Release 0.1

.gitignore

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+*~

Dockerfile

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+FROM golang:wheezy
+
+ENV DIST /go/src/github.com/k8sp/graphviz
+
+RUN apt-get update
+RUN apt-get install -y graphviz
+
+COPY . $DIST
+RUN cd $DIST && go get ./... && go get .
+
+EXPOSE 9090
+VOLUME ["/cache"]
+ENTRYPOINT ["graphviz"]
+CMD ["-addr=:9090", "-dir=/cache"]

README.md

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+`graphviz` is an HTTP server which calls
+[GraphViz](http://www.graphviz.org/) to visualize a specified .dot
+file.
+
+## Build and Run from Source Code
+
+if we already got GraphViz and [Go](https://golang.org/) installed, we
+can run this program as follows
+
+```
+go get github.com/k8sp/graphviz
+$GOPATH/bin/graphviz -addr=:9090
+```
+
+Then we can direct our Web browser to
+
+```
+http://localhost:9090/?dot=https://gist.githubusercontent.com/wangkuiyi/c4e0015211dd1b9bde2e20455a6cd38e/raw/4d5ec099f98a5f326cf6f108bcf510cadba1a0b4/ci-arch.dot
+```
+
+so to visualize the
+[Gist file `ci-arch.dot`](https://gist.github.com/wangkuiyi/c4e0015211dd1b9bde2e20455a6cd38e)
+in the Web browser window.
+
+## Build and Run the Docker Image
+
+If we have Docker installed, we can build `graphviz` into a Docker
+image without installing GraphViz and Go:
+
+```
+go get github.com/k8sp/graphviz
+cd $GOPATH/src/github.com/k8sp/graphviz
+docker build -t graphviz .
+```
+
+and run it as a Docker container:
+
+```
+docker run -p 9090:9090 -v /tmp:/cache graphviz
+```
+
+Now we can direct our Web browser to above link.
+
+## Run with Images on DockerHub.com
+
+We can also run the Docker images built from stable releases by
+DockerHub.com:
+
+```
+docker run -p 9090:9090 -v /tmp:/cache k8sp/graphviz
+```
+
+<!--  LocalWords:  graphviz GraphViz GOPATH addr ci cd
+ -->

graphviz.go

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+// graphviz is an HTTP server which calls GraphViz's dot command to
+// visualize a .dot file given in the `dot` parameter.  For example,
+// we can run this program as follows
+//
+//   go run graphviz.go
+//
+// and access it from the Web browser with URL:
+//
+//   http://localhost:8080/?dot=https://gist.githubusercontent.com/wangkuiyi/c4e0015211dd1b9bde2e20455a6cd38e/raw/4d5ec099f98a5f326cf6f108bcf510cadba1a0b4/ci-arch.dot
+//
+// then the visualization of ci-arch.dot should appear in the browser window.
+//
+package main
+
+import (
+	"crypto/md5"
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"os"
+	"os/exec"
+	"path"
+
+	"github.com/topicai/candy"
+)
+
+func main() {
+	dir := flag.String("dir", "/tmp", "The cache directory")
+	addr := flag.String("addr", ":8080", "The listening address")
+	flag.Parse()
+
+	http.HandleFunc("/",
+		makeSafeHandler(func(w http.ResponseWriter, r *http.Request) {
+			if source := r.FormValue("dot"); len(source) > 0 {
+				dot, e := candy.HTTPGet(source, 0)
+				candy.Must(e)
+
+				id := fmt.Sprintf("%015x", md5.Sum(dot))
+				dotFile := path.Join(*dir, id) + ".dot"
+				pngFile := path.Join(*dir, id) + ".png"
+
+				if _, e := os.Stat(pngFile); os.IsNotExist(e) {
+					// TODO(yi): Here we adopt an unlimted-size disk-based cache.  We should
+					// either introduce LRU and limit the size, or periodically clean it.
+					log.Printf("Update cache for %s", pngFile)
+					candy.Must(ioutil.WriteFile(dotFile, dot, 0755))
+					png, e := exec.Command("dot", "-Tpng", dotFile).Output()
+					candy.Must(e)
+					candy.Must(ioutil.WriteFile(pngFile, png, 0755))
+				}
+
+				png, e := ioutil.ReadFile(pngFile)
+				candy.Must(e)
+				_, e = w.Write(png)
+				candy.Must(e)
+			}
+		}))
+
+	candy.Must(http.ListenAndServe(*addr, nil))
+}
+
+func makeSafeHandler(h http.HandlerFunc) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		defer func() {
+			if e := recover(); e != nil {
+				http.Error(w, fmt.Sprint(e), http.StatusInternalServerError)
+			}
+		}()
+		h(w, r)
+	}
+}