HeartSaVioR commented on code in PR #38430:
URL: https://github.com/apache/spark/pull/38430#discussion_r1008968288
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sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/HDFSMetadataLog.scala:
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@@ -64,6 +67,17 @@ class HDFSMetadataLog[T <: AnyRef : ClassTag](sparkSession:
SparkSession, path:
fileManager.mkdirs(metadataPath)
}
+ protected val metadataCacheEnabled: Boolean
+ =
sparkSession.sessionState.conf.getConf(SQLConf.STREAMING_METADATA_CACHE_ENABLED)
+
+ /**
+ * Cache the latest two batches. [[StreamExecution]] usually just accesses
the latest two batches
+ * when committing offsets, this cache will save some file system operations.
+ */
+ protected[sql] val batchCache = Collections.synchronizedMap(new
LinkedHashMap[Long, T](2) {
Review Comment:
In the previous implementation we didn't use Guava cache. We don't want to
add more coupling to Guava unless it is quite bothering to implement by our own.
I provided the diff upon caching offset seq, see here
https://github.com/apache/spark/pull/31495
This is a generalization of previous cache from offset seq to
HDFSMetadataLog, which I actually got requested in my PR as well. As of now,
the cache is only effective to offset seq, but we plan to propose
functionalities/features where caching commit log would be helpful.
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