Support static Status messages

Summary: Provide a way to specify a detailed static error message for a Status without incurring a memcpy.  Let me know what people think of this approach.

Test Plan: added simple test

Reviewers: igor, yhchiang, rven, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D44259

CMakeLists.txt

@@ -191,6 +191,7 @@ set(SOURCES
         util/sst_dump_tool.cc
         util/statistics.cc
         util/status.cc
+        util/status_message.cc
         util/string_util.cc
         util/sync_point.cc
         util/testharness.cc

include/rocksdb/status.h

@@ -25,7 +25,7 @@ namespace rocksdb {
 class Status {
  public:
   // Create a success status.
-  Status() : code_(kOk), state_(nullptr) { }
+  Status() : code_(kOk), subcode_(kNone), state_(nullptr) {}
   ~Status() { delete[] state_; }
 
   // Copy the specified status.
@@ -34,6 +34,35 @@ class Status {
   bool operator==(const Status& rhs) const;
   bool operator!=(const Status& rhs) const;
 
+  enum Code {
+    kOk = 0,
+    kNotFound = 1,
+    kCorruption = 2,
+    kNotSupported = 3,
+    kInvalidArgument = 4,
+    kIOError = 5,
+    kMergeInProgress = 6,
+    kIncomplete = 7,
+    kShutdownInProgress = 8,
+    kTimedOut = 9,
+    kAborted = 10,
+    kBusy = 11,
+    kExpired = 12,
+    kTryAgain = 13
+  };
+
+  Code code() const { return code_; }
+
+  enum SubCode {
+    kNone = 0,
+    kMutexTimeout = 1,
+    kLockTimeout = 2,
+    kLockLimit = 3,
+    kMaxSubCode
+  };
+
+  SubCode subcode() const { return subcode_; }
+
   // Return a success status.
   static Status OK() { return Status(); }
 
@@ -42,51 +71,76 @@ class Status {
     return Status(kNotFound, msg, msg2);
   }
   // Fast path for not found without malloc;
-  static Status NotFound() {
-    return Status(kNotFound);
-  }
+  static Status NotFound(SubCode msg = kNone) { return Status(kNotFound, msg); }
+
   static Status Corruption(const Slice& msg, const Slice& msg2 = Slice()) {
     return Status(kCorruption, msg, msg2);
   }
+  static Status Corruption(SubCode msg = kNone) {
+    return Status(kCorruption, msg);
+  }
+
   static Status NotSupported(const Slice& msg, const Slice& msg2 = Slice()) {
     return Status(kNotSupported, msg, msg2);
   }
+  static Status NotSupported(SubCode msg = kNone) {
+    return Status(kNotSupported, msg);
+  }
+
   static Status InvalidArgument(const Slice& msg, const Slice& msg2 = Slice()) {
     return Status(kInvalidArgument, msg, msg2);
   }
+  static Status InvalidArgument(SubCode msg = kNone) {
+    return Status(kInvalidArgument, msg);
+  }
+
   static Status IOError(const Slice& msg, const Slice& msg2 = Slice()) {
     return Status(kIOError, msg, msg2);
   }
-  static Status MergeInProgress() { return Status(kMergeInProgress); }
+  static Status IOError(SubCode msg = kNone) { return Status(kIOError, msg); }
+
+  static Status MergeInProgress(const Slice& msg, const Slice& msg2 = Slice()) {
+    return Status(kMergeInProgress, msg, msg2);
+  }
+  static Status MergeInProgress(SubCode msg = kNone) {
+    return Status(kMergeInProgress, msg);
+  }
+
   static Status Incomplete(const Slice& msg, const Slice& msg2 = Slice()) {
     return Status(kIncomplete, msg, msg2);
   }
-  static Status ShutdownInProgress() {
-    return Status(kShutdownInProgress);
+  static Status Incomplete(SubCode msg = kNone) {
+    return Status(kIncomplete, msg);
+  }
+
+  static Status ShutdownInProgress(SubCode msg = kNone) {
+    return Status(kShutdownInProgress, msg);
   }
   static Status ShutdownInProgress(const Slice& msg,
                                    const Slice& msg2 = Slice()) {
     return Status(kShutdownInProgress, msg, msg2);
   }
-  static Status Aborted() {
-    return Status(kAborted);
-  }
+  static Status Aborted(SubCode msg = kNone) { return Status(kAborted, msg); }
   static Status Aborted(const Slice& msg, const Slice& msg2 = Slice()) {
     return Status(kAborted, msg, msg2);
   }
-  static Status Busy() { return Status(kBusy); }
+
+  static Status Busy(SubCode msg = kNone) { return Status(kBusy, msg); }
   static Status Busy(const Slice& msg, const Slice& msg2 = Slice()) {
     return Status(kBusy, msg, msg2);
   }
-  static Status TimedOut() { return Status(kTimedOut); }
+
+  static Status TimedOut(SubCode msg = kNone) { return Status(kTimedOut, msg); }
   static Status TimedOut(const Slice& msg, const Slice& msg2 = Slice()) {
     return Status(kTimedOut, msg, msg2);
   }
-  static Status Expired() { return Status(kExpired); }
+
+  static Status Expired(SubCode msg = kNone) { return Status(kExpired, msg); }
   static Status Expired(const Slice& msg, const Slice& msg2 = Slice()) {
     return Status(kExpired, msg, msg2);
   }
-  static Status TryAgain() { return Status(kTryAgain); }
+
+  static Status TryAgain(SubCode msg = kNone) { return Status(kTryAgain, msg); }
   static Status TryAgain(const Slice& msg, const Slice& msg2 = Slice()) {
     return Status(kTryAgain, msg, msg2);
   }
@@ -138,26 +192,6 @@ class Status {
   // Returns the string "OK" for success.
   std::string ToString() const;
 
