json-caching-proxy 
Node caching HTTP proxy built on top of express-http-proxy. Persists requests and responses to an in-memory HAR-like data structure based on HAR1.2 . Caches JSON content-type responses by default with the ability to cache an entire site; including content-types describing images. Useful for testing front end code, mocking api, and saving the cache to a HAR file which can be used for further tests.
Installation
Requires Node >= 14
Command line tool:
$ npm install -g json-caching-proxy
Programmatic:
$ npm install -D json-caching-proxy
Command line usage
Usage: json-caching-proxy [options]
Options:
-h, --help output usage information
-V, --version output the version number
-c, --config [path] load a config file of options. Command line args will be overridden
-u, --url [url] remote server (e.g. https://network:8080)
-p, --port [number] port for the local proxy server
-H, --har [path] load entries from a HAR file and hydrate the cache
-b, --bust [list] a list of cache busting query params to ignore. (e.g. --bust _:cacheSlayer:time:dc)
-e, --exclude [regex] exclude specific routes from cache, (e.g. --exclude "GET /api/keep-alive/.*")
-S, --excludeStatus [regex] exclude specific status from cache, (e.g. --excludeStatus "503|404")
-a, --all cache everything from the remote server (Default is to cache just JSON responses)
-P, --disablePlayback disables cache playback
-R, --disableRecord disables recording to cache
-C, --cmdPrefix [prefix] change the prefix for the proxy's web admin endpoints
-I, --header [header] change the response header property for identifying cached responses
-l, --log print log output to console
-t, --timeout change the timeout for proxy server
-d, --deleteCookieDomain remove the Domain portion of all cookies
-o, --overrideCors [url] override Access-Control-Allow-Origin
-z, --useCorsCredentials set Access-Control-Allow-Credentials to true
Example - basic JSON caching with output
$ json-caching-proxy -u http://remote:8080 -l
Example - bypassing CORS when proxying to a 3rd party api server
$ json-caching-proxy -u http://cors-api.example.com -o localhost:9000 -z
This use case occurs when developing a browser application against an api server on a different host with CORS restrictions.
In this example we might be running a dev server that's hosting a frontend application on http://localhost:9000 and there is
browser javascript that needs to fetch from http://cors-api.example.com. The -z option tells the proxy to set up auth headers
in case the code uses cookies or tokens (e.g. Bearer tokens)
Example - hydrating the cache
$ json-caching-proxy -u http://remote:8080 -p 3001 -H chromeDevTools.har -l
You may have a HAR file that was generated elsewhere (e.g. Chrome Developer tools). You can load this file and initialize the cache
Example - advanced arguments
$ json-caching-proxy -u http://remote:8080 -p 3001 -b time:dc -e '/keepalive' -H hydrate.har -a -l
- Routes requests to
http://remote:8080 - Runs the proxy on port
3001on the host machine - Removes matching query parameters
timeordc. (e.g. /rest/status?time=1234567).:is the delimiter - Excludes any
/keepaliverequests from the proxy. Any valid js regular expression works here - Loads an existing HAR file and hydrates the cache. Supports any HAR file that conforms to HAR spec 1.2
- Caches everything. This includes JSON as well as other content-types such as images. It's essentially a site backup.
- Logs output to the console
Example - loading options from a config file
/* Complete list of config.json options for the caching proxy */
{
"remoteServerUrl": "http://wikimapia.org",
"proxyPort": 3001,
"inputHarFile": "./test/test.har",
"cacheEverything": true,
"cacheBustingParams": ["_", "dc", "cacheSlayer"],
"excludedRouteMatchers": ["/*.js", "/*.png"],
"excludedStatusMatchers": ["503", "404"],
"showConsoleOutput": true,
"dataPlayback": true,
"dataRecord": true,
"commandPrefix": "proxy",
"proxyHeaderIdentifier": "proxy-cache-playback",
"proxyTimeout": 500000,
"deleteCookieDomain": true,
"overrideCors": "localhost:8080",
"useCorsCredentials": true
}$ json-caching-proxy --config config.json
Programmatic Usage
import JsonCachingProxy from 'json-caching-proxy';
// Complete list of options
let jsonCachingProxy = new JsonCachingProxy({
remoteServerUrl: 'http://localhost:8080',
proxyPort: 3001,
harObject: null,
commandPrefix: 'proxy',
proxyHeaderIdentifier: 'caching-proxy-playback',
middlewareList: [{ route: '/browser-sync', handle: (req, res, next) => res.send('bypass proxy')}],
excludedRouteMatchers: [new RegExp('/site/*.js')],
excludedStatusMatchers: [new RegExp('503|404')],
cacheBustingParams: ['time', 'dc'],
cacheEverything: false,
dataPlayback: true,
dataRecord: true,
showConsoleOutput: false,
proxyTimeout: 500000,
deleteCookieDomain: true,
overrideCors: "localhost:8080",
useCorsCredentials: true
});
jsonCachingProxy.start();Example - passing in a HAR object
If you have a method of generating a HAR object, the proxy can load the HAR entries and hydrate the cache. The proxy has a commandline utility for loading HAR files but you may want to load your own or modify the objects before passing them into the proxy. More info can be found here: HAR 1.2 spec
// Example HAR object
let harObject = {
log: {
version: '1.2',
creator: {
name: npmPackage.name,
version: npmPackage.version
},
entries: [{
request: {
startedDateTime: '',
method: 'GET',
url: '/test',
cookies: [],
headers: [],
queryString: [],
headersSize: -1,
bodySize: -1
},
response: {
status: 200,
cookies: [],
headers: [],
content: {
size: -1,
mimeType: 'application/json; charset=utf-8',
text: '{"a":1,"b":"Some Value"}',
encoding: 'utf8'
},
headersSize: -1,
bodySize: -1
}
},
{
request: {
startedDateTime: '',
method: 'GET',
url: '/another',
cookies: [],
headers: [],
queryString: [],
headersSize: -1,
bodySize: -1
},
response: {
status: 200,
cookies: [],
headers: [],
content: {
size: -1,
mimeType: 'application/json; charset=utf-8',
text: '{"a":1,"b":"Some Value"}',
encoding: 'utf8'
},
headersSize: -1,
bodySize: -1
}
}]
}
};Example - using special middleware
Bypasses the remote server and allows your own middleware to be executed:
let middlewareList = [
{ route: '/what', handle: (req, res, next) => res.send('what') },
{ route: '/hello', handle: (req, res, next) => res.send('hello') }
];Example - excluding specific routes
You can specify a list of regular expressions to match against. Currently supports matching against the method and uri:
excludedRouteMatchers: [new RegExp('/site/*.js'), new RegExp('GET /site/*.gif'), new RegExp('POST /account/666')]Example - cache busting
Many times, there are cache busting query strings that are appended to GET requests, you may specify a list of these query string names. The proxy will ignore these parameters when building the cache. Otherwise every request will be different
cacheBustingParams: ['time', 'dc', 'cacheSlayer', '_']Controlling the Proxy
Once the proxy has started on a port (e.g. 3001), you may point your browser to the following urls to affect the state of the proxy:
http://localhost:3001/proxy/playback?enabled=[true|false] - Start/Stop replaying cached requests.
http://localhost:3001/proxy/record?enabled=[true|false] - Start/Stop recording request/responses to the cache.
http://localhost:3001/proxy/har - Download cache to json-caching-proxy.har
http://localhost:3001/proxy/clear - Empty the in-memory cache.
License
MIT
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