From 2699bf618778808dcb25fea2ceab6889540bbe26 Mon Sep 17 00:00:00 2001
From: Jack Christensen <jack@jackchristensen.com>
Date: Mon, 5 Aug 2013 13:08:45 -0500
Subject: [PATCH] Added example url shortener
---
examples/url_shortener/README.md | 25 ++++++
examples/url_shortener/main.go | 120 +++++++++++++++++++++++++++
examples/url_shortener/structure.sql | 4 +
3 files changed, 149 insertions(+)
create mode 100644 examples/url_shortener/README.md
create mode 100644 examples/url_shortener/main.go
create mode 100644 examples/url_shortener/structure.sql
diff --git a/examples/url_shortener/README.md b/examples/url_shortener/README.md
new file mode 100644
index 00000000..cc04d600
--- /dev/null
+++ b/examples/url_shortener/README.md
@@ -0,0 +1,25 @@
+# Description
+
+This is a sample REST URL shortener service implemented using pgx as the connector to a PostgreSQL data store.
+
+# Usage
+
+Create a PostgreSQL database and run structure.sql into it to create the necessary data schema.
+
+Edit connectionOptions in main.go with the location and credentials for your database.
+
+Run main.go:
+
+ go run main.go
+
+## Create or Update a Shortened URL
+
+ curl -X PUT -d 'http://www.google.com' http://localhost:8080/google
+
+## Get a Shortened URL
+
+ curl http://localhost:8080/google
+
+## Delete a Shortened URL
+
+ curl -X DELETE http://localhost:8080/google
diff --git a/examples/url_shortener/main.go b/examples/url_shortener/main.go
new file mode 100644
index 00000000..54df21ba
--- /dev/null
+++ b/examples/url_shortener/main.go
@@ -0,0 +1,120 @@
+package main
+
+import (
+ "fmt"
+ "github.com/jackc/pgx"
+ "io/ioutil"
+ "net/http"
+ "os"
+)
+
+var pool *pgx.ConnectionPool
+
+// afterConnect creates the prepared statements that this application uses
+func afterConnect(conn *pgx.Connection) (err error) {
+ err = conn.Prepare("getUrl", `
+ select url from shortened_urls where id=$1
+ `)
+ if err != nil {
+ return
+ }
+
+ err = conn.Prepare("deleteUrl", `
+ delete from shortened_urls where id=$1
+ `)
+ if err != nil {
+ return
+ }
+
+ // There technically is a small race condition in doing an upsert with a CTE
+ // where one of two simultaneous requests to the shortened URL would fail
+ // with a unique index violation. As the point of this demo is pgx usage and
+ // not how to perfectly upsert in PostgreSQL it is deemed acceptable.
+ err = conn.Prepare("putUrl", `
+ with upsert as (
+ update shortened_urls
+ set url=$2
+ where id=$1
+ returning *
+ )
+ insert into shortened_urls(id, url)
+ select $1, $2 where not exists(select 1 from upsert)
+ `)
+ return
+}
+
+func getUrlHandler(w http.ResponseWriter, req *http.Request) {
+ if url, err := pool.SelectValue("getUrl", req.URL.Path); err == nil {
+ http.Redirect(w, req, url.(string), http.StatusSeeOther)
+ } else if _, ok := err.(pgx.NotSingleRowError); ok {
+ http.NotFound(w, req)
+ } else {
+ http.Error(w, "Internal server error", http.StatusInternalServerError)
+ }
+}
+
+func putUrlHandler(w http.ResponseWriter, req *http.Request) {
+ id := req.URL.Path
+ var url string
+ if body, err := ioutil.ReadAll(req.Body); err == nil {
+ url = string(body)
+ } else {
+ http.Error(w, "Internal server error", http.StatusInternalServerError)
+ return
+ }
+
+ if _, err := pool.Execute("putUrl", id, url); err == nil {
+ w.WriteHeader(http.StatusOK)
+ } else {
+ http.Error(w, "Internal server error", http.StatusInternalServerError)
+ }
+}
+
+func deleteUrlHandler(w http.ResponseWriter, req *http.Request) {
+ if _, err := pool.Execute("deleteUrl", req.URL.Path); err == nil {
+ w.WriteHeader(http.StatusOK)
+ } else {
+ http.Error(w, "Internal server error", http.StatusInternalServerError)
+ }
+}
+
+func urlHandler(w http.ResponseWriter, req *http.Request) {
+ switch req.Method {
+ case "GET":
+ getUrlHandler(w, req)
+
+ case "PUT":
+ putUrlHandler(w, req)
+
+ case "DELETE":
+ deleteUrlHandler(w, req)
+
+ default:
+ w.Header().Add("Allow", "GET, PUT, DELETE")
+ w.WriteHeader(http.StatusMethodNotAllowed)
+ }
+}
+
+func main() {
+ var err error
+ connectionOptions := pgx.ConnectionParameters{
+ Host: "127.0.0.1",
+ User: "jack",
+ Password: "jack",
+ Database: "url_shortener"}
+ poolOptions := pgx.ConnectionPoolOptions{MaxConnections: 5, AfterConnect: afterConnect}
+ pool, err = pgx.NewConnectionPool(connectionOptions, poolOptions)
+ if err != nil {
+ fmt.Fprintf(os.Stderr, "Unable to create connection pool: %v\n", err)
+ os.Exit(1)
+ }
+
+ http.HandleFunc("/", urlHandler)
+
+ fmt.Println("Starting URL shortener on localhost:8080...")
+ err = http.ListenAndServe("localhost:8080", nil)
+ if err != nil {
+ fmt.Fprintf(os.Stderr, "Unable to start web server: %v\n", err)
+ os.Exit(1)
+ }
+}
diff --git a/examples/url_shortener/structure.sql b/examples/url_shortener/structure.sql
new file mode 100644
index 00000000..0b9de259
--- /dev/null
+++ b/examples/url_shortener/structure.sql
@@ -0,0 +1,4 @@
+create table shortened_urls (
+ id text primary key,
+ url text not null
+);
\ No newline at end of file