92 lines
3 KiB
Markdown
92 lines
3 KiB
Markdown
# HTTP Caching for Angel3
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[](https://pub.dartlang.org/packages/angel3_cache)
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[](https://dart.dev/null-safety)
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[](https://gitter.im/angel_dart/discussion)
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[](https://github.com/dukefirehawk/angel/tree/angel3/packages/cache/LICENSE)
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A service that provides HTTP caching to the response data for [Angel3](https://github.com/dukefirehawk/angel).
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## `CacheService`
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A `Service` class that caches data from one service, storing it in another. An imaginable use case is storing results from MongoDB or another database in MemcacheD/Redis.
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## `cacheSerializationResults`
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A middleware that enables the caching of response serialization.
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This can improve the performance of sending objects that are complex to serialize. You can pass a [shouldCache] callback to determine which values should be cached.
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```dart
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void main() async {
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var app = Angel()..lazyParseBodies = true;
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app.use(
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'/api/todos',
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CacheService(
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database: AnonymousService(
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index: ([params]) {
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print('Fetched directly from the underlying service at ${new DateTime.now()}!');
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return ['foo', 'bar', 'baz'];
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},
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read: (id, [params]) {
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return {id: '$id at ${new DateTime.now()}'};
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}
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),
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),
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);
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}
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```
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## `ResponseCache`
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A flexible response cache for Angel3.
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Use this to improve real and perceived response of Web applications, as well as to memoize expensive responses.
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Supports the `If-Modified-Since` header, as well as storing the contents of response buffers in memory.
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To initialize a simple cache:
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```dart
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Future configureServer(Angel app) async {
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// Simple instance.
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var cache = ResponseCache();
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// You can also pass an invalidation timeout.
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var cache = ResponseCache(timeout: const Duration(days: 2));
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// Close the cache when the application closes.
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app.shutdownHooks.add((_) => cache.close());
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// Use `patterns` to specify which resources should be cached.
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cache.patterns.addAll([
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'robots.txt',
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RegExp(r'\.(png|jpg|gif|txt)$'),
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Glob('public/**/*'),
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]);
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// REQUIRED: The middleware that serves cached responses
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app.use(cache.handleRequest);
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// REQUIRED: The response finalizer that saves responses to the cache
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app.responseFinalizers.add(cache.responseFinalizer);
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}
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```
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### Purging the Cache
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Call `invalidate` to remove a resource from a `ResponseCache`.
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Some servers expect a reverse proxy or caching layer to support `PURGE` requests. If this is your case, make sure to include some sort of validation (maybe IP-based) to ensure no arbitrary attacker can hack your cache:
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```dart
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Future configureServer(Angel app) async {
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app.addRoute('PURGE', '*', (req, res) {
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if (req.ip != '127.0.0.1')
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throw AngelHttpException.forbidden();
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return cache.purge(req.uri.path);
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});
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}
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```
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