-  enum Code {
-    kOk = 0,
-    kNotFound = 1,
-    kCorruption = 2,
-    kNotSupported = 3,
-    kInvalidArgument = 4,
-    kIOError = 5,
-    kMergeInProgress = 6,
-    kIncomplete = 7,
-    kShutdownInProgress = 8,
-    kTimedOut = 9,
-    kAborted = 10,
-    kBusy = 11,
-    kExpired = 12,
-    kTryAgain = 13
-  };
-
-  Code code() const {
-    return code_;
-  }
  private:
   // A nullptr state_ (which is always the case for OK) means the message
   // is empty.
@@ -165,21 +199,26 @@ class Status {
   //    state_[0..3] == length of message
   //    state_[4..]  == message
   Code code_;
+  SubCode subcode_;
   const char* state_;
 
-  explicit Status(Code _code) : code_(_code), state_(nullptr) {}
+  static const char* msgs[static_cast<int>(kMaxSubCode)];
+
+  explicit Status(Code _code, SubCode _subcode = kNone)
+      : code_(_code), subcode_(_subcode), state_(nullptr) {}
+
   Status(Code _code, const Slice& msg, const Slice& msg2);
   static const char* CopyState(const char* s);
 };
 
-inline Status::Status(const Status& s) {
-  code_ = s.code_;
+inline Status::Status(const Status& s) : code_(s.code_), subcode_(s.subcode_) {
   state_ = (s.state_ == nullptr) ? nullptr : CopyState(s.state_);
 }
 inline void Status::operator=(const Status& s) {
   // The following condition catches both aliasing (when this == &s),
   // and the common case where both s and *this are ok.
   code_ = s.code_;
+  subcode_ = s.subcode_;
   if (state_ != s.state_) {
     delete[] state_;
     state_ = (s.state_ == nullptr) ? nullptr : CopyState(s.state_);

src.mk

@@ -145,6 +145,7 @@ LIB_SOURCES =                                                   \
   util/sst_dump_tool.cc                                         \
   util/statistics.cc                                            \
   util/status.cc                                                \
+  util/status_message.cc                                        \
   util/string_util.cc                                           \
   util/sync_point.cc                                            \
   util/thread_local.cc                                          \

util/status.cc

@@ -21,7 +21,8 @@ const char* Status::CopyState(const char* state) {
   return result;
 }
 
-Status::Status(Code _code, const Slice& msg, const Slice& msg2) : code_(_code) {
+Status::Status(Code _code, const Slice& msg, const Slice& msg2)
+    : code_(_code), subcode_(kNone) {
   assert(code_ != kOk);
   const uint32_t len1 = static_cast<uint32_t>(msg.size());
   const uint32_t len2 = static_cast<uint32_t>(msg2.size());
@@ -89,6 +90,12 @@ std::string Status::ToString() const {
       break;
   }
   std::string result(type);
+  if (subcode_ != kNone) {
+    uint32_t index = static_cast<int32_t>(subcode_);
+    assert(sizeof(msgs) > index);
+    result.append(msgs[index]);
+  }
+
   if (state_ != nullptr) {
     uint32_t length;
     memcpy(&length, state_, sizeof(length));

util/status_message.cc

@@ -0,0 +1,17 @@
+// Copyright (c) 2015, Facebook, Inc.  All rights reserved.
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+
+#include "rocksdb/status.h"
+
+namespace rocksdb {
+
+const char* Status::msgs[] = {
+    "",                                                  // kNone
+    "Timeout Acquiring Mutex",                           // kMutexTimeout
+    "Timeout waiting to lock key",                       // kLockTimeout
+    "Failed to acquire lock due to max_num_locks limit"  // kLockLimit
+};
+
+}  // namespace rocksdb

utilities/transactions/transaction_lock_mgr.cc

@@ -232,7 +232,7 @@ Status TransactionLockMgr::AcquireWithTimeout(LockMap* lock_map,
 
   if (!locked) {
     // timeout acquiring mutex
-    return Status::TimedOut("Timeout Acquiring Mutex");
+    return Status::TimedOut(Status::SubCode::kMutexTimeout);
   }
 
   // Acquire lock if we are able to
@@ -313,15 +313,14 @@ Status TransactionLockMgr::AcquireLocked(LockMap* lock_map,
         lock_info.expiration_time = txn_lock_info.expiration_time;
         // lock_cnt does not change
       } else {
-        result = Status::TimedOut("lock held");
+        result = Status::TimedOut(Status::SubCode::kLockTimeout);
       }
     }
   } else {  // Lock not held.
     // Check lock limit
     if (max_num_locks_ > 0 &&
         lock_map->lock_cnt.load(std::memory_order_acquire) >= max_num_locks_) {
-      result =
-          Status::Busy("Failed to acquire lock due to max_num_locks limit");
+      result = Status::Busy(Status::SubCode::kLockLimit);
     } else {
       // acquire lock
       stripe->keys.insert({key, txn_lock_info});

utilities/transactions/transaction_test.cc

@@ -1564,6 +1564,7 @@ TEST_F(TransactionTest, TimeoutTest) {
   // txn2 has a smaller lock timeout than txn1's expiration, so it will time out
   s = txn2->Delete("asdf");
   ASSERT_TRUE(s.IsTimedOut());
+  ASSERT_EQ(s.ToString(), "Operation timed out: Timeout waiting to lock key");
 
   s = txn1->Commit();
   ASSERT_OK(s);