<p>Does anybody know how to run Beam Python pipelines with Flink when Flink is running as pods in Kubernetes?</p>

<p>I have successfully managed to run a Beam Python pipeline using the Portable runner and the job service pointing to a local Flink server running in Docker containers. </p>

<p>I was able to achieve that mounting the Docker socket in my Flink containers, and running Flink as root process, so the class DockerEnvironmentFactory can create the Python harness container. </p>

<p>Unfortunately, I can't use the same solution when Flink is running in Kubernetes. Moreover, I don't want to create the Python harness container using the Docker command from my pods. </p>

<p>It seems that Bean runner automatically selects Docker for executing  Python pipelines. However, I noticed there is an implementation called ExternalEnvironmentFactory, but I am not sure how to use it. </p>

<p>Is there a way to deploy a side container and use a different factory to run the Python harness process? What is the correct approach? </p>

<p>This is the patch for DockerEnvironmentFactory:</p>

<pre><code>diff -pr beam-release-2.15.0/runners/java-fn-execution/src/main/java/org/apache/beam/runners/fnexecution/environment/DockerEnvironmentFactory.java beam-release-2.15.0-1/runners/java-fn-execution/src/main/java/org/apache/beam/runners/fnexecution/environment/DockerEnvironmentFactory.java
*** beam-release-2.15.0/runners/java-fn-execution/src/main/java/org/apache/beam/runners/fnexecution/environment/DockerEnvironmentFactory.java   2019-08-14 22:33:41.000000000 +0100
--- beam-release-2.15.0-1/runners/java-fn-execution/src/main/java/org/apache/beam/runners/fnexecution/environment/DockerEnvironmentFactory.java 2019-09-09 16:02:07.000000000 +0100
*************** package org.apache.beam.runners.fnexecut
*** 19,24 ****
--- 19,26 ----

  import static org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.MoreObjects.firstNonNull;

+ import java.net.InetAddress;
+ import java.net.UnknownHostException;
  import java.nio.file.Files;
  import java.nio.file.Paths;
  import java.time.Duration;
*************** public class DockerEnvironmentFactory im
*** 127,133 ****
          ImmutableList.&lt;String&gt;builder()
              .addAll(gcsCredentialArgs())
              // NOTE: Host networking does not work on Mac, but the command line flag is accepted.
!             .add("--network=host")
              // We need to pass on the information about Docker-on-Mac environment (due to missing
              // host networking on Mac)
              .add("--env=DOCKER_MAC_CONTAINER=" + System.getenv("DOCKER_MAC_CONTAINER"));
--- 129,135 ----
          ImmutableList.&lt;String&gt;builder()
              .addAll(gcsCredentialArgs())
              // NOTE: Host networking does not work on Mac, but the command line flag is accepted.
!             .add("--network=flink")
              // We need to pass on the information about Docker-on-Mac environment (due to missing
              // host networking on Mac)
              .add("--env=DOCKER_MAC_CONTAINER=" + System.getenv("DOCKER_MAC_CONTAINER"));
*************** public class DockerEnvironmentFactory im
*** 222,228 ****

      private static ServerFactory getServerFactory() {
        ServerFactory.UrlFactory dockerUrlFactory =
!           (host, port) -&gt; HostAndPort.fromParts(DOCKER_FOR_MAC_HOST, port).toString();
        if (RUNNING_INSIDE_DOCKER_ON_MAC) {
          // If we're already running in a container, we need to use a fixed port range due to
          // non-existing host networking in Docker-for-Mac. The port range needs to be published
--- 224,230 ----

      private static ServerFactory getServerFactory() {
        ServerFactory.UrlFactory dockerUrlFactory =
!               (host, port) -&gt; HostAndPort.fromParts(getCanonicalHostName(), port).toString();
        if (RUNNING_INSIDE_DOCKER_ON_MAC) {
          // If we're already running in a container, we need to use a fixed port range due to
          // non-existing host networking in Docker-for-Mac. The port range needs to be published
*************** public class DockerEnvironmentFactory im
*** 237,242 ****
--- 239,252 ----
      }
    }

