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+%
+% Copyright (C) 2015-2016 Sebastian 'tokkee' Harl <sh@tokkee.org>
+% All rights reserved.
+%
+% Redistribution and use in source and binary forms, with or without
+% modification, are permitted provided that the following conditions
+% are met:
+% 1. Redistributions of source code must retain the above copyright
+% notice, this list of conditions and the following disclaimer.
+% 2. Redistributions in binary form must reproduce the above copyright
+% notice, this list of conditions and the following disclaimer in the
+% documentation and/or other materials provided with the distribution.
+%
+% THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+% ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+% TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+% PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR
+% CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+% EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+% PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+% OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+% WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+% OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+% ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+%
+\documentclass[presentation]{beamer}
+\uselanguage{German}
+
+\usetheme{tokkee}
+\usefonttheme{professionalfonts}
+
+\setbeamercolor*{block body}{fg=black,bg=white}
+\setbeamercolor*{block title}{use=titlelike,fg=titlelike.fg!80!black,bg=black!10}
+
+\usepackage{fontspec,xunicode,polyglossia}
+\setdefaultlanguage[spelling=new]{german}
+
+\usepackage{graphicx}
+\usepackage{xcolor}
+\definecolor{darkgreen}{rgb}{0,0.39,0}
+
+\usepackage{listings}
+\lstset{
+ basicstyle=\scriptsize,
+ language=Go,
+ frame=single,
+ numbers=left,
+ keywordstyle=\bfseries\color{darkgreen},
+ commentstyle=\itshape\color{blue},
+ stringstyle=\color{red},
+ showstringspaces=false,
+ backgroundcolor=\color{lightgray!25},
+ literate=%
+ {Ö}{{\"O}}1
+ {Ä}{{\"A}}1
+ {Ü}{{\"U}}1
+ {ß}{{\ss}}1
+ {ü}{{\"u}}1
+ {ä}{{\"a}}1
+ {ö}{{\"o}}1,
+}
+
+\usepackage[overlay,absolute]{textpos}
+
+\usepackage{tikz}
+\usetikzlibrary{shadows}
+\usetikzlibrary{shapes}
+
+\newcommand{\collectd}{\textsf{\textbf{collect}d}}
+
+\title{Web-Services mit Go}
+\subtitle{Go-Features an Hand von Beispielen}
+
+\titlegraphic{}
+
+\copyrightinfo{\copyright{} 2015-2016 Sebastian `tokkee' Harl}
+
+\author[Sebastian Harl]{Sebastian `tokkee' Harl\\
+ $<$sh@tokkee.org$>$}
+
+\date[2015-2016]{}
+
+\AtBeginSection[]
+{
+ \begin{frame}
+ \begin{center}
+ \Large
+ \titlebox{\secname}
+ \end{center}
+ \end{frame}
+}
+
+\begin{document}
+
+\begin{frame}[plain]
+ \titlepage
+\end{frame}
+
+\begin{frame}{Überblick}
+ \textbf{Was ist Go?}
+
+ \textit{Go is an open source programming language that makes it easy to
+ build simple, reliable, and efficient software.}\\[10mm]
+
+ \url{https://golang.org}
+
+ \begin{tikzpicture}[remember picture,overlay]
+ \node[anchor=north east] at (current page.east)
+ {\includegraphics[width=.7\textwidth]{gopher}};
+ \end{tikzpicture}
+\end{frame}
+
+\begin{frame}{Web-Services}
+ \begin{itemize}
+ \item HTTP Frontend
+ \begin{itemize}
+ \item Viele parallele Client-Anfragen
+ \item Eine oder mehrere Verbindungen zu Backends
+ \end{itemize}
+ \item Backend ("`Business Logic"')
+ \begin{itemize}
+ \item Viele parallele Anfragen vom Frontend
+ \item Eine oder mehrere Datenbank-Verbindungen oder Interaktion mit
+ anderen Backends
+ \end{itemize}
+ \item Datenbank\\[3mm]
+
+ \item[$\Rightarrow$] skalierbare Micro-Services~/ \textbf{lose
+ Kopplung}\\[5mm]
+ \end{itemize}
+
+ \textbf{Auch:} Gleiche Prinzipien bei Integration mit anderen Lösungen
+\end{frame}
+
+\begin{frame}{Einschub: Go Standard Bibliothek}
+ \url{https://golang.org/pkg/}\\[5mm]
+
+ \begin{itemize}
+ \item Crypto
+ \item Datenbanken
+ \item Go Parser
+ \item Netzwerk, HTTP, SMTP, etc.
