electrode-react-ssr-caching

Support profiling React Server Side Rendering time and component caching to help you speed up SSR.

Installing

npm i electrode-react-ssr-caching

Usage

Note that since this module patches React's source code to inject the caching logic, it must be loaded before the React module.

For example:

import SSRCaching from "electrode-react-ssr-caching";
import React from 'react';
import ReactDOM from 'react-dom/server';

Profiling

You can use this module to inspect the time each component took to render.

import SSRCaching from "electrode-react-ssr-caching";
import { renderToString } from "react-dom/server";
import MyComponent from "mycomponent";

// First you should render your component in a loop to prime the JS engine (i.e: V8 for NodeJS)
for( let i = 0; i < 10; i ++ ) {
    renderToString(<MyComponent />);
}

SSRCaching.clearProfileData();
SSRCaching.enableProfiling();
const html = renderToString(<MyComponent />);
SSRCaching.enableProfiling(false);
console.log(JSON.stringify(SSRCaching.profileData, null, 2));

Caching

Once you determined the most expensive components with profiling, you can enable component caching this module provides to speed up SSR performance.

The basic steps to enabling caching are:

import SSRCaching from "electrode-react-ssr-caching";

SSRCaching.enableCaching();
SSRCaching.setCachingConfig(cacheConfig);

Where cacheConfig contains information on what component to apply caching. See below for details.

In order for the enableCaching() method to work, you'll also need NODE_ENV set to production, or else it will throw an error.

cacheConfig

SSR component caching was first demonstrated in Sasha Aickin's talk.

His demo requires each component to provide a function for generating the cache key.

Here we implemented two cache key generation strategies: simple and template.

You are required to pass in the cacheConfig to tell this module what component to apply caching.

For example:

const cacheConfig = {
    components: {
        "Component1": {
            strategy: "simple",
            enable: true
        },
        "Component2": {
            strategy: "template",
            enable: true
        }
    }
}

SSRCaching.setCachingConfig(cacheConfig);

Caching Strategies

simple

The simple caching strategy is basically doing a JSON.stringify on the component's props. You can also specify a callback in cacheConfig to return the key.

For example:

const cacheConfig = {
    components: {
        Component1: {
            strategy: "simple",
            enable: true,
            genCacheKey: (props) => JSON.stringify(props)
        }
    }
};

This strategy is not very flexible. You need a cache entry for each different props. However it requires very little processing time.

template

The template caching strategy is more complex but flexible.

The idea is akin to generating logic-less handlebars template from your React components and then use string replace to process the template with different props.

If you have this component:

class Hello extends Component {
    render() {
        return <div>Hello, {this.props.name}.  {this.props.message}</div>
    }
}

And you render it with props:

const props = { name: "Bob", message: "How're you?" }

You get back HTML string:

<div>Hello, <span>Bob</span>.  <span>How&#x27;re you?</span></div>

Now if you replace values in props with tokens, and you remember that @0@ refers to props.name and @1@ refers to props.message:

const tokenProps = { name: "@0@", message: "@1@" }

You get back HTML string that could be akin to a handlebars template:

<div>Hello, <span>@0@</span>.  <span>@1@</span></div>

We cache this template html using the tokenized props as cache key. When we need to render the same component with a different props later, we can just lookup the template from cache and use string replace to apply the values:

cachedTemplateHtml.replace( /@0@/g, props.name ).replace( /@1@/g, props.message );

That's the gist of the template strategy. Of course there are many small details such as handling the encoding of special characters, preserving props that can't be tokenized, avoid tokenizing non-string props, or preserving data-reactid and data-react-checksum.

To specify a component to be cached with the template strategy:

const cacheConfig = {
    components: {
        Hello: {
            strategy: "template",
            enable: true,
            preserveKeys: [ "key1", "key2" ],
            preserveEmptyKeys: [ "key3", "key4" ],
            ignoreKeys: [ "key5", "key6" ],
            whiteListNonStringKeys: [ "key7", "key8" ]
        }
    }
};

• preserveKeys - List of keys that should not be tokenized.
• preserveEmptyKeys - List of keys that should not be tokenized if they are empty string ""
• ignoreKeys - List of keys that should be completely ignored as part of the template cache key.
• whiteListNonStringKeys - List of non-string keys that should be tokenized.

API

enableProfiling(flag)

Enable profiling according to flag

• undefined or true - enable profiling
• false - disable profiling

enableCaching(flag)

Enable cache according to flag

• undefined or true - enable caching
• false - disable caching

enableCachingDebug(flag)

Enable cache debugging according to flag.

Caching must be enabled for this to have any effect.

• undefined or true - enable cache debugging
• false - disable cache debugging

setCachingConfig(config)

Set caching config to config.

stripUrlProtocol(flag)

Remove http: or https: from prop values that are URLs according to flag.

Caching must be enabled for this to have any effect.

• undefined or true - strip URL protocol
• false - don't strip

shouldHashKeys(flag, [hashFn])

Set whether the template strategy should hash the cache key and use that instead.

Caching must be enabled for this to have any effect.

• flag
  • undefined or true - use a hash value of the cache key
  • false - don't use a hash valueo f the cache key
• hashFn - optional, a custom callback to generate the hash from the cache key, which is passed in as a string
  • i.e. function customHashFn(key) { return hash(key); }

If no hashFn is provided, then farmhash is used if it's available, otherwise hashing is turned off.

clearProfileData()

Clear profiling data

clearCache()

Clear caching data

cacheEntries()

Get total number of cache entries

cacheHitReport()

Returns an object with information about cache entry hits

Built with ❤️ by Team Electrode @WalmartLabs.