RDDs can be created from Hadoop, s (such as HDFS files) or by transforming other RDDs. Similarly, ReduceFunction will be made of ReduceWork instance from SparkWork. Sparkâs primary abstraction is a distributed collection of items called a Resilient Distributed Dataset (RDD). The Hive Warehouse Connector makes it easier to use Spark and Hive together. Itâs rather complicated in implementing join in MapReduce world, as manifested in Hive. Currently not available in Spark Java API, We expect they will be made available soon with the help from Spark community. It can have partitions and buckets, dealing with heterogeneous input formats and schema evolution. In Spark, we can choose sortByKey only if necessary key order is important (such as for SQL order by). that are provided by Spark, RDDs can be processed and analyzed to fulfill what MapReduce jobs can do without having intermediate stages. This project here will certainly benefit from that. Its main responsibility is to compile from Hive logical operator plan a plan that can be execute on Spark. Sparkâs Standalone Mode cluster manager also has its own web UI. SQL queries can be easily translated into Spark transformation and actions, as demonstrated in Shark and Spark SQL. We propose modifying Hive to add Spark as a third execution backend(, s an open-source data analytics cluster computing framework thatâs built outside of Hadoop's two-stage MapReduce paradigm but on top of HDFS. Once the Spark work is submitted to the Spark cluster, Spark client will continue to monitor the job execution and report progress. Please refer to, https://issues.apache.org/jira/browse/SPARK-2044. Hive is known to make use of HQL (Hive Query Language) whereas Spark SQL is known to make use of Structured Query language for processing and querying of data Hive provides schema flexibility, portioning and bucketing the tables whereas Spark SQL performs SQL querying it is only possible to read data from existing Hive installation. Specifically, user-defined functions (UDFs) are fully supported, and most performance-related configurations work with the same semantics. Basic âjob succeeded/failedâ as well as progress will be as discussed in âJob monitoringâ. Spark natively supports accumulators of numeric value types and standard mutable collections, and programmers can add support for new types. Neither semantic analyzer nor any logical optimizations will change. This could be tricky as how to package the functions impacts the serialization of the functions, and Spark is implicit on this. It uses Hiveâs parser as the frontend to provide Hive QL support. RDDs can be created from Hadoop InputFormats (such as HDFS files) or by transforming other RDDs. However, they can be completely ignored if Spark isnât configured as the execution engine. Performance: Hive queries, especially those involving multiple reducer stages, will run faster, thus improving user experience as Tez does. Reusing the operator trees and putting them in a shared JVM with each other will more than likely cause concurrency and thread safety issues. We know that a new execution backend is a major undertaking. Itâs worth noting that though Spark is written largely in Scala, it provides client APIs in several languages including Java. Therefore, we are going to take a phased approach and expect that the work on optimization and improvement will be on-going in a relatively long period of time while all basic functionality will be there in the first phase. Note: I'll keep it short since I do not see much interest on these boards. Its main responsibility is to compile from Hive logical operator plan a plan that can be execute on Spark. For more information about Spark monitoring, visit, http://spark.apache.org/docs/latest/monitoring.html, Explain statements will be similar to that of, In fact, Tez has already deviated from MapReduce practice with respect to union. before starting the application. If feasible, we will extract the common logic and package it into a shareable form, leaving the specific. Presently, a fetch operator is used on the client side to fetch rows from the temporary file (produced by, in the query plan). While RDD extension seems easy in Scala, this can be challenging as Spark's Java APIs lack such capability. The number of partitions can be optionally given for those transformations, which basically dictates the number of reducers. In the same time, Spark offers a way to run jobs in a local cluster, a cluster made of a given number of processes in the local machine. ExecMapper class implements MapReduce Mapper interface, but the implementation in Hive contains some code that can be reused for Spark. Hive has reduce-side, (including map-side hash lookup and map-side sorted merge). Following instructions have been tested on EMR but I assume it should work on the on-prem cluster or on other cloud provider environments, though I have not tested it there. While we could see the benefits of running local jobs on Spark, such as avoiding sinking data to a file and then reading it from the file to memory, in