EXPERT KNOWLEDGE AT A GLANCE

Tag: hadoop

Apache Hive Architecture – Data Warehouse System for free

Apache Hive Architecture – On the way to Industry 4.0, companies are trying to record all business processes as far as possible in order to subsequently optimize them through analysis.
Data warehouse systems provide central data management. Thus, only one data truth exists. In addition to persistence, these information systems take care of sorting, preprocessing, translation and data analysis.
If you want to know more about what a data warehouse system is, check out our article on the subject.

What is Apache Hive

Hive is a data warehousing software project and part of Apache, an open source and free web server software. Learn more about Apache here.
It is built on the Big Data framework Apache Hadoop and was released in 2010. Since then it has been continuously improved and extended by an industrious community.

hive
Apache Hive Architecture – Built on top of Hadoop

The query language used by Hive, called HiveQL, is SQL based and allows querying, aggregation and analysis of unstructured data. Hive does not work with the schema-on-write (SoW) approach like relational databases, but uses the so-called schema-on-read (SoR) approach.

What are the biggest advantages of Hive?

Data from relational databases is automatically converted into MapReduce or Tez or Spark jobs. Hadoopclusters are based on MapReduce, a Google programming model for concurrent computation on computer clusters, and powerful stream-based data analysis pipelines can be created with Apache Spark. This ensures full compatibility with the Apache ecosystem, which can be modularly tailored to the needs of an application.

The figure shows the main Apache Hive features
Apache Hive Features

Another advantage of Hive is that the tables are similar to the tables in a relational database. Data is queried using HiveQL. A declarative SQL-like language.
HiveQL allows multiple users to query data simultaneously. Hive supports a variety of data formats and provides a lightweight but powerful translation feature.
For data analysis, custom MapReduce processes can be written and run on clusters in parallel for high performance.

Apache Hive Architecture

Basically, the architecture of Hive can be divided into three core areas. Hive communicates with other applications via the client area. The integration is then executed via the service area. In the last layer, Hive stores the metadata, for example, or computes the data via Hadoop.

The figure shows the basic three-part core architecture of Apache Hive.
Apache Hive Architecture

Hive Clients

Apache Hive can be accessed via different clients. In addition to Open Database Connectivity (ODBC), an SQL-based application programming interface (API) created by Microsoft, there is Java Database Connectivity (JDBC), an SQL-based API developed by Sun Microsystems to allow Java applications to use SQL for database access. Hive also provides a high-performance Apache Thrift connection.

Hive Services

The core and central control of the Hive Services is the so-called driver. This
receives HiveQL commands and is responsible for their execution against the Hadoop system. It typically consists of a compiler that translates HiveQL requests into abstract syntax and executable tasks, an optimizer that aggregates, splits, and optimizes for better performance and scalability, and an executor that interacts with Hadoop’s job tracker and passes tasks to the system for execution.

Apache Hive also provides the ability to submit these tasks directly to the driver. Using the Command Line and User Interface (CLI + UI), it is possible to directly influence the process.

Metadata about persistent relational entities, i.e. databases, tables, columns and partitions are managed by the metastore.

Hive Storage and Computer

The metadata is stored here in a persistence. The results of the query and the data loaded into the tables are stored on HDFS in the Hadoop cluster.

Apache Avro – Effective Big Data Serialization Solution for Kafka

In this article we will explain everything you need to know about Apache Avro, an open source big data serialization solution and why you should not do without it.


You can serialize data objects, i.e. put them into a sequential representation, in order to store or send them independent of the programming language. The text structure reflects your data hierarchy. Known serialization formats are for example XML and JSON. If you want to know more about both formats, read our articles on the topics. To read, you have to deserialize the text, i.e. convert it back into an object.

In times of Big Data, every computing process must be optimized. Even small computing delays can lead to long delays with a correspondingly large data throughput, and large data formats can block too many resources. The decisive factors are therefore speed and the smallest possible data formats that are stored. Avro is developed by the Apache community and is optimized for Big Data use. It offers you a fast and space-saving open source solution. If you don’t know what Apache means, look here. Here we have summarized everything you need to know about it and introduce you to some other Apache open source projects you should know about.

Apache Avro – Open Source Big Data Serialization Solution

With Apache Avro, you get not only a remote procedure call framework, but also a data serialization framework. So on the one hand you can call functions in other address spaces and on the other hand you can convert data into a more compact binary or text format. This duality gives you some advantages when you have cross-network data pipelines and is justified by its development history.

