Opt in mode for Singularity emails

SingularityClient/src/main/java/com/hubspot/singularity/client/SingularityClient.java

@@ -265,6 +265,11 @@ public class SingularityClient {
   private static final String PRIORITY_FORMAT = "%s/priority";
   private static final String PRIORITY_FREEZE_FORMAT = PRIORITY_FORMAT + "/freeze";
 
+  private static final String NOTIFICATION_FORMAT = "%s/notifications";
+  private static final String ALLOWLIST_FORMAT = NOTIFICATION_FORMAT + "/allowlist";
+  private static final String SUBSCRIBE_FORMAT = NOTIFICATION_FORMAT + "/subscribe";
+  private static final String UNSUBSCRIBE_FORMAT = NOTIFICATION_FORMAT + "/unsubscribe";
+
   private static final TypeReference<Collection<SingularityRequestParent>> REQUESTS_COLLECTION = new TypeReference<Collection<SingularityRequestParent>>() {};
   private static final TypeReference<Collection<SingularityPendingRequest>> PENDING_REQUESTS_COLLECTION = new TypeReference<Collection<SingularityPendingRequest>>() {};
   private static final TypeReference<Collection<SingularityRequestCleanup>> CLEANUP_REQUESTS_COLLECTION = new TypeReference<Collection<SingularityRequestCleanup>>() {};
@@ -2791,4 +2796,27 @@ public Optional<SingularityTaskState> getTaskState(String requestId, String runI
       SingularityTaskState.class
     );
   }
+
+  //
+  // Notification Settings
+  //
+
+  public Collection<String> getNotificationAllowlist() {
+    final Function<String, String> requestUri = host ->
+      String.format(ALLOWLIST_FORMAT, getApiBase(host));
+
+    return getCollection(requestUri, "subscribe allowlist", STRING_COLLECTION);
+  }
+
+  public void subscribeToNotifications(String email) {
+    final Function<String, String> requestUri = host ->
+      String.format(SUBSCRIBE_FORMAT, getApiBase(host));
+    this.post(requestUri, "subscribe email", Optional.of(email), Optional.empty());
+  }
+
+  public void unsubscribeFromNotification(String email) {
+    final Function<String, String> requestUri = host ->
+      String.format(UNSUBSCRIBE_FORMAT, getApiBase(host));
+    this.post(requestUri, "unsubscribe email", Optional.of(email), Optional.empty());
+  }
 }

SingularityService/src/main/java/com/hubspot/singularity/config/SingularityConfiguration.java

@@ -437,6 +437,9 @@ public class SingularityConfiguration extends Configuration {
   // Audits the usage of ZooKeeper
   private boolean useLoggingCuratorFramework = false;
 
+  // Defines whether to use a blocklist or allowlist for Singularity emails
+  private boolean optInEmailMode = false;
+
   public long getAskDriverToKillTasksAgainAfterMillis() {
     return askDriverToKillTasksAgainAfterMillis;
   }
@@ -2047,4 +2050,12 @@ public boolean useLoggingCuratorFramework() {
   public void setUseLoggingCuratorFramework(boolean useLoggingCuratorFramework) {
     this.useLoggingCuratorFramework = useLoggingCuratorFramework;
   }
+
+  public boolean isOptInEmailMode() {
+    return optInEmailMode;
+  }
+
+  public void setOptInEmailMode(boolean optInEmailMode) {
+    this.optInEmailMode = optInEmailMode;
+  }
 }

SingularityService/src/main/java/com/hubspot/singularity/data/NotificationsManager.java

@@ -14,6 +14,7 @@
 public class NotificationsManager extends CuratorManager {
   private static final String NOTIFICATIONS_ROOT = "/notifications";
   private static final String BLOCKLIST_ROOT = NOTIFICATIONS_ROOT + "/blacklist";
+  private static final String ALLOWLIST_ROOT = NOTIFICATIONS_ROOT + "/allowlist";
 
   LoadingCache<String, List<String>> cache;
 
@@ -39,21 +40,49 @@ public List<String> load(String key) throws Exception {
         );
   }
 