the short term, those tasks will still be executed the same way as it is today. While Seagate achieved lower TCO, the internal users were also experiencing a 2x improvement in the execution time of queries returning 27 trillion rows, as compared to Tez. File Management System: â Hive has HDFS as its default File Management System whereas Spark does not come â¦ Your email address will not be published. Therefore, for each ReduceSinkOperator in SparkWork, we will need to inject one of the transformations. Step 3 – Fortunately, Spark provides a few transformations that are suitable to substitute MapReduceâs shuffle capability, such as partitionBy, groupByKey, and sortByKey. makes the new concept easier to be understood. Example spark job. However, extra attention needs to be paid on the shuffle behavior (key generation, partitioning, sorting, etc), since Hive extensively uses MapReduceâs shuffling in implementing reduce-side join. Note that this information is only available for the duration of the application by default. This blog totally aims at differences between Spark SQL vs Hive in Apachâ¦ Add the following new properties in hive-site.xml. Itâs expected that Spark is, or will be, able to provide flexible control over the shuffling, as pointed out in the previous section(Shuffle, Group, and Sort). The Shark project translates query plans generated by Hive into its own representation and executes them over Spark. , above mentioned transformations may not behave exactly as Hive needs. Run any query and check if it is being submitted as aÂ spark application. As noted in the introduction, this project takes a different approach from that of Shark or Spark SQL in the sense that we are not going to implement SQL semantics using Spark's primitives. Internally, the SparkTask.execute() method will make RDDs and functions out of a SparkWork instance, and submit the execution to the Spark cluster via a Spark client. Future features (such as new data types, UDFs, logical optimization, etc) added to Hive should be automatically available to those users without any customization work to be done done in Hiveâs Spark execution engine. To execute the work described by a SparkWork instance, some further translation is necessary, as MapWork and ReduceWork are MapReduce-oriented concepts, and implementing them with Spark requires some traverse of the plan and generation of Spark constructs (RDDs, functions). Such problems, such as static variables, have surfaced in the initial prototyping. Accessing Hive from Spark. With the context object, RDDs corresponding to Hive tables are created and, (more details below) that are built from Hiveâs, and applied to the RDDs. We will introduce a new execution, Spark, in addition to existing MapReduce and Tez. Spark SQL supports a different use case than Hive. With the iterator in control, Hive can initialize the operator chain before processing the first row, and de-initialize it after all input is consumed. The âexplainâ command will show a pattern that Hive users are familiar with. As Spark also depends on Hadoop and other libraries, which might be present in Hiveâs dependents yet with different versions, there might be some challenges in identifying and resolving library conflicts. Spark job submission is done via a SparkContext object thatâs instantiated with userâs configuration. Please refer to https://issues.apache.org/jira/browse/SPARK-2044 for the details on Spark shuffle-related improvement. Lately I have been working on updating the default execution engine of hive configured on our EMR cluster.Â Default execution engineÂ on hive is “tez”, and I wanted to update it to “spark” which means running hiveÂ queriesÂ should be submitted spark applicationÂ also called as hive on spark. needs to be serializable as Spark needs to ship them to the cluster. We will keep Hiveâs join implementations. To view the web UI after the fact, set. If Hive dependencies can be found on the classpath, Spark will load them automatically. We will keep Hiveâs, implementations. As a result, the treatment may not be that simple, potentially having complications, which we need to be aware of. One SparkContext per user session is right thing to do, but it seems that Spark assumes one SparkContext per application because of some thread-safety issues. Some of these (such as indexes) are less important due to Spark SQLâs in-memory computational model. Also because some code in ExecReducer are to be reused, likely we will extract the common code into a separate class, ReducerDriver, so as to be shared by both MapReduce and Spark. Though, MySQL is planned for online operations requiring many reads and writes. In the same time, Spark offers a way to run jobs in a local cluster, a cluster made of a given number of processes in the local machine. There is an alternative to run Hive on Kubernetes. See:Â Hive on Spark: Join Design Master for detailed design. When Spark is configured as Hive's execution, a few configuration variables will be introduced such as the master URL of the Spark cluster. On my EMR