com.datastax.driver.core

Class Native

java.lang.Object

com.datastax.driver.core.Native

public final class Native
extends Object

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:

1. currentTimeMicros(): thanks to a system call to gettimeofday(), the driver is able to generate timestamps with true microsecond precision (see AtomicMonotonicTimestampGenerator or ThreadLocalMonotonicTimestampGenerator for more information);
2. processId(): thanks to a system call to 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 UUIDs for more information).

The availability of the aforementioned system calls depends on the underlying operation system's capabilities. For instance, gettimeofday() is not available under Windows systems. You can check if any of the system calls exposed through this class is available by calling isGettimeofdayAvailable() or 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 Also:

JNR library on Github

Constructor Summary

Constructors

Constructor and Description
Native()

Method Summary

Modifier and Type	Method and Description
static long	currentTimeMicros() Returns the current timestamp with microsecond precision via a system call to gettimeofday, through JNR C library.
static boolean	isGetpidAvailable() Returns true if JNR POSIX library is loaded and a call to getpid is possible through this library on this system, and false otherwise.
static boolean	isGettimeofdayAvailable() Returns true if JNR C library is loaded and a call to gettimeofday is possible through this library on this system, and false otherwise.
static int	processId() Returns the JVM's process identifier (PID) via a system call to getpid.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Native

public Native()

Method Detail

isGettimeofdayAvailable

public static boolean isGettimeofdayAvailable()

Returns true if JNR C library is loaded and a call to gettimeofday is possible through this library on this system, and false otherwise.

Returns:

true if JNR C library is loaded and a call to gettimeofday is possible.

isGetpidAvailable

public static boolean isGetpidAvailable()

Returns true if JNR POSIX library is loaded and a call to getpid is possible through this library on this system, and false otherwise.

Returns:

true if JNR POSIX library is loaded and a call to getpid is possible.

currentTimeMicros

public static long currentTimeMicros()

Returns the current timestamp with microsecond precision via a system call to gettimeofday, through JNR C library.

Returns:

the current timestamp with microsecond precision.

Throws:

UnsupportedOperationException - if JNR C library is not loaded or gettimeofday is not available.

IllegalStateException - if the call to gettimeofday did not complete with return code 0.

processId

public static int processId()

Returns the JVM's process identifier (PID) via a system call to getpid.

Returns:

the JVM's process identifier (PID).

Throws:

UnsupportedOperationException - if JNR POSIX library is not loaded or getpid is not available.