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Add PathNotFound subcode to IOError #4745

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Add PathNotFound subcode to IOError #4745

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1 change: 1 addition & 0 deletions HISTORY.md
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Original file line number Diff line number Diff line change
Expand Up @@ -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.
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8 changes: 5 additions & 3 deletions env/env_hdfs.cc
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Expand Up @@ -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,
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3 changes: 3 additions & 0 deletions env/io_posix.h
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Expand Up @@ -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));
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14 changes: 14 additions & 0 deletions include/rocksdb/status.h
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Expand Up @@ -73,6 +73,7 @@ class Status {
kStaleFile = 6,
kMemoryLimit = 7,
kSpaceLimit = 8,
kPathNotFound = 9,
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Don't we already use kNotFound for this specific case? So, why do we need a new one?

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The Code::kNotFound is intended to denote key-value pair is not found. File not found is an IOError and should be represented with the combination of IOError and a proper subcode. Let me know if I have missed any background context on the meaning of kNotFound.

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@sagar0 sagar0 Dec 4, 2018 •
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I said that because we use Status::NotFound() at various places when combined with Env::FileExists() check too.

rocksdb/include/rocksdb/env.h

Lines 225 to 230 in 2f1ca4e

// Returns OK if the named file exists.
// NotFound if the named file does not exist,
// the calling process does not have permission to determine
// whether this file exists, or if the path is invalid.
// IOError if an IO Error was encountered
virtual Status FileExists(const std::string& fname) = 0;

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Oh this makes sense. Thanks!

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Chatted offline with @siying . Opening a non-existing file for read is an IOError.
TableCache should return IOError instead of NotFound when the file does not exist. Therefore, we still need a new subcode.

kMaxSubCode
};

Expand Down Expand Up @@ -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; }

Expand Down Expand Up @@ -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;
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12 changes: 7 additions & 5 deletions port/win/io_win.h
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Expand Up @@ -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) {
Expand All @@ -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))
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May be these instances could be changed to Status::NotFound() ?

: Status::IOError(context, strerror(err_number));
}

class WinFileData;
Expand Down Expand Up @@ -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() {
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3 changes: 2 additions & 1 deletion util/status.cc
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Expand Up @@ -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,
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