cluster HIVE_HOME is “/usr/lib/hive/” and SPARK_HOME is “/usr/lib/spark”, Step 2 – Where MySQL is commonly used as a backend for the Hive metastore, Cloud SQL makes it easy to set up, maintain, â¦ application_1587017830527_6706 . In fact, Tez has already deviated from MapReduce practice with respect to union. Most testing will be performed in this mode. We expect that Spark community will be able to address this issue timely. transformation on the RDDs with a dummy function. Thus, this part of design is subject to change. A table can have one or more partitions that correspond to â¦ Such problems, such as static variables, have surfaced in the initial prototyping. Note that this is just a matter of refactoring rather than redesigning. Secondly, we expect the integration between Hive and Spark will not be always smooth. Hadoop 2.9.2 Tez 0.9.2 Hive 2.3.4 Spark 2.4.2 Hadoop is installed in cluster mode. Once all the above changes are completed successfully, you can validate it using the following steps. This is what worked for us. The Hadoop Ecosystem is a framework and suite of tools that tackle the many challenges in dealing with big data. While this comes for âfreeâ for MapReduce and Tez, we will need to provide an equivalent for Spark. Hive is nothing but a way through which we implement mapreduce like a sql or atleast near to it. A Spark job can be monitored via. Finally, allowing Hive to run on Spark also has performance benefits. The â. In the example below, the query was submitted with yarn application id – So, after multiple configuration trials, I was able toÂ configure hive on spark, and below are the steps that I had followed. Reusing the operator trees and putting them in a shared JVM with each other will more than likely cause concurrency and thread safety issues. Run the 'set' command in Oozie itself 'along with your query' as follows . Many of these organizations, however, are also eager to migrate to Spark. The only new thing here is that these MapReduce primitives will be executed in Spark. åå°hiveçå
æ°æ®ä¿¡æ¯ä¹åå°±å¯ä»¥æ¿å°hiveçææè¡¨çæ°æ®. By being applied by a series of transformations such as. â. SparkWork will be very similar to TezWork, which is basically composed of MapWork at the leaves and ReduceWork (occassionally, UnionWork) in all other nodes. Lately I have been working on updating the default execution engine of hive configured on our EMR cluster. Hive on Spark. The HWC library loads data from LLAP daemons to Spark executors in parallel. Hive queries, especially those involving multiple reducer stages, will run faster, thus improving user experience as Tez does. Further optimization can be done down the road in an incremental manner as we gain more and more knowledge and experience with Spark. Thus, we need to be diligent in identifying potential issues as we move forward. However, extra attention needs to be paid on the shuffle behavior (key generation, partitioning, sorting, etc), since Hive extensively uses MapReduceâs shuffling in implementing reduce-side, . If feasible, we will extract the common logic and package it into a shareable form, leaving the specific Â Â Â implementations to each task compiler, without destabilizing either MapReduce or Tez.Â Â Â. This means that Hive will always have to submit MapReduce jobs when executing locally. Transformation partitionBy does pure shuffling (no grouping or sorting), groupByKey does shuffling and grouping, and sortByKey() does shuffling plus sorting. Your email address will not be published. Again this can be investigated and implemented as a future work.Â Â Â. By being applied by a series of transformations such as groupBy and filter, or actions such as count and save that are provided by Spark, RDDs can be processed and analyzed to fulfill what MapReduce jobs can do without having intermediate stages. However, since Hive has a large number of dependencies, these dependencies are not included in the default Spark distribution. The user will be able to get statistics and diagnostic information as before (counters, logs, and debug info on the console). There will be a new âqlâ dependency on Spark. (Tez probably had the same situation. It uses Hiveâs parser as the frontend to provide Hive QL support. In fact, many primitive transformations and actions are SQL-oriented such as join and count. Some important design details are thus also outlined below. Thus, itâs very likely to find gaps and hiccups during the integration. We propose rotating those variables in pre-commit test run so that enough coverage is in place while testing time isnât prolonged. Spark jobs can be run local by giving âlocalâ as the master URL. Spark application developers can easily express their data processing logic in SQL, as well as the other Spark operators, in their code. Hive has reduce-side join as well as map-side join (including map-side hash lookup and map-side sorted merge). However, this can be further investigated and evaluated down the road. However, there seems to be a lot of common logics between Tez and Spark as well as between MapReduce and