Use TAR instead of DOCKER build type before 6.7.0 (elastic#40723)

In 6.7.0 (elastic#39378) we added a build type of DOCKER for the docker images, but
unfortunately earlier versions do not understand this and will reject any
transport messages that mention this build type.

This commit fixes this by reporting TAR instead of DOCKER when talking to older
nodes.

Relates (but does not fix) elastic#40511
Relates elastic#39378

Author: DaveCTurner

server/src/main/java/org/elasticsearch/Build.java

@@ -241,7 +241,13 @@ public static void writeBuild(Build build, StreamOutput out) throws IOException
             out.writeString(build.flavor().displayName());
         }
         if (out.getVersion().onOrAfter(Version.V_6_3_0)) {
-            out.writeString(build.type().displayName());
+            final Type buildType;
+            if (out.getVersion().before(Version.V_6_7_0) && build.type() == Type.DOCKER) {
+                buildType = Type.TAR;
+            } else {
+                buildType = build.type();
+            }
+            out.writeString(buildType.displayName());
         }
         out.writeString(build.shortHash());
         out.writeString(build.date());

server/src/test/java/org/elasticsearch/BuildTests.java

@@ -20,15 +20,23 @@
 package org.elasticsearch;
 
 import org.elasticsearch.common.io.FileSystemUtils;
+import org.elasticsearch.common.io.stream.StreamInput;
+import org.elasticsearch.common.io.stream.StreamOutput;
+import org.elasticsearch.common.io.stream.Writeable;
 import org.elasticsearch.test.ESTestCase;
+import org.elasticsearch.test.EqualsHashCodeTestUtils;
 
 import java.io.IOException;
 import java.io.InputStream;
 import java.net.URL;
 import java.util.Arrays;
+import java.util.List;
+import java.util.Objects;
 import java.util.Set;
 import java.util.stream.Collectors;
 
+import static org.hamcrest.Matchers.equalTo;
+
 public class BuildTests extends ESTestCase {
 
