top: make output tabular

Make the output of top tabular to be compatible with Docker.  Please
note, that any user-input for `GetContainerPidInformation(...)` will be
ignored until we have found a way to generically and reliably parse ps-1
output or until there is a go-lib to extract all the data from /proc in
a ps-1 compatible fashion.

Fixes: #458
Signed-off-by: Valentin Rothberg <vrothberg@suse.com>

Closes: #939
Approved by: rhatdan

cmd/podman/top.go

@@ -2,6 +2,8 @@ package main
 
 import (
 	"fmt"
+	"os"
+	"text/tabwriter"
 
 	"github.com/pkg/errors"
 	"github.com/projectatomic/libpod/cmd/podman/libpodruntime"
@@ -34,8 +36,7 @@ func topCmd(c *cli.Context) error {
 	var container *libpod.Container
 	var err error
 	args := c.Args()
-	var psArgs []string
-	psOpts := []string{"-o", "uid,pid,ppid,c,stime,tname,time,cmd"}
+
 	if len(args) < 1 && !c.Bool("latest") {
 		return errors.Errorf("you must provide the name or id of a running container")
 	}
@@ -48,9 +49,6 @@ func topCmd(c *cli.Context) error {
 		return errors.Wrapf(err, "error creating libpod runtime")
 	}
 	defer runtime.Shutdown(false)
-	if len(args) > 1 {
-		psOpts = args[1:]
-	}
 
 	if c.Bool("latest") {
 		container, err = runtime.GetLatestContainer()
@@ -69,14 +67,15 @@ func topCmd(c *cli.Context) error {
 		return errors.Errorf("top can only be used on running containers")
 	}
 
-	psArgs = append(psArgs, psOpts...)
-
-	psOutput, err := container.GetContainerPidInformation(psArgs)
+	psOutput, err := container.GetContainerPidInformation([]string{})
 	if err != nil {
 		return err
 	}
-	for _, line := range psOutput {
-		fmt.Println(line)
+
+	w := tabwriter.NewWriter(os.Stdout, 20, 1, 3, ' ', 0)
+	for _, proc := range psOutput {
+		fmt.Fprintln(w, proc)
 	}
+	w.Flush()
 	return nil
 }

libpod/container_top.go

@@ -44,8 +44,20 @@ func (c *Container) getContainerPids() ([]string, error) {
 }
 
 // GetContainerPidInformation calls ps with the appropriate options and returns
-// the results as a string and the container's PIDs as a []string
+// the results as a string and the container's PIDs as a []string.  Note that
+// the ps output columns of each string are separated by a '\t\'.  Currently,
+// the args argument is overwriten with []string{"-ef"} until there is a
+// portable library for ps-1 or to parse the procFS to extract all data.
 func (c *Container) GetContainerPidInformation(args []string) ([]string, error) {
+	// XXX(ps-issue): args is overwriten with []{"-ef"} as the ps-1 tool
+	// doesn't support a generic way of splitting columns, rendering its
+	// output hard to parse.  Docker first deterimes the number of columns
+	// and merges all exceeding ones into the last one.  We believe that
+	// writing a go library which parses procFS in a ps-compatible way may
+	// be more beneficial in the long run.  Until then, args will be
+	// ignored.
+	args = []string{"-ef"}
+
 	if !c.batched {
 		c.lock.Lock()
 		defer c.lock.Unlock()
@@ -80,7 +92,7 @@ func filterPids(psOutput string, pids []string) ([]string, error) {
 	// Pids that don't belong.
 
 	// append the headers back in
-	output = append(output, results[0])
+	output = append(output, strings.Join(headers, "\t"))
 
 	pidIndex := -1
 	for i, header := range headers {
@@ -98,7 +110,13 @@ func filterPids(psOutput string, pids []string) ([]string, error) {
 		cols := fieldsASCII(l)
 		pid := cols[pidIndex]
 		if util.StringInSlice(pid, pids) {
-			output = append(output, l)
+			// XXX(ps-issue): Strip cols down to the header's size
+			// and merge exceeding fields. This is required to
+			// "merge" the overhanging CMD entries which can
+			// contain white spaces.
+			out := cols[:len(headers)-1]
+			out = append(out, strings.Join(cols[len(headers)-1:], " "))
+			output = append(output, strings.Join(out, "\t"))
 		}
 	}
 	return output, nil

test/e2e/top_test.go

@@ -59,7 +59,14 @@ var _ = Describe("Podman top", func() {
 		Expect(len(result.OutputToStringArray())).To(BeNumerically(">", 1))
 	})
 
+	//      XXX(ps-issue): for the time being, podman-top and the libpod API
+	//      GetContainerPidInformation(...) will ignore any arguments passed to ps,
+	//      so we have to disable the tests below.  Please refer to
+	//      https://github.com/projectatomic/libpod/pull/939 for more background
+	//      information.
+
 	It("podman top with options", func() {
+		Skip("podman-top with options: options are temporarily ignored")
 		session := podmanTest.Podman([]string{"run", "-d", ALPINE, "top", "-d", "2"})
 		session.WaitWithDefaultTimeout()
 		Expect(session.ExitCode()).To(Equal(0))
@@ -71,6 +78,7 @@ var _ = Describe("Podman top", func() {
 	})
 
 	It("podman top on container invalid options", func() {
+		Skip("podman-top with invalid options: options are temporarily ignored")
 		top := podmanTest.RunTopContainer("")
 		top.WaitWithDefaultTimeout()
 		Expect(top.ExitCode()).To(Equal(0))