wangle::FilePersistenceLayer< K, V > Class Template Reference

#include <FilePersistentCache-inl.h>

Inheritance diagram for wangle::FilePersistenceLayer< K, V >:

Public Member Functions
	FilePersistenceLayer (const std::string &file)
	~FilePersistenceLayer () override
bool	persist (const folly::dynamic &arrayOfKvPairs) noexceptoverride
folly::Optional< folly::dynamic >	load () noexceptoverride
void	clear () override
Public Member Functions inherited from wangle::CachePersistence< K, V >
	CachePersistence ()
virtual	~CachePersistence ()=default
bool	persistVersionedData (const folly::dynamic &kvPairs, const CacheDataVersion &version)
virtual CacheDataVersion	getLastPersistedVersion () const
virtual void	setPersistedVersion (CacheDataVersion version) noexcept

Private Attributes
std::string	file_

Detailed Description

template<typename K, typename V>
class wangle::FilePersistenceLayer< K, V >

Definition at line 26 of file FilePersistentCache-inl.h.

Constructor & Destructor Documentation

template<typename K , typename V >

wangle::FilePersistenceLayer< K, V >::FilePersistenceLayer ( const std::string &  file )

inlineexplicit

Definition at line 28 of file FilePersistentCache-inl.h.

: file_(file) {}

template<typename K , typename V >

wangle::FilePersistenceLayer< K, V >::~FilePersistenceLayer ( )

inlineoverride

Definition at line 29 of file FilePersistentCache-inl.h.

References wangle::FilePersistenceLayer< K, V >::clear(), wangle::FilePersistenceLayer< K, V >::load(), folly::pushmi::__adl::noexcept(), and wangle::FilePersistenceLayer< K, V >::persist().

{}

Member Function Documentation

template<typename K , typename V >

void wangle::FilePersistenceLayer< K, V >::clear ( )

overridevirtual

Clears Persistent cache

Implements wangle::CachePersistence< K, V >.

Definition at line 108 of file FilePersistentCache-inl.h.

References wangle::FilePersistenceLayer< K, V >::file_.

Referenced by wangle::FilePersistenceLayer< K, V >::~FilePersistenceLayer().

                                       {
  // This may fail but it's ok
  ::unlink(file_.c_str());
}

template<typename K , typename V >

folly::Optional< folly::dynamic > wangle::FilePersistenceLayer< K, V >::load ( )

overridevirtualnoexcept

Returns a list of key value pairs that are present in this persistence store.

Implements wangle::CachePersistence< K, V >.

Definition at line 87 of file FilePersistentCache-inl.h.

References folly::json::serialization_opts::allow_non_string_keys, wangle::FilePersistenceLayer< K, V >::file_, folly::none, folly::parseJson(), folly::readFile(), and string.

Referenced by wangle::FilePersistenceLayer< K, V >::~FilePersistenceLayer().

                                                                      {
  std::string serializedCache;
  // not being able to read the backing storage means we just
  // start with an empty cache. Failing to deserialize, or write,
  // is a real error so we report errors there.
  if (!folly::readFile(file_.c_str(), serializedCache)) {
    return folly::none;
  }

  try {
    folly::json::serialization_opts opts;
    opts.allow_non_string_keys = true;
    return folly::parseJson(serializedCache, opts);
  } catch (const std::exception& err) {
    LOG(ERROR) << "Deserialization of cache file " << file_
               << " failed with parse error: " << err.what();
  }
  return folly::none;
}

template<typename K , typename V >

bool wangle::FilePersistenceLayer< K, V >::persist ( const folly::dynamic &  kvPairs )

overridevirtualnoexcept

Persist a folly::dynamic array of key value pairs. Returns true on success.

Implements wangle::CachePersistence< K, V >.

Definition at line 42 of file FilePersistentCache-inl.h.

References folly::json::serialization_opts::allow_non_string_keys, folly::closeNoInt(), folly::fdatasyncNoInt(), wangle::FilePersistenceLayer< K, V >::file_, folly::openNoInt(), folly::json::serialize(), string, and folly::writeFull().

Referenced by wangle::FilePersistenceLayer< K, V >::~FilePersistenceLayer().

                                       {
  std::string serializedCache;
  try {
    folly::json::serialization_opts opts;
    opts.allow_non_string_keys = true;
    serializedCache = folly::json::serialize(dynObj, opts);
  } catch (const std::exception& err) {
    LOG(ERROR) << "Serializing to JSON failed with error: " << err.what();
    return false;
  }
  bool persisted = false;
  const auto fd = folly::openNoInt(
    file_.c_str(),
    O_WRONLY | O_CREAT | O_TRUNC,
    S_IRUSR | S_IWUSR
  );
  if (fd == -1) {
    return false;
  }
  const auto nWritten = folly::writeFull(
    fd,
    serializedCache.data(),
    serializedCache.size()
  );
  persisted = nWritten >= 0 &&
    (static_cast<size_t>(nWritten) == serializedCache.size());
  if (!persisted) {
    LOG(ERROR) << "Failed to write to " << file_ << ":";
    if (nWritten == -1) {
      LOG(ERROR) << "write failed with errno " << errno;
    }
  }
  if (folly::fdatasyncNoInt(fd) != 0) {
    LOG(ERROR) << "Failed to sync " << file_ << ": errno " << errno;
    persisted = false;
  }
  if (folly::closeNoInt(fd) != 0) {
    LOG(ERROR) << "Failed to close " << file_ << ": errno " << errno;
    persisted = false;
  }
  return persisted;
}

Member Data Documentation

template<typename K , typename V >

std::string wangle::FilePersistenceLayer< K, V >::file_

private

Definition at line 38 of file FilePersistentCache-inl.h.

Referenced by wangle::FilePersistenceLayer< K, V >::clear(), wangle::FilePersistenceLayer< K, V >::load(), and wangle::FilePersistenceLayer< K, V >::persist().

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The documentation for this class was generated from the following file:

• proxygen/wangle/wangle/client/persistence/FilePersistentCache-inl.h