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| <h2 title="Class ReadPointCalculationLock" class="title">Class ReadPointCalculationLock</h2> |
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| <pre>@InterfaceAudience.Private |
| public class <a href="../../../../../src-html/org/apache/hadoop/hbase/regionserver/ReadPointCalculationLock.html#line.42">ReadPointCalculationLock</a> |
| extends <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html?is-external=true" title="class or interface in java.lang">Object</a></pre> |
| <div class="block">Lock to manage concurrency between <a href="../../../../../org/apache/hadoop/hbase/regionserver/RegionScanner.html" title="interface in org.apache.hadoop.hbase.regionserver"><code>RegionScanner</code></a> and |
| <a href="../../../../../org/apache/hadoop/hbase/regionserver/HRegion.html#getSmallestReadPoint--"><code>HRegion.getSmallestReadPoint()</code></a>. We need to ensure that while we are calculating the |
| smallest read point, no new scanners can modify the scannerReadPoints Map. We used to achieve |
| this by synchronizing on the scannerReadPoints object. But this may block the read thread and |
| reduce the read performance. Since the scannerReadPoints object is a |
| <a href="https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentHashMap.html?is-external=true" title="class or interface in java.util.concurrent"><code>ConcurrentHashMap</code></a>, which is thread-safe, so the |
| <a href="../../../../../org/apache/hadoop/hbase/regionserver/RegionScanner.html" title="interface in org.apache.hadoop.hbase.regionserver"><code>RegionScanner</code></a> can record their read points concurrently, what it needs to do is just |
| acquiring a shared lock. When we calculate the smallest read point, we need to acquire an |
| exclusive lock. This can improve read performance in most scenarios, only not when we have a lot |
| of delta operations, like <a href="../../../../../org/apache/hadoop/hbase/client/Append.html" title="class in org.apache.hadoop.hbase.client"><code>Append</code></a> or |
| <a href="../../../../../org/apache/hadoop/hbase/client/Increment.html" title="class in org.apache.hadoop.hbase.client"><code>Increment</code></a>. So we introduce a flag to enable/disable this |
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| <td class="colFirst"><code>static class </code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/hadoop/hbase/regionserver/ReadPointCalculationLock.LockType.html" title="enum in org.apache.hadoop.hbase.regionserver">ReadPointCalculationLock.LockType</a></span></code> </td> |
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| <td class="colFirst"><code>private <a href="https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/locks/Lock.html?is-external=true" title="class or interface in java.util.concurrent.locks">Lock</a></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/hadoop/hbase/regionserver/ReadPointCalculationLock.html#lock">lock</a></span></code> </td> |
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| <td class="colFirst"><code>private <a href="https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/locks/ReadWriteLock.html?is-external=true" title="class or interface in java.util.concurrent.locks">ReadWriteLock</a></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/hadoop/hbase/regionserver/ReadPointCalculationLock.html#readWriteLock">readWriteLock</a></span></code> </td> |
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| <td class="colFirst"><code>private boolean</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/hadoop/hbase/regionserver/ReadPointCalculationLock.html#useReadWriteLockForReadPoints">useReadWriteLockForReadPoints</a></span></code> </td> |
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| <td class="colOne"><code><span class="memberNameLink"><a href="../../../../../org/apache/hadoop/hbase/regionserver/ReadPointCalculationLock.html#ReadPointCalculationLock-org.apache.hadoop.conf.Configuration-">ReadPointCalculationLock</a></span>(org.apache.hadoop.conf.Configuration conf)</code> </td> |
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| <td class="colFirst"><code>(package private) void</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/hadoop/hbase/regionserver/ReadPointCalculationLock.html#lock-org.apache.hadoop.hbase.regionserver.ReadPointCalculationLock.LockType-">lock</a></span>(<a href="../../../../../org/apache/hadoop/hbase/regionserver/ReadPointCalculationLock.LockType.html" title="enum in org.apache.hadoop.hbase.regionserver">ReadPointCalculationLock.LockType</a> lockType)</code> </td> |
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| <td class="colFirst"><code>(package private) void</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/hadoop/hbase/regionserver/ReadPointCalculationLock.html#unlock-org.apache.hadoop.hbase.regionserver.ReadPointCalculationLock.LockType-">unlock</a></span>(<a href="../../../../../org/apache/hadoop/hbase/regionserver/ReadPointCalculationLock.LockType.html" title="enum in org.apache.hadoop.hbase.regionserver">ReadPointCalculationLock.LockType</a> lockType)</code> </td> |
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| <h4>useReadWriteLockForReadPoints</h4> |
| <pre>private final boolean <a href="../../../../../src-html/org/apache/hadoop/hbase/regionserver/ReadPointCalculationLock.html#line.49">useReadWriteLockForReadPoints</a></pre> |
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| <h4>lock</h4> |
| <pre>private <a href="https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/locks/Lock.html?is-external=true" title="class or interface in java.util.concurrent.locks">Lock</a> <a href="../../../../../src-html/org/apache/hadoop/hbase/regionserver/ReadPointCalculationLock.html#line.50">lock</a></pre> |
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| <h4>readWriteLock</h4> |
| <pre>private <a href="https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/locks/ReadWriteLock.html?is-external=true" title="class or interface in java.util.concurrent.locks">ReadWriteLock</a> <a href="../../../../../src-html/org/apache/hadoop/hbase/regionserver/ReadPointCalculationLock.html#line.51">readWriteLock</a></pre> |
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| <pre><a href="../../../../../src-html/org/apache/hadoop/hbase/regionserver/ReadPointCalculationLock.html#line.53">ReadPointCalculationLock</a>(org.apache.hadoop.conf.Configuration conf)</pre> |
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| <pre>void <a href="../../../../../src-html/org/apache/hadoop/hbase/regionserver/ReadPointCalculationLock.html#line.63">lock</a>(<a href="../../../../../org/apache/hadoop/hbase/regionserver/ReadPointCalculationLock.LockType.html" title="enum in org.apache.hadoop.hbase.regionserver">ReadPointCalculationLock.LockType</a> lockType)</pre> |
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| <pre>void <a href="../../../../../src-html/org/apache/hadoop/hbase/regionserver/ReadPointCalculationLock.html#line.77">unlock</a>(<a href="../../../../../org/apache/hadoop/hbase/regionserver/ReadPointCalculationLock.LockType.html" title="enum in org.apache.hadoop.hbase.regionserver">ReadPointCalculationLock.LockType</a> lockType)</pre> |
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