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HBaseCon 2013: A Developer’s Guide to Coprocessors


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Presented by: John Weatherford, Telescope

Published in: Technology
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HBaseCon 2013: A Developer’s Guide to Coprocessors

  1. 1. A Developers Guide To Coprocessors Hbasecon 2013John Weatherford
  2. 2. Telescope is the leading provider of interactive television, audience participation and customer engagement solutions. Clients include TV networks, producers, digital platforms, studios, and sponsors seeking to reach, engage, and retain mass-audiences and consumers in real-time. Who Is Telescope?
  3. 3. Arbitrary code that can run on each server Extendthe functionality of Hbase Avoid bothering the core committers What Is A Coprocessor
  4. 4. Region 2 Endpoint Region 3 Post-Action Endpoint Endpoints Call a function explicitly Execute code on all regions Action Observers React to an event Run code before or after Two Types of Coprocessors Pre-ActionClient Region 1 Endpoint Client
  5. 5. What Can I Do With Coprocessors Ideas what can be done Access Control Secondary Indexes Optimized Search Data Aggregation Control compaction times Real Time Analytics Reduce result sets Cache Request Email split alerts
  6. 6. Getting Started With Code preGet(ObserverContext<RegionCoprocessorEnvironment> c, Get get, List<KeyValue> result) postGet(ObserverContext<RegionCoprocessorEnvironment> c, Get get, List<KeyValue> result) prePut(ObserverContext<RegionCoprocessorEnvironment> c, Put put, WALEdit edit, boolean writeToWAL) postPut(ObserverContext<RegionCoprocessorEnvironment> c, Put put, WALEdit edit, boolean writeToWAL) preDelete(ObserverContext<RegionCoprocessorEnvironment> c, Delete delete, WALEdit edit, boolean writeToWAL) postDelete(ObserverContext<RegionCoprocessorEnvironment> c, Delete delete, WALEdit edit, boolean writeToWAL)
  7. 7. Our First Observer Intercept and modify the action Consider all circumstances that will trigger the observer Compile your jar to the same version of Java running your Hbase Regions Look for output from the coprocessor
  8. 8. key: id-1332343 twitter:name: “loljk4u” twitter:message: “<3” twitter:length: 0x2 twitter:registered: 0xFF favorite:name: “Taylor” favorite:song: “I knew you were trouble” Our First Observer Motivation Apache flume only writes one column per put {twitter: { name: “loljk4u”, message: “<3”, length: 2, registered: true }, favorite: { name: “Taylor” ... JSON key: id-1332343 family: twitter qualifier: json_raw value: “{twitter: {name: “loljk4u”, message: “<3”, length: 2, registered: true ... Single Row Put preput() put
  9. 9. JsonColumnExpander //get the arguments on the coprocessor public void start(CoprocessorEnvironment env) throws IOException { Configuration c = env.getConfiguration(); families = c.get("families", "").split(":"); } public void prePut(ObserverContext<…> e, Put put, WALEdit edit, boolean waL) { if(!put.has(FAMILY, JSON_COLUMN)) { return; } //check for the json_raw column String json = Bytes.toString(put.get(FAMILY, JSON_COLUMN).get(0).getValue()); for(Entry<String, ?> column : columns.entrySet()) { //loop through the json String value = (String) column.getValue(); put.add(family, Bytes.toBytes(column.getKey()), Bytes.toBytes(value)); } //remove the original json from the put put.add(FAMILY, JSON_COLUMN, "--removed--".getBytes()); }
  10. 10. Loading the Coprocessor Push the jar to where your cluster can find it $>hadoop fs –put JsonColumnExpander.jar / Alter the table to enable the coprocessor $> alter „test', METHOD => 'table_att', 'coprocessor'=>'hdfs:///JsonColumnExpander.jar|telesco pe.hbase.JsonColumnExpander|1001|arg1=1,arg2=2„ Verify the load by checking the master web UI.
  11. 11. Running The Code Trigger the coprocessor with a put on the table Put put = new Put(“rowkey”); Put.add(“twitter”.toBytes(), “json_raw”.toBytes(), json_data); Check each server’s local logs http://regionnode:60030/logs/ hbase-hbase-regionserver-node2.
  12. 12. Creating Your First Endpoint Define the available methods a protocol Implement the protocol Extend BaseRegionEndpoint Load the endpoint on the table
  13. 13. Endpoint Example public interface TrendsProtocol extends CoprocessorProtocol{ HashMap<String, Long> getData() throws IOException; } //The endpoint class implements the protocol we wrote above public class TrendsEndpoint extends BaseEndpointCoprocessor implements TrendsProtocol { @Override public HashMap<String, Long> getTrends() throws IOException { RegionCoprocessorEnvironment environment = getEnvironment(); InternalScanner scanner = environment.getRegion().getScanner(s); try { List<KeyValue> curVals = new ArrayList<KeyValue>(); do { curVals.clear(); for(KeyValue pair : curVals){ //loop through values on the region and process } }while(!done); } } }
  14. 14. Endpoint Returned Results htable = HBaseDB.getTable(connection, “hbase_demo"); Map<byte[], HashMap<String, Long>> results = null; results = m_analytics.coprocessorExec( TrendsProtocol.class, null, //start row null, //end row new Batch.Call<TrendsProtocol, HashMap<String, Long>>(){ @Override public HashMap<String, Long> call(TrendsProtocol trends)throws IOException { return trends.getData(); } } ); for (Map.Entry<byte[], Boolean> entry : results.entrySet()) { //process results from each region server }
  15. 15. Addendum to Endpoints 0.96 is changing Endpoints to use protobuf public static abstract class RowCountService implements { ... public interface Interface { public abstract void getRowCount( controller, CountRequest request, done); public abstract void getKeyValueCount( controller, CountRequest request, done); } }
  16. 16. Telescope’s Coprocessors Observers collect real time analytics data for our moderation platform as well as to create aggregate tables for the steaming data Endpoints optimize searches and transmit only the necessary data. Perform simple reporting queries that don’t need the full power of mapreduce.
  17. 17. Questions? Alreadyusing coprocessors? I would love to hear about it. Curious to know more about a specific part? All code samples and table definitions can be found at