requests or bug reports. See ableron.github.io for details.

License

Licensed under MIT.