Backport #69390 to 24.8: Fix undefined behavior if all connection tries fail

src/Client/ConnectionPoolWithFailover.cpp

@@ -168,7 +168,7 @@ std::vector<ConnectionPoolWithFailover::TryResult> ConnectionPoolWithFailover::g
     { return tryGetEntry(pool, timeouts, fail_message, settings, &table_to_check, /*async_callback=*/ {}); };
 
     return getManyImpl(settings, pool_mode, try_get_entry,
-        /*skip_unavailable_endpoints=*/ std::nullopt,
+        /*skip_unavailable_endpoints=*/ false, /// skip_unavailable_endpoints is used to get the min number of entries, and we need at least one
         /*priority_func=*/ {},
         settings.distributed_insert_skip_read_only_replicas);
 }

src/Client/ConnectionPoolWithFailover.h

@@ -42,7 +42,7 @@ public:
             size_t max_error_cap = DBMS_CONNECTION_POOL_WITH_FAILOVER_MAX_ERROR_COUNT);
 
     using Entry = IConnectionPool::Entry;
-    using PoolWithFailoverBase<IConnectionPool>::isTryResultInvalid;
+    using PoolWithFailoverBase<IConnectionPool>::getValidTryResult;
 
     /** Allocates connection to work. */
     Entry get(const ConnectionTimeouts & timeouts) override;
@@ -98,7 +98,7 @@ public:
 
     std::vector<Base::ShuffledPool> getShuffledPools(const Settings & settings, GetPriorityFunc priority_func = {}, bool use_slowdown_count = false);
 
-    size_t getMaxErrorCup() const { return Base::max_error_cap; }
+    size_t getMaxErrorCap() const { return Base::max_error_cap; }
 
     void updateSharedError(std::vector<ShuffledPool> & shuffled_pools)
     {

src/Client/HedgedConnectionsFactory.cpp

@@ -327,7 +327,7 @@ HedgedConnectionsFactory::State HedgedConnectionsFactory::processFinishedConnect
         ShuffledPool & shuffled_pool = shuffled_pools[index];
         LOG_INFO(log, "Connection failed at try №{}, reason: {}", (shuffled_pool.error_count + 1), fail_message);
 
-        shuffled_pool.error_count = std::min(pool->getMaxErrorCup(), shuffled_pool.error_count + 1);
+        shuffled_pool.error_count = std::min(pool->getMaxErrorCap(), shuffled_pool.error_count + 1);
         shuffled_pool.slowdown_count = 0;
 
         if (shuffled_pool.error_count >= max_tries)

src/Common/PoolWithFailoverBase.h

@@ -122,6 +122,20 @@ public:
         return result.entry.isNull() || !result.is_usable || (skip_read_only_replicas && result.is_readonly);
     }
 
+    TryResult getValidTryResult(const std::vector<TryResult> & results, bool skip_read_only_replicas) const
+    {
+        if (results.empty())
+            throw DB::Exception(DB::ErrorCodes::ALL_CONNECTION_TRIES_FAILED, "Cannot get any valid connection because all connection tries failed");
+
+        auto result = results.front();
+        if (isTryResultInvalid(result, skip_read_only_replicas))
+            throw DB::Exception(DB::ErrorCodes::LOGICAL_ERROR,
+                "Got an invalid connection result: entry.isNull {}, is_usable {}, is_up_to_date {}, delay {}, is_readonly {}, skip_read_only_replicas {}",
+                result.entry.isNull(), result.is_usable, result.is_up_to_date, result.delay, result.is_readonly, skip_read_only_replicas);
+
+        return result;
+    }
+
     size_t getPoolSize() const { return nested_pools.size(); }
 
 protected:

src/Core/Defines.h

@@ -40,7 +40,7 @@ static constexpr auto SHOW_CHARS_ON_SYNTAX_ERROR = ptrdiff_t(160);
 /// each period reduces the error counter by 2 times
 /// too short a period can cause errors to disappear immediately after creation.
 static constexpr auto DBMS_CONNECTION_POOL_WITH_FAILOVER_DEFAULT_DECREASE_ERROR_PERIOD = 60;
-/// replica error max cap, this is to prevent replica from accumulating too many errors and taking to long to recover.
+/// replica error max cap, this is to prevent replica from accumulating too many errors and taking too long to recover.
 static constexpr auto DBMS_CONNECTION_POOL_WITH_FAILOVER_MAX_ERROR_COUNT = 1000;
 
