mirror of https://github.com/hashicorp/consul
108 lines
3.8 KiB
Markdown
108 lines
3.8 KiB
Markdown
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# cachecontrol: HTTP Caching Parser and Interpretation
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[](https://godoc.org/github.com/pquerna/cachecontrol)[](https://travis-ci.org/pquerna/cachecontrol)
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`cachecontrol` implements [RFC 7234](http://tools.ietf.org/html/rfc7234) __Hypertext Transfer Protocol (HTTP/1.1): Caching__. It does this by parsing the `Cache-Control` and other headers, providing information about requests and responses -- but `cachecontrol` does not implement an actual cache backend, just the control plane to make decisions about if a particular response is cachable.
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# Usage
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`cachecontrol.CachableResponse` returns an array of [reasons](https://godoc.org/github.com/pquerna/cachecontrol/cacheobject#Reason) why a response should not be cached and when it expires. In the case that `len(reasons) == 0`, the response is cachable according to the RFC. However, some people want non-compliant caches for various business use cases, so each reason is specifically named, so if your cache wants to cache `POST` requests, it can easily do that, but still be RFC compliant in other situations.
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# Examples
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## Can you cache Example.com?
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```go
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package main
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import (
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"github.com/pquerna/cachecontrol"
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"fmt"
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"io/ioutil"
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"net/http"
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)
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func main() {
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req, _ := http.NewRequest("GET", "http://www.example.com/", nil)
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res, _ := http.DefaultClient.Do(req)
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_, _ = ioutil.ReadAll(res.Body)
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reasons, expires, _ := cachecontrol.CachableResponse(req, res, cachecontrol.Options{})
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fmt.Println("Reasons to not cache: ", reasons)
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fmt.Println("Expiration: ", expires.String())
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}
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```
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## Can I use this in a high performance caching server?
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`cachecontrol` is divided into two packages: `cachecontrol` with a high level API, and a lower level `cacheobject` package. Use [Object](https://godoc.org/github.com/pquerna/cachecontrol/cacheobject#Object) in a high performance use case where you have previously parsed headers containing dates or would like to avoid memory allocations.
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```go
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package main
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import (
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"github.com/pquerna/cachecontrol/cacheobject"
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"fmt"
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"io/ioutil"
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"net/http"
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)
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func main() {
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req, _ := http.NewRequest("GET", "http://www.example.com/", nil)
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res, _ := http.DefaultClient.Do(req)
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_, _ = ioutil.ReadAll(res.Body)
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reqDir, _ := cacheobject.ParseRequestCacheControl(req.Header.Get("Cache-Control"))
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resDir, _ := cacheobject.ParseResponseCacheControl(res.Header.Get("Cache-Control"))
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expiresHeader, _ := http.ParseTime(res.Header.Get("Expires"))
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dateHeader, _ := http.ParseTime(res.Header.Get("Date"))
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lastModifiedHeader, _ := http.ParseTime(res.Header.Get("Last-Modified"))
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obj := cacheobject.Object{
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RespDirectives: resDir,
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RespHeaders: res.Header,
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RespStatusCode: res.StatusCode,
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RespExpiresHeader: expiresHeader,
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RespDateHeader: dateHeader,
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RespLastModifiedHeader: lastModifiedHeader,
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ReqDirectives: reqDir,
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ReqHeaders: req.Header,
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ReqMethod: req.Method,
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NowUTC: time.Now().UTC(),
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}
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rv := cacheobject.ObjectResults{}
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cacheobject.CachableObject(&obj, &rv)
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cacheobject.ExpirationObject(&obj, &rv)
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fmt.Println("Errors: ", rv.OutErr)
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fmt.Println("Reasons to not cache: ", rv.OutReasons)
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fmt.Println("Warning headers to add: ", rv.OutWarnings)
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fmt.Println("Expiration: ", rv.OutExpirationTime.String())
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}
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```
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## Improvements, bugs, adding features, and taking cachecontrol new directions!
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Please [open issues in Github](https://github.com/pquerna/cachecontrol/issues) for ideas, bugs, and general thoughts. Pull requests are of course preferred :)
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# Credits
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`cachecontrol` has recieved significant contributions from:
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* [Paul Querna](https://github.com/pquerna)
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## License
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`cachecontrol` is licensed under the [Apache License, Version 2.0](./LICENSE)
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