+   private static String getCanonicalHostName() throws RuntimeException {
+     try {
+       return InetAddress.getLocalHost().getCanonicalHostName();
+     } catch (UnknownHostException e) {
+       throw new RuntimeException(e);
+     }
+   }
+
    /** Provider for DockerEnvironmentFactory. */
    public static class Provider implements EnvironmentFactory.Provider {
      private final boolean retainDockerContainer;
*************** public class DockerEnvironmentFactory im
*** 269,275 ****
      public ServerFactory getServerFactory() {
        switch (getPlatform()) {
          case LINUX:
!           return ServerFactory.createDefault();
          case MAC:
            return DockerOnMac.getServerFactory();
          default:
--- 279,286 ----
      public ServerFactory getServerFactory() {
        switch (getPlatform()) {
          case LINUX:
!           return DockerOnMac.getServerFactory();
! //          return ServerFactory.createDefault();
          case MAC:
            return DockerOnMac.getServerFactory();
          default:
</code></pre>

<p>This is the Docker compose file I use to run Flink:</p>

<pre><code>version: '3.4'
services:
  jobmanager:
    image: tenx/flink:1.8.1
    command: 'jobmanager'
    environment:
      JOB_MANAGER_RPC_ADDRESS: 'jobmanager'
      DOCKER_MAC_CONTAINER: 1
      FLINK_JM_HEAP: 128
    volumes:
      - jobmanager-data:/data
      - /var/run/docker.sock:/var/run/docker.sock
    ports:
      - target: 8081
        published: 8081
        protocol: tcp
        mode: ingress
    networks:
      - flink
  taskmanager:
    image: tenx/flink:1.8.1
    command: 'taskmanager'
    environment:
      JOB_MANAGER_RPC_ADDRESS: 'jobmanager'
      DOCKER_MAC_CONTAINER: 1
      FLINK_TM_HEAP: 1024
      TASK_MANAGER_NUMBER_OF_TASK_SLOTS: 2
    networks:
      - flink
    volumes:
      - taskmanager-data:/data
      - /var/run/docker.sock:/var/run/docker.sock
      - /var/folders:/var/folders
volumes:
    jobmanager-data:
    taskmanager-data:
networks:
  flink:
    external: true
</code></pre>

<p>This is my Python pipeline:</p>

<pre><code>import apache_beam as beam
import logging

class LogElements(beam.PTransform):

    class _LoggingFn(beam.DoFn):

        def __init__(self, prefix=''):
            super(LogElements._LoggingFn, self).__init__()
            self.prefix = prefix

        def process(self, element, **kwargs):
            logging.info(self.prefix + str(element))
            yield element

    def __init__(self, label=None, prefix=''):
        super(LogElements, self).__init__(label)
        self.prefix = prefix

    def expand(self, input):
        input | beam.ParDo(self._LoggingFn(self.prefix))


from apache_beam.options.pipeline_options import PipelineOptions

options = PipelineOptions(["--runner=PortableRunner", "--job_endpoint=localhost:8099"])

p = beam.Pipeline(options=options)

(p | beam.Create([1, 2, 3, 4, 5]) | LogElements())

p.run()
</code></pre>

<p>This is how I run the job service:</p>

<blockquote>
  <p>gradle :runners:flink:1.8:job-server:runShadow -PflinkMasterUrl=localhost:8081</p>
</blockquote>

<p>Docker is automatically selected for executing the Python harness.</p>

<p>I can change the image used to run the Python container:</p>

<blockquote>
  <p>options = PipelineOptions(["--runner=PortableRunner", "--job_endpoint=localhost:8099", "--environment_type=DOCKER", "--environment_config=beam/python:latest"])</p>
</blockquote>

<p>I can disable Docker and enable the ExternalEnvironmentFactory: </p>

<blockquote>
  <p>options = PipelineOptions(["--runner=PortableRunner", "--job_endpoint=localhost:8099", "--environment_type=EXTERNAL", "--environment_config=server"])</p>
</blockquote>

<p>but I have to implement some callback answering on <a href="http://server:80" rel="nofollow noreferrer">http://server:80</a>.</p>

<p>Is there an implementation available?</p>

Andrea Medeghini
<p>To answer the question above, basically you want to add beam_worker_pool container along side with the flink task manager container in the same pods. So in the yaml file that you use to deploy flink task managers, add a new container:</p>
<pre><code>  - name: beam-worker-pool
    image: apache/beam_python3.7_sdk:2.22.0
    args: [&quot;--worker_pool&quot;]
    ports:
    - containerPort: 50000
      name: pool
    livenessProbe:
      tcpSocket:
        port: 50000
      initialDelaySeconds: 30
      periodSeconds: 60
    volumeMounts:
    - name: flink-config-volume
      mountPath: /opt/flink/conf/
    securityContext:
      runAsUser: 9999
</code></pre>
