Cache invalidation in revel framework - go

Question

I'm looking for a way to invalidate cached static content upon version change. Preferably using commit id to invalidate. Is there anyway to do this in revel framework ?
I would prefer if its automatic but I could live with updating it each time if its a single place I have to edit.
The current strategy I have is changing the name of the static content route to include version but this requires several changes. In places that feel unnatural, for instance in the routing file.

Answer 1

You could do it manually via a config variable and an intercept method.
resourceversion.go
Create this file in your controllers folder:
package controllers
import (
"github.com/revel/revel"
)
// interceptor method, called before every request.
// Sets a template variable to the resourceVersion read from app.conf
func SetVersion(c *revel.Controller) revel.Result {
c.RenderArgs["resourceVersion"] = revel.Config.StringDefault("resourceVersion", "1")
return nil
}
init.go
In the init() method, append this line:
revel.InterceptMethod(controllers.SetVersion, revel.BEFORE)
templates
In your templates, where you want to use the resource version:
<link rel="stylesheet" type="text/css" href="/public/css/style.css?{{.resourceVersion}}">
app.conf
And finally, the place you will update it - add this line above the dev section to apply to dev and prod, or have a different one in each, whatever suits.
resourceVersion=20150716
I guess you could create a script as part of your build and release process that would automatically edit this config variable.

Answer 2

I did the things that Colin Nicholson suggested but I also created a controller called staticversionbasedcacheinvalidator and placed it in the controller folder. You can find it below. It allows you to ignore the first part of the request string allowing you to use a wildcard path to your public folder. For instance I use this route config row
GET /public/*filepath StaticVersionbasedCacheInvalidator.Serve("public")
I then added the {{.resourceVersion}} in my route instead of as a query param.
package controllers
import (
"github.com/revel/revel"
"os"
fpath "path/filepath"
"strings"
"syscall"
)
type StaticVersionbasedCacheInvalidator struct {
*revel.Controller
}
// This method handles requests for files. The supplied prefix may be absolute
// or relative. If the prefix is relative it is assumed to be relative to the
// application directory. The filepath may either be just a file or an
// additional filepath to search for the given file. This response may return
// the following responses in the event of an error or invalid request;
// 403(Forbidden): If the prefix filepath combination results in a directory.
// 404(Not found): If the prefix and filepath combination results in a non-existent file.
// 500(Internal Server Error): There are a few edge cases that would likely indicate some configuration error outside of revel.
//
// Note that when defining routes in routes/conf the parameters must not have
// spaces around the comma.
// Bad: StaticVersionbasedCacheInvalidator.Serve("public/img", "favicon.png")
// Good: StaticVersionbasedCacheInvalidator.Serve("public/img","favicon.png")
//
// Examples:
// Serving a directory
// Route (conf/routes):
// GET /public/{<.*>filepath} StaticVersionbasedCacheInvalidator.Serve("public")
// Request:
// public/js/sessvars.js
// Calls
// StaticVersionbasedCacheInvalidator.Serve("public","js/sessvars.js")
//
// Serving a file
// Route (conf/routes):
// GET /favicon.ico StaticVersionbasedCacheInvalidator.Serve("public/img","favicon.png")
// Request:
// favicon.ico
// Calls:
// StaticVersionbasedCacheInvalidator.Serve("public/img", "favicon.png")
func (c StaticVersionbasedCacheInvalidator) Serve(prefix, filepath string) revel.Result {
firstSplice := strings.Index(filepath,"/")
if(firstSplice != -1) {
filepath = filepath[firstSplice:len(filepath)];
}
// Fix for #503.
prefix = c.Params.Fixed.Get("prefix")
if prefix == "" {
return c.NotFound("")
}
return serve(c, prefix, filepath)
}
// This method allows modules to serve binary files. The parameters are the same
// as StaticVersionbasedCacheInvalidator.Serve with the additional module name pre-pended to the list of
// arguments.
func (c StaticVersionbasedCacheInvalidator) ServeModule(moduleName, prefix, filepath string) revel.Result {
// Fix for #503.
prefix = c.Params.Fixed.Get("prefix")
if prefix == "" {
return c.NotFound("")
}
var basePath string
for _, module := range revel.Modules {
if module.Name == moduleName {
basePath = module.Path
}
}
absPath := fpath.Join(basePath, fpath.FromSlash(prefix))
return serve(c, absPath, filepath)
}
// This method allows StaticVersionbasedCacheInvalidator serving of application files in a verified manner.
func serve(c StaticVersionbasedCacheInvalidator, prefix, filepath string) revel.Result {
var basePath string
if !fpath.IsAbs(prefix) {
basePath = revel.BasePath
}
basePathPrefix := fpath.Join(basePath, fpath.FromSlash(prefix))
fname := fpath.Join(basePathPrefix, fpath.FromSlash(filepath))
// Verify the request file path is within the application's scope of access
if !strings.HasPrefix(fname, basePathPrefix) {
revel.WARN.Printf("Attempted to read file outside of base path: %s", fname)
return c.NotFound("")
}
// Verify file path is accessible
finfo, err := os.Stat(fname)
if err != nil {
if os.IsNotExist(err) || err.(*os.PathError).Err == syscall.ENOTDIR {
revel.WARN.Printf("File not found (%s): %s ", fname, err)
return c.NotFound("File not found")
}
revel.ERROR.Printf("Error trying to get fileinfo for '%s': %s", fname, err)
return c.RenderError(err)
}
// Disallow directory listing
if finfo.Mode().IsDir() {
revel.WARN.Printf("Attempted directory listing of %s", fname)
return c.Forbidden("Directory listing not allowed")
}
// Open request file path
file, err := os.Open(fname)
if err != nil {
if os.IsNotExist(err) {
revel.WARN.Printf("File not found (%s): %s ", fname, err)
return c.NotFound("File not found")
}
revel.ERROR.Printf("Error opening '%s': %s", fname, err)
return c.RenderError(err)
}
return c.RenderFile(file, revel.Inline)
}