[JENKINS-41316] don’t override entrypoint but double check the command is well executed and warn user if this is not the case

Signed-off-by: Nicolas De Loof <[email protected]>

Author: ndeloof

src/main/java/org/jenkinsci/plugins/docker/workflow/WithContainerStep.java

@@ -182,6 +182,12 @@ public static class Execution extends AbstractStepExecutionImpl {
             }
 
             container = dockerClient.run(env, step.image, step.args, ws, volumes, volumesFromContainers, envReduced, dockerClient.whoAmI(), /* expected to hang until killed */ "cat");
+            final List<String> ps = dockerClient.listProcess(env, container);
+            if (!ps.contains("cat")) {
+                listener.error("The container started but didn't ran the expected command. Please double check your Entrypoint does execute the command passed as docker run argument. See https://docs.docker.com/engine/userguide/eng-image/dockerfile_best-practices/#entrypoint for entrypoint best practices.");
+                throw new IOException("Failed to run container with CMD `cat`");
+            }
+
             DockerFingerprints.addRunFacet(dockerClient.getContainerRecord(env, container), run);
             ImageAction.add(step.image, run);
             getContext().newBodyInvoker().

src/main/java/org/jenkinsci/plugins/docker/workflow/client/DockerClient.java

@@ -35,17 +35,22 @@
 
 import javax.annotation.CheckForNull;
 import javax.annotation.Nonnull;
+import java.io.BufferedReader;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
+import java.io.Reader;
+import java.io.StringReader;
 import java.nio.charset.Charset;
 import java.text.ParseException;
 import java.text.SimpleDateFormat;
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Date;
 import java.util.Map;
 import java.util.List;
 import java.util.Arrays;
+import java.util.StringTokenizer;
 import java.util.concurrent.TimeUnit;
 import java.util.logging.Level;
 import java.util.logging.Logger;
@@ -131,6 +136,30 @@ public String run(@Nonnull EnvVars launchEnv, @Nonnull String image, @CheckForNu
         }
     }
 
+    public List<String> listProcess(@Nonnull EnvVars launchEnv, @Nonnull String containerId) throws IOException, InterruptedException {
+        LaunchResult result = launch(launchEnv, false, "top", containerId);
+        if (result.getStatus() != 0) {
+            throw new IOException(String.format("Failed to run top '%s'. Error: %s", containerId, result.getErr()));
+        }
+        List<String> processes = new ArrayList<>();
+        try (Reader r = new StringReader(result.getOut());
+             BufferedReader in = new BufferedReader(r)) {
+            String line;
+            in.readLine(); // ps header
+            while ((line = in.readLine()) != null) {
+                final StringTokenizer stringTokenizer = new StringTokenizer(line, " ");
+                if (stringTokenizer.countTokens() < 4) {
+                    throw new IOException("Unexpected `docker top` output : "+line);
+                }
+                stringTokenizer.nextToken(); // PID
+                stringTokenizer.nextToken(); // USER
+                stringTokenizer.nextToken(); // TIME
+                processes.add(stringTokenizer.nextToken()); // COMMAND
+            }
+        }
+        return processes;
+    }
+
     /**
      * Stop a container.
      *