+ \item Datenstrukturen\\[7mm]
+ \end{itemize}
+
+ \textbf{Mehr?} $\Rightarrow$ \url{https://godoc.org/}
+\end{frame}
+
+\begin{frame}[fragile]{Ein Webserver}
+ \begin{lstlisting}
+import (...)
+
+func main() {
+ http.HandleFunc("/hallo", sageHallo)
+ log.Fatal(http.ListenAndServe(":9999", nil))
+}
+
+func sageHallo(w http.ResponseWriter, r *http.Request) {
+ fmt.Fprintf(w, "Hallo %s", r.RemoteAddr)
+}
+\end{lstlisting}
+
+ \begin{itemize}
+ \item \url{https://golang.org/pkg/log/}
+ \item \url{https://golang.org/pkg/net/http/}
+ \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]{Ein Webserver -- Templates}
+ \begin{lstlisting}
+var tmpl = template.Must(
+ template.New("results").Parse(`
+<html><head>
+<title>{{.Title}}</title>
+</head>
+
+<body>
+<h1>Hallo {{.Name}}</h1>
+</body></html>
+`))
+ \end{lstlisting}
+
+ \begin{itemize}
+ \item \url{https://golang.org/pkg/html/template/}
+ \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]{Ein Webserver -- Templates (2)}
+ \begin{lstlisting}
+func sageHallo(...) {
+ d := struct {
+ Title, Name string
+ }{"Hallo Welt", r.RemoteAddr}
+
+ var buf bytes.Buffer
+ if err := tmpl.Execute(&buf, d); err != nil {
+ http.Error(w, err.Error(), http.StatusInternalServerError)
+ return
+ }
+ io.Copy(w, &buf)
+}
+ \end{lstlisting}
+
+ \begin{itemize}
+ \item \url{https://golang.org/pkg/bytes/}
+ \item \url{https://golang.org/pkg/io/}
+ \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]{Einschub: io.Writer}
+ \begin{itemize}
+ \item Warum funktioniert fmt.Printf, tmpl.Execute, http.Error, io.Copy
+ eigentlich mit dem http.ResponseWriter und bytes.Buffer?
+ \end{itemize}
+
+ \begin{lstlisting}
+package io
+type Writer interface {
+ Write(p []byte) (n int, err error)
+}
+ \end{lstlisting}
+
+ \begin{itemize}
+ \item[$\Rightarrow$] \textbf{Sehr} einfaches Interface
+ \item[$\Rightarrow$] \texttt{http.ResponseWriter} und
+ \texttt{bytes.Buffer} implementieren es\\[7mm]
+ \end{itemize}
+
+ Viele andere Beispiele ...
+\end{frame}
+
+\begin{frame}[fragile]{Viele Backend-Abfragen}
+ \begin{lstlisting}
+func Query(*Request) (*Response, error) { ... }
+
+func anfrage(w http.ResponseWriter, r *http.Request) {
+ requests := []*Request{...}
+
+ responses := make([]*Reponse, len(requests))
+ errCh := make(chan error, len(requests))
+
+ for i, req := range requests {
+ go func(i int, req *Request) {
+ var err error
+ responses[i], err = Query(req)
+ errCh <- err
+ }(i, req)
+ }
+
+ // ...
+ \end{lstlisting}
+\end{frame}
+
+\begin{frame}[fragile]{Viele Backend-Abfragen (2)}
+ \begin{lstlisting}
+ ...
+ timeout := time.After(50*time.Millisecond)
+
+ for range requests {
+ select {
+ case err := <-errCh:
+ if err != nil {
+ http.Error(w, err.Error(), http.StatusBadRequest)
+ return
+ }
+ case <-timeout:
+ http.Error(w, "timeout", http.StatusRequestTimeout)
+ return
+ }
+ }
+ // Alle Ergebnisse verfügbar.
