Bryan Beaudreault created HBASE-28009:
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Summary: Document netty memory tunings
Key: HBASE-28009
URL: https://issues.apache.org/jira/browse/HBASE-28009
Project: HBase
Issue Type: Improvement
Components: netty
Reporter: Bryan Beaudreault
Netty can work pretty well out of the box, but you can protect your deployment
from edge cases by tuning a few knobs:
{code:java}
-Dorg.apache.hbase.thirdparty.io.netty.maxDirectMemory
By default, netty will use your -XX:MaxDirectMemorySize as the limit for its
own off-heap memory usage. If you use any other off-heap memory features of
hbase, this could cause a problem. For example, ByteBuffAllocator, BucketCache,
or off-heap memstore. You should set netty's maxDirectMemory explicitly, and
make sure to offset HBASE_OFFHEAPSIZE accordingly. Otherwise you risk OOM if
netty comes under heavy load.
-Dorg.apache.hbase.thirdparty.io.netty.tryReflectionSetAccessible=true
If you are running java9 or greater, the above maxDirectMemory setting will
not take effect unless you also set this. Java9+ has extra security features
which would typically cause a reflective setAccessible call to fail. But HBase
uses a variety of --add-opens calls to enable access to Unsafe libraries, and
these will also enable setAccessible to work for netty. Setting this to true
will enable the feature which allows your custom maxDirectMemory to be be
honored.{code}
We will be adding further protections in HBASE-27947 which we can also document
here, but those have not been finalized yet.
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