[client] make metacache reset safe

I noticed that the newly added TxnManagerTest.BeginManyTransactions test scenario started failing with ASAN heap-use-after-free warnings. After looking a that, it turned out that the original code was assuming the cache wouldn't be ever reset before calling the MetaCache's destructor. However, changelist 232474a introduced a new method MetaCache::ClearCache() and since then the method is being called upon altering a table if the partitioning scheme has been updated. This patch resolves the issue by introducing so-called tablet server registry that's never reset indeed, where entries in the tablet server cache are just references to the entries in the registry (they are raw pointers, actually). The newly added test scenario was reliably producing AddressSanitizer's heap-use-after-free warnings every time I ran it using ASAN build. Below is a snapshot of the relevant traces captured when running the new test scenario without the changes in the client metacache. AddressSanitizer: heap-use-after-free on address 0x608000129e20 at pc 0x00000078bd54 bp 0x7fa731d0b240 sp 0x7fa731d0b238 READ of size 4 at 0x608000129e20 thread T149 (rpc reactor-146) #0 0x78bd53 in base::subtle::NoBarrier_Load(int const volatile*) src/kudu/gutil/atomicops-internals-x86.h:200:10 #1 0x7fa79520e227 in base::SpinLock::SpinLoop(long, int*) src/kudu/gutil/spinlock.cc:86:10 #2 0x7fa79520e38b in base::SpinLock::SlowLock() src/kudu/gutil/spinlock.cc:104:25 #3 0x7fa7a099aab0 in std::unique_lock<kudu::simple_spinlock>::lock() ../../../include/c++/8/bits/std_mutex.h:267:17 #4 0x7fa7a0991e3e in std::unique_lock<kudu::simple_spinlock>::unique_lock(kudu::simple_spinlock&) ../../../include/c++/8/bits/std_mutex.h:197:2 #5 0x7fa7a0abfda1 in kudu::client::internal::RemoteTabletServer::InitProxy(kudu::client::KuduClient*, std::function<void (kudu::Status const&)> const&) src/kudu/client/meta_cache.cc:145:39 #6 0x7fa7a0ac60f5 in kudu::client::internal::MetaCacheServerPicker::PickLeader(std::function<void (kudu::Status const&, kudu::client::internal::RemoteTabletServer*)> const&, kudu::MonoTime const&) src/kudu/client/meta_cache.cc:524:11 #7 0x7fa7a09b2dcf in kudu::rpc::RetriableRpc<kudu::client::internal::RemoteTabletServer, kudu::tserver::WriteRequestPB, kudu::tserver::WriteResponsePB>::SendRpc() src/kudu/rpc/retriable_rpc.h:163:19 #8 0x7fa7a09ac6cc in kudu::client::internal::Batcher::FlushBuffer(kudu::client::internal::RemoteTablet*, std::vector<kudu::client::internal::InFlightOp*, std::allocator<kudu::client::internal::InFlightOp*> > const&) src/kudu/client/batcher.cc:911:8 #9 0x7fa7a09a9e38 in kudu::client::internal::Batcher::FlushBuffersIfReady() src/kudu/client/batcher.cc:884:5 #10 0x7fa7a09abd2d in kudu::client::internal::Batcher::TabletLookupFinished(kudu::client::internal::InFlightOp*, kudu::Status const&) src/kudu/client/batcher.cc:851:3 #11 0x7fa7a0acec66 in kudu::client::internal::LookupRpc::SendRpcCb(kudu::Status const&) src/kudu/client/meta_cache.cc:923:3 #12 0x7fa7a0ab8800 in kudu::client::internal::AsyncLeaderMasterRpc<kudu::master::GetTableLocationsRequestPB, kudu::master::GetTableLocationsResponsePB>::SendRpc()::'lambda'()::operator()() const src/kudu/client/master_proxy_rpc.cc:130:26 0x608000129e20 is located 0 bytes inside of 96-byte region [0x608000129e20,0x608000129e80) freed by thread T163 here: #0 0x65c650 in operator delete(void*) thirdparty/src/llvm-9.0.0.src/projects/compiler-rt/lib/asan/asan_new_delete.cc:160:399 #1 0x7fa7a0aec859 in void STLDeleteContainerPairSecondPointers<std::__detail::_Node_iterator<std::pair<std::string const, kudu::client::internal::RemoteTabletServer*>, false, true> >(std::__detail::_Node_iterator<std::pair<std::string const, kudu::client::internal::RemoteTabletServer*>, false, true>, std::__detail::_Node_iterator<std::pair<std::string const, kudu::client::internal::RemoteTabletServer*>, false, true>) src/kudu/gutil/stl_util.h:199:5 #2 0x7fa7a0ad96d1 in void STLDeleteValues<std::unordered_map<std::string, kudu::client::internal::RemoteTabletServer*, std::hash<std::string>, std::equal_to<std::string>, std::allocator<std::pair<std::string