From 7e98e8a9a5a069cc6885608a20e576a89262438f Mon Sep 17 00:00:00 2001
From: Andrew Chang <andrewrchang@meta.com>
Date: Wed, 8 Jan 2025 15:40:06 -0800
Subject: [PATCH] Add test_follower flag to crash test

---
 db_stress_tool/db_stress_common.h     |  2 ++
 db_stress_tool/db_stress_gflags.cc    |  7 +++++++
 db_stress_tool/db_stress_stat.cc      |  1 +
 db_stress_tool/db_stress_stat.h       |  1 +
 db_stress_tool/db_stress_test_base.cc |  4 ++++
 db_stress_tool/db_stress_tool.cc      | 16 ++++++++++++++++
 6 files changed, 31 insertions(+)

diff --git a/db_stress_tool/db_stress_common.h b/db_stress_tool/db_stress_common.h
index 0c1ef4e11369..d51dd3ab63da 100644
--- a/db_stress_tool/db_stress_common.h
+++ b/db_stress_tool/db_stress_common.h
@@ -176,7 +176,9 @@ DECLARE_int32(index_type);
 DECLARE_int32(data_block_index_type);
 DECLARE_string(db);
 DECLARE_string(secondaries_base);
+DECLARE_string(followers_base);
 DECLARE_bool(test_secondary);
+DECLARE_bool(test_follower);
 DECLARE_string(expected_values_dir);
 DECLARE_bool(verify_checksum);
 DECLARE_bool(mmap_read);
diff --git a/db_stress_tool/db_stress_gflags.cc b/db_stress_tool/db_stress_gflags.cc
index 1859e6940fb9..42147fb1e10a 100644
--- a/db_stress_tool/db_stress_gflags.cc
+++ b/db_stress_tool/db_stress_gflags.cc
@@ -618,10 +618,17 @@ DEFINE_string(db, "", "Use the db with the following name.");
 DEFINE_string(secondaries_base, "",
               "Use this path as the base path for secondary instances.");
 
+DEFINE_string(followers_base, "",
+              "Use this path as the base path for follower instances.");
+
 DEFINE_bool(test_secondary, false,
             "If true, start an additional secondary instance which can be used "
             "for verification.");
 
+DEFINE_bool(test_follower, false,
+            "If true, start an additional follower instance which can be used "
+            "for verification.");
+
 DEFINE_string(
     expected_values_dir, "",
     "Dir where files containing info about the latest/historical values will "
diff --git a/db_stress_tool/db_stress_stat.cc b/db_stress_tool/db_stress_stat.cc
index 6a7883a52ac7..c2e8d127e03f 100644
--- a/db_stress_tool/db_stress_stat.cc
+++ b/db_stress_tool/db_stress_stat.cc
@@ -11,6 +11,7 @@ namespace ROCKSDB_NAMESPACE {
 
 std::shared_ptr<ROCKSDB_NAMESPACE::Statistics> dbstats;
 std::shared_ptr<ROCKSDB_NAMESPACE::Statistics> dbstats_secondaries;
+std::shared_ptr<ROCKSDB_NAMESPACE::Statistics> dbstats_followers;
 
 }  // namespace ROCKSDB_NAMESPACE
 
diff --git a/db_stress_tool/db_stress_stat.h b/db_stress_tool/db_stress_stat.h
index 5b38c6e2bb5d..0eb2463f6fda 100644
--- a/db_stress_tool/db_stress_stat.h
+++ b/db_stress_tool/db_stress_stat.h
@@ -25,6 +25,7 @@ namespace ROCKSDB_NAMESPACE {
 // Database statistics
 extern std::shared_ptr<ROCKSDB_NAMESPACE::Statistics> dbstats;
 extern std::shared_ptr<ROCKSDB_NAMESPACE::Statistics> dbstats_secondaries;
+extern std::shared_ptr<ROCKSDB_NAMESPACE::Statistics> dbstats_followers;
 
 class Stats {
  private:
diff --git a/db_stress_tool/db_stress_test_base.cc b/db_stress_tool/db_stress_test_base.cc
index 3e4e719a7625..1a5b482cecd0 100644
--- a/db_stress_tool/db_stress_test_base.cc
+++ b/db_stress_tool/db_stress_test_base.cc
@@ -645,6 +645,10 @@ void StressTest::PrintStatistics() {
     fprintf(stdout, "Secondary instances STATISTICS:\n%s\n",
             dbstats_secondaries->ToString().c_str());
   }
+  if (dbstats_followers) {
+    fprintf(stdout, "Follower instances STATISTICS:\n%s\n",
+            dbstats_followers->ToString().c_str());
+  }
 }
 
 // Currently PreloadDb has to be single-threaded.
diff --git a/db_stress_tool/db_stress_tool.cc b/db_stress_tool/db_stress_tool.cc
index ca43b699c8f9..55b8530b7f6b 100644
--- a/db_stress_tool/db_stress_tool.cc
+++ b/db_stress_tool/db_stress_tool.cc
@@ -58,6 +58,9 @@ int db_stress_tool(int argc, char** argv) {
     if (FLAGS_test_secondary) {
       dbstats_secondaries = ROCKSDB_NAMESPACE::CreateDBStatistics();
     }
+    if (FLAGS_test_follower) {
+      dbstats_followers = ROCKSDB_NAMESPACE::CreateDBStatistics();
+    }
   }
   compression_type_e = StringToCompressionType(FLAGS_compression_type.c_str());
   bottommost_compression_type_e =
@@ -231,6 +234,19 @@ int db_stress_tool(int argc, char** argv) {
     FLAGS_secondaries_base = default_secondaries_path;
   }
 
+  if (FLAGS_test_follower && FLAGS_followers_base.empty()) {
+    std::string default_followers_path;
+    db_stress_env->GetTestDirectory(&default_followers_path);
+    default_followers_path += "/dbstress_followers";
+    s = db_stress_env->CreateDirIfMissing(default_followers_path);
+    if (!s.ok()) {
+      fprintf(stderr, "Failed to create directory %s: %s\n",
+              default_followers_path.c_str(), s.ToString().c_str());
+      exit(1);
+    }
+    FLAGS_followers_base = default_followers_path;
+  }
+
   if (FLAGS_best_efforts_recovery &&
       !(FLAGS_skip_verifydb && FLAGS_disable_wal)) {
     fprintf(stderr,