Misha Dmitriev created SENTRY-1827:
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Summary: Minimize TPathsDump thrift message used in HDFS sync
Key: SENTRY-1827
URL: https://issues.apache.org/jira/browse/SENