HBase or Cassandra? - cassandra

In my lambda architecture, i am debating on whether to use HDFS or Cassandra to store my immutable data. I need Cassandra to serve the online requests etc. so it is the mandatory part of the tech stack. Now, I do not want to introduce new tool (HDFS) into the stack if I don't have to. So my question is, what will I be missing if I don't use HDFS and use Cassandra to host my immutable data as well.
EDIT:
I understand HDFS is a distributed filesystem and Cassandra is NoSQL DB. Still, both support data replication, both support high-throughput writes. In addition Cassandra supports low latent data retrieval. So am I right saying that HDFS isn't going to provide me much lift?

As I understand You are trying to clarify your Serving Layer of your Lambda Architecture.
If it is true, you want to store your batch views and real-time views into a Database.
And as I understand you do not have Hadoop cluster in your batch layer.
And your batch views have not been completed in HDFS.
At this point your architecture is outside of HDFS.
HBase is a distributed column-oriented database built on top of the Hadoop file system. It is an open-source project and is horizontally scalable.
If you dont want a hadoop cluster, omit HBase.
Cassandra is distributed NoSQL Database(column-oriented) and it works outside the Hadoop cluster and HDFS.
If I understand your architecture and your needs right, I think Cassandra is best for you.
Additionally, you can get quick info about Lambda architecture from this link;
http://artofbigdata.blogspot.com.tr/2016/01/lambda-architecture.html

HDFS supports different file formats to store. For example, sequence files, Avro and Parquet etc..so that you can choose a file format suitable to your application needs.
Also note that you can efficiently read the data using SQL-like queries.
So different data models are available in HDFS over Cassandra to host the data.

Related

Spark as Data Ingestion/Onboarding to HDFS

While exploring various tools like [Nifi, Gobblin etc.], I have observed that Databricks is now promoting for using Spark for data ingestion/on-boarding.
We have a spark[scala] based application running on YARN. So far we are working on a hadoop and spark cluster where we manually place required data files in HDFS first and then run our spark jobs later.
Now when we are planning to make our application available for the client we are expecting any type and number of files [mainly csv, jason, xml etc.] from any data source [ftp, sftp, any relational and nosql database] of huge size [ranging from GB to PB].
Keeping this in mind we are looking for options which could be used for data on-boarding and data sanity before pushing data into HDFS.
Options which we are looking for based on priority:
1) Spark for data ingestion and sanity: As our application is written and is running on spark cluster, we are planning to use the same for data ingestion and sanity task as well.
We are bit worried about Spark's support for many datasources/file types/etc. Also, we are not sure if we try to copy data from let's say any FTP/SFTP then will all workers will write data on HDFS in parallel? Is there any limitation while using it? Is there any Audit trail maintained by Spark while this data copy?
2) Nifi in clustered mode: How good Nifi would be for this purpose? Can it be used for any datasource and for any size of file? Will be maintain the Audit trail? Would Nifi we able to handle such large files? How large cluster would be required in case we try to copy GB - PB of data and perform certain sanity on top of that data before pushing it to HDFS?
3) Gobblin in clustered mode: Would like to hear similar answers as that for Nifi?
4) If at all there is any other good option available for this purpose with lesser infra/cost involved and better performance?
Any guidance/pointers/comparisions for above mentioned tools and technologies would be appreciated.
Best Regards,
Bhupesh
After doing certain R&D and considering the fact that using NIFI or goblin will demand for more infrastructure cost. I have started testing Spark for data on-boarding.
SO far I have tried using Spark job for importing data [present at a remote staging area/node] into my HDFS and I am able to do that by mounting that remote location with all my spark cluster worker nodes. Doing this made that location local to those workers, hence spark job ran properly and data is on-boarded to my HDFS.
Since my whole project is going to be on Spark, hence keeping data on-boarding part on spark would not cost anything extra to me. So far I am going good. Hence I would suggest to others as well, if you already have spark cluster and hadoop cluster up and running then instead of adding extra cost [where cost could be a major constraint] go for spark job for data on-boarding.

Spark goodness with Cassandra?

