From e6dca26cce5a5368dbb5c031bc00aa2f8b45dad2 Mon Sep 17 00:00:00 2001
From: Muthu Chidambaram <mchidambaram@yugabyte.com>
Date: Mon, 4 Mar 2024 06:17:28 +0000
Subject: [PATCH] [PLAT-11862] Turning off background tasks for YBA follower

Summary: Today follower YBA operates almost exactly the same as HA leader, except for API being disabled. We also want any background tasks/threads that are started during AppInit to be skipped for follower YBA, as there isn't a reason it should be operational and it could lead to more corner cases where universes were operated on with incorrect metadata.

Test Plan: Start up follower with diff, ensure that standby promotion and all still works but that AppInit doesn't fire off taskGC and others.

Reviewers: dshubin, sanketh, nsingh, amalyshev

Reviewed By: nsingh, amalyshev

Subscribers: yugaware

Differential Revision: https://phorge.dev.yugabyte.com/D32719
---
 .../java/com/yugabyte/yw/commissioner/TaskExecutor.java   | 8 ++++++++
 .../java/com/yugabyte/yw/common/PlatformScheduler.java    | 8 ++++++--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/managed/src/main/java/com/yugabyte/yw/commissioner/TaskExecutor.java b/managed/src/main/java/com/yugabyte/yw/commissioner/TaskExecutor.java
index 62908eb67395..956e8aecabca 100644
--- a/managed/src/main/java/com/yugabyte/yw/commissioner/TaskExecutor.java
+++ b/managed/src/main/java/com/yugabyte/yw/commissioner/TaskExecutor.java
@@ -27,6 +27,7 @@
 import com.yugabyte.yw.common.ha.PlatformReplicationManager;
 import com.yugabyte.yw.forms.ITaskParams;
 import com.yugabyte.yw.models.CustomerTask;
+import com.yugabyte.yw.models.HighAvailabilityConfig;
 import com.yugabyte.yw.models.ScheduleTask;
 import com.yugabyte.yw.models.TaskInfo;
 import com.yugabyte.yw.models.TaskInfo.State;
@@ -288,6 +289,12 @@ private void checkTaskExecutorState() {
     }
   }
 
+  private void checkHAFollowerState() {
+    if (HighAvailabilityConfig.isFollower()) {
+      throw new IllegalStateException("Can not submit task on HA follower");
+    }
+  }
+
   /**
    * Instantiates the task for the task class.
    *
@@ -344,6 +351,7 @@ public RunnableTask createRunnableTask(ITask task, UUID taskUUID) {
    */
   public UUID submit(RunnableTask runnableTask, ExecutorService taskExecutorService) {
     checkTaskExecutorState();
+    checkHAFollowerState();
     checkNotNull(runnableTask, "Task runnable must not be null");
     checkNotNull(taskExecutorService, "Task executor service must not be null");
     UUID taskUUID = runnableTask.getTaskUUID();
diff --git a/managed/src/main/java/com/yugabyte/yw/common/PlatformScheduler.java b/managed/src/main/java/com/yugabyte/yw/common/PlatformScheduler.java
index fad24639b56e..214a3ad7c0a0 100644
--- a/managed/src/main/java/com/yugabyte/yw/common/PlatformScheduler.java
+++ b/managed/src/main/java/com/yugabyte/yw/common/PlatformScheduler.java
@@ -2,6 +2,7 @@
 
 package com.yugabyte.yw.common;
 
+import com.yugabyte.yw.models.HighAvailabilityConfig;
 import java.time.Duration;
 import java.util.concurrent.atomic.AtomicBoolean;
 import javax.inject.Inject;
@@ -46,7 +47,9 @@ public Cancellable schedule(
                   synchronized (lock) {
                     // Synchronized block in shutdown and this should be serialized.
                     shouldRun =
-                        !shutdownHookHandler.isShutdown() && isRunning.compareAndSet(false, true);
+                        !shutdownHookHandler.isShutdown()
+                            && !HighAvailabilityConfig.isFollower()
+                            && isRunning.compareAndSet(false, true);
                   }
                   if (shouldRun) {
                     try {
@@ -61,7 +64,8 @@ public Cancellable schedule(
                     }
                   } else {
                     log.warn(
-                        "Previous run of scheduler {} is in progress or it is being shut down",
+                        "Previous run of scheduler {} is in progress, is being shut down, or YBA is"
+                            + " in follower mode.",
                         name);
                   }
                 },