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Use nonzero default value of maxQueuedBytes. (#12840)

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* Use nonzero default value of maxQueuedBytes.

The purpose of this parameter is to prevent the Broker from running out
of memory. The prior default is unlimited; this patch changes it to a
relatively conservative 25MB.

This may be too low for larger clusters. The risk is that throughput
can decrease for queries with large resultsets or large amounts of intermediate
data. However, I think this is better than the risk of the prior default, which
is that these queries can cause the Broker to go OOM.

* Alter calculation.
This commit is contained in:
Gian Merlino 2022-08-02 17:57:27 -07:00 committed by GitHub
parent 0ca37c20a6
commit 2912a36a20
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2 changed files with 15 additions and 3 deletions
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2
docs/configuration/index.md
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@ -1793,7 +1793,7 @@ client has the following configuration options.
|`druid.broker.http.compressionCodec`|Compression codec the Broker uses to communicate with Historical and real-time processes. May be "gzip" or "identity".|`gzip`|
|`druid.broker.http.readTimeout`|The timeout for data reads from Historical servers and real-time tasks.|`PT15M`|
|`druid.broker.http.unusedConnectionTimeout`|The timeout for idle connections in connection pool. The connection in the pool will be closed after this timeout and a new one will be established. This timeout should be less than `druid.broker.http.readTimeout`. Set this timeout = ~90% of `druid.broker.http.readTimeout`|`PT4M`|
|`druid.broker.http.maxQueuedBytes`|Maximum number of bytes queued per query before exerting backpressure on the channel to the data server. Similar to `druid.server.http.maxScatterGatherBytes`, except unlike that configuration, this one will trigger backpressure rather than query failure. Zero means disabled. Can be overridden by the ["maxQueuedBytes" query context parameter](../querying/query-context.md). Human-readable format is supported, see [here](human-readable-byte.md). |`0` (disabled)|
|`druid.broker.http.maxQueuedBytes`|Maximum number of bytes queued per query before exerting backpressure on channels to the data servers.<br /><br />Similar to `druid.server.http.maxScatterGatherBytes`, except unlike that configuration, this one will trigger backpressure rather than query failure. Zero means disabled. Can be overridden by the ["maxQueuedBytes" query context parameter](../querying/query-context.md). Human-readable format is supported, see [here](human-readable-byte.md). |`25MB` or 2% of maximum Broker heap size, whichever is greater|
|`druid.broker.http.numMaxThreads`|`Maximum number of I/O worker threads|max(10, ((number of cores * 17) / 16 + 2) + 30)`|
##### Retry Policy

16
server/src/main/java/org/apache/druid/guice/http/DruidHttpClientConfig.java
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@ -29,11 +29,13 @@ import org.joda.time.Period;
import javax.validation.constraints.Min;
/**
*
*/
public class DruidHttpClientConfig
{
private final String DEFAULT_COMPRESSION_CODEC = "gzip";
private static final String DEFAULT_COMPRESSION_CODEC = "gzip";
private static final double DEFAULT_MAX_QUEUED_BYTES_HEAP_FRACTION = 0.02; // Per query, so 2% is reasonably safe
private static final Logger LOG = new Logger(DruidHttpClientConfig.class);
@JsonProperty
@ -65,7 +67,7 @@ public class DruidHttpClientConfig
* respected by CachingClusteredClient (broker -> data server communication).
*/
@JsonProperty
private HumanReadableBytes maxQueuedBytes = HumanReadableBytes.ZERO;
private HumanReadableBytes maxQueuedBytes = computeDefaultMaxQueuedBytes();
@JsonProperty
private boolean eagerInitialization = true;
@ -123,4 +125,14 @@ public class DruidHttpClientConfig
{
return eagerInitialization;
}
private static HumanReadableBytes computeDefaultMaxQueuedBytes()
{
return HumanReadableBytes.valueOf(
Math.max(
25_000_000,
(long) (JvmUtils.getRuntimeInfo().getMaxHeapSizeBytes() * DEFAULT_MAX_QUEUED_BYTES_HEAP_FRACTION)
)
);
}
}