rabbah commented on a change in pull request #5: The go proxy 
URL: 
https://github.com/apache/incubator-openwhisk-runtime-go/pull/5#discussion_r179725739
 
 

 ##########
 File path: openwhisk/executor.go
 ##########
 @@ -0,0 +1,208 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package openwhisk
+
+import (
+       "bufio"
+       "fmt"
+       "log"
+       "os"
+       "os/exec"
+       "runtime"
+       "time"
+)
+
+// TIMEOUT to wait for process to start
+// and log to be produced
+const TIMEOUT = 5 * time.Millisecond
+
+// Executor is the container and the guardian  of a child process
+// It starts a command, feeds input and output, read logs and control its 
termination
+type Executor struct {
+       io      chan string
+       log     chan bool
+       exit    chan error
+       _cmd    *exec.Cmd
+       _input  *bufio.Writer
+       _output *bufio.Scanner
+       _logout *bufio.Scanner
+       _logerr *bufio.Scanner
+}
+
+// NewExecutor creates a child subprocess using the provided command line.
+// You can then start it getting a communication channel
+func NewExecutor(command string, args ...string) (proc *Executor) {
+       cmd := exec.Command(command, args...)
+
+       stdin, err := cmd.StdinPipe()
+       if err != nil {
+               return nil
+       }
+
+       stdout, err := cmd.StdoutPipe()
+       if err != nil {
+               return nil
+       }
+
+       stderr, err := cmd.StderrPipe()
+       if err != nil {
+               return nil
+       }
+
+       pipeOut, pipeIn, err := os.Pipe()
+       if err != nil {
+               return nil
+       }
+       cmd.ExtraFiles = []*os.File{pipeIn}
+
+       return &Executor{
+               make(chan string),
+               make(chan bool),
+               make(chan error),
+               cmd,
+               bufio.NewWriter(stdin),
+               bufio.NewScanner(pipeOut),
+               bufio.NewScanner(stdout),
+               bufio.NewScanner(stderr),
+       }
+}
+
+// collect log from a stream
+func _collect(ch chan string, scan *bufio.Scanner) {
+       for scan.Scan() {
+               ch <- scan.Text()
+       }
+}
+
+// loop over the command executing
+// returning when the command exits
+func (proc *Executor) run() {
+       log.Println("run: start")
+       err := proc._cmd.Start()
+       if err != nil {
+               proc.exit <- err
+               log.Println("run: early exit")
+               proc._cmd = nil // do not kill
+               return
+       }
+       // wait for the exit
+       proc.exit <- proc._cmd.Wait()
+       proc._cmd = nil // do not kill
+       log.Println("run: end")
+}
+
+// manage copying stdout and stder in output
+// with log guards
+func (proc *Executor) logger() {
+       log.Println("logger: start")
+       // poll stdout and stderr
+       chOut := make(chan string)
+       go _collect(chOut, proc._logout)
+       chErr := make(chan string)
+       go _collect(chErr, proc._logerr)
+
+       // wait for the signal
+       for <-proc.log {
+               // flush stdout
+               runtime.Gosched()
+               for loop := true; loop; {
+                       select {
+                       case buf := <-chOut:
+                               fmt.Println(buf)
+                       case <-time.After(TIMEOUT):
+                               loop = false
+                       }
+               }
+               fmt.Println("XXX_THE_END_OF_A_WHISK_ACTIVATION_XXX")
+
+               // flush stderr
+               runtime.Gosched()
+               for loop := true; loop; {
+                       select {
+                       case buf := <-chErr:
+                               fmt.Println(buf)
+                       case <-time.After(TIMEOUT):
+                               loop = false
+                       }
+               }
+               fmt.Println("XXX_THE_END_OF_A_WHISK_ACTIVATION_XXX")
+       }
+       log.Printf("logger: end")
+}
+
+// main service function
+// writing in input
+// and reading in output
+// using the provide channels
+func (proc *Executor) service() {
+       log.Println("service: start")
+       for {
+               in := <-proc.io
+               if in == "" {
+                       log.Println("terminated upon request")
+                       break
+               }
+               // input/output with the process
+               log.Printf(">>>%s\n", in)
+               proc._input.WriteString(in + "\n")
+               proc._input.Flush()
+               if proc._output.Scan() {
+                       out := proc._output.Text()
+                       log.Printf("<<<%s\n", out)
+                       proc.io <- out
+                       if out == "" {
+                               break
+                       }
+               }
+       }
+       log.Printf("service: end")
+}
+
+// Start execution of the command
+// returns an error if the program fails
+func (proc *Executor) Start() error {
+       // start the underlying executable
+       // check if died
+       go proc.run()
+       select {
+       case <-proc.exit:
+               // oops, it died
+               return fmt.Errorf("command exited")
+       case <-time.After(TIMEOUT):
+               // ok let's process it
+               go proc.service()
+               go proc.logger()
+       }
+       return nil
+}
+
+// Stop will kill the process
+// and close the channels
+func (proc *Executor) Stop() {
+       log.Println("stopping")
 
 Review comment:
   hehe - no worries you can leave it. I was able to follow the code nicely 
even though I’ve written a grand total of 100 lines of go code.

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