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CASSANDRA-17225 Add batch_metrics virtual table #1372

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CASSANDRA-17225 Add batch_metrics virtual table #1372

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CASSANDRA-17225 Add batch_metrics virtual table to retrieve unlogged,…
burmanm Dec 23, 2021
c53b87a
Modify test to write directly to BatchMetrics, separate HistogramSnap…
burmanm Jan 14, 2022
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3 changes: 2 additions & 1 deletion src/java/org/apache/cassandra/db/virtual/BatchMetricsTable.java
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Expand Up @@ -21,6 +21,7 @@
import com.codahale.metrics.Snapshot;
import org.apache.cassandra.cql3.statements.BatchStatement;
import org.apache.cassandra.db.marshal.DoubleType;
import org.apache.cassandra.db.marshal.LongType;
import org.apache.cassandra.db.marshal.UTF8Type;
import org.apache.cassandra.dht.LocalPartitioner;
import org.apache.cassandra.metrics.BatchMetrics;
Expand All @@ -46,7 +47,7 @@ public class BatchMetricsTable extends AbstractVirtualTable
.addRegularColumn(P50, DoubleType.instance)
.addRegularColumn(P99, DoubleType.instance)
.addRegularColumn(P999, DoubleType.instance)
.addRegularColumn(MAX, DoubleType.instance)
.addRegularColumn(MAX, LongType.instance)
.build());
}

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51 changes: 26 additions & 25 deletions test/unit/org/apache/cassandra/db/virtual/BatchMetricsTableTest.java
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Expand Up @@ -25,7 +25,6 @@
import org.junit.BeforeClass;
import org.junit.Test;

import com.codahale.metrics.Histogram;
import com.codahale.metrics.Snapshot;
import com.datastax.driver.core.ResultSet;
import org.apache.cassandra.cql3.CQLTester;
Expand All @@ -38,7 +37,6 @@
public class BatchMetricsTableTest extends CQLTester
{
private static final String KS_NAME = "vts";
private BatchMetricsTable table;

@BeforeClass
public static void setUpClass()
Expand All @@ -49,42 +47,45 @@ public static void setUpClass()
@Before
public void config()
{
table = new BatchMetricsTable(KS_NAME);
BatchMetricsTable table = new BatchMetricsTable(KS_NAME);
VirtualKeyspaceRegistry.instance.register(new VirtualKeyspace(KS_NAME, ImmutableList.of(table)));
}

@Test
void testSelectAll() throws Throwable
public void testSelectAll() throws Throwable
{
String ks = createKeyspace("CREATE KEYSPACE %s WITH replication={ 'class' : 'SimpleStrategy', 'replication_factor' : 1 }");
String tbl = createTable(ks, "CREATE TABLE %s (id int primary key, val int)");
BatchMetrics metrics = BatchStatement.metrics;

String batch = format("BEGIN BATCH " +
"INSERT INTO %s.%s (id, val) VALUES (0, 0) USING TTL %d; " +
"INSERT INTO %s.%s (id, val) VALUES (1, 1) USING TTL %d; " +
"APPLY BATCH;",
ks, tbl, 1,
ks, tbl, 1);
execute(batch);
for (int i = 0; i < 10; i++)
{
metrics.partitionsPerLoggedBatch.update(i);
metrics.partitionsPerUnloggedBatch.update(i + 10);
metrics.partitionsPerCounterBatch.update(i * 10);
}

BatchMetrics metrics = BatchStatement.metrics;
ResultSet result = executeNet("SELECT * FROM vts.batch_metrics");
ResultSet result = executeNet(format("SELECT * FROM %s.batch_metrics", KS_NAME));
assertEquals(5, result.getColumnDefinitions().size());
AtomicInteger rowCount = new AtomicInteger(0);
result.forEach(r -> {
Snapshot snapshot;
if(r.getString("name").equals("partitions_per_logged_batch")) {
snapshot = metrics.partitionsPerLoggedBatch.getSnapshot();
} else if(r.getString("name").equals("partitions_per_unlogged_batch")) {
snapshot = metrics.partitionsPerUnloggedBatch.getSnapshot();
} else {
snapshot = metrics.partitionsPerCounterBatch.getSnapshot();
}
assertEquals(r.getDouble("p50"), snapshot.getMedian(), 1.0);
assertEquals(r.getDouble("p99"), snapshot.get99thPercentile(), 1.0);
Snapshot snapshot = getExpectedHistogramSnapshot(metrics, r.getString("name"));
assertEquals(snapshot.getMedian(), r.getDouble("p50th"), 0.0);
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assertEquals(snapshot.get99thPercentile(), r.getDouble("p99th"), 0.0);
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Shouldn't we have p999th and max here tested as well?

rowCount.addAndGet(1);
});

assertEquals(3, rowCount.get());
}

private Snapshot getExpectedHistogramSnapshot(BatchMetrics metrics, String tableName)
{
if ("partitions_per_logged_batch".equals(tableName))
{
return metrics.partitionsPerLoggedBatch.getSnapshot();
}
else if ("partitions_per_unlogged_batch".equals(tableName))
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I would probably skip the else :-) Just it reads better something like that:

        if ("partitions_per_logged_batch".equals(tableName))
            return metrics.partitionsPerLoggedBatch.getSnapshot();
        
        
        if ("partitions_per_unlogged_batch".equals(tableName))
            return metrics.partitionsPerUnloggedBatch.getSnapshot();

        return metrics.partitionsPerCounterBatch.getSnapshot();

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I see both approaches used in the code base, I'm personally on the "else" camp usually - to me it makes it easier to follow the flow, with the added bonus of being able to hide the whole conditional flow in the editor with a single click (does not matter in this case, but in general).

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I also prefer avoiding any unecessary code as it can only create confusion and for simple condition braces are normally skipped.

{
return metrics.partitionsPerUnloggedBatch.getSnapshot();
}
return metrics.partitionsPerCounterBatch.getSnapshot();
}
}