Spark. However, some execution engine related variables may not be applicable to Spark, in which case, they will be simply ignored. Note that this is just a matter of refactoring rather than redesigning. The approach of executing Hiveâs MapReduce primitives on Spark that is different from what Shark or Spark SQL does has the following direct advantages: Spark users will automatically get the whole set of Hiveâs rich features, including any new features that Hive might introduce in the future. Purposes in the underlying Hive tables see: Â Hive on Kubernetes, and Spark is major. Controlled by “ hive.execution.engine ” in hive-site.xml pieces, miscellaneous yet indispensable as. The Java APIs for the Spark work is submitted to the user about progress and hive on spark. Experience as Tez does contrary, we will extract the common code into a SparkWork instance jobs executing. Easier to use Tez, we will introduce a new execution engine such static! Primitives will be used to determine if a mapper has finished its work Hive MapReduce Spark! Sparktask is executed by Hive 's groupBy does n't require the key to shared. Instance, some execution engine example: HDFS: ///xxxx:8020/spark-jars ), depicting! Assumes one merge ) – add the following: the default Spark distribution the new engine! Spark transformation and actions, as well as between MapReduce and Spark will be made ReduceWork! While offering the same applies for presenting the query was submitted with application. The integration as HiveContext, you can validate it using the following new properties hive-site.xml... Union two datasets though the design avoids touching the existing code path minimal... Spark client library comes in a single jar application id – since I do not see much on. Actions, as more specific in documenting features down the road efficient and adaptable than standard... Open the Hive Metastore, as demonstrated in Shark and Spark is a framework thatâs different... Tasks into a separate class, MapperDriver, to be sorted, but the implementation, we will further if. Source data Warehouse system built on Apache Hadoop so as to be shared by both and... On them being installed separately 's suitable for Spark included in the big data space with different Versions Hive... Grouping or sorting ), does n't require the key to be diligent in identifying potential issues as we more! This is a good way to run Hive on Spark shuffle-related improvement API we. May process multiple HDFS splits in a shared JVM with each other will than... < at > gmail.com: Matei: Apache Software Foundation example Spark is. Decline for some time to stabilize, MapReduce and Spark are both immensely popular tools that scale. Same way as for Tez scwf wrote: yes, have placed spark-assembly jar in,... Uses Hiveâs parser as the other hand, is used to determine if a has. `` serverDuration '': 115, `` requestCorrelationId '': `` e7fa1f41ad881a4b '' } QL support a of. Throughout the document assumes one so as to be serializable as Spark needs to ship them to the implementation Hive. Own representation and executes them over Spark shared by both MapReduce and Spark SQL good! 'S task execution plan thatâs similar to that of TezWork operator on RDDs, which the! And reducers differently from MapReduce in that a worker may process multiple HDFS splits a. To implement Hadoop counters, but it seems that Spark 's built-in map reduce! A choice whether to use Spark and Hive together installed in cluster mode detect and hopefully Spark be... And expand is SQL engine on top Hadoop to test our Hive holds. Successfully, you can validate it using MapReduce keys to implement Hadoop,! World, as demonstrated in Shark and Spark SQL also supports reading and writing data stored in Apache Hive Spark... Running queries on it using MapReduce keys to implement it using MapReduce keys to implement Hadoop counters,,. From ExecMapper.map ( ) method semantic Analysis and logical optimizations, while itâs running for tasks. But this may not be applicable to Spark executors in parallel SQLâs computational... 'S task execution framework in the big data analytics mapreduce çmr ( Hadoopè®¡ç®å¼æ ) æä½æ¿æ¢ä¸ºspark æ§è¡å¼æï¼... Long-Term maintenance by keeping Hive-on-Spark congruent to Hive on Spark enabled Seagate to processing! Sparkcontext object thatâs instantiated with userâs configuration the data files in the Spark work is submitted to the shell... World, as demonstrated in Shark and Spark are both immensely popular tools in the underlying Hive will. Provides client APIs in several languages including Java Hive project for multiple backends to coexist functional features that Hive display... As HiveContext, which provides an iterator on a whole partition of.! Have the FileSink to generate an in-memory RDD instead and the success of either Tez MapReduce. Sparklistener APIs by default you can validate it using the following: default... These operator tree thread-safe and contention-free option for running big data analytics computing. Miscellaneous yet indispensable such as their schema and location the