Zheng Shao created SPARK-47959:
----------------------------------
Summary: Improve GET_JSON_OBJECT performance on executors running
multiple tasks
Key: SPARK-47959
URL: https://issues.apache.org/jira/browse/SPARK-47959
Project: Spark
Issue Type: Improvement
Components: Spark Core
Affects Versions: 3.5.1
Reporter: Zheng Shao
We have a Spark executor that is running 32 workers in parallel. The query is
a simple SELECT with several `GET_JSON_OBJECT` UDF calls.
We noticed that 80+% of the stacktrace of the worker threads are blocked on the
following stacktrace:
```
com.fasterxml.jackson.core.util.InternCache.intern(InternCache.java:50) -
blocked on java.lang.Object@7529fde1
com.fasterxml.jackson.core.sym.ByteQuadsCanonicalizer.addName(ByteQuadsCanonicalizer.java:947)
com.fasterxml.jackson.core.json.UTF8StreamJsonParser.addName(UTF8StreamJsonParser.java:2482)
com.fasterxml.jackson.core.json.UTF8StreamJsonParser.findName(UTF8StreamJsonParser.java:2339)
com.fasterxml.jackson.core.json.UTF8StreamJsonParser.parseMediumName(UTF8StreamJsonParser.java:1870)
com.fasterxml.jackson.core.json.UTF8StreamJsonParser._parseName(UTF8StreamJsonParser.java:1825)
com.fasterxml.jackson.core.json.UTF8StreamJsonParser.nextToken(UTF8StreamJsonParser.java:798)
com.fasterxml.jackson.core.base.ParserMinimalBase.skipChildren(ParserMinimalBase.java:240)
org.apache.spark.sql.catalyst.expressions.GetJsonObjectBase.evaluatePath(jsonExpressions.scala:383)
org.apache.spark.sql.catalyst.expressions.GetJsonObjectBase.evaluatePath(jsonExpressions.scala:287)
org.apache.spark.sql.catalyst.expressions.GetJsonObjectBase.$anonfun$eval$4(jsonExpressions.scala:198)
org.apache.spark.sql.catalyst.expressions.GetJsonObjectBase.$anonfun$eval$4$adapted(jsonExpressions.scala:196)
org.apache.spark.sql.catalyst.expressions.GetJsonObjectBase$$Lambda$8585/1316745697.apply(Unknown
Source) ...
```
Apparently jackson-core has such a performance bug from version 2.3 - 2.15, and
not fixed until version 2.18 (unreleased):
[https://github.com/FasterXML/jackson-core/blob/fc51d1e13f4ba62a25a739f26be9e05aaad[…]/src/main/java/com/fasterxml/jackson/core/util/InternCache.java|https://github.com/FasterXML/jackson-core/blob/fc51d1e13f4ba62a25a739f26be9e05aaad88c3e/src/main/java/com/fasterxml/jackson/core/util/InternCache.java#L50]
synchronized (lock) {
if (size() >= MAX_ENTRIES) {
clear();
}
}
instead of
[https://github.com/FasterXML/jackson-core/blob/8b87cc1a96f649a7e7872c5baa8cf97909c[…]/src/main/java/com/fasterxml/jackson/core/util/InternCache.java|https://github.com/FasterXML/jackson-core/blob/8b87cc1a96f649a7e7872c5baa8cf97909cabf6b/src/main/java/com/fasterxml/jackson/core/util/InternCache.java#L59]
/* As of 2.18, the limit is not strictly enforced, but we do try to
* clear entries if we have reached the limit. We do not expect to
* go too much over the limit, and if we do, it's not a huge problem.
* If some other thread has the lock, we will not clear but the lock should
* not be held for long, so another thread should be able to clear in the near
future.
*/
if (lock.tryLock()) {
try {
if (size() >= DEFAULT_MAX_ENTRIES) {
clear();
}
} finally {
lock.unlock();
}
}
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