[HTTP Cache] Prevent memory backend from exceeding its max size

net/disk_cache/backend_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stdint.h>
 
 #include "base/files/file.h"
 #include "base/files/file_util.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/field_trial.h"
@@ skipping 498 matching lines @@
       cache_path_, cache_thread.task_runner(), NULL));
   int rv = cache->Init(cb.callback());
   EXPECT_THAT(cb.GetResult(rv), IsError(net::ERR_FAILED));
   base::ThreadRestrictions::SetIOAllowed(prev);
 
   cache.reset();
   DisableIntegrityCheck();
 }
 
 TEST_F(DiskCacheBackendTest, MemCacheMemoryDump) {
-  memory_only_ = true;
+  SetMemoryOnlyMode();
   BackendBasics();
   base::trace_event::MemoryDumpArgs args = {
       base::trace_event::MemoryDumpLevelOfDetail::BACKGROUND};
   base::trace_event::ProcessMemoryDump pmd(nullptr, args);
   base::trace_event::MemoryAllocatorDump* parent =
       pmd.CreateAllocatorDump("net/url_request_context/main/0x123/http_cache");
 
   ASSERT_LT(0u, cache_->DumpMemoryStats(&pmd, parent->absolute_name()));
   EXPECT_EQ(2u, pmd.allocator_dumps().size());
   const base::trace_event::MemoryAllocatorDump* sub_dump =
@@ skipping 2643 matching lines @@
   ASSERT_THAT(CreateEntry("first parent", &entry), IsOk());
   disk_cache::ScopedEntryPtr first_parent(entry);
 
   // Create a ton of entries, and keep them open, to put the cache well above
   // its eviction threshhold.
   const int kTooManyEntriesCount = kMaxEntryCount * 2;
   std::list<disk_cache::ScopedEntryPtr> open_entries;
   std::string key_prefix("prefix");
   for (int i = 0; i < kTooManyEntriesCount; ++i) {
     ASSERT_THAT(CreateEntry(key_prefix + base::IntToString(i), &entry), IsOk());
-    EXPECT_EQ(kWriteSize,
-              WriteData(entry, 1, 0, buffer.get(), kWriteSize, false));
+    WriteData(entry, 1, 0, buffer.get(), kWriteSize, false);

[Randy Smith (Not in Mondays), 2017/03/30 16:38:11]

Comments about why you're not checking the result?  (I'm sorta assuming the
eviction threshold is lower than the size limit, and it's just that you're going
way over?)

[jkarlin, 2017/03/30 17:18:27]

Done.

     open_entries.push_back(disk_cache::ScopedEntryPtr(entry));
   }
-  EXPECT_LT(kMaxSize, CalculateSizeOfAllEntries());
 
   // Writing this sparse data should not crash.
-  EXPECT_EQ(1024, first_parent->WriteSparseData(32768, buffer.get(), 1024,
-                                                net::CompletionCallback()));
+  first_parent->WriteSparseData(32768, buffer.get(), 1024,
+                                net::CompletionCallback());
+}
+
+TEST_F(DiskCacheBackendTest, MemoryCapsWritesToMaxSize) {
+  // Verify that the memory backend won't grow beyond its max size if lots of
+  // open entries (each smaller than the max entry size) are trying to write
+  // beyond the max size.
+  SetMemoryOnlyMode();
+
+  const int kMaxSize = 100 * 1024;       // 100KB cache
+  const int kNumEntries = 20;            // 20 entries to write
+  const int kWriteSize = kMaxSize / 10;  // Each entry writes 1/10th the max
+
+  SetMaxSize(kMaxSize);
+  InitCache();
+
+  scoped_refptr<net::IOBuffer> buffer(new net::IOBuffer(kWriteSize));
+  CacheTestFillBuffer(buffer->data(), kWriteSize, false);
+
+  // Create an entry to be the final entry that gets written later.
+  disk_cache::Entry* entry;
+  ASSERT_THAT(CreateEntry("final", &entry), IsOk());
+  disk_cache::ScopedEntryPtr final_entry(entry);
+
+  // Create a ton of entries, write to the cache, and keep the entries open.
+  // They should start failing writes once the cache fills.
+  std::list<disk_cache::ScopedEntryPtr> open_entries;
+  std::string key_prefix("prefix");
+  for (int i = 0; i < kNumEntries; ++i) {
+    ASSERT_THAT(CreateEntry(key_prefix + base::IntToString(i), &entry), IsOk());
+    WriteData(entry, 1, 0, buffer.get(), kWriteSize, false);
+    open_entries.push_back(disk_cache::ScopedEntryPtr(entry));
+  }
+  EXPECT_GE(kMaxSize, CalculateSizeOfAllEntries());
+
+  // Any more writing at this point should cause an error.
+  EXPECT_THAT(
+      WriteData(final_entry.get(), 1, 0, buffer.get(), kWriteSize, false),
+      IsError(net::ERR_INSUFFICIENT_RESOURCES));
 }
 
 TEST_F(DiskCacheTest, Backend_UsageStatsTimer) {
   MessageLoopHelper helper;
 
   ASSERT_TRUE(CleanupCacheDir());
   std::unique_ptr<disk_cache::BackendImpl> cache;
   cache.reset(new disk_cache::BackendImpl(
       cache_path_, base::ThreadTaskRunnerHandle::Get(), NULL));
   ASSERT_TRUE(NULL != cache.get());
@@ skipping 789 matching lines @@
   // because that would advance the cache directory mtime and invalidate the
   // index.
   entry2->Doom();
   entry2->Close();
 
   DisableFirstCleanup();
   InitCache();
   EXPECT_EQ(disk_cache::SimpleIndex::INITIALIZE_METHOD_LOADED,
             simple_cache_impl_->index()->init_method());
 }