1 files changed, 98 insertions, 0 deletions
diff --git a/content/context/server/server.go b/content/context/server/server.go
new file mode 100644
index 0000000..bbab5b0
--- /dev/null
+++ b/content/context/server/server.go
@@ -0,0 +1,98 @@
+// The server program issues Google search requests and demonstrates the use of
+// the go.net Context API. It serves on port 8080.
+//
+// The /search endpoint accepts these query params:
+//   q=the Google search query
+//   timeout=a timeout for the request, in time.Duration format
+//
+// For example, http://localhost:8080/search?q=golang&timeout=1s serves the
+// first few Google search results for "golang" or a "deadline exceeded" error
+// if the timeout expires.
+package main
+
+import (
+	"html/template"
+	"log"
+	"net/http"
+	"time"
+
+	"code.google.com/p/go.blog/content/context/google"
+	"code.google.com/p/go.blog/content/context/userip"
+	"code.google.com/p/go.net/context"
+)
+
+func main() {
+	http.HandleFunc("/search", handleSearch)
+	log.Fatal(http.ListenAndServe(":8080", nil))
+}
+
+// handleSearch handles URLs like /search?q=golang&timeout=1s by forwarding the
+// query to google.Search. If the query param includes timeout, the search is
+// canceled after that duration elapses.
+func handleSearch(w http.ResponseWriter, req *http.Request) {
+	// ctx is the Context for this handler. Calling cancel closes the
+	// ctx.Done channel, which is the cancellation signal for requests
+	// started by this handler.
+	var (
+		ctx    context.Context
+		cancel context.CancelFunc
+	)
+	timeout, err := time.ParseDuration(req.FormValue("timeout"))
+	if err == nil {
+		// The request has a timeout, so create a context that is
+		// canceled automatically when the timeout expires.
+		ctx, cancel = context.WithTimeout(context.Background(), timeout)
+	} else {
+		ctx, cancel = context.WithCancel(context.Background())
+	}
+	defer cancel() // Cancel ctx as soon as handleSearch returns.
+
+	// Check the search query.
+	query := req.FormValue("q")
+	if query == "" {
+		http.Error(w, "no query", http.StatusBadRequest)
+		return
+	}
+
+	// Store the user IP in ctx for use by code in other packages.
+	userIP, err := userip.FromRequest(req)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusBadRequest)
+		return
+	}
+	ctx = userip.NewContext(ctx, userIP)
+
+	// Run the Google search and print the results.
+	start := time.Now()
+	results, err := google.Search(ctx, query)
+	elapsed := time.Since(start)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	if err := resultsTemplate.Execute(w, struct {
+		Results          google.Results
+		Timeout, Elapsed time.Duration
+	}{
+		Results: results,
+		Timeout: timeout,
+		Elapsed: elapsed,
+	}); err != nil {
+		log.Print(err)
+		return
+	}
+}
+
+var resultsTemplate = template.Must(template.New("results").Parse(`
+<html>
+<head/>
+<body>
+  <ol>
+  {{range .Results}}
+    <li>{{.Title}} - <a href="{{.URL}}">{{.URL}}</a></li>
+  {{end}}
+  </ol>
+  <p>{{len .Results}} results in {{.Elapsed}}; timeout {{.Timeout}}</p>
+</body>
+</html>
+`))