org.cloudcoder.daemon

Class Util

java.lang.Object

org.cloudcoder.daemon.Util

public class Util
extends java.lang.Object

Utility methods. Most of these are to perform system-y type things like starting processes, checking the status of a process, creating FIFOs, etc. In theory these will work on any Unix, but in practice they are probably only tested on Linux.

This class also has some general-purpose utility methods such as loadPropertiesFromResource(ClassLoader, String) that might be useful for applications.

Author:

David Hovemeyer

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.String	MKFIFO_PATH Path to mkfifo executable, or null if it can't be found.
static java.lang.String	PS_PATH Path to ps executable, or null if it can't be found.
static java.lang.String	SH_PATH Path to sh executable, or null if it can't be found.

Constructor Summary

Constructors

Constructor and Description
Util()

Method Summary

Modifier and Type	Method and Description
static void	cleanup(java.lang.String instanceName, java.lang.Integer pid) Clean up the pid file and FIFO used by the given instance.
static void	deleteFile(java.lang.String fileName) Delete a file.
static int	exec(java.lang.String... cmd) Execute a process.
static java.lang.String	findCodeBase(java.lang.Class<?> cls) Return the codebase from which the given class was loaded, in a form suitable for using as a component of a classpath.
static java.lang.String	findExe(java.lang.String exeName, java.lang.String... path) Find the executable with the given name by checking the directories in the given path in order.
static java.lang.String[]	getenvp() Get the current environment variables in a form that can be passed as an envp array to Runtime.exec(String[], String[]).
static java.lang.String	getExternalizedFileName(java.lang.ClassLoader clsLoader, java.lang.String resourceName) Deprecated. don't call this: call getExternalizedFileName(ClassLoader, String, File) so that the temporary directory where the externalized file will be placed is specified explicitly
static java.lang.String	getExternalizedFileName(java.lang.ClassLoader clsLoader, java.lang.String resourceName, java.io.File tempDir) Take a resource that is loadable from the given classloader and make it available as a file in the filesystem.
static java.lang.String	getFifoName(java.lang.String instanceName, java.lang.Integer pid) Get the name of the FIFO for given instance name and process id.
static java.lang.Object	getJvmExecutablePath() Get the path of the JVM executable.
static java.lang.Integer	getPid() Get this process's pid.
static java.lang.String	getPidFileName(java.lang.String instanceName) Get the name of the pid file for given instance name.
static boolean	hasShellMetaCharacters(java.lang.String s) Determine whether or not given string contains any shell metacharacters.
static boolean	isRunning(java.lang.Integer pid) Is there a process running with the given pid?
static java.util.Properties	loadPropertiesFromResource(java.lang.ClassLoader clsLoader, java.lang.String resourcePath) Load properties from a resource embedded in the classpath.
static java.lang.Integer	readPid(java.lang.String instanceName) Read the pid file for given instance, returning the pid.
static java.io.BufferedReader	readProcess(java.lang.String... cmd) Read lines of text from a process.
static void	sendCommand(java.lang.String instanceName, java.lang.Integer pid, java.lang.String command) Send a command to the daemon process.
static void	waitForExit(java.lang.Integer pid, java.lang.Runnable callback) Wait for given process to exit.
static void	writePid(java.lang.String instanceName, java.lang.Integer pid) Write a pid file for instance.

Methods inherited from class java.lang.Object

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

Field Detail

SH_PATH

public static final java.lang.String SH_PATH

Path to sh executable, or null if it can't be found.

PS_PATH

public static final java.lang.String PS_PATH

Path to ps executable, or null if it can't be found.

MKFIFO_PATH

public static final java.lang.String MKFIFO_PATH

Path to mkfifo executable, or null if it can't be found.

Constructor Detail

Util

public Util()

Method Detail

findExe

public static java.lang.String findExe(java.lang.String exeName,
                                       java.lang.String... path)

Find the executable with the given name by checking the directories in the given path in order.

Parameters:

exeName - an executable name (e.g., "mkfifo")

path - a path (e.g., "/bin", "/usr/bin")

Returns:

full path to the executable, or null if the executable can't be found

Throws:

DaemonException

readPid

public static java.lang.Integer readPid(java.lang.String instanceName)
                                 throws DaemonException

Read the pid file for given instance, returning the pid.

Parameters:

instanceName - the instance name

Returns:

the contents of the pid file for this instance, or null if there is no pid file (or an invalid pid file)

Throws:

java.io.IOException

DaemonException

writePid

public static void writePid(java.lang.String instanceName,
                            java.lang.Integer pid)
                     throws DaemonException

Write a pid file for instance.

Parameters:

instanceName - name of the instance

pid - the pid

Throws:

DaemonException

getPidFileName

public static java.lang.String getPidFileName(java.lang.String instanceName)

Get the name of the pid file for given instance name.

Parameters:

instanceName - an instance name

Returns:

the pid file name for that instance name

getFifoName

public static java.lang.String getFifoName(java.lang.String instanceName,
                                           java.lang.Integer pid)

Get the name of the FIFO for given instance name and process id.

