Add image tag into info output, add ability to print info output on demand and prevent multiple instances of runmqserver being run

cmd/runmqserver/process.go

@@ -0,0 +1,63 @@
+/*
+© Copyright IBM Corporation 2018
+
+Licensed 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 main
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/ibm-messaging/mq-container/internal/command"
+)
+
+// Verifies that we are the main or only instance of this program
+func verifySingleProcess() error {
+	programName, err := determineExecutable()
+	if err != nil {
+		return fmt.Errorf("Failed to determine name of this program - %v", err)
+	}
+
+	// Verify that there is only one runmqserver
+	_, err = verifyOnlyOne(programName)
+	if err != nil {
+		return fmt.Errorf("You cannot run more than one instance of this program")
+	}
+
+	return nil
+}
+
+// Verifies that there is only one instance running of the given program name.
+func verifyOnlyOne(programName string) (int, error) {
+	out, _, _ := command.Run("ps", "-e", "--format", "cmd")
+	//if this goes wrong then assume we are the only one
+	numOfProg := strings.Count(out, programName)
+	if numOfProg != 1 {
+		return numOfProg, fmt.Errorf("Expected there to be only 1 instance of %s but found %d", programName, numOfProg)
+	}
+	return numOfProg, nil
+}
+
+// Determines the name of the currently running executable.
+func determineExecutable() (string, error) {
+	file, err := os.Executable()
+	if err != nil {
+		return "", err
+	}
+
+	_, exec := filepath.Split(file)
+	return exec, nil
+}