Return error if Get/Multi() fails in Prefetching Filter blocks (#7543)

Summary:
Right now all I/O failures under
PartitionFilterBlock::CacheDependencies() is swallowed. Return error in
case prefetch fails.

On returning error in PartitionedFilterBlockReader::CacheDependencies was causing stress test failure because PrefetchBuffer is initialized with enable_ = true, as result when PosixMmapReadableFile::Read is called from Prefetch, scratch is ignored causing buffer to fill with garbage values. Initializing prefetch buffer by CreatePrefetchBuffer that sets enable_ with !ioptions.allow_mmap_reads fixed the problem as it returns without prefetching data if allow_mmap_reads is set.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7543

Test Plan:
make check -j64;
python -u tools/db_crashtest.py --simple blackbox

Reviewed By: anand1976

Differential Revision: D24284596

Pulled By: akankshamahajan15

fbshipit-source-id: f3f0fd44b59dcf60645730436f28564a07884868

file/file_prefetch_buffer.cc

@@ -91,17 +91,19 @@ Status FilePrefetchBuffer::Prefetch(const IOOptions& opts,
   size_t read_len = static_cast<size_t>(roundup_len - chunk_len);
   s = reader->Read(opts, rounddown_offset + chunk_len, read_len, &result,
                    buffer_.BufferStart() + chunk_len, nullptr, for_compaction);
+  if (!s.ok()) {
+    return s;
+  }
+
 #ifndef NDEBUG
-  if (!s.ok() || result.size() < read_len) {
+  if (result.size() < read_len) {
     // Fake an IO error to force db_stress fault injection to ignore
     // truncated read errors
     IGNORE_STATUS_IF_ERROR(Status::IOError());
   }
 #endif
-  if (s.ok()) {
-    buffer_offset_ = rounddown_offset;
-    buffer_.Size(static_cast<size_t>(chunk_len) + result.size());
-  }
+  buffer_offset_ = rounddown_offset;
+  buffer_.Size(static_cast<size_t>(chunk_len) + result.size());
   return s;
 }
 

table/block_based/block_based_table_reader.cc

@@ -1070,12 +1070,15 @@ Status BlockBasedTable::PrefetchIndexAndFilterBlocks(
     auto filter = new_table->CreateFilterBlockReader(
         ro, prefetch_buffer, use_cache, prefetch_filter, pin_filter,
         lookup_context);
+
     if (filter) {
       // Refer to the comment above about paritioned indexes always being cached
       if (prefetch_all || pin_partition) {
-        filter->CacheDependencies(ro, pin_partition);
+        s = filter->CacheDependencies(ro, pin_partition);
+        if (!s.ok()) {
+          return s;
+        }
       }
-
       rep_->filter = std::move(filter);
     }
   }

table/block_based/filter_block.h

@@ -153,7 +153,9 @@ class FilterBlockReader {
     return error_msg;
   }
 
-  virtual void CacheDependencies(const ReadOptions& /*ro*/, bool /*pin*/) {}
+  virtual Status CacheDependencies(const ReadOptions& /*ro*/, bool /*pin*/) {
+    return Status::OK();
+  }
 
   virtual bool RangeMayExist(const Slice* /*iterate_upper_bound*/,
                              const Slice& user_key,

table/block_based/partitioned_filter_block.cc

@@ -412,8 +412,8 @@ size_t PartitionedFilterBlockReader::ApproximateMemoryUsage() const {
 }
 
 // TODO(myabandeh): merge this with the same function in IndexReader
-void PartitionedFilterBlockReader::CacheDependencies(const ReadOptions& ro,
-                                                     bool pin) {
+Status PartitionedFilterBlockReader::CacheDependencies(const ReadOptions& ro,
+                                                       bool pin) {
   assert(table());
 
   const BlockBasedTable::Rep* const rep = table()->get_rep();
@@ -426,12 +426,11 @@ void PartitionedFilterBlockReader::CacheDependencies(const ReadOptions& ro,
   Status s = GetOrReadFilterBlock(false /* no_io */, nullptr /* get_context */,
                                   &lookup_context, &filter_block);
   if (!s.ok()) {
-    ROCKS_LOG_WARN(rep->ioptions.info_log,
-                   "Error retrieving top-level filter block while trying to "
-                   "cache filter partitions: %s",
-                   s.ToString().c_str());
-    IGNORE_STATUS_IF_ERROR(s);
-    return;
+    ROCKS_LOG_ERROR(rep->ioptions.info_log,
+                    "Error retrieving top-level filter block while trying to "
+                    "cache filter partitions: %s",
+                    s.ToString().c_str());
+    return s;
   }
 
   // Before read partitions, prefetch them to avoid lots of IOs
@@ -457,14 +456,17 @@ void PartitionedFilterBlockReader::CacheDependencies(const ReadOptions& ro,
   uint64_t last_off = handle.offset() + handle.size() + kBlockTrailerSize;
   uint64_t prefetch_len = last_off - prefetch_off;
   std::unique_ptr<FilePrefetchBuffer> prefetch_buffer;
+  rep->CreateFilePrefetchBuffer(0, 0, &prefetch_buffer);
 
-  prefetch_buffer.reset(new FilePrefetchBuffer());
   IOOptions opts;
   s = PrepareIOFromReadOptions(ro, rep->file->env(), opts);
   if (s.ok()) {
     s = prefetch_buffer->Prefetch(opts, rep->file.get(), prefetch_off,
                                   static_cast<size_t>(prefetch_len));
   }
+  if (!s.ok()) {
+    return s;
+  }
 
   // After prefetch, read the partitions one by one
   for (biter.SeekToFirst(); biter.Valid(); biter.Next()) {
@@ -477,17 +479,20 @@ void PartitionedFilterBlockReader::CacheDependencies(const ReadOptions& ro,
         prefetch_buffer.get(), ro, handle, UncompressionDict::GetEmptyDict(),
         &block, BlockType::kFilter, nullptr /* get_context */, &lookup_context,
         nullptr /* contents */);
-
+    if (!s.ok()) {
+      return s;
+    }
     assert(s.ok() || block.GetValue() == nullptr);
-    if (s.ok() && block.GetValue() != nullptr) {
+
+    if (block.GetValue() != nullptr) {
       if (block.IsCached()) {
         if (pin) {
           filter_map_[handle.offset()] = std::move(block);
         }
       }
     }
-    IGNORE_STATUS_IF_ERROR(s);
   }
+  return biter.status();
 }
 
 const InternalKeyComparator* PartitionedFilterBlockReader::internal_comparator()

table/block_based/partitioned_filter_block.h

@@ -130,7 +130,7 @@ class PartitionedFilterBlockReader : public FilterBlockReaderCommon<Block> {
                          uint64_t block_offset, BlockHandle filter_handle,
                          bool no_io, BlockCacheLookupContext* lookup_context,
                          FilterManyFunction filter_function) const;
-  void CacheDependencies(const ReadOptions& ro, bool pin) override;
+  Status CacheDependencies(const ReadOptions& ro, bool pin) override;
 
   const InternalKeyComparator* internal_comparator() const;
   bool index_key_includes_seq() const;