 /// The boundary on which the blocks for asynchronous file operations should be aligned.

src/Storages/Distributed/DistributedAsyncInsertBatch.cpp

@@ -243,10 +243,7 @@ void DistributedAsyncInsertBatch::sendBatch(const SettingsChanges & settings_cha
 
                 auto timeouts = ConnectionTimeouts::getTCPTimeoutsWithFailover(insert_settings);
                 auto results = parent.pool->getManyCheckedForInsert(timeouts, insert_settings, PoolMode::GET_ONE, parent.storage.remote_storage.getQualifiedName());
-                auto result = results.front();
+                auto result = parent.pool->getValidTryResult(results, insert_settings.distributed_insert_skip_read_only_replicas);
-                if (parent.pool->isTryResultInvalid(result, insert_settings.distributed_insert_skip_read_only_replicas))
-                    throw Exception(ErrorCodes::LOGICAL_ERROR, "Got an invalid connection result");
-
                 connection = std::move(result.entry);
                 compression_expected = connection->getCompression() == Protocol::Compression::Enable;
 
@@ -305,10 +302,7 @@ void DistributedAsyncInsertBatch::sendSeparateFiles(const SettingsChanges & sett
 
             auto timeouts = ConnectionTimeouts::getTCPTimeoutsWithFailover(insert_settings);
             auto results = parent.pool->getManyCheckedForInsert(timeouts, insert_settings, PoolMode::GET_ONE, parent.storage.remote_storage.getQualifiedName());
-            auto result = results.front();
+            auto result = parent.pool->getValidTryResult(results, insert_settings.distributed_insert_skip_read_only_replicas);
-            if (parent.pool->isTryResultInvalid(result, insert_settings.distributed_insert_skip_read_only_replicas))
-                throw Exception(ErrorCodes::LOGICAL_ERROR, "Got an invalid connection result");
-
             auto connection = std::move(result.entry);
             bool compression_expected = connection->getCompression() == Protocol::Compression::Enable;
 

src/Storages/Distributed/DistributedAsyncInsertDirectoryQueue.cpp

@@ -413,10 +413,7 @@ void DistributedAsyncInsertDirectoryQueue::processFile(std::string & file_path,
 
         auto timeouts = ConnectionTimeouts::getTCPTimeoutsWithFailover(insert_settings);
         auto results = pool->getManyCheckedForInsert(timeouts, insert_settings, PoolMode::GET_ONE, storage.remote_storage.getQualifiedName());
-        auto result = results.front();
+        auto result = pool->getValidTryResult(results, insert_settings.distributed_insert_skip_read_only_replicas);
-        if (pool->isTryResultInvalid(result, insert_settings.distributed_insert_skip_read_only_replicas))
-            throw Exception(ErrorCodes::LOGICAL_ERROR, "Got an invalid connection result");
-
         auto connection = std::move(result.entry);
 
         LOG_DEBUG(log, "Sending `{}` to {} ({} rows, {} bytes)",

src/Storages/Distributed/DistributedSink.cpp

@@ -377,10 +377,7 @@ DistributedSink::runWritingJob(JobReplica & job, const Block & current_block, si
                     /// NOTE: INSERT will also take into account max_replica_delay_for_distributed_queries
                     /// (anyway fallback_to_stale_replicas_for_distributed_queries=true by default)
                     auto results = shard_info.pool->getManyCheckedForInsert(timeouts, settings, PoolMode::GET_ONE, storage.remote_storage.getQualifiedName());
-                    auto result = results.front();
+                    auto result = shard_info.pool->getValidTryResult(results, settings.distributed_insert_skip_read_only_replicas);
-                    if (shard_info.pool->isTryResultInvalid(result, settings.distributed_insert_skip_read_only_replicas))
-                        throw Exception(ErrorCodes::LOGICAL_ERROR, "Got an invalid connection result");
-
                     job.connection_entry = std::move(result.entry);
                 }
                 else