const, kudu::client::internal::RemoteTabletServer*> > > >(std::unordered_map<std::string, kudu::client::internal::RemoteTabletServer*, std::hash<std::string>, std::equal_to<std::string>, std::allocator<std::pair<std::string const, kudu::client::internal::RemoteTabletServer*> > >*) src/kudu/gutil/stl_util.h:400:3 #3 0x7fa7a0ad4188 in kudu::client::internal::MetaCache::ClearCache() src/kudu/client/meta_cache.cc:1257:3 previously allocated by thread T149 (rpc reactor-146) here: #0 0x65bc98 in operator new(unsigned long) thirdparty/src/llvm-9.0.0.src/projects/compiler-rt/lib/asan/asan_new_delete.cc:99:386 #1 0x7fa7a0ac7bcb in kudu::client::internal::MetaCache::UpdateTabletServerUnlocked(kudu::master::TSInfoPB const&) src/kudu/client/meta_cache.cc:596:48 #2 0x7fa7a0ad0802 in kudu::client::internal::MetaCache::ProcessGetTableLocationsResponse(kudu::client::KuduTable const*, std::string const&, bool, kudu::master::GetTableLocationsResponsePB const&, kudu::client::internal::MetaCacheEntry*, int) src/kudu/client/meta_cache.cc:1030:7 #3 0x7fa7a0acf9c0 in kudu::client::internal::MetaCache::ProcessLookupResponse(kudu::client::internal::LookupRpc const&, kudu::client::internal::MetaCacheEntry*, int) src/kudu/client/meta_cache.cc:941:10 #4 0x7fa7a0ace64e in kudu::client::internal::LookupRpc::SendRpcCb(kudu::Status const&) src/kudu/client/meta_cache.cc:911:31 #5 0x7fa7a0ab8800 in kudu::client::internal::AsyncLeaderMasterRpc<kudu::master::GetTableLocationsRequestPB, kudu::master::GetTableLocationsResponsePB>::SendRpc()::'lambda'()::operator()() const src/kudu/client/master_proxy_rpc.cc:130:26 #6 0x7fa79b2c1620 in kudu::rpc::OutboundCall::CallCallback() src/kudu/rpc/outbound_call.cc:274:5 #7 0x7fa79b2c1af0 in kudu::rpc::OutboundCall::SetResponse(std::unique_ptr<kudu::rpc::CallResponse, std::default_delete<kudu::rpc::CallResponse> >) src/kudu/rpc/outbound_call.cc:306:5 #8 0x7fa79b26ef5e in kudu::rpc::Connection::HandleCallResponse(std::unique_ptr<kudu::rpc::InboundTransfer, std::default_delete<kudu::rpc::InboundTransfer> >) src/kudu/rpc/connection.cc:735:14 #9 0x7fa79b26e0d6 in kudu::rpc::Connection::ReadHandler(ev::io&, int) src/kudu/rpc/connection.cc:673:7 SUMMARY: AddressSanitizer: heap-use-after-free src/kudu/gutil/atomicops-internals-x86.h:200:10 in base::subtle::NoBarrier_Load(int const volatile*) Shadow bytes around the buggy address: 0x0c108001d370: fa fa fa fa 00 00 00 00 00 00 00 00 00 00 00 fa 0x0c108001d380: fa fa fa fa fd fd fd fd fd fd fd fd fd fd fd fd 0x0c108001d390: fa fa fa fa 00 00 00 00 00 00 00 00 00 00 00 fa 0x0c108001d3a0: fa fa fa fa fd fd fd fd fd fd fd fd fd fd fd fd 0x0c108001d3b0: fa fa fa fa 00 00 00 00 00 00 00 00 00 00 00 fa =>0x0c108001d3c0: fa fa fa fa[fd]fd fd fd fd fd fd fd fd fd fd fd 0x0c108001d3d0: fa fa fa fa 00 00 00 00 00 00 00 00 00 00 00 fa 0x0c108001d3e0: fa fa fa fa fd fd fd fd fd fd fd fd fd fd fd fd 0x0c108001d3f0: fa fa fa fa 00 00 00 00 00 00 00 00 00 00 00 fa 0x0c108001d400: fa fa fa fa 00 00 00 00 00 00 00 00 00 00 00 fa 0x0c108001d410: fa fa fa fa 00 00 00 00 00 00 00 00 00 00 00 fa Change-Id: I03ec9318526fbfc2da9b068eb3bbd9cd996efbca Reviewed-on: http://gerrit.cloudera.org:8080/16839 Tested-by: Alexey Serbin <[email protected]> Reviewed-by: Andrew Wong <[email protected]> (cherry picked from commit ae45cd1) Conflicts: src/kudu/client/client-test.cc src/kudu/client/client.h src/kudu/client/meta_cache.cc src/kudu/client/meta_cache.h Reviewed-on: http://gerrit.cloudera.org:8080/16862 Tested-by: Kudu Jenkins
apache · Dec 11, 2020 · bd24791 · bd24791
1 parent 4502d36
commit bd24791
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Showing 4 changed files with 67 additions and 15 deletions.
diff --git a/src/kudu/client/client-test.cc b/src/kudu/client/client-test.cc
@@ -116,6 +116,7 @@
 #include "kudu/util/random_util.h"
 #include "kudu/util/semaphore.h"
 #include "kudu/util/slice.h"
+#include "kudu/util/scoped_cleanup.h"
 #include "kudu/util/status.h"
 #include "kudu/util/stopwatch.h"
 #include "kudu/util/test_macros.h"
@@ -2077,11 +2078,40 @@ TEST_F(ClientTest, TestMetaCacheExpiry) {
   ASSERT_FALSE(meta_cache->LookupEntryByKeyFastPath(client_table_.get(), "", &entry));
 
