com.datastax.driver.core.Native Maven / Gradle / Ivy
/*
* Copyright (C) 2012-2015 DataStax Inc.
*
* 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.
*/
package com.datastax.driver.core;
import jnr.ffi.LibraryLoader;
import jnr.ffi.Pointer;
import jnr.ffi.Runtime;
import jnr.ffi.Struct;
import jnr.ffi.annotations.Out;
import jnr.ffi.annotations.Transient;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.lang.reflect.Method;
/**
* Helper class to deal with native system calls through the
* JNR library.
*
* The driver can benefit from native system calls to improve its performance and accuracy
* in some situations.
*
* Currently, the following features may be used by the driver when available:
*
* - {@link #currentTimeMicros()}: thanks to a system call to {@code gettimeofday()},
* the driver is able to generate timestamps with true microsecond precision
* (see {@link AtomicMonotonicTimestampGenerator} or {@link ThreadLocalMonotonicTimestampGenerator} for
* more information);
* - {@link #processId()}: thanks to a system call to {@code getpid()},
* the driver has access to the JVM's process ID it is running under – which
* makes time-based UUID generation easier and more reliable (see {@link com.datastax.driver.core.utils.UUIDs UUIDs}
* for more information).
*
*
* The availability of the aforementioned system calls depends on the underlying operation system's
* capabilities. For instance, {@code gettimeofday()} is not available under Windows systems.
* You can check if any of the system calls exposed through this class is available
* by calling {@link #isGettimeofdayAvailable()} or {@link #isGetpidAvailable()}.
*
* Note: This class is public because it needs to be accessible from other packages of the Java driver,
* but it is not meant to be used directly by client code.
*
* @see JNR library on Github
*/
public final class Native {
private static final Logger LOGGER = LoggerFactory.getLogger(Native.class);
private static class LibCLoader {
/**
* Timeval struct.
*
* @see GETTIMEOFDAY(2)
*/
static class Timeval extends Struct {
public final time_t tv_sec = new time_t();
public final Unsigned32 tv_usec = new Unsigned32();
public Timeval(Runtime runtime) {
super(runtime);
}
}
/**
* Interface for LIBC calls through JNR.
* Note that this interface must be declared public.
*/
public interface LibC {
/**
* JNR call to {@code gettimeofday}.
*
* @param tv Timeval struct
* @param unused Timezone struct (unused)
* @return 0 for success, or -1 for failure
* @see GETTIMEOFDAY(2)
*/
int gettimeofday(@Out @Transient Timeval tv, Pointer unused);
}
private static final LibC LIB_C;
private static final Runtime LIB_C_RUNTIME;
private static final boolean GETTIMEOFDAY_AVAILABLE;
static {
LibC libc;
Runtime runtime = null;
try {
libc = LibraryLoader.create(LibC.class).load("c");
runtime = Runtime.getRuntime(libc);
} catch (Throwable t) {
libc = null; // dereference proxy to library if runtime could not be loaded
if (LOGGER.isDebugEnabled())
LOGGER.debug("Could not load JNR C Library, native system calls through this library will not be available", t);
else
LOGGER.info("Could not load JNR C Library, native system calls through this library will not be available " +
"(set this logger level to DEBUG to see the full stack trace).");
}
LIB_C = libc;
LIB_C_RUNTIME = runtime;
boolean gettimeofday = false;
if (LIB_C_RUNTIME != null) {
try {
gettimeofday = LIB_C.gettimeofday(new Timeval(LIB_C_RUNTIME), null) == 0;
} catch (Throwable t) {
if (LOGGER.isDebugEnabled())
LOGGER.debug("Native calls to gettimeofday() not available on this system.", t);
else
LOGGER.info("Native calls to gettimeofday() not available on this system " +
"(set this logger level to DEBUG to see the full stack trace).");
}
}
GETTIMEOFDAY_AVAILABLE = gettimeofday;
}
}
private static class PosixLoader {
public static final jnr.posix.POSIX POSIX;
private static final boolean GETPID_AVAILABLE;
static {
jnr.posix.POSIX posix;
try {
// use reflection below to get the classloader a chance to load this class
Class posixHandler = Class.forName("jnr.posix.POSIXHandler");
Class defaultPosixHandler = Class.forName("jnr.posix.util.DefaultPOSIXHandler");
Class posixFactory = Class.forName("jnr.posix.POSIXFactory");
Method getPOSIX = posixFactory.getMethod("getPOSIX", posixHandler, Boolean.TYPE);
posix = (jnr.posix.POSIX) getPOSIX.invoke(null, defaultPosixHandler.newInstance(), true);
} catch (Throwable t) {
posix = null;
if (LOGGER.isDebugEnabled())
LOGGER.debug("Could not load JNR POSIX Library, native system calls through this library will not be available.", t);
else
LOGGER.info("Could not load JNR POSIX Library, native system calls through this library will not be available " +
"(set this logger level to DEBUG to see the full stack trace).");
}
POSIX = posix;
boolean getpid = false;
if (POSIX != null) {
try {
POSIX.getpid();
getpid = true;
} catch (Throwable t) {
if (LOGGER.isDebugEnabled())
LOGGER.debug("Native calls to getpid() not available on this system.", t);
else
LOGGER.info("Native calls to getpid() not available on this system " +
"(set this logger level to DEBUG to see the full stack trace).");
}
}
GETPID_AVAILABLE = getpid;
}
}
/**
* Returns {@code true} if JNR C library is loaded and
* a call to {@code gettimeofday} is possible through this library
* on this system, and {@code false} otherwise.
*
* @return {@code true} if JNR C library is loaded and
* a call to {@code gettimeofday} is possible.
*/
public static boolean isGettimeofdayAvailable() {
try {
return LibCLoader.GETTIMEOFDAY_AVAILABLE;
} catch (NoClassDefFoundError e) {
return false;
}
}
/**
* Returns {@code true} if JNR POSIX library is loaded and
* a call to {@code getpid} is possible through this library
* on this system, and {@code false} otherwise.
*
* @return {@code true} if JNR POSIX library is loaded and
* a call to {@code getpid} is possible.
*/
public static boolean isGetpidAvailable() {
try {
return PosixLoader.GETPID_AVAILABLE;
} catch (NoClassDefFoundError e) {
return false;
}
}
/**
* Returns the current timestamp with microsecond precision
* via a system call to {@code gettimeofday}, through JNR C library.
*
* @return the current timestamp with microsecond precision.
* @throws UnsupportedOperationException if JNR C library is not loaded or {@code gettimeofday} is not available.
* @throws IllegalStateException if the call to {@code gettimeofday} did not complete with return code 0.
*/
public static long currentTimeMicros() {
if (!isGettimeofdayAvailable())
throw new UnsupportedOperationException("JNR C library not loaded or gettimeofday not available");
LibCLoader.Timeval tv = new LibCLoader.Timeval(LibCLoader.LIB_C_RUNTIME);
int res = LibCLoader.LIB_C.gettimeofday(tv, null);
if (res != 0)
throw new IllegalStateException("Call to gettimeofday failed with result " + res);
return tv.tv_sec.get() * 1000000 + tv.tv_usec.get();
}
/**
* Returns the JVM's process identifier (PID)
* via a system call to {@code getpid}.
*
* @return the JVM's process identifier (PID).
* @throws UnsupportedOperationException if JNR POSIX library is not loaded or {@code getpid} is not available.
*/
public static int processId() {
if (!isGetpidAvailable())
throw new UnsupportedOperationException("JNR POSIX library not loaded or getpid not available");
return PosixLoader.POSIX.getpid();
}
}