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Server Side Render Caching + Profiling

Optimize React SSR with profiling and component caching. The electrode-react-ssr-caching module supports profiling React Server Side Rendering time to enable component caching to help you speed up Server Side Rendering of your components.

electrode-react-ssr-caching module can be used a standalone module and is agnostic of your web-server framework. In this tutorial we will demonstrate how to use this module in Electrode, Express.js and Hapi.js applications.

Module: electrode-react-ssr-caching #

Install via npm #

$ npm install --save electrode-react-ssr-caching

Example Applications #

Usage #

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 />);

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

Caching #

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

The basic steps to enabling caching are:

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


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

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


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 templates 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, avoiding 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.


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() #

Print out cache entries and number of hits each one has.