Skip to content
Permalink
Branch: master
Find file Copy path
Find file Copy path
@trygve-lie trygve-lie Badges 5bfd5f9 Feb 21, 2019
3 contributors

Users who have contributed to this file

@trygve-lie @digitalsadhu @greenkeeper
405 lines (295 sloc) 11.4 KB

@podium/layout

Module for composing full page layouts out of page fragments in a micro frontend architecture.

Dependencies Build Status Greenkeeper badge Known Vulnerabilities

Module for building a layout server. A layout server is mainly responsible for fetching HTML fragments and stitching these fragments into an full HTML page.

To do this, a layout instance provides three core features:

  • @podium/client used to fetch content from podlets
  • @podium/context used to set request bound information on the requests from the layout to podlets when fetching their content
  • @podium/proxy makes it possible to publicly expose data endpoints in a podlet or in any backend service

This module can be used together with a plain node.js HTTP server or any HTTP framework and any templating language of your choosing (or none if you prefer). Though; Connect compatible middleware based frameworks (such as Express) is first class in Podium so this module comes with a .middleware() method for convenience.

For writing layout servers with other http frameworks the following modules exist:

Installation

$ npm install @podium/layout

Simple usage

Build a simple layout server including a single podlet using Express:

const express = require('express');
const Layout = require('@podium/layout');

const layout = new Layout({
    name: 'myLayout',
    pathname: '/',
});

const podlet = layout.client.register({
    name: 'myPodlet',
    uri: 'http://localhost:7100/manifest.json',
});

const app = express();
app.use(layout.middleware());

app.get('/', (req, res, next) => {
    const ctx = res.locals.podium.context;
    Promise.all([podlet.fetch(ctx)]).then(result => {
        res.status(200).send(`
                <html><body>
                    <section>${result[0]}</section>
                </body></html>
            `);
    });
});

app.listen(7000);

Constructor

Create a new Layout instance.

const layout = new Layout(options);

options

option default type required details
name null string true Name that the layout identifies itself by
pathname null string true Pathname of where a Layout is mounted in a http server
logger null object false A logger which conform to a log4j interface
context null object false Options to be passed on to the internal @podium/context constructor
client null object false Options to be passed on to the internal @podium/client constructor
proxy null object false Options to be passed on to the internal @podium/proxy constructor

name

Name that the layout identifies itself by. The name value must be in camelCase.

Example:

const layout = new Layout({
    name: 'myLayoutName',
    pathname: '/foo',
});

pathname

The Pathname of where the Layout is mounted into the HTTP server. It is important that this value matches where the entry point of a route is in the HTTP server since this value is used to mount the proxy and tell podlets (through the context) where they are mounted and where the proxy is mounted.

If the layout is mounted at the server "root", set pathname to /:

const app = express();
const layout = new Layout({
    name: 'myLayout',
    pathname: '/',
});

app.use(layout.middleware());

app.get('/', (req, res, next) => {
    [ ... ]
});

If the layout is mounted at /foo, set pathname to /foo:

const app = express();
const layout = new Layout({
    name: 'myLayout',
    pathname: '/foo',
});

app.use('/foo', layout.middleware());

app.get('/foo', (req, res, next) => {
    [ ... ]
});

app.get('/foo/:id', (req, res, next) => {
    [ ... ]
});

There is also a helper method for retrieving the set pathname which can be used to get the pathname from the Layout object when defining routes. See .pathname() for further details.

logger

Any log4j compatible logger can be passed in and will be used for logging. Console is also supported for easy test / development.

Example:

const layout = new Layout({
    name: 'myLayout',
    pathname: '/foo',
    logger: console,
});

Under the hood abslog is used to abstract out logging. Please see abslog for further details.

context

Options to be passed on to the internal [@podium/context constructor].

Please see the [@podium/context constructor] for which options can be set.

Example of setting the debug context to default true:

const layout = new Layout({
    name: 'myLayout',
    pathname: '/foo',
    context: {
        debug: {
            enabled: true,
        },
    },
});

client

Options to be passed on to the internal @podium/client constructor.

Please see @podium/client constructor for which options which can be set.

Example of setting the retries on the client to 6:

const layout = new Layout({
    name: 'myLayout',
    pathname: '/foo',
    client: {
        retries: 6,
    },
});

proxy

Options to be passed on to the internal @podium/proxy constructor.

Please see @podium/proxy constructor for which options which can be set.

Example of setting the timeout on the proxy to 30 seconds:

const layout = new Layout({
    name: 'myLayout',
    pathname: '/foo',
    proxy: {
        timeout: 30000,
    },
});

API

The Layout instance has the following API:

.process(HttpIncoming)

Metod for processing an incoming HTTP request. This method is intended to be used to implement support for multiple HTTP frameworks and should not really be used directly in a layout server.

What it does:

  • Runs @podium/context parsers on the incoming request and sets an object with the context at HttpIncoming.context which can be passed on to the client when requesting content from podlets.
  • Mounts the @podium/proxy so each podlet can do transparent proxy requests if needed.

Returns a Promise. If the inbound request matches a proxy endpoint the returned Promise will resolve with undefined. If the inbound request does not match a proxy endpoint the returned Promise will resolve with the passed in HttpIncoming object.

The method take the following arguments:

HttpIncoming (required)

An instance of an HttpIncoming class.

const { HttpIncoming } = require('@podium/utils');
const Layout = require('@podium/layout');

const layout = new Layout({
    name: 'myLayout',
    pathname: '/',
});

app.use(async (req, res, next) => {
    const incoming = new HttpIncoming(req, res, res.locals);
    try {
        const result = await layout.process(incoming);
        if (result) {
            res.locals.podium = result;
            next();
        }
    } catch (error) {
        next(error);
    }
});

.middleware()

A Connect compatible middleware which takes care of the operations needed for a layout to fully work. It is more or less a wrapper for the .process() method.

Important: This middleware must be mounted before defining any routes.

Example

const app = express();
app.use(layout.middleware());

The context generated by the middleware will be stored at res.locals.podium.context.

Returns an Array of internal middleware performing the tasks described above.

.pathname()

A helper method to retrieve the pathname set on the constructor. This can be handy to use in defining routes since the pathname set in the constructor must match whatever is defined as root in each route in a HTTP router.

Example:

const layout = new Layout({
    name: 'myLayout',
    pathname: '/foo'
});

app.get(layout.pathname(), (req, res, next) => {
    [ ... ]
});

app.get(`${layout.pathname()}/bar`, (req, res, next) => {
    [ ... ]
});

app.get(`${layout.pathname()}/bar/:id`, (req, res, next) => {
    [ ... ]
});

.client

A property that exposes an instance of the @podium/client for fetching content from podlets.

Example of registering a podlet and fetching it:

const layout = new Layout({
    name: 'myLayout',
    pathname: '/',
});

const podlet = layout.client.register({
    name: 'myPodlet',
    uri: 'http://localhost:7100/manifest.json',
});

podlet.fetch({}).then(result => {
    console.log(result);
});

Please see @podium/client for full documentation.

.context

A property that exposes an instance of the @podium/context used to create a context.

Example of registering a custom third party context parser to the context:

const Parser = require('my-custom-parser');

const layout = new Layout({
    name: 'myLayout',
    pathname: '/',
});

layout.context.register('customParser', new Parser('someConfig'));

Please see @podium/context for full documentation.

.metrics

Property that exposes a metric stream. This stream joins all internal metrics streams into one stream resulting in all metrics from all sub modules being exposed here.

Please see @metrics/metric for full documentation.

License

Copyright (c) 2019 FINN.no

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

You can’t perform that action at this time.