I've been reading about Apache Cassandra lately to learn how it works and how to use it for IoT projects, especially in the need of time series based database..
However, I started to notice that Apache Spark is often mentioned when people talk about Cassandra too.
The question is, as long as I can use Cassandra cluster of nodes to serve my app, to store and read data, why would I need Apache Spark? any useful use-cases are appreciated!
The answer is broad but summarizing ... Cassandra is highly scalable and there are lot of scenarios where it fits but CQL sintax has some limitations if you don't have your schema ready for some queries.
If you want to make use of your data without restrictions and doing analytical workloads with your cassandra data or join with other tables Spark is the most appropriate complement. Spark has a tight integration with Cassandra.
I recommend you to check this slides: http://www.slideshare.net/patrickmcfadin/apache-cassandra-and-spark-you-got-the-the-lighter-lets-start-the-fire?qid=48e2528c-a03c-49b4-879e-45599b2aff34&v=&b=&from_search=5
Cassandra is for storing data where as Spark is for performing some computation on top of it. Analogy with Hadoop: Cassandra is like HDFS where as Spark is like Map Reduce.
Especially with computations, when using DataStax Cassandra connector, data locality can be exploited. If you need to do some computation which modifies a row (but doesn't really depend on anything else), then that operation is optimized to run locally on each machine in cluster without any data movement in network.
Same goes with a lot of other Spark workload, the actions(some function which modifies the data) are done locally and only result is sent to client. As far as I know, when you want to do analytics on top of data stored in Cassandra, Spark is well supported and popular choice. If you don't need to do any operations on the data, still you can use Spark for other purposes like I mentioned below.
Spark streaming can be used to ingest or export data from Cassandra ( I used it a lot personally). The same data import/export can be achieved with small hand-written JDBC agents but Spark streaming code I wrote for ingesting 10GB data from Cassandra contains less than 20 lines of code with multi machine-multi threading built-in and an admin UI where I can see the job progress.
With Spark+Zeppelin, we can visualize Cassandra data using Spark, we can build beautiful UIs with little Spark code where users can even enter input and see the result as graph/table etc.
Note: Actually, visualization can be better with Kibana/ElasticSearch or Solr/Banana when used with Cassandra but they are very hard to setup and indexing has it's own issues to deal with.
There are a lot of other use cases, but personally I used Spark as a Swiss army knife for multiple tasks.
Apache cassandra is have feature like fast read and write so you can use it with the apache spark streaming to write your data directly into cassandra without legacy.
For use case you can consider any video application to upload video with the help of streaming and directly store it into cassandra blob.

What specific benefits can we get by using SparkSQL to access Hive tables compared to using JDBC to read tables from SQL server?

I just got this question while designing the storage part for a Hadoop-based platform. If we want to have data scientists to have access to the tables which have already been stored in a relational database (e.g.SQL-server of a Azure Virtual Machine), then will there be any particular benefits if we import the tables from SQL-server to HDFS (e.g. WASB) and create Hive tables on top of them?
In other words, since Spark allows users to read data from other databases using JDBC,is there any performance improvement if we persist the tables from the database in appropriate format (avro, parquet etc.) in HDFS and use SparkSQL to access them using HQL?
I am sorry if this question has been asked, I have done some research but could not get a comparison between the two methodologies.
I think there will be a big performance improvement as the data is local (assuming Spark is running on same Hadoop cluster where the data is stored on HDFS). Using JDBC if the actions/processing performed is interactive then user has to wait for the data to be loaded through JDBC from another machine (N/W latency and IO throughput) whereas if that is done upfront then user (data scientist) can concentrate on performing the actions straight away.

Apache Spark vs Apache Ignite [closed]