+ \end{lstlisting}
+
+ \begin{itemize}
+ \item Siehe auch \url{https://golang.org/pkg/sync/#WaitGroup}
+ \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]{Spezielle Fehlerbehandlung}
+ \begin{lstlisting}
+ go func(req *Request) {
+ var err error
+ defer func() {
+ if e := recover(); e != nil {
+ err = fmt.Errorf("error while querying backend: %v", e)
+ }
+ errCh <- err
+ }()
+
+ responses[i], err = Query(req)
+ }(req)
+ \end{lstlisting}
+\end{frame}
+
+\begin{frame}{Backends -- gRPC}
+ \textbf{Beispiel: Backend Kommunikation~/ API}\\[5mm]
+
+ \textit{A high performance, open source, general RPC framework that puts
+ mobile and HTTP/2 first.}\\[10mm]
+
+ \url{https://grpc.io}\\
+ \hfill\includegraphics[width=.3\textwidth]{grpc}
+\end{frame}
+
+\begin{frame}{gRPC Überblick}
+ \url{https://github.com/google/protobuf}\\[5mm]
+
+ \begin{itemize}
+ \item gRPC basiert auf Protocol Buffers
+ \item Unterstützung diverser Sprachen\newline
+ C++, Java, Go, Python, \ldots
+ \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]{gRPC Beispiel}
+ \begin{lstlisting}[morekeywords={syntax,service,message}]
+syntax "proto3";
+
+package mein_service;
+
+service Backend {
+ rpc Query(QueryRequest) return (QueryResponse);
+
+ // ...
+}
+
+message QueryRequest {
+ string query = 1;
+}
+
+message QueryResponse {
+ string type = 1;
+ int64 n = 2;
+}
+ \end{lstlisting}
+\end{frame}
+
+\begin{frame}{gRPC mit Go}
+ \begin{itemize}
+ \item Die "`protobuf"' Datei muss mittels des Protobuf Compilers und einer
+ gRPC Compiler-Erweiterung übersetzt werden
+ \item Der Compiler erzeugt Go Code, welcher Interfaces und generischen
+ Code erzeugt
+ \item Das Interface entspricht im Wesentlichen der \texttt{service}
+ Definition
+ \item Das Interface muss für den Server implementiert werden
+ \item Generischer Client-Code sollte ausreichen\newline
+ $\rightarrow$ API Entwurf!\\[7mm]
+ \end{itemize}
+
+ \url{https://github.com/grpc/grpc-go}\\
+ \url{https://golang.org/x/net/context}
+\end{frame}
+
+\begin{frame}[fragile]{gRPC mit Go: Server}
+ \begin{lstlisting}
+import pb "tokkee.net/mein_service/service_proto"
+
+type server struct{}
+
+func (*server) Query(ctx context.Context,
+ in *pb.QueryRequest) (*pb.QueryResponse, error) {
+
+ n, err := runQuery(in.Query)
+ if err != nil {
+ return nil, err
+ }
+ return &pb.QueryResponse{
+ Type: "irgendwas",
+ N: n,
+ }, nil
+}
+ \end{lstlisting}
+\end{frame}
+
+\begin{frame}[fragile]{gRPC mit Go: Server (2)}
+ \begin{lstlisting}
+func main() {
+ l, err := net.Listen("tcp", port)
+ if err != nil {
+ log.Fatal(err)
+ }
+
+ s := grpc.NewServer()
+ pb.RegisterBackendServer(s, &server{})
+ s.Serve(l)
+}
+ \end{lstlisting}
+\end{frame}
+
+\begin{frame}[fragile]{gRPC mit Go: Client}
+ \begin{lstlisting}
+func main() {
+ ctx := context.Background()
+
+ conn, err := grpc.Dial("localhost:50051", grpc.WithInsecure())
+ if err != nil {
+ log.Fatal(err)
+ }
+ defer conn.Close()
+ c := pb.NewBackendClient(conn)
+
+ res, err := c.Query(ctx, &pb.QueryRequest{
+ Query: "ein query",
+ })
+ if err != nil {
+ log.Fatal(err)
+ }
+ fmt.Printf("Antwort vom Typ %q: %d\n", res.Type, res.N)
+}
+ \end{lstlisting}
+\end{frame}
+
+\begin{frame}{\inserttitle}
+ \begin{center}
+ Danke für die Aufmerksamkeit\\[2mm]
+ {\Large Fragen, Kommentare?}\\[6mm]
+
+ \url{https://golang.org}\quad—\quad
+ \url{https://github.com/grpc/grpc-go}
+ \end{center}
+\end{frame}
+
+\end{document}
+
+% vim: set shiftwidth=2 softtabstop=2 tabstop=8 noexpandtab spelllang=de_de :