upcache
=======

Caching proxy having cache keys configured by the upstream application,
by setting http response headers.

Upcache has several ways of changing the cache keys:

- [tag](./README-tag.md), version resources by zones
- [lock](./README-lock.md), vary on client json web token grants
- [vary](./README-vary.md), vary by grouping selected request headers
- [map](./README-map.md), maps a request uri to another request uri

**Breaking change**: server.d/upcache.conf is now server.d/upcache-memcached.conf

Requirements
------------

In debian/12 these packages are easy to install:

- nginx
- libnginx-mod-http-srcache-filter
- libnginx-mod-http-set-misc
- libnginx-mod-http-memc (if using memcached, or for running the test suite
- memcached or redis
- lua-resty-core
- lua-resty-lrucache

- a Node.js express app

Install
-------

The Node.js app need the module

```sh
npm install upcache
```

The nginx configuration need the module

```sh
luarocks install upcache
```

nginx is easily configured with the set of files described in (depending on
where npm installs the module) `./node_modules/upcache/nginx/README.md`.

Usage
-----

Once installed, load appropriate helpers with

```js
const app = express();
const { tag, lock } = require('upcache');
const mlock = lock(config);

app.get('/route', tag('ugc', 'global'), mlock.restrict('logged'), ...);
app.post('/route', tag(), mlock.restrict('logged'), ...);

```

See README-tag.md and README-lock.md for documentation,
and test/ for more examples.

Mind that `srcache` module honours cache control headers - if the application
sends responses with `Cache-Control: max-age=0`, the resource is not cached,
and `tag().for()` is a facility for doing cache control.

To cache something, resources must be tagged, so lock/vary won't work without tag.

Detection by upstream
---------------------

Upcache adds a `X-Upcache: <version>` header to requests, so upstream application
can detect it is enabled, and which features are available.

Testing
-------

A pre-configured nginx environment is available for testing a Node.js application
that listens on port 3000, with nginx on port 3001 and memcached on port 3002,
simply by launching (depending on ./node_modules/.bin being on PATH or not)

```sh
npm run upcache
```

which also has an option for filtering output `-g <regexp pattern>`.

`mocha` relies on it for integration tests. No root permissions are needed.

License
-------

See LICENSE file.