Hadoop @ eBay Marketplaces

1. Hadoop @ eBay Marketplaces Ming Ma June 27th, 2013

2. Overview Hadoopgrowth @ eBay Marketplaces Availability study Opportunities ahead

3. Big Data @ eBay Marketplaces 120+ Million Active users 300+ Million search queries every single day 350+ Million items available hadoop @ eBay Marketplaces

4. Data Sets • Inventory Data • Product Listings, Catalogue, Quantity etc. • Transactional Data • Buying, Returning etc. • User Behavioral Data • Click stream, comments, suggestions, user activities etc. • Customer profiles • Buyer, Seller, Partner information etc. • Machine data • Logs, application data etc. hadoop @ eBay Marketplaces

5. Hadoop Evolution @ eBay Marketplaces • 2013 • Shared clusters • 4k+ node • 40,000+ core • 50s PB • HDP • 2012 • Shared clusters • 1000s node • 10,000+ core • 10s PB • 2011 • Shared clusters • 1000s node • 10,000+ core • 10s PB • Wilma (0.20) • 2010 • Shared cluster • 100s nodes • 1000s + core • PB • CDH2 • 2009 • Search • 10s- nodes • 2007 • Single digit nodes hadoop @ eBay Marketplaces

6. Dedicated clusters Very specific use cases like Index Building Tight SLAs for jobs (in order of minutes) Immediate revenue impact Usually smaller than our shared clusters, but still big (100s of nodes…) Shared vs. Dedicated Clusters Shared clusters • 10s of PB and 10s of thousands of slots per cluster • Run HDP 1.2 • Used primarily for analytics of user behavior and inventory • Mix of production and ad-hoc jobs • Mix of MR, Hive, PIG, Cascading etc. • Hadoop and HBase security enabled hadoop @ eBay Marketplaces

7. Job Distribution by Type hadoop @ eBay Marketplaces

8. Use Case Examples • Cassini, full re-write of eBay’s search engine: • Use MR to build full and incremental near-real-time indexes • Data for indexing is stored in HBase for efficient updates and random read • Strong SLAs • Run on dedicated clusters • Related and similar Items recommendations: • Use transactional data, click stream data, search index, etc. • Production MR jobs on a shared cluster • Analytics dashboard: • Run Mobius MR jobs to join click stream data and transactional data • Store summary data in HBase • Web application to query HBase hadoop @ eBay Marketplaces

9. eBay Hadoop Data Platform Tools Clients Data Catalog ETL Monitor Java Pig Mobius Scala Hive Cascading Metadata Mgmt User Mgmt Data Ingest Data Access Java POJO Hive UDF Extract Transform Pig UDF Load Validate Metadata Metastore Type System API Service Hadoop Behavioral Transactional Inventory hadoop @ eBay Marketplaces

10. Platform Innovation • Many reliability improvements • New Security features • Multi-realm support • Encryption • https in hadoop 1 • Hadoop 2.0 • MR 1 and YARN binary compatibility • Automation for operations • Machine decommission and re-commission process • Data and user management • Metadata management • User account provisioning hadoop @ eBay Marketplaces

11. Overview Hadoopgrowth @ eBay Availability study Next steps

12. Case study – defective applications • HBase: A test app created heavy write load • Test app used all region server RPC threads • All RPCs are blocked by region flush • RPC requests from production HBase MR job timed out • HDFS: An app created lots of small files inside map tasks • NN RPC Queue length spiked • DN heartbeat RPC can’t be processed • HDFS replication storm hadoop @ eBay Marketplaces

13. Case study – platform bugs • Hadoop: • DFSClient.LeaseChecker thread leak in job tracker -> bi-weekly JT restart • dfs.datanode.balance.bandwidthPerSec set to 200MB -> big performance impact • JVM: • leap second bug -> All clusters were down the same time • GC setting -> NN full GC happened regularly • OS: • “Divide by zero” in CentOS and RH 6.1 -> machine reboot hadoop @ eBay Marketplaces

14. Case study – cluster maintenance • Code rollout: • NN SPOF • RPC compatibility between old and new versions • Hadoopconfiguration change: • Likely required Hadoop JVM restart • Rolling restart has impact on job latency • Datanode rolling restart caused HBase region servers to exit • Machines re-commission: • Hadoop version drift • OS configuration bug reappeared hadoop @ eBay Marketplaces

15. Metrics • Definition: • Availability = MTBF ( mean time between failure ) / MTBF + MDT ( mean down time ) • Down time includes planned maintenance • Measurement: • Synthetic transactionapproach • Run regular canary work count MR job • Canary job times out in X minutes hadoop @ eBay Marketplaces

16. More about metrics • Availability != MTTR ( mean time to recover ) • MTTR is more important for applications like Cassini index build • What is considered “available”? • Performance degradation • % of live slave nodes • Other entry points such as Web UI • Core data set availability • Multi-tenancy scenario hadoop @ eBay Marketplaces

17. Ways to improve availability • Automation • Use puppet and daemontools • Monitor system health • Redundancy • Namenode HA • Hot standby region server • Isolation • HDFS federation • Region server grouping • Congestion control • RPC congestion control, Hadoop-9640 • Apply to both HDFS and HBase • Features to enable “no downtime maintenance” • Dynamic configuration update • RPC compatibility • Better ways to do rolling restart hadoop @ eBay Marketplaces

18. Overview Hadoopgrowth @ eBay Availability study Next steps

19. Opportunities ahead • More automation • Availability and scalability • Hadoop 2.0 • HBase fast recovery time • Multi-tenancy • Run production jobs with strong SLAs in big shared clusters • QoS in HDFS and HBase • New scenarios • Interactive Analysis with SQL language • Direct Hadoop Access from dev machines hadoop @ eBay Marketplaces