Watcher: Ensure mail message ids are unique per watch action (#30112)

Email message IDs are supposed to be unique. In order to guarantee this,
we need to take the action id of a watch action into account as well,
not just the watch id from the watch execution context. This prevents
that two actions from the same watch execution end up with the same
message id.

x-pack/plugin/watcher/src/main/java/org/elasticsearch/xpack/watcher/actions/email/ExecutableEmailAction.java

@@ -63,7 +63,7 @@ public Action.Result execute(String actionId, WatchExecutionContext ctx, Payload
         }
 
         Email.Builder email = action.getEmail().render(templateEngine, model, htmlSanitizer, attachments);
-        email.id(ctx.id().value());
+        email.id(actionId + "_" + ctx.id().value());
 
         if (ctx.simulateAction(actionId)) {
             return new EmailAction.Result.Simulated(email.build());

x-pack/plugin/watcher/src/main/java/org/elasticsearch/xpack/watcher/notification/email/Email.java

@@ -354,7 +354,7 @@ public Builder attach(Attachment attachment) {
          * after this is called is incorrect.
          */
         public Email build() {
-            assert id != null : "email id should not be null (should be set to the watch id";
+            assert id != null : "email id should not be null";
             Email email = new Email(id, from, replyTo, priority, sentDate, to, cc, bcc, subject, textBody, htmlBody,
                     unmodifiableMap(attachments));
             attachments = null;

x-pack/plugin/watcher/src/test/java/org/elasticsearch/xpack/watcher/actions/email/EmailActionTests.java

@@ -171,7 +171,7 @@ public void testExecute() throws Exception {
         assertThat(result, instanceOf(EmailAction.Result.Success.class));
         assertThat(((EmailAction.Result.Success) result).account(), equalTo(account));
         Email actualEmail = ((EmailAction.Result.Success) result).email();
-        assertThat(actualEmail.id(), is(wid.value()));
+        assertThat(actualEmail.id(), is("_id_" + wid.value()));
         assertThat(actualEmail, notNullValue());
         assertThat(actualEmail.subject(), is(subject == null ? null : subject.getTemplate()));
         assertThat(actualEmail.textBody(), is(textBody == null ? null : textBody.getTemplate()));

x-pack/plugin/watcher/src/test/java/org/elasticsearch/xpack/watcher/actions/email/EmailMessageIdTests.java

@@ -0,0 +1,88 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+package org.elasticsearch.xpack.watcher.actions.email;
+
+import org.elasticsearch.common.settings.ClusterSettings;
+import org.elasticsearch.common.settings.Setting;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.test.ESTestCase;
+import org.elasticsearch.xpack.core.watcher.execution.WatchExecutionContext;
+import org.elasticsearch.xpack.core.watcher.watch.Payload;
+import org.elasticsearch.xpack.watcher.common.text.TextTemplateEngine;
+import org.elasticsearch.xpack.watcher.notification.email.EmailService;
+import org.elasticsearch.xpack.watcher.notification.email.EmailTemplate;
+import org.elasticsearch.xpack.watcher.notification.email.HtmlSanitizer;
+import org.elasticsearch.xpack.watcher.notification.email.support.EmailServer;
+import org.elasticsearch.xpack.watcher.test.MockTextTemplateEngine;
+import org.elasticsearch.xpack.watcher.test.WatcherTestUtils;
+import org.junit.After;
+import org.junit.Before;
+
+import javax.mail.internet.MimeMessage;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+import static org.hamcrest.Matchers.hasSize;
+
+public class EmailMessageIdTests extends ESTestCase {
+
+    private EmailServer server;
+    private TextTemplateEngine textTemplateEngine = new MockTextTemplateEngine();
+    private HtmlSanitizer htmlSanitizer = new HtmlSanitizer(Settings.EMPTY);
+    private EmailService emailService;
+    private EmailAction emailAction;
+
+    @Before
+    public void startSmtpServer() {
+        server = EmailServer.localhost(logger);
+
+        Settings settings = Settings.builder()
+                .put("xpack.notification.email.account.test.smtp.auth", true)
+                .put("xpack.notification.email.account.test.smtp.user", EmailServer.USERNAME)
+                .put("xpack.notification.email.account.test.smtp.password", EmailServer.PASSWORD)
+                .put("xpack.notification.email.account.test.smtp.port", server.port())
+                .put("xpack.notification.email.account.test.smtp.host", "localhost")
+                .build();
+
+        Set<Setting<?>> registeredSettings = new HashSet<>(ClusterSettings.BUILT_IN_CLUSTER_SETTINGS);
+        registeredSettings.addAll(EmailService.getSettings());
+        ClusterSettings clusterSettings = new ClusterSettings(settings, registeredSettings);
+        emailService = new EmailService(settings, null, clusterSettings);
+        EmailTemplate emailTemplate = EmailTemplate.builder().from("from@example.org").to("to@example.org")
+                .subject("subject").textBody("body").build();
+        emailAction = new EmailAction(emailTemplate, null, null, null, null, null);
+    }
+
+    @After
+    public void stopSmtpServer() {
+        server.stop();
+    }
+
+    public void testThatMessageIdIsUnique() throws Exception {
+        List<MimeMessage> messages = new ArrayList<>();
+        server.addListener(messages::add);
+        ExecutableEmailAction firstEmailAction = new ExecutableEmailAction(emailAction, logger, emailService, textTemplateEngine,
+                htmlSanitizer, Collections.emptyMap());
+        ExecutableEmailAction secondEmailAction = new ExecutableEmailAction(emailAction, logger, emailService, textTemplateEngine,
+                htmlSanitizer, Collections.emptyMap());
+
+        WatchExecutionContext ctx = WatcherTestUtils.createWatchExecutionContext(logger);
+        firstEmailAction.execute("my_first_action_id", ctx, Payload.EMPTY);
+        secondEmailAction.execute("my_second_action_id", ctx, Payload.EMPTY);
+
+        assertThat(messages, hasSize(2));
+        // check for unique message ids, should be two as well
+        Set<String> messageIds = new HashSet<>();
+        for (MimeMessage message : messages) {
+            messageIds.add(message.getMessageID());
+        }
+        assertThat(messageIds, hasSize(2));
+    }
+}
+