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Apache Accumulo 1.8.0 Overview

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This talk will be an overview of the new features and improvements currently implemented for the Apache Accumulo 1.8.0 release. This will be a discussion about some of these exciting changes with a focus on what is of the most importance for users.

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Apache Accumulo 1.8.0 Overview

  1. 1. Apache Accumulo 1.8.0 Overview Josh Elser Apache Accumulo Meetup Group 2016/06/27
  2. 2. 2 © Hortonworks Inc. 2011 – 2016. All Rights Reserved Apache Accumulo 1.8.0  First release candidate in the works  A “minor” release, but significantly more work required than a “patch” release – ContinuousIngest and verification – RandomWalk  Long time coming..
  3. 3. 3 © Hortonworks Inc. 2011 – 2016. All Rights Reserved Semantic Versioning  Defines a set of rules for software projects to adhere to across different versions.  Clear understanding on compatibility  Rules are defined in terms of a “public API” – Defined by the project adopting SemVer  Major – Incompatible changes, deprecations removed  Minor – Backwards-compatible features added  Patch – Backwards-compatible bug-fixes only (no features) http://semver.org - major.minor.patch
  4. 4. 4 © Hortonworks Inc. 2011 – 2016. All Rights Reserved Apache Accumulo and Semantic Versioning  Apache Accumulo defines a public API – Made up of Java classes, defined by packages – The goal is to describe how user code should function across releases – Recursively, all public types in (excluding impl, thrift, or crypto) • org.apache.accumulo.core.{client,data,security} • org.apache.accumulo.minicluster  Other concerns for compatibility too – RPC classes – Persistent data (RFiles and ZooKeeper)  Not comprehensive! – Not all user facing code is yet included in the public API • Monitoring UIs and data • Start/stop scripts • The Accumulo Shell
  5. 5. 5 © Hortonworks Inc. 2011 – 2016. All Rights Reserved Apache Accumulo and Semantic Versioning  Is it guaranteed that your application from 1.7.1 work against 1.8.0?  What about a 1.6.5 application?  Are you guaranteed to be able to roll back an upgrade from 1.8.0 to 1.7.1?  Is it guaranteed that your 1.8.0 application work against 1.7.0? POP QUIZ!
  6. 6. 6 © Hortonworks Inc. 2011 – 2016. All Rights Reserved Notable changes currently staged for Apache Accumulo 1.8.0
  7. 7. 7 © Hortonworks Inc. 2011 – 2016. All Rights Reserved System Administrator Changes  [ACCUMULO-925] - Launch scripts should use a PIDfile – New script: start-daemon.sh – Encapsulates only the things that need to happen on the machine starting a process • No SSH’ing – Support for PID files to track processes – Rotating .out and .err files on start • Critical for delayed JVM layer issues
  8. 8. 8 © Hortonworks Inc. 2011 – 2016. All Rights Reserved Performance!  [ACCUMULO-3423] - Speed up write-ahead log (WAL) roll-overs – Changes how references to WALs are stored by Accumulo – Reduces the number of writes when switching to a new WAL – Uses ZooKeeper to track the state, copies into tablet row before recovery starts – 10-30% faster over previous implementation (while exacerbating the problem)  [ACCUMULO-1124] - Optimize index size in RFile – RFiles have “data” and “index” blocks; index from RowID to data block containing that RowID – Large RowIDs bloat the index (e.g. inverted URL) – Fewer index blocks can be cached – Related work: [ACCUMULO-4164] and [ACCUMULO-4314]
  9. 9. 9 © Hortonworks Inc. 2011 – 2016. All Rights Reserved New Features  [ACCUMULO-3913] - Add per table sampling – Helpful in running analytics over some percentage of the total data – Can automatically create samples during compaction or on the fly using Iterators – Configurable hashing to ensure consistency across “index” and “data” tables • No dangling references index records or unreachable data records – Consider snapshot’ing a sample of a table. After compaction, just a “normal” table  [ACCUMULO-4187] - Rate limiting of major compactions – Compactions can strain system resources: hardware, JVM and HDFS – Normally, desirable to process compactions as fast as possible – Can negatively affect low-latency workloads – Configure a limit in bytes per seconds that a TabletServer should process during compaction
  10. 10. 10 © Hortonworks Inc. 2011 – 2016. All Rights Reserved New Features (pt.2)  [ACCUMULO-3948] - Enable A/B testing of scan iterators on a table – Classpath context is a definition of JARs which the TabletServer should dynamically load – Configuration allows a context to be specified when using a [Batch]Scanner – Multiple implementations of the same SKVIterator classes can co-exist – Useful in testing new implementations of iterators on real data before switching production  [ACCUMULO-626] - Create an iterator fuzz tester – Writing SKVIterators is notoriously difficult – Many common pitfalls and gotcha’s, often not appearing until “real” use – A testing framework codifies these edge cases and can automatically test iterators • Similar to ”security fuzzing” – Users must provide data sets and the expected outcome from using their SKVIterator – A supplement to unit testing and MiniAccumuloCluster, not a replacement – Test cases implicitly encourage good design of SKVIterators
  11. 11. 11 © Hortonworks Inc. 2011 – 2016. All Rights Reserved New APIs  [ACCUMULO-2883] - Add API to fetch current locations of Tablets – Long-standing feature request (order of years) – Extremely useful for distributed execution engines for locality aware computation • Apache Hive, Presto, Apache Drill, Apache Spark, etc – Smart placement can reduce client <--> Accumulo network traffic • Locality with Accumulo Tablets also implies locality with HDFS data (over time)  [ACCUMULO-4165] - Create a user level API for RFile – Example of a “glaring” hole in the public API – Only stable way to create an RFile is via MapReduce – Provides a supported API for reading and writing RFiles – Simplifies implementation and use of RFile access internally too
  12. 12. 12 © Hortonworks Inc. 2011 – 2016. All Rights Reserved Changes to be wary of  [ACCUMULO-3409] - Move default ports out of ephemeral range – Traditional ephemeral range on Linux: [32768, 61000] – Transient connections can prevent processes from starting – Monitor HTTP port moves from 50095 to 9995  [ACCUMULO-4077] - Upgrade to Apache Thrift 0.9.3 – Thrift is used by Accumulo for RPCs – Serialized messages are compatible (with caveats) across releases, but Java classes are not – A massive pain for downstream integrations – If you require a different version of Thrift and want to use Accumulo 1.8.0 • Shade+Relocate your version of Thrift in your application • Upgrade to Apache Thrift 0.9.3
  13. 13. 13 © Hortonworks Inc. 2011 – 2016. All Rights Reserved Thank You Email: elserj@apache.org Twitter: @josh_elser Mailing list: dev@accumulo.apache.org

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