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+package engine

+

+import (

+	"path"

+	"net/http"

+)

+

+// ServeHTTP executes a job as specified by the http request `r`, and sends the

+// result as an http response.

+// This method allows an Engine instance to be passed as a standard http.Handler interface.

+//

+// Note that the protocol used in this methid is a convenience wrapper and is not the canonical

+// implementation of remote job execution. This is because HTTP/1 does not handle stream multiplexing,

+// and so cannot differentiate stdout from stderr. Additionally, headers cannot be added to a response

+// once data has been written to the body, which makes it inconvenient to return metadata such

+// as the exit status.

+//

+func (eng *Engine) ServeHTTP(w http.ResponseWriter, r *http.Request) {

+	jobName := path.Base(r.URL.Path)

+	jobArgs, exists := r.URL.Query()["a"]

+	if !exists {

+		jobArgs = []string{}

+	}

+	w.Header().Set("Job-Name", jobName)

+	for _, arg := range(jobArgs) {

+		w.Header().Add("Job-Args", arg)

+	}

+	job := eng.Job(jobName, jobArgs...)

+	job.Stdout.Add(w)

+	job.Stderr.Add(w)

+	// FIXME: distinguish job status from engine error in Run()

+	// The former should be passed as a special header, the former

+	// should cause a 500 status

+	w.WriteHeader(http.StatusOK)

+	// The exit status cannot be sent reliably with HTTP1, because headers

+	// can only be sent before the body.

+	// (we could possibly use http footers via chunked encoding, but I couldn't find

+	// how to use them in net/http)

+	job.Run()

+}