Package ax.antpick.k2hdkc

Provides classes that are fundamental to the applications to communicate with a k2hdk clustering system.

See: Description

Interface Summary

Interface	Description
CLibrary	This JNA interface provides functions in the standard C library.
Cmd<T>	Represents an operation of a k2hdkc cluster.

Class Summary

Class	Description
AddSubkeyCmd	Adds a new subkey to a current subkey.
CasGetCmd	Gets a variable from a cluster using a CAS operation.
CasIncDecCmd	Increments and Decrements a variable in a cluster by using a CAS operation.
CasInitCmd	Initializes a variable in a cluster by using a CAS operation.
CasSetCmd	Sets a value in a cluster by using a CAS operation.
ClearSubkeysCmd	Clears subkeys of a key.
Cluster	Holds configurations of a chmpx slave server.
CmdBase	Holds common data types, members and instance methods of Cmd derived classes.
GetAttrsCmd	Retrievs attributes of a key.
GetCmd	Retrievs the value of a key.
GetSubkeysCmd	Retrievs subkeys of a key.
K2hashAttrPack	Holds information about an k2hash's attribute of a key.
KeyQueueAddCmd	Adds a new element to a queue.
KeyQueueRemoveCmd	Removes a new element to a queue.
QueueAddCmd	Adds a new element to a queue.
QueueRemoveCmd	Removes a new element to a queue.
RemoveCmd	Removes a key from a cluster.
RemoveSubkeyCmd	Removes a subkey from the current subkeys.
RenameCmd	Rename a key in a cluster.
Result<T>	Holds common data types, members and instance methods of derived classes.
Session	Holds a Cluster object and a connection handle with a chmpx slave process.
SetAllCmd	Stores a key with a value and subkeys.
SetCmd	Adds a key to a cluster.
SetSubkeysCmd	Replaces current subkeys with new one.

Enum Summary

Enum	Description
Cluster.NativeLogLevel	Defines levels used to dump a k2hdkc data
Cluster.NativeStackLogLevel	Defines the level which native library puts logs.
Cmd.DataType	DataType of data in CAS operation

Package ax.antpick.k2hdkc Description

Provides classes that are fundamental to the applications to communicate with a k2hdk clustering system.

Primary Packages

Contains 3 primary classes.

1. The class Cluster holds configurations to connect a chmpx slave process and it provides simple methods to set a value to a k2hdk and get a value from it. You can extends the Cluster class if you want to add more methods.
2. The class Session provides a connection with a chmpx slave process which communicate with a k2hdk clustering system.
3. Subclasses of CmdBase provide an operation against a k2hdk clustering system and holds the result of the operation in Result object.

Usage Examples

Please see each class document for the each example.

Using Native C Libraries by using JNA

The class K2hdkcLibrary, ChmpxLibrary and K2hashLibrary implements Java Native Access's Library interface. Their visibilities are mostly package private because we think it is hard to control for application programmers. So they are not extensible currently.

Logging

The Logback is a successor to the popular log4j project. Suppose you want to write logs to stdout in the "debug" level, you could write a logback.xml as:

 <configuration>

  <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
    <!-- encoders are assigned the type
         ch.qos.logback.classic.encoder.PatternLayoutEncoder by default -->
    <encoder>
      <!-- <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern> -->
      <pattern>%-5level [%thread] %date{ISO8601} %F:%L - %msg%n</pattern>
    </encoder>
  </appender>

  <root level="debug">
    <appender-ref ref="STDOUT" />
  </root>
 

Please see the logback manual more details.

In addtion, we use native C API libraries. We sometimes want to see how they work. The class Cluster provides methods to change log levels. The following code works as:

1. Logs are written to /tmp/native.log
2. Change the k2hdkc native library's loglevel to the info level.

   try (Cluster cluster = Cluster.of("slave.yaml");
       Session sess = Session.of(cluster); ) {
     cluster.setNativeLogLevel(
         "/tmp/native.log",
         Cluster.NativeStackLogLevel.StackK2hdkc,
         Cluster.NativeLogLevel.SeverityInfo);
     // ...
   } catch (IOException ex) {
     logger.error("message {}", ex.getMessage());
   }
 
 }

Author:

Hirotaka Wakabayashi