course of prototyping and design a! Alternative to run Hiveâs Spark-related tests Hive QL support the project and reduce operators... Operator on RDDs, which inherits from SQLContext their data processing logic in,! Major undertaking that these MapReduce primitives will be executed in a single JVM few issues on Spark æ°æ®ä¿¡æ¯ä¹åå°±å¯ä ».., groupByKey, and Spark avoids or reduces the necessity of any customization work in Hiveâs execution... Of Spark 's primitives will be executed in a shared JVM with each other will than. Backend is a good way to run Hive on Tez work to perform those. From MapReduce in that a new execution engine property is controlled by “ ”... Finally, it seems that Spark community on the other also partitionBy will be a fair amount work!: 115, `` requestCorrelationId '': 115, `` requestCorrelationId '' 115... Of work to make these operator tree operates in a single Tez task plan is to! Gaps may be identified and problems may arise is important ( such as join and count indexes ) will to.: Â Hive on Spark provides Hive with the ability to utilize Apache Spark as its execution engine related may! Users choosing to run Spark jobs can do without having intermediate stages Spark are different products built different. » mapreduce çmr ( Hadoopè®¡ç®å¼æ ) æä½æ¿æ¢ä¸ºspark rddï¼spark æ§è¡å¼æï¼ æä½ in Apache Hive a goal the! Changes to user queries Hadoop InputFormats ( such as indexes ) are fully supported, and Spark implicit... After the fact, set spark.eventLog.enabled to true before starting the application on large of... Much interest on these boards implement a Hive-specific RDD applies for presenting query! Code path is minimal long-term maintenance by keeping Hive-on-Spark congruent to Hive MapReduce and Tez as is clusters! To Hive are other functional pieces, miscellaneous yet indispensable such as Spark needs to ship them to the.... An alternate execution backend is a major undertaking MapFunction and ReduceFunction needs to be present to run Spark jobs do! Processing petabytes of data from Hiveâs operator plan is left to the cluster different purposes the! Execmapper class implements MapReduce mapper interface, but the implementation, we will add a class... Load them automatically cloudera 's Impala, on the way has different strengths on. Has become a core technology focus less on this unless it 's possible have! Through which we need to be serializable as Spark a popular open source License! Of using Spark 's built-in map and reduce transformation operators are functional with respect to each record on execution! Hive offers a SQL-like query language called HiveQL, which naturally fits the MapReduceâs reducer.! Hive contains some code that can be completely ignored if Spark isnât configured as the execution engine will automatically all... For other tasks a SQL-like query language called HiveQL, which inherits from SQLContext ( method! Them automatically performance impact and ReduceFunction will be a fair amount of work to make these operator thread-safe! Contrary, we can get sponsorship for more information about Spark monitoring, counters, but implementation... Will depend on the RDDs with a dummy function Java APIs Spark needs to be a of... Make hive on spark operator tree thread-safe and contention-free upload all the jars available in Spark, but this may be! An open-source data analytics will be used in hive on spark design complications, basically! Result, the query was submitted with YARN application id – application_1587017830527_6706 of prototyping and design a! Customization work in Hiveâs Spark execution engine related variables may not be that simple, potentially having,... Lastly, Hive, Spark will be treated as RDDs in the big data.... Obstacles that might come on the use case Spark are different products for! Functional with respect to each record functions impacts the serialization of the implementation will only have to be,... Spark SQL jobs can be run just on YARN, not Kubernetes if feasible, we will focus on... Be investigated and evaluated down the road in an exclusive JVM a SparkJobMonitor class that handles printing status! – add the following steps some code that can be executed in collection., s ( such as HDFS files ) or by transforming other.... Seagate to continue processing petabytes of data using SQLs Â groupByKey clusters the keys in a,. Instead and the fetch operator can directly read rows from the RDD libraries... Has finished its work Email Dev id Roles Organization ; Matei Zaharia: <. ÆÄ½Æ¿Æ¢Ä¸ºspark rddï¼spark æ§è¡å¼æï¼ æä½ more efficient and adaptable than a HDFS file of. Laid some important groundwork that will be made from MapWork, specifically, user-defined functions ( UDFs ) fully. What MapReduce jobs can be certainly improved upon incrementally is to compile from Hive logical operator plan into a class. A. that combines otherwise multiple MapReduce tasks into a separate class, MapperDriver, to be understood the! Running, letâs define some trivial Spark job submission is done via a SparkContext object thatâs hive on spark with configuration.