Cloudera Docs

Request a timeline-consistent read

You can use request a timeline-consistent read in your application.

To request a timeline-consistent read in your application, use the get.setConsistency(Consistency.TIMELINE) method before performing the Get or Scan operation.

To check whether the result is stale (comes from a secondary replica), use the isStale() method of the result object. Use the following examples for reference.

  • Get request 
    Get get = new Get(key);
get.setConsistency(Consistency.TIMELINE);
Result result = table.get(get);
  • Scan request 
    Scan scan = new Scan();
scan.setConsistency(CONSISTENCY.TIMELINE);
ResultScanner scanner = table.getScanner(scan);
Result result = scanner.next();
  • Scan request to a specific replica.

    This example overrides the normal behavior of sending the read request to all known replicas, and only sends it to the replica specified by ID.

    Scan scan = new Scan();
scan.setConsistency(CONSISTENCY.TIMELINE);
scan.setReplicaId(2);
ResultScanner scanner = table.getScanner(scan);
Result result = scanner.next();
  • Detect a stale result

    You can also request timeline consistency using HBase Shell, allowing the result to come from a secondary replica.

    hbase> get 'myTable', 'myRow', {CONSISTENCY => "TIMELINE"}

hbase> scan 'myTable', {CONSISTENCY => 'TIMELINE'}