   // Force a lookup and ensure the entry is refreshed.
-  CHECK_NOTNULL(MetaCacheLookup(client_table_.get(), "").get());
+  ASSERT_NE(nullptr, MetaCacheLookup(client_table_.get(), ""));
+  ASSERT_TRUE(entry.stale());
   ASSERT_TRUE(meta_cache->LookupEntryByKeyFastPath(client_table_.get(), "", &entry));
   ASSERT_FALSE(entry.stale());
 }
 
+// This test scenario verifies that reset of the metacache is safe while working
+// with the client. The scenario calls MetaCache::ClearCache() in a rather
+// synthetic way, but the natural control flow does something similar to that
+// when alterting a table by adding a new range partition (see
+// KuduTableAlterer::Alter() for details).
+TEST_F(ClientTest, ClearCacheAndConcurrentWorkload) {
+  CountDownLatch latch(1);
+  thread cache_cleaner([&]() {
+    const auto sleep_interval = MonoDelta::FromMilliseconds(3);
+    while (!latch.WaitFor(sleep_interval)) {
+      client_->data_->meta_cache_->ClearCache();
+    }
+  });
+  auto thread_joiner = MakeScopedCleanup([&] {
+    latch.CountDown();
+    cache_cleaner.join();
+  });
+
+  constexpr const int kLowIdx = 0;
+  constexpr const int kHighIdx = 1000;
+  const auto runUntil = MonoTime::Now() + MonoDelta::FromSeconds(1);
+  while (MonoTime::Now() < runUntil) {
+    NO_FATALS(InsertTestRows(client_table_.get(), kHighIdx, kLowIdx));
+    NO_FATALS(UpdateTestRows(client_table_.get(), kLowIdx, kHighIdx));
+    NO_FATALS(DeleteTestRows(client_table_.get(), kLowIdx, kHighIdx));
+  }
+}
+
 TEST_F(ClientTest, TestGetTabletServerBlacklist) {
   shared_ptr<KuduTable> table;
   NO_FATALS(CreateTable("blacklist",

diff --git a/src/kudu/client/client.h b/src/kudu/client/client.h
@@ -629,6 +629,7 @@ class KUDU_EXPORT KuduClient : public sp::enable_shared_from_this<KuduClient> {
   friend class tools::RemoteKsckCluster;
 
   FRIEND_TEST(kudu::ClientStressTest, TestUniqueClientIds);
+  FRIEND_TEST(ClientTest, ClearCacheAndConcurrentWorkload);
   FRIEND_TEST(ClientTest, TestCacheAuthzTokens);
   FRIEND_TEST(ClientTest, TestGetSecurityInfoFromMaster);
   FRIEND_TEST(ClientTest, TestGetTabletServerBlacklist);

diff --git a/src/kudu/client/meta_cache.cc b/src/kudu/client/meta_cache.cc
@@ -41,7 +41,6 @@
 #include "kudu/gutil/basictypes.h"
 #include "kudu/gutil/map-util.h"
 #include "kudu/gutil/port.h"
-#include "kudu/gutil/stl_util.h"
 #include "kudu/gutil/strings/substitute.h"
 #include "kudu/master/master.pb.h"
 #include "kudu/master/master.proxy.h"
@@ -567,20 +566,30 @@ MetaCache::MetaCache(KuduClient* client,
       replica_visibility_(replica_visibility) {
 }
 
