gengliangwang opened a new pull request, #38567:
URL: https://github.com/apache/spark/pull/38567
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### What changes were proposed in this pull request?
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Support using RocksDB as the KVStore in live UI. The location of RocksDB can
be set via configuration `spark.ui.store.path`. The configuration is optional.
The default KV store will still be in memory.
Note: let's make it ROCKSDB only for now instead of supporting both LevelDB
and RocksDB. RocksDB is built based on LevelDB with improvements on writes and
reads. Furthermore, we can reuse the RocksDBFileManager in streaming for
replicating the local RocksDB file to DFS. The replication in DFS can be used
for the Spark history server.
### Why are the changes needed?
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The current architecture of Spark live UI and Spark history server(SHS) is
too simple to serve large clusters and heavy workloads:
- Spark stores all the live UI date in memory. The size can be a few GBs and
affects the driver's stability (OOM).
- There is a limitation of storing 1000 queries only. Note that we can’t
simply increase the limitation under the current Architecture. I did a memory
profiling. Storing one query execution detail can take 800KB while storing one
task requires 0.3KB. So for 1000 SQL queries with 1000* 2000 tasks, the memory
usage for query execution and task data will be 1.4GB. Spark UI stores UI data
for jobs/stages/executors as well. So to store 10k queries, it may take more
than 14GB.
- SHS has to parse JSON format event log for the initial start. The
uncompressed event logs can be as big as a few GBs, and the parse can be quite
slow. Some users reported they had to wait for more than half an hour.
With RocksDB as KVStore, we can improve the stability of Spark driver and
fasten the startup of SHS.
### Does this PR introduce _any_ user-facing change?
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Yes, supporting RocksDB as the KVStore in live UI. The location of RocksDB
can be set via configuration `spark.ui.store.path`. The configuration is
optional. The default KV store will still be in memory.
### How was this patch tested?
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New UT
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