Parameters:

instanceName - the instance name

pid - the pid

Returns:

the FIFO name for the isntance name and process id

isRunning

public static boolean isRunning(java.lang.Integer pid)
                         throws DaemonException

Is there a process running with the given pid?

Parameters:

pid - the pid

Returns:

true if a process is running with the given pid, false otherwise

Throws:

java.io.IOException

DaemonException

readProcess

public static java.io.BufferedReader readProcess(java.lang.String... cmd)
                                          throws java.io.IOException

Read lines of text from a process.

Parameters:

cmd - command (array of strings, first is program) to be used to start the process

Returns:

a BufferedReader reading from the process

Throws:

java.io.IOException

getenvp

public static java.lang.String[] getenvp()

Get the current environment variables in a form that can be passed as an envp array to Runtime.exec(String[], String[]).

Returns:

current environment variables

findCodeBase

public static java.lang.String findCodeBase(java.lang.Class<?> cls)

Return the codebase from which the given class was loaded, in a form suitable for using as a component of a classpath.

Parameters:

cls - the class to determine the codebase of

Returns:

the class's codebase, in a form suitable for use in a classpath

deleteFile

public static void deleteFile(java.lang.String fileName)

Delete a file.

Parameters:

fileName - name of the file to delete

sendCommand

public static void sendCommand(java.lang.String instanceName,
                               java.lang.Integer pid,
                               java.lang.String command)
                        throws DaemonException

Send a command to the daemon process.

Parameters:

instanceName - the instance name

pid - the pid of the daemon process

command - the command to send

Throws:

DaemonException

exec

public static int exec(java.lang.String... cmd)
                throws DaemonException

Execute a process.

Parameters:

cmd - the command (program and arguments)

Returns:

the process's exit code

Throws:

DaemonException

getPid

public static java.lang.Integer getPid()
                                throws DaemonException

Get this process's pid.

Returns:

this process's pid

Throws:

DaemonException

See Also:

http://blog.igorminar.com/2007/03/how-java-application-can-discover-its.html

waitForExit

public static void waitForExit(java.lang.Integer pid,
                               java.lang.Runnable callback)
                        throws DaemonException

Wait for given process to exit.

Parameters:

pid - the pid of the process to wait for

callback - callback whose run() method is called periodically (once per second) if the process is still running

Throws:

DaemonException

cleanup

public static void cleanup(java.lang.String instanceName,
                           java.lang.Integer pid)

Clean up the pid file and FIFO used by the given instance. The instance should have exited before this is called.

Parameters:

instanceName - the instance name

pid - the pid of the exited instance

hasShellMetaCharacters

public static boolean hasShellMetaCharacters(java.lang.String s)

Determine whether or not given string contains any shell metacharacters.

Parameters:

s -

Returns:

true if the string contains shell metacharacters, false otherwise

getJvmExecutablePath

public static java.lang.Object getJvmExecutablePath()

Get the path of the JVM executable. Tries to identify the same JVM executable as the one that is executing currently. Otherwise, just returns "java". Note that the full JVM executable path will (probably) only be found on Linux/Unix for JRE/JDK installations that use the standard directory layout.

Returns:

path to JVM executable

loadPropertiesFromResource

public static java.util.Properties loadPropertiesFromResource(java.lang.ClassLoader clsLoader,
                                                              java.lang.String resourcePath)

Load properties from a resource embedded in the classpath. Note that an IllegalStateException is thrown if the properties cannot be loaded from the resource: therefore, this method should probably only be used to load properties that are guaranteed to be present.

Parameters:

clsLoader - the ClassLoader to load the resource from

resourcePath - the resource from which the properties should be loaded

Returns:

the Properties loaded from the resource

Throws:

java.lang.IllegalStateException - if the properties cannot be loaded

getExternalizedFileName

public static java.lang.String getExternalizedFileName(java.lang.ClassLoader clsLoader,
                                                       java.lang.String resourceName)
                                                throws java.io.IOException

Deprecated. don't call this: call getExternalizedFileName(ClassLoader, String, File) so that the temporary directory where the externalized file will be placed is specified explicitly

Take a resource that is loadable from the given classloader and make it available as a file in the filesystem. If the app is running from a jarfile, loaded resources aren't directly available as files (the way they would be if the app is running out of a directory containing the app's class files.) This method will copy an internal resource to an external file in the system temporary directory if necessary.

Parameters:

clsLoader - the ClassLoader containing the resource

resourceName - the name of the resource to externalize

Returns:

the filename of the externalized resource

Throws:

java.io.IOException - if the resource can't be externalized

getExternalizedFileName

public static java.lang.String getExternalizedFileName(java.lang.ClassLoader clsLoader,
                                                       java.lang.String resourceName,
                                                       java.io.File tempDir)
                                                throws java.io.IOException

Take a resource that is loadable from the given classloader and make it available as a file in the filesystem. If the app is running from a jarfile, loaded resources aren't directly available as files (the way they would be if the app is running out of a directory containing the app's class files.) This method will copy an internal resource to an external file in the specified if necessary.

Parameters:

clsLoader - the ClassLoader containing the resource

resourceName - the name of the resource to externalize

Returns:

the filename of the externalized resource

Throws:

java.io.IOException - if the resource can't be externalized