Avro was released back in 2011 as a part of Apache Hadoop. Here, Avro was supposed to provide a serialization format for data persistence as well as a data transfer format for communication between Hadoop nodes. To provide functionality in a Hadoop cluster, Avro needed to be able to access other address spaces. Due to its ability to serialize large amounts of data, cost-efficiently, Avro can now be used Hadoop-independently. 

You can access Avro via special API’s with many common programming languages (Java, C#, C, C++, Python and Ruby). So you can implement it very flexible.

In the following figure we have summarized some reasons what makes the framework so ingenious. But what really makes Avro so fast?

The schema clearly shows all the features that Apache Avro offers the user and why he should use it
Features Apache Avro

What makes Avro so fast?

The trick is that a schema is used for serialization and deserialization. About that the data hierarchy, i.e. the metadata, is stored separately in a file. The data types and protocols are defined via a JSON format. These are to be assigned unambiguously by ID to the actual values and can be called for the further data processing constantly. This schema is sent along with the data exchange via RPC calls.

Creating a schema registry is especially useful when processing data streams with Apache Kafka.

Apache Avro and Apache Kafka

Here you can save a lot of performance if you store the metadata separately and call it only when you really need it. In the following figure we have shown you this process schematically.

avro kafka

When you let Avro manage your schema registration, it provides you with comprehensive, flexible and automatic schema development. This means that you can add additional fields and delete fields. Even renaming is allowed within certain limits. At the same time, Avro schema is backward and forward compatible. This means that the schema versions of the Reader and Writer can differ. Schema registration management solutions exist, with Google Protocol Buffers and Apache Thrift, among others. However, the JSON data structure makes Avro the most popular choice.

What is Apache Hadoop?

Overview

– Open Source Big Data Framework for scalable, distributed software
– written in Java
– Linux-based
– is based on the MapReduce algorithm from Google
– enables intensive computing processes of large amounts of data by parallelization on computer clusters (== a number of networked computers) using simple programming models

Components

– consists of several components that work together

hadoop 1
Hadoop ecosystem

Hadoop Common

→interface for all other components + connects Hadoop to the computers’ file system + contains libraries

HDFS – Hadoop Distributed File System

– distributed file system for the storage of very large amounts of data
– organized in clusters of servers (with master and slave nodes)
Masternode organizes the storage of files + metadata in the individual slave nodes
– within a cluster, the data is stored on several computers (nodes)
– the files are partitioned in data blocks and distributed redundantly to the nodes

YARN – Yet Another Resource Negotiator


– Resource Manager
→ controls the distribution of individual tasks to the available resources (CPU and memory)

Map Reduce Algorithm

– provides configurable classes for map, reduce and combination phases
Map: takes a set of data and converts it into another set of data, in which the individual elements of the data are combined into tuples (key/value pairs)
Reduce: combines the formed tuples into smaller amounts of tuples
– is currently replaced by engines based on Directred-Acyclic-Graph (DAG)

hadoop MapReduce 1
Googles Map Reduce Algorithm principle

How a Hadoop cluster works

Overview

== hardware connected together for storing and processing large data sets

– these computers are in a connection with a dedicated server which acts as a master

Components

hadoop cluster component

Master Nodes

NameNode and Resource Manager are running on the master

– collecting data in the Hadoop Distributed File System (HDFS)

– store data with parallel computation by applying MapReduce

Slave Nodes

responsible for the collection of data

Client Nodes

– responsible to load the data into the cluster

Architecture

hadoop cluster architecture

JobTracker and TaskTrackers

– control the job execution process

Client submits a MapReduce job to the JobTracker to process a particular file

→ determines the DataNodes that store the blocks for that file by consulting the NameNode

→ assigns tasks to different TaskTrackers based on the information received from the NameNode + monitors the status of each task

NameNode and DataNodes

NamenNode maintains the filesystem metadata of HDFS (keeps track of all files that are broken down into blocks)

DataNodes store and retrieve these blocks

Secondary NameNode

communicates with the NameNode on a periodic interval to take the snapshot of the HDFS metadata

– information is used in case of NameNode failure

single-node clusters vs multi-node clusters

single-node

– deployed over a single machine

– all the processes run on one Java Virtual Machine instance

multi-node

– deployed on several machines

– master-slave architecture (NameNode on master + DataNode on slave)