foundationdb/fdbrpc/IAsyncFile.h

/*
 * IAsyncFile.h
 *
 * This source file is part of the FoundationDB open source project
 *
 * Copyright 2013-2018 Apple Inc. and the FoundationDB project authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef FLOW_IASYNCFILE_H
#define FLOW_IASYNCFILE_H
#include <string>
#pragma once

#include <ctime>
#include "flow/flow.h"
#include "flow/WriteOnlySet.h"
#include "fdbrpc/IRateControl.h"

// All outstanding operations must be cancelled before the destructor of IAsyncFile is called.
// The desirability of the above semantic is disputed. Some classes (AsyncFileS3BlobStore,
// AsyncFileCached) maintain references, while others (AsyncFileNonDurable) don't, and the comment
// is unapplicable to some others as well (AsyncFileKAIO). It's safest to assume that all operations
// must complete or cancel, but you should probably look at the file implementations you'll be using.
class IAsyncFile {
public:
	virtual ~IAsyncFile();
	// Pass these to g_network->open to get an IAsyncFile
	enum {
		// Implementation relies on the low bits being the same as the SQLite flags (this is validated by a
		// static_assert there)
		OPEN_READONLY = 0x1,
		OPEN_READWRITE = 0x2,
		OPEN_CREATE = 0x4,
		OPEN_EXCLUSIVE = 0x10,

		// Further flag values are arbitrary bits
		OPEN_UNBUFFERED = 0x10000,
		OPEN_UNCACHED = 0x20000,
		OPEN_LOCK = 0x40000,
		OPEN_ATOMIC_WRITE_AND_CREATE = 0x80000, // A temporary file is opened, and on the first call to sync() it is
		                                        // atomically renamed to the given filename
		OPEN_LARGE_PAGES = 0x100000,
		OPEN_NO_AIO =
		    0x200000, // Don't use AsyncFileKAIO or similar implementations that rely on filesystem support for AIO
		OPEN_CACHED_READ_ONLY = 0x400000, // AsyncFileCached opens files read/write even if you specify read only
		OPEN_ENCRYPTED = 0x800000 // File is encrypted using AES-128-GCM (must be either read-only or write-only)
	};

	virtual void addref() = 0;
	virtual void delref() = 0;

	// For read() and write(), the data buffer must remain valid until the future is ready
	virtual Future<int> read(void* data,
	                         int length,
	                         int64_t offset) = 0; // Returns number of bytes actually read (from [0,length])
	virtual Future<Void> write(void const* data, int length, int64_t offset) = 0;
	// The zeroed data is not guaranteed to be durable after `zeroRange` returns.  A call to sync() would be required.
	// This operation holds a reference to the AsyncFile, and does not need to be cancelled before a reference is
	// dropped.
	virtual Future<Void> zeroRange(int64_t offset, int64_t length);
	virtual Future<Void> truncate(int64_t size) = 0;
	virtual Future<Void> sync() = 0;
	virtual Future<Void> flush() {
		return Void();
	} // Sends previous writes to the OS if they have been buffered in memory, but does not make them power safe
	virtual Future<int64_t> size() const = 0;
	virtual std::string getFilename() const = 0;

	// Attempt to read the *length bytes at offset without copying.  If successful, a pointer to the
	//   requested bytes is written to *data, and the number of bytes successfully read is
	//   written to *length.  If unsuccessful, *data and *length are undefined.
	// readZeroCopy may fail (returning io_error) at any time, even if the requested bytes are readable.
	//   For example, an implementation of IAsyncFile may not implement readZeroCopy or may implement it
	//   only in certain cases (e.g. when the requested range does not cross a page boundary).  So callers
	//   should always retry a failed readZeroCopy as a read().
	// Once readZeroCopy succeeds, the returned bytes will be pinned in memory until releaseZeroCopy is
	//   called, so the caller must always ensure that a matching call to releaseZeroCopy takes place.
	// Between readZeroCopy and releaseZeroCopy, it is illegal (undefined behavior) to concurrently write
	//   to an overlapping range of bytes, whether or not using the same IAsyncFile handle.
	virtual Future<Void> readZeroCopy(void** data, int* length, int64_t offset) { return io_error(); }
	virtual void releaseZeroCopy(void* data, int length, int64_t offset) {}

	virtual int64_t debugFD() const = 0;

	// Used for rate control, at present, only AsyncFileCached supports it
	virtual Reference<IRateControl> const& getRateControl() { throw unsupported_operation(); }
	virtual void setRateControl(Reference<IRateControl> const& rc) { throw unsupported_operation(); }
};

typedef void (*runCycleFuncPtr)();

class IAsyncFileSystem {
public:
	// Opens a file for asynchronous I/O
	virtual Future<Reference<class IAsyncFile>> open(const std::string& filename, int64_t flags, int64_t mode) = 0;

	// Deletes the given file.  If mustBeDurable, returns only when the file is guaranteed to be deleted even after a
	// power failure.
	virtual Future<Void> deleteFile(const std::string& filename, bool mustBeDurable) = 0;

	// renames the file, doesn't sync the directory
	virtual Future<Void> renameFile(std::string const& from, std::string const& to) = 0;

	// Unlinks a file and then deletes it slowly by truncating the file repeatedly.
	// If mustBeDurable, returns only when the file is guaranteed to be deleted even after a power failure.
	virtual Future<Void> incrementalDeleteFile(const std::string& filename, bool mustBeDurable);

	// Returns the time of the last modification of the file.
	virtual Future<std::time_t> lastWriteTime(const std::string& filename) = 0;

#ifdef ENABLE_SAMPLING
	// Returns the shared memory data structure used to store actor lineages.
	virtual ActorLineageSet& getActorLineageSet() = 0;
#endif

	static IAsyncFileSystem* filesystem() { return filesystem(g_network); }
	static runCycleFuncPtr runCycleFunc() {
		return reinterpret_cast<runCycleFuncPtr>(
		    reinterpret_cast<flowGlobalType>(g_network->global(INetwork::enRunCycleFunc)));
	}

	static IAsyncFileSystem* filesystem(INetwork* networkPtr) {
		return static_cast<IAsyncFileSystem*>(networkPtr->global(INetwork::enFileSystem));
	}

protected:
	IAsyncFileSystem() {}
	virtual ~IAsyncFileSystem() {} // Please don't try to delete through this interface!
};

#endif