org.rvpf.store.server.sink

Class PipeSink

Object

SinkModule.Abstract

PipeSink

All Implemented Interfaces:

SinkModule

public final class PipeSink
extends SinkModule.Abstract

Pipe sink.

This sink feeds values to an external program. It communicates with this program thru 'pipes' on the program's standard input ('stdin'), output ('stdout') and error ('stderr') streams.

Lines sent to the process

1. The request header:
   1. A request ID (long).
   2. The request format version (currently 1).
   3. A request type:
      • +: Update.
      • -: Delete.
2. The value description:
   1. The name of the point.
   2. The timestamp.
   3. The state inside '[]' (update).
   4. The value between '"' (update).

Line received from the process

1. The request ID (long).
2. A response summary:
   • < 0: The request failed.
   • = 0: The request did nothing.
   • = 1: Notify.

Loop

The program is expected to loop on the requests until it receives a line containing a single field holding only the digit '0'.

Notes

• On each line, the items are separated by spaces.
• A point may be identified by its UUID.
• The timestamp has the ISO 8601 format.
• A null state or value is indicated by a missing field.
• The request ID is used for synchronization verification and must be returned verbatim.
• Leading spaces are stripped from the lines received from the process; resulting empty lines are ignored.
• The state is encoded by replacing ']' by '[]' and '[' by ']['.
• The value is encoded by replacing '"' by '""'.

Nested Class Summary

Nested classes/interfaces inherited from interface SinkModule

SinkModule.Abstract

Field Summary

Fields

Modifier and Type	Field and Description
static String	ARG_PROPERTY An argument for the process.
static String	CHARSET_PROPERTY Specifies the java Charset to use instead of the local default for communication with the external program.
static String	COMMAND_PROPERTY The operating system command used to activate the process.
static String	DIRECTORY_PROPERTY Specifies the working directory into which the external program should execute.
static String	HOLD_PROPERTY The time in millis during which an idle external program will be held.
static String	KILL_DELAY_PROPERTY The delay before killing a process after closing its input.
static String	NAME_PROPERTY An identifying name for the pipe program.
static String	PIPE_PROPERTIES The pipe properties group.
static String	PROGRAM_PROPERTY The path to the program file.
static String	SET_PROPERTY Sets an environment variable.

Constructor Summary

Constructors

Constructor and Description
PipeSink()

Method Summary

Modifier and Type	Method and Description
void	close() Closes this sink.
boolean	delete(VersionedValue versionedValue) Deletes a value.
boolean	setUp(SinkServiceAppImpl sinkAppImpl) Sets up the sink for action.
void	tearDown() Tears down what has been set up.
boolean	update(VersionedValue versionedValue) Updates a value.

Methods inherited from class SinkModule.Abstract

abort, getMetadata, getSinkAppImpl, getThisLogger, open

Methods inherited from class Object

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

Field Detail

ARG_PROPERTY

public static final String ARG_PROPERTY

An argument for the process.

See Also:

Constant Field Values

CHARSET_PROPERTY

public static final String CHARSET_PROPERTY

Specifies the java Charset to use instead of the local default for communication with the external program.

See Also:

Constant Field Values

COMMAND_PROPERTY

public static final String COMMAND_PROPERTY

The operating system command used to activate the process.

See Also:

Constant Field Values

DIRECTORY_PROPERTY

public static final String DIRECTORY_PROPERTY

Specifies the working directory into which the external program should execute.

See Also:

Constant Field Values

HOLD_PROPERTY

public static final String HOLD_PROPERTY

The time in millis during which an idle external program will be held. A negative value means no limit, zero means immediate termination after use. Defaults to no limit.

See Also:

Constant Field Values

KILL_DELAY_PROPERTY

public static final String KILL_DELAY_PROPERTY

The delay before killing a process after closing its input.

See Also:

Constant Field Values

NAME_PROPERTY

public static final String NAME_PROPERTY

An identifying name for the pipe program.

See Also:

Constant Field Values

PIPE_PROPERTIES

public static final String PIPE_PROPERTIES

The pipe properties group.

See Also:

Constant Field Values

PROGRAM_PROPERTY

public static final String PROGRAM_PROPERTY

The path to the program file.

See Also:

Constant Field Values

SET_PROPERTY

public static final String SET_PROPERTY

Sets an environment variable.

See Also:

Constant Field Values

Constructor Detail

PipeSink

public PipeSink()

Method Detail

close

public void close()

Closes this sink.

Specified by:

close in interface SinkModule

Overrides:

close in class SinkModule.Abstract

delete

public boolean delete(VersionedValue versionedValue)

Deletes a value.

Specified by:

delete in interface SinkModule

Overrides:

delete in class SinkModule.Abstract

Parameters:

versionedValue - The point value to delete.

Returns:

True if notification may proceed.

setUp

public boolean setUp(SinkServiceAppImpl sinkAppImpl)

Sets up the sink for action.

Specified by:

setUp in interface SinkModule

Overrides:

setUp in class SinkModule.Abstract

Parameters:

sinkAppImpl - The sink application implementation.

Returns:

True on success.

tearDown

public void tearDown()

Tears down what has been set up.

Specified by:

tearDown in interface SinkModule

Overrides:

tearDown in class SinkModule.Abstract

update

public boolean update(VersionedValue versionedValue)

Updates a value.

Specified by:

update in interface SinkModule

Overrides:

update in class SinkModule.Abstract

Parameters:

versionedValue - The new point value.

Returns:

True if notification may proceed.