Michael Ho has uploaded this change for review. ( http://gerrit.cloudera.org:8080/12987
Change subject: IMPALA-8341: Data cache for remote reads ...................................................................... IMPALA-8341: Data cache for remote reads This is a patch based on PhilZ's prototype: https://gerrit.cloudera.org/#/c/12683/ This change implements an IO data cache which is backed by local storage. It implicitly relies on the OS page cache management to shuffle data between memory and the storage device. This is useful for caching data read from remote filesystems (e.g. remote HDFS data node, S3, ABFS, ADLS). A data cache is divided into one or more partitions based on the configuration string which is a list of <directory>:<quota> pairs, separated by comma. An example configuration string: --data_cache_config=/data/0:150GB,/data/1:150GB Each partition has a meta-data cache which tracks the mappings of cache keys to the locations of the cached data. A cache key is a tuple of (file's name, file's modification time, file offset) and a cache entry is a tuple of (backing file, offset in the backing file, length of the cached data, optional checksum). Each partition stores its set of cached data in backing files created on local storage. When inserting new data into the cache, the data is appended to the current backing file in use. The storage consumption of each cache entry counts towards the quota of that partition. When a partition reaches its capacity, the least recently used (LRU) data in that partition is evicted. Evicted data is removed from the underlying storage by punching holes in the backing file it's stored in. As a backing file reaches a certain size (by default 4TB), new data will stop being appended to it and a new file will be created instead. Note that due to hole punching, the backing file is actually sparse. Optionally, checksumming can be enabled to verify read from the cache is consistent with what was inserted and to verify that multiple attempted insertions with the same cache key have the same cache content. To probe for cached data in the cache, the interface Lookup() is used; To insert data into the cache, the interface Store() is used. Please note that eviction happens inline currently during Store(). Testing done: a new BE test was added; core test with cache enabled. Perf: - 16-streams TPCDS at 3TB in a 20 node S3 cluster shows about 30% improvement over runs without the cache. Each node has a cache size of 150GB per node. Change-Id: I734803c1c1787c858dc3ffa0a2c0e33e77b12edc --- M be/src/exec/hdfs-scan-node-base.cc M be/src/exec/hdfs-scan-node-base.h M be/src/runtime/io/CMakeLists.txt A be/src/runtime/io/data-cache-test.cc A be/src/runtime/io/data-cache.cc A be/src/runtime/io/data-cache.h M be/src/runtime/io/disk-io-mgr.cc M be/src/runtime/io/disk-io-mgr.h M be/src/runtime/io/hdfs-file-reader.cc M be/src/runtime/io/hdfs-file-reader.h M be/src/runtime/io/request-context.h M be/src/util/impalad-metrics.cc M be/src/util/impalad-metrics.h M common/thrift/metrics.json 14 files changed, 1,115 insertions(+), 9 deletions(-) git pull ssh://gerrit.cloudera.org:29418/Impala-ASF refs/changes/87/12987/1 -- To view, visit http://gerrit.cloudera.org:8080/12987 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-Project: Impala-ASF Gerrit-Branch: master Gerrit-MessageType: newchange Gerrit-Change-Id: I734803c1c1787c858dc3ffa0a2c0e33e77b12edc Gerrit-Change-Number: 12987 Gerrit-PatchSet: 1 Gerrit-Owner: Michael Ho <k...@cloudera.com>