     /** Asking for the jar metadata should not throw exception in tests, no matter how configured */
@@ -115,4 +123,103 @@ public void testEqualsAndHashCode() {
         );
         assertNotEquals(build, differentVersion);
     }
+
+    private static class WriteableBuild implements Writeable {
+        private final Build build;
+
+        WriteableBuild(StreamInput in) throws IOException {
+            build = Build.readBuild(in);
+        }
+
+        WriteableBuild(Build build) {
+            this.build = build;
+        }
+
+        @Override
+        public void writeTo(StreamOutput out) throws IOException {
+            Build.writeBuild(build, out);
+        }
+
+        @Override
+        public boolean equals(Object o) {
+            if (this == o) return true;
+            if (o == null || getClass() != o.getClass()) return false;
+            WriteableBuild that = (WriteableBuild) o;
+            return build.equals(that.build);
+        }
+
+        @Override
+        public int hashCode() {
+            return Objects.hash(build);
+        }
+    }
+
+    private static String randomStringExcept(final String s) {
+        return randomAlphaOfLength(13 - s.length());
+    }
+
+    public void testSerialization() {
+        EqualsHashCodeTestUtils.checkEqualsAndHashCode(new WriteableBuild(new Build(
+                randomFrom(Build.Flavor.values()), randomFrom(Build.Type.values()),
+                randomAlphaOfLength(6), randomAlphaOfLength(6), randomBoolean(), randomAlphaOfLength(6))),
+            b -> copyWriteable(b, writableRegistry(), WriteableBuild::new, Version.CURRENT),
+            b -> {
+                switch (randomIntBetween(1, 6)) {
+                    case 1:
+                        return new WriteableBuild(new Build(
+                            randomValueOtherThan(b.build.flavor(), () -> randomFrom(Build.Flavor.values())), b.build.type(),
+                            b.build.shortHash(), b.build.date(), b.build.isSnapshot(), b.build.getQualifiedVersion()));
+                    case 2:
+                        return new WriteableBuild(new Build(b.build.flavor(),
+                            randomValueOtherThan(b.build.type(), () -> randomFrom(Build.Type.values())),
+                            b.build.shortHash(), b.build.date(), b.build.isSnapshot(), b.build.getQualifiedVersion()));
+                    case 3:
+                        return new WriteableBuild(new Build(b.build.flavor(), b.build.type(),
+                            randomStringExcept(b.build.shortHash()), b.build.date(), b.build.isSnapshot(), b.build.getQualifiedVersion()));
+                    case 4:
+                        return new WriteableBuild(new Build(b.build.flavor(), b.build.type(),
+                            b.build.shortHash(), randomStringExcept(b.build.date()), b.build.isSnapshot(), b.build.getQualifiedVersion()));
+                    case 5:
+                        return new WriteableBuild(new Build(b.build.flavor(), b.build.type(),
+                            b.build.shortHash(), b.build.date(), b.build.isSnapshot() == false, b.build.getQualifiedVersion()));
+                    case 6:
+                        return new WriteableBuild(new Build(b.build.flavor(), b.build.type(),
+                            b.build.shortHash(), b.build.date(), b.build.isSnapshot(), randomStringExcept(b.build.getQualifiedVersion())));
+                }
+                throw new AssertionError();
+            });
+    }
+
+    public void testSerializationBWC() throws IOException {
+        final WriteableBuild dockerBuild = new WriteableBuild(new Build(randomFrom(Build.Flavor.values()), Build.Type.DOCKER,
+            randomAlphaOfLength(6), randomAlphaOfLength(6), randomBoolean(), randomAlphaOfLength(6)));
+
+        final List<Version> versions = Version.getDeclaredVersions(Version.class);
+        final Version pre63Version = randomFrom(versions.stream().filter(v -> v.before(Version.V_6_3_0)).collect(Collectors.toList()));
+        final Version post63Pre67Version = randomFrom(versions.stream()
+            .filter(v -> v.onOrAfter(Version.V_6_3_0) && v.before(Version.V_6_7_0)).collect(Collectors.toList()));
+        final Version post67Pre70Version = randomFrom(versions.stream()
+            .filter(v -> v.onOrAfter(Version.V_6_7_0) && v.before(Version.V_7_0_0)).collect(Collectors.toList()));
+        final Version post70Version = randomFrom(versions.stream().filter(v -> v.onOrAfter(Version.V_7_0_0)).collect(Collectors.toList()));
+
+        final WriteableBuild pre63 = copyWriteable(dockerBuild, writableRegistry(), WriteableBuild::new, pre63Version);
+        final WriteableBuild post63pre67 = copyWriteable(dockerBuild, writableRegistry(), WriteableBuild::new, post63Pre67Version);
+        final WriteableBuild post67pre70 = copyWriteable(dockerBuild, writableRegistry(), WriteableBuild::new, post67Pre70Version);
+        final WriteableBuild post70 = copyWriteable(dockerBuild, writableRegistry(), WriteableBuild::new, post70Version);
+
+        assertThat(pre63.build.flavor(), equalTo(Build.Flavor.OSS));
+        assertThat(post63pre67.build.flavor(), equalTo(dockerBuild.build.flavor()));
+        assertThat(post67pre70.build.flavor(), equalTo(dockerBuild.build.flavor()));
+        assertThat(post70.build.flavor(), equalTo(dockerBuild.build.flavor()));
+
+        assertThat(pre63.build.type(), equalTo(Build.Type.UNKNOWN));
+        assertThat(post63pre67.build.type(), equalTo(Build.Type.TAR));
+        assertThat(post67pre70.build.type(), equalTo(dockerBuild.build.type()));
+        assertThat(post70.build.type(), equalTo(dockerBuild.build.type()));
+
+        assertThat(pre63.build.getQualifiedVersion(), equalTo(pre63Version.toString()));
+        assertThat(post63pre67.build.getQualifiedVersion(), equalTo(post63Pre67Version.toString()));
+        assertThat(post67pre70.build.getQualifiedVersion(), equalTo(post67Pre70Version.toString()));
+        assertThat(post70.build.getQualifiedVersion(), equalTo(dockerBuild.build.getQualifiedVersion()));
+    }
 }