Don't pull the probe image if we already have it.

Its freshness is not a concern.

helios-testing/src/main/java/com/spotify/helios/testing/HeliosSoloDeployment.java

@@ -31,6 +31,7 @@
 import com.spotify.docker.client.DockerClient;
 import com.spotify.docker.client.DockerException;
 import com.spotify.docker.client.DockerHost;
+import com.spotify.docker.client.ImageNotFoundException;
 import com.spotify.docker.client.messages.ContainerConfig;
 import com.spotify.docker.client.messages.ContainerCreation;
 import com.spotify.docker.client.messages.ContainerExit;
@@ -209,9 +210,10 @@ private String checkDockerAndGetGateway() throws HeliosDeploymentException {
             .cmd(probeCommand(probeName))
             .build();
 
+
     final ContainerCreation creation;
     try {
-      dockerClient.pull(PROBE_IMAGE);
+      pullIfAbsent(PROBE_IMAGE);
       creation = dockerClient.createContainer(containerConfig, probeName);
     } catch (DockerException | InterruptedException e) {
       throw new HeliosDeploymentException("helios-solo probe container creation failed", e);
@@ -245,6 +247,17 @@ private String checkDockerAndGetGateway() throws HeliosDeploymentException {
     return gateway;
   }
 
+  private void pullIfAbsent(final String image) throws DockerException, InterruptedException {
+    try {
+      dockerClient.inspectImage(image);
+      log.info("helios-solo image {} is present. Not pulling it.", image);
+      return;
+    } catch (ImageNotFoundException e) {
+      log.info("helios-solo pulling new image: {}", image);
+    }
+    dockerClient.pull(PROBE_IMAGE);
+  }
+
   private List<String> probeCommand(final String probeName) {
     final List<String> cmd = new ArrayList<>(ImmutableList.of("curl", "-f"));
     switch (containerDockerHost.uri().getScheme()) {

helios-testing/src/test/java/com/spotify/helios/testing/HeliosSoloDeploymentTest.java

@@ -23,10 +23,12 @@
 
 import com.spotify.docker.client.DockerClient;
 import com.spotify.docker.client.DockerHost;
+import com.spotify.docker.client.ImageNotFoundException;
 import com.spotify.docker.client.messages.ContainerConfig;
 import com.spotify.docker.client.messages.ContainerCreation;
 import com.spotify.docker.client.messages.ContainerExit;
 import com.spotify.docker.client.messages.ContainerInfo;
+import com.spotify.docker.client.messages.ImageInfo;
 import com.spotify.docker.client.messages.Info;
 import com.spotify.docker.client.messages.NetworkSettings;
 import com.spotify.docker.client.messages.PortBinding;
@@ -46,6 +48,8 @@
 import static org.junit.Assert.assertTrue;
 import static org.mockito.Matchers.anyString;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
 public class HeliosSoloDeploymentTest {
@@ -155,4 +159,28 @@ public void testConfig() throws Exception {
     assertTrue("Could not find helios-solo container creation", foundSolo);
 
   }
+
+  @Test
+  public void testDoesNotPullPresentProbeImage() throws Exception {
+    when(this.dockerClient.inspectImage(HeliosSoloDeployment.PROBE_IMAGE))
+        .thenReturn(mock(ImageInfo.class));
+
+    HeliosSoloDeployment.builder()
+        .dockerClient(this.dockerClient)
+        .build();
+
+    verify(this.dockerClient, never()).pull(HeliosSoloDeployment.PROBE_IMAGE);
+  }
+
+  @Test
+  public void testDoesPullAbsentProbeImage() throws Exception {
+    when(this.dockerClient.inspectImage(HeliosSoloDeployment.PROBE_IMAGE))
+        .thenThrow(new ImageNotFoundException(HeliosSoloDeployment.PROBE_IMAGE));
+
+    HeliosSoloDeployment.builder()
+        .dockerClient(this.dockerClient)
+        .build();
+
+    verify(this.dockerClient).pull(HeliosSoloDeployment.PROBE_IMAGE);
+  }
 }