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Currently I'm studying Apache spark and Apache ignite frameworks.
Some principle differences between them are described in this article ignite vs spark But I realized that I still don't understand their purposes.
I mean for which problems spark more preferable than ignite and vice versa?
I would say that Spark is a good product for interactive analytics, while Ignite is better for real-time analytics and high performance transactional processing. Ignite achieves this by providing efficient and scalable in-memory key-value storage, as well as rich capabilities for indexing, querying the data and running computations.
Another common use for Ignite is distributed caching, which is often used to improve performance of applications that interact with relational databases or any other data sources.
Apache Ignite is a high-performance, integrated and distributed in-memory platform for computing and transacting on large-scale data sets in real-time.Ignite is a data-source-agnostic platform and can distribute and cache data across multiple servers in RAM to deliver unprecedented processing speed and massive application scalability.
Apache Spark(cluster computing framework) is a fast, in-memory data processing engine with expressive development APIs to allow data workers to efficiently execute streaming, machine learning or SQL workloads that require fast iterative access to datasets.
By allowing user programs to load data into a cluster’s memory and query it repeatedly, Spark is well suited for high-performance computing and machine learning algorithms.
Some conceptual differences:
Spark doesn’t store data, it loads data for processing from other storages, usually disk-based, and then discards the data when the processing is finished. Ignite, on the other hand, provides a distributed in-memory key-value store (distributed cache or data grid) with ACID transactions and SQL querying capabilities.
Spark is for non-transactional, read-only data (RDDs don’t support in-place mutation), while Ignite supports both non-transactional (OLAP) payloads as well as fully ACID compliant transactions (OLTP)
Ignite fully supports pure computational payloads (HPC/MPP) that can be “dataless”. Spark is based on RDDs and works only on data-driven payloads.
Conclusion:
Ignite and Spark are both in-memory computing solutions but they target different use cases.
In many cases, they are used together to achieve superior results:
Ignite can provide shared storage, so the state can be passed from one Spark application or job to another.
Ignite can provide SQL with indexing so Spark SQL can be accelerated over 1,000x (spark doesn’t index the data)
When working with files instead of RDDs, the Apache Ignite In-Memory File System (IGFS) can also share state between Spark jobs and applications
Does Spark and Ignite works together?
Yes, Spark and Ignite works together.
In short
Ignite vs. Spark
Ignite is an in-memory distributed database more focused on data storage and handles transnational updates on data, then serves client requests. Apache Spark is an MPP compute engine which is more inclined towards analytics, ML, Graph, and ETL specific payloads.
In detail
Apache Spark is an OLAP tool
Apache Spark is a general-purpose cluster computing system. It's an optimized engine that supports general execution graphs. It also supports a rich set of higher-level tools including Spark SQL for SQL and structured data processing, MLlib for machine learning, GraphX for graph processing, and Spark Streaming.
Spark with other components
Deployment topology
Spark on YARN typology is discussed here.
Apache Ignite is an OLTP tool
Ignite is a memory-centric distributed database, caching, and processing platform for transnational, analytical, and streaming workloads delivering in-memory speeds at the petabyte scale. Ignite also includes first-class level support for cluster management and operations, cluster-aware messaging, and zero-deployment technologies. Ignite also provides support for full ACID transactions spanning memory and optional data sources.
SQL Overview
Deployment topology
Apache Spark is a processing framework. You tell it where to get data, provide some code about how to process that data, and then tell it where to put the results. It's a way to easily reliably run computing logic across a bunch of nodes in a cluster on data from any source (which is then kept in-memory during processing). It's primarily meant for large-scale analysis on data from various sources (even from multiple databases at once), or from streaming sources like Kafka. It can also be used for ETL, like transforming and joining data together before putting the final results in some other database system.
Apache Ignite is more of an in-memory distributed database, at least that's how it started. It has a key/value and SQL API, so you can store and read data in various ways, and run queries like you would any other SQL database. It also supports running your own code (similar to Spark) so you can do processing that wouldn't really work with SQL, while also reading and writing the data all in the same system. It also can read/write data to other database systems while acting as a cache layer in the middle. Eventually, as of 2018, it also supports on-disk storage so now you can use it as an all-in-one distributed database, cache, and processing framework.
Apache Spark is still better for more complex analytics, and you can have Spark read data from Apache Ignite, but for many scenarios it's now possible to consolidate processing and storage into a single system with Apache Ignite.
Although Apache Spark and Apache Ignite utilize the power of in-memory computing, they address different use cases. Spark processes but doesn’t store data. It loads the data, processes it, then discards it. Ignite, on the other hand, can be used to process data and it also provides a distributed in-memory key-value store with ACID compliant transactions and SQL support.
Spark is also for non-transactional, read-only data while Ignite supports non-transactional and transactional workloads. Finally, Apache Ignite also supports purely computational payloads for HPC and MPP use cases while Spark works only on data-driven payloads.
Spark and Ignite can complement each other very well. Ignite can provide shared storage for Spark so state can be passed from one Spark application or job to another. Ignite can also be used to provide distributed SQL with indexing that accelerates Spark SQL by up to 1,000x.
By Nikita Ivanov: http://www.odbms.org/blog/2017/06/on-apache-ignite-apache-spark-and-mysql-interview-with-nikita-ivanov/
Although both Apache Spark and Apache Ignite utilize the power of in-memory computing, they address somewhat different use cases and rarely “compete” for the same task. Some conceptual differences:
Spark doesn’t store data, it loads data for processing from other storages, usually disk-based, and then discards the data when the processing is finished. Ignite, on the other hand, provides a distributed in-memory key-value store (distributed cache or data grid) with ACID transactions and SQL querying capabilities.
Spark is for non-transactional, read-only data (RDDs don’t support in-place mutation), while Ignite supports both non-transactional (OLAP) payloads as well as fully ACID compliant transactions (OLTP)
Ignite fully supports pure computational payloads (HPC/MPP) that can be “dataless”. Spark is based on RDDs and works only on data-driven payloads.
I am late to answer this question, but let me try to share my view on this.
Ignite may not be ready to use in production for enterprise application as some important features such as Security is only available in Gridgain(wrapper over Ignite)
Complete list of features can be found from below link
https://www.gridgain.com/products/gridgain-vs-ignite

Can we use Apache Spark to store Data? or is it only a Data processing tool?

I am new to Apache Spark, I would like to know is it possible to store data using Apache Spark. Or is it only a processing tool?
Thanks for spending your time,
Satya
Spark is not a database so it cannot "store data". It processes data and stores it temporarily in memory, but that's not presistent storage.
In real life use-case you usually have database, or data repository frome where you access data from spark.
Spark can access data that's in:
SQL Databases (Anything that can be connected using JDBC driver)
Local files
Cloud storage (eg. Amazon S3)
NoSQL databases.
Hadoop File System (HDFS)
and many more...
Detailed description can be found here: http://spark.apache.org/docs/latest/sql-programming-guide.html#sql
Apache Spark is primarily processing engine. It works with underlying file systems such as HDFS, s3 and other supported file systems. It has capabilities to read the data from relational databases as well. But primarily it is in memory distributed processing tool.
As you can read in Wikipedia, Apache Spark is defined as:
is an open source cluster computing framework
When we refer about computing, it's related to a processing tool, in essence it allows to work as a pipeline scheme (or somehow ETL), you read the dataset, you process the data, and then you store the data processed, or models that describe the data.
If your main objective is to distribute your data, there are some good alternatives like HDFS (Hadoop File System), and others.

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