+  public void unsubscribe(String email) {
+    removeFromAllowlist(email);
+    addToBlocklist(email);
+  }
+
+  public void subscribe(String email) {
+    addToAllowlist(email);
+    removeFromBlocklist(email);
+  }
+
   public void addToBlocklist(String email) {
-    create(getEmailPath(email));
+    create(getBlockListEmailPath(email));
     cache.invalidate(BLOCKLIST_ROOT);
   }
 
   public void removeFromBlocklist(String email) {
-    delete(getEmailPath(email));
+    delete(getBlockListEmailPath(email));
     cache.invalidate(BLOCKLIST_ROOT);
   }
 
   public List<String> getBlocklist() {
     return cache.getUnchecked(BLOCKLIST_ROOT);
   }
 
-  private String getEmailPath(String email) {
+  private String getBlockListEmailPath(String email) {
     return ZKPaths.makePath(BLOCKLIST_ROOT, email);
   }
+
+  public void addToAllowlist(String email) {
+    create(getAllowlistEmailPath(email));
+    cache.invalidate(ALLOWLIST_ROOT);
+  }
+
+  public void removeFromAllowlist(String email) {
+    delete(getAllowlistEmailPath(email));
+    cache.invalidate(ALLOWLIST_ROOT);
+  }
+
+  public List<String> getAllowlist() {
+    return cache.getUnchecked(ALLOWLIST_ROOT);
+  }
+
+  public String getAllowlistEmailPath(String email) {
+    return ZKPaths.makePath(ALLOWLIST_ROOT, email);
+  }
 }

SingularityService/src/main/java/com/hubspot/singularity/resources/NotificationsResource.java

@@ -49,6 +49,13 @@ public List<String> getBlacklist(@Parameter(hidden = true) @Auth SingularityUser
     return notificationsManager.getBlocklist();
   }
 
+  @GET
+  @Path("/allowlist")
+  @Operation(summary = "Retrieve the list of emails subscribed to Singularity")
+  public List<String> getAllowlist(@Parameter(hidden = true) @Auth SingularityUser user) {
+    return notificationsManager.getAllowlist();
+  }
+
   @POST
   @Path("/unsubscribe")
   @Operation(summary = "Unsubscribe from Singularity emails.")
@@ -60,37 +67,21 @@ public void unsubscribe(
     ) String email,
     @Context HttpServletRequest requestContext
   ) {
-    maybeProxyToLeader(
-      requestContext,
-      Void.class,
-      email,
-      () -> {
-        notificationsManager.addToBlocklist(getFormattedEmail(email));
-        return null;
-      }
-    );
+    notificationsManager.unsubscribe(getFormattedEmail(email));
   }
 
   @POST
   @Path("/subscribe")
-  @Operation(summary = "Delete an unsubscription for an email address")
+  @Operation(summary = "Subscribe to Singularity emails")
   public void subscribe(
     @Parameter(hidden = true) @Auth SingularityUser user,
     @RequestBody(
       required = true,
-      description = "The email address to re-subscribe"
+      description = "The email address to subscribe"
     ) String email,
     @Context HttpServletRequest requestContext
   ) {
-    maybeProxyToLeader(
-      requestContext,
-      Void.class,
-      email,
-      () -> {
-        notificationsManager.removeFromBlocklist(getFormattedEmail(email));
-        return null;
-      }
-    );
+    notificationsManager.subscribe(getFormattedEmail(email));
   }
 
   private String getFormattedEmail(String email) {

SingularityService/src/main/java/com/hubspot/singularity/smtp/SmtpMailer.java

@@ -1095,9 +1095,15 @@ private void queueMail(
       }
     }
 
-    Set<String> emailBlacklist = Sets.newHashSet(notificationsManager.getBlocklist());
-    toList.removeAll(emailBlacklist);
-    ccList.removeAll(emailBlacklist);
+    if (configuration.isOptInEmailMode()) {
+      Set<String> emailAllowlist = Sets.newHashSet(notificationsManager.getAllowlist());
+      toList.retainAll(emailAllowlist);
+      ccList.retainAll(emailAllowlist);
+    } else {
+      Set<String> emailBlocklist = Sets.newHashSet(notificationsManager.getBlocklist());
+      toList.removeAll(emailBlocklist);
+      ccList.removeAll(emailBlocklist);
+    }
 
     smtpSender.queueMail(
       Lists.newArrayList(toList),