serialization in hadoop

be serializable compatible, so you need to ensure that different versions of the class have different serialversionuid.The Java serialization algorithm takes into account these things:Outputs the class metadata related to the object instance.Recursively outputs a superclass description of a class until there are no more super-classes.After the class metadata is finished, start outputting the actual data values of the object instances from the topmost

Serialization principles from Hadoop Writable serialization framework to java After the previous module, the analysis content comes to the Hadoop IO-related module. The module of the IO system is a relatively large module, In the Hadoop Common io, it consists of two major su

instancesSo Java serialization is very powerful, the serialization of the information is very detailed, but the serialization of memory.2.Hadoop serializationCompared to the JDK relatively concise, in the urgent mass of information transmission is mainly by these serialized byte building to pass, so faster speed, smal

Directory1. Why serialize?2. What is serialization?3. Why not use Java serialization?4. Why is serialization important for Hadoop?5. What serialization-related interfaces are defined in Hadoop?6.

stream and transmits it to another process over the network. Another process receives the byte stream and returns it to a structured object through deserialization, to achieve inter-process communication. In Hadoop, the serialization and deserialization technologies must be used for communication between Mapper, Combiner, and CER stages. For example, the intermediate result ( ) Needs to be written to the

Reprinted please indicate Source Address: http://blog.csdn.net/lastsweetop/article/details/9249411 All source code on GitHub, https://github.com/lastsweetop/styhadoop Introduction In hadoop, writable implementation classes are a huge family. Here we will briefly introduce some of the commonly used implementations for serialization. Except for char, all Java Native types have corresponding writable classes,

-transient and non-static member variables, and all of its parent classes will be written. Date d = new Date (), outputstream out = new Bytearrayoutputstream (), ObjectOutputStream objout = new ObjectOutputStream (out) ; Objout.writeobject (d);If you want to serialize a basic type, ObjectOutputStream also provides a variety of methods such as Writeboolean, WriteByte, etc.The reverse sequence process is similar, only need to call ObjectInputStream's ReadObject (), and downward transformation, you

Reprinted please indicate Source Address: http://blog.csdn.net/lastsweetop/article/details/9193907 All source code on GitHub, https://github.com/lastsweetop/styhadoopSerialization and deserialization are conversions between structured objects and throttling. They are mainly used for communication and persistent storage of internal processes. The communication format requires that hadoop uses RPC for internal communication between nodes. RPC translates

Hadoop differs from the Java-brought serialization mechanism by providing a set of serialization system interfaces and classes. For basic data types, the writable interface represents the data that can be serialized, and this interface defines 2 methods, where the Write method can serialize the data to the DataOutput byte array given by the parameter. The Readfi

Because of the need for communication between the MapReduce and HDFs of Hadoop, the communication object needs to be serialized. Hadoop does not use Java serialization, but ratherintroduced its own system.A large number of serializable objects are defined in Org.apache.hadoop.io, and they all implement the writable interface. A typical example of a writable inter

Because of the need for communication between the MapReduce and HDFs of Hadoop, the communication object needs to be serialized. Hadoop does not use Java serialization, but ratherintroduced its own system.A large number of serializable objects are defined in Org.apache.hadoop.io, and they all implement the writable interface. A typical example of a writable inter

This article address: http://www.cnblogs.com/archimedes/p/hadoop-writable-interface.html, reprint please indicate source address.Introduction serialization and deserialization are transitions between structured objects and byte streams, primarily in the context of internal process communication and persistent storage.Communication Format RequirementsHadoop's internal communication between nodes uses the RPC

in the persistence of storage, but in fact it remains the four points: 1. Compressed, less space occupied 2. Fast, can read and write quickly 3. Scalable, old data can be read in old format 4. Good compatibility, can support reading and writing in multiple languages Serialization format for Hadoop The serialized storage format for Hadoop itself is the clas

Avro Introduction Schema File composition Header and DataBlock declaration code Test code Serialization and deserialization Specific Generic Resources Avro IntroductionAvro is a data serialization system created by Doug Cutting (the father of Hadoop) designed to address the lack of wr

Brief introduction In Hadoop, the implementation class of the writable is a huge family, and we are here to briefly describe some of the parts that are often used for serialization. Java Native type Except for the char type, all native types have corresponding writable classes, and their values are available through get and set methods. Intwritable and longwritable also have corresponding variable-lengt

Introduction to the Framework MapReduce can only support writable do key,value? The answer is in the negative. In fact, all types are supported by just one small condition: each type is transmitted in binary streams. This Hadoop provides a serialization framework to support the types that writable can serve as mapreduce support in the Org.apache.hadoop.io.serializer package as well as the fact that there a

Writable that writes an instance with it's class name.* Handles arrays, strings and primitive types without a writable wrapper.*/Public class Objectwritable implements writable, configurable { Private Class Declaredclass;Private Object instance;Private Configuration conf; --------------------------------------------------------------------------------------------------------------- ---------------------------- Writable writable = Writablefactories.newinstance (Instanceclass, conf);Writable.rea

This article address: http://www.cnblogs.com/archimedes/p/hadoop-writable-class.html, reprint please indicate source address.The Org.apache.hadoop.io package in Hadoop comes with a wide range of writable classes to choose from, which form the hierarchical structure shown:Java basic types of writable wrappersThe writable class provides encapsulation of Java primitives, except for short and char, all packages

1 Overview The Zookeeper distributed service framework is a sub-project of Apache Hadoop. It is mainly used to solve some data management problems frequently encountered in distributed applications, such: unified Naming Service, status Synchronization Service, cluster management, and management of distributed application configuration items. ZooKeeper can be installed and run in Standalone mode. However, ZooKeeper ensures the stability and availabili

Reprinted please indicate Source Address: http://blog.csdn.net/lastsweetop/article/details/9773233 All source code on GitHub, https://github.com/lastsweetop/styhadoop In many cases, Avro is used to transform the original system. The framework format has been defined. We can only use Avro to integrate the original data. (If you are creating a new system, you 'd better use Avro's datafile. The next chapter describes datafile)Prepare to save the schema as the stringpair. AVSC file and put it in th