Add PathNotFound subcode to IOError

Summary: As titled. Returning error about non-existing path can help user
better handle them.

Test Plan:
```
$make clean && make -j32 all check
```

Reviewers:

Subscribers:

Tasks:

Tags:

HISTORY.md

@@ -4,6 +4,7 @@
 * Enabled checkpoint on readonly db (DBImplReadOnly).
 * Make DB ignore dropped column families while committing results of atomic flush.
 * RocksDB may choose to preopen some files even if options.max_open_files != -1. This may make DB open slightly longer.
+* Introduce a new IOError subcode, PathNotFound, to indicate trying to open a nonexistent file or directory for read.
 
 ### Public API Change
 * Transaction::GetForUpdate is extended with a do_validate parameter with default value of true. If false it skips validating the snapshot before doing the read. Similarly ::Merge, ::Put, ::Delete, and ::SingleDelete are extended with assume_tracked with default value of false. If true it indicates that call is assumed to be after a ::GetForUpdate.

env/env_hdfs.cc

@@ -36,9 +36,11 @@ namespace {
 
 // Log error message
 static Status IOError(const std::string& context, int err_number) {
-  return (err_number == ENOSPC) ?
-      Status::NoSpace(context, strerror(err_number)) :
-      Status::IOError(context, strerror(err_number));
+  return (err_number == ENOSPC)
+             ? Status::NoSpace(context, strerror(err_number))
+             : (err_number == ENOENT)
+                   ? Status::PathNotFound(context, strerror(err_number))
+                   : Status::IOError(context, strerror(err_number));
 }
 
 // assume that there is one global logger for now. It is not thread-safe,

env/io_posix.h

@@ -41,6 +41,9 @@ static Status IOError(const std::string& context, const std::string& file_name,
                            strerror(err_number));
   case ESTALE:
     return Status::IOError(Status::kStaleFile);
+  case ENOENT:
+    return Status::PathNotFound(IOErrorMsg(context, file_name),
+                                strerror(err_number));
   default:
     return Status::IOError(IOErrorMsg(context, file_name),
                            strerror(err_number));

include/rocksdb/status.h

@@ -73,6 +73,7 @@ class Status {
     kStaleFile = 6,
     kMemoryLimit = 7,
     kSpaceLimit = 8,
+    kPathNotFound = 9,
     kMaxSubCode
   };
 
@@ -198,6 +199,11 @@ class Status {
     return Status(kIOError, kSpaceLimit, msg, msg2);
   }
 
+  static Status PathNotFound() { return Status(kIOError, kPathNotFound); }
+  static Status PathNotFound(const Slice& msg, const Slice& msg2 = Slice()) {
+    return Status(kIOError, kPathNotFound, msg, msg2);
+  }
+
   // Returns true iff the status indicates success.
   bool ok() const { return code() == kOk; }
 
@@ -266,6 +272,14 @@ class Status {
     return (code() == kAborted) && (subcode() == kMemoryLimit);
   }
 
+  // Returns true iff the status indicates a PathNotFound error
+  // This is caused by an I/O error returning the specific "no such file or
+  // directory" error condition. A PathNotFound error is an I/O error with
+  // a specific subcode, enabling users to take appropriate action if necessary
+  bool IsPathNotFound() const {
+    return (code() == kIOError) && (subcode() == kPathNotFound);
+  }
+
   // Return a string representation of this status suitable for printing.
   // Returns the string "OK" for success.
   std::string ToString() const;

port/win/io_win.h

@@ -27,7 +27,9 @@ std::string GetWindowsErrSz(DWORD err);
 inline Status IOErrorFromWindowsError(const std::string& context, DWORD err) {
   return ((err == ERROR_HANDLE_DISK_FULL) || (err == ERROR_DISK_FULL))
              ? Status::NoSpace(context, GetWindowsErrSz(err))
-             : Status::IOError(context, GetWindowsErrSz(err));
+             : ((err == ERROR_FILE_NOT_FOUND) || (err == ERROR_PATH_NOT_FOUND))
+                   ? Status::PathNotFound(context, GetWindowsErrSz(err))
+                   : Status::IOError(context, GetWindowsErrSz(err));
 }
 
 inline Status IOErrorFromLastWindowsError(const std::string& context) {
@@ -37,7 +39,9 @@ inline Status IOErrorFromLastWindowsError(const std::string& context) {
 inline Status IOError(const std::string& context, int err_number) {
   return (err_number == ENOSPC)
              ? Status::NoSpace(context, strerror(err_number))
-             : Status::IOError(context, strerror(err_number));
+             : (err_number == ENOENT)
+                   ? Status::PathNotFound(context, strerror(err_number))
+                   : Status::IOError(context, strerror(err_number));
 }
 
 class WinFileData;
@@ -426,9 +430,7 @@ class WinMemoryMappedBuffer : public MemoryMappedFileBuffer {
 class WinDirectory : public Directory {
   HANDLE handle_;
  public:
-  explicit
-  WinDirectory(HANDLE h) noexcept : 
-    handle_(h) {
+  explicit WinDirectory(HANDLE h) noexcept : handle_(h) {
     assert(handle_ != INVALID_HANDLE_VALUE);
   }
   ~WinDirectory() {

util/status.cc

@@ -41,7 +41,8 @@ static const char* msgs[static_cast<int>(Status::kMaxSubCode)] = {
     "Deadlock",                                           // kDeadlock
     "Stale file handle",                                  // kStaleFile
     "Memory limit reached",                               // kMemoryLimit
-    "Space limit reached"                                 // kSpaceLimit
+    "Space limit reached",                                // kSpaceLimit
+    "No such file or directory",                          // kPathNotFound
 };
 
 Status::Status(Code _code, SubCode _subcode, const Slice& msg,