-MetaCache::~MetaCache() {
-  STLDeleteValues(&ts_cache_);
-}
-
 void MetaCache::UpdateTabletServer(const TSInfoPB& pb) {
   DCHECK(lock_.is_write_locked());
-  RemoteTabletServer* ts = FindPtrOrNull(ts_cache_, pb.permanent_uuid());
+  const auto& ts_uuid = pb.permanent_uuid();
+  auto* ts = FindPtrOrNull(ts_cache_, ts_uuid);
   if (ts) {
     ts->Update(pb);
     return;
   }
 
-  VLOG(1) << "Client caching new TabletServer " << pb.permanent_uuid();
-  InsertOrDie(&ts_cache_, pb.permanent_uuid(), new RemoteTabletServer(pb));
+  // First check whether the information about the tablet server is already
+  // present in the registry.
+  ts = FindPointeeOrNull(ts_registry_, ts_uuid);
+  if (ts) {
+    // If the tablet server is already registered, update the existing entry.
+    ts->Update(pb);
+  } else {
+    // If the tablet server isn't registered, add a new entry.
+    unique_ptr<RemoteTabletServer> entry(new RemoteTabletServer(pb));
+    ts = entry.get();
+    EmplaceOrDie(&ts_registry_, ts_uuid, std::move(entry));
+  }
+  // Now add the entry into the cache.
+  VLOG(1) << Substitute("client caching new TabletServer $0", ts_uuid);
+  InsertOrDie(&ts_cache_, ts_uuid, ts);
 }
 
 
@@ -1056,7 +1065,7 @@ void MetaCache::ClearNonCoveredRangeEntries(const std::string& table_id) {
 void MetaCache::ClearCache() {
   VLOG(3) << "Clearing cache";
   std::lock_guard<percpu_rwlock> l(lock_);
-  STLDeleteValues(&ts_cache_);
+  ts_cache_.clear();
   tablets_by_id_.clear();
   tablets_by_table_and_key_.clear();
 }

diff --git a/src/kudu/client/meta_cache.h b/src/kudu/client/meta_cache.h
@@ -146,6 +146,8 @@ struct RemoteReplica {
   bool failed;
 };
 
+typedef std::unordered_map<std::string, std::unique_ptr<RemoteTabletServer>>
+    TabletServerRegistry;
 typedef std::unordered_map<std::string, RemoteTabletServer*> TabletServerMap;
 
 // A ServerPicker for tablets servers, backed by the MetaCache.
@@ -394,7 +396,7 @@ class MetaCache : public RefCountedThreadSafe<MetaCache> {
  public:
   // The passed 'client' object must remain valid as long as MetaCache is alive.
   MetaCache(KuduClient* client, ReplicaController::Visibility replica_visibility);
-  ~MetaCache();
+  ~MetaCache() = default;
 
   // Determines what type of operation a MetaCache lookup is being done for.
   enum class LookupType {
@@ -493,11 +495,21 @@ class MetaCache : public RefCountedThreadSafe<MetaCache> {
 
   percpu_rwlock lock_;
 
-  // Cache of Tablet Server locations: TS UUID -> RemoteTabletServer*.
+  // Registry of all tablet servers as a map of tablet server's
+  // UUID -> std::unique_ptr<RemoteTabletServer>.
+  //
+  // Given that the set of tablet servers in a cluster is bounded by physical
+  // machines and every tablet server has its unique identifier, we never remove
+  // entries from this map until the MetaCache is destructed. Note that the
+  // ClearCache() method doesn't touch this registry, but updates ts_cache_ map
+  // below which contains raw pointers to the elements in this registry.
+  // So, there is no need to use shared_ptr and alike for the entries.
   //
-  // Given that the set of tablet servers is bounded by physical machines, we never
-  // evict entries from this map until the MetaCache is destructed. So, no need to use
-  // shared_ptr, etc.
+  // Protected by lock_.
+  TabletServerRegistry ts_registry_;
+
+  // Cache of Tablet Server locations: TS UUID -> RemoteTabletServer*.
+  // The cache can be cleared by the ClearCache() method.
   //
   // Protected by lock_.
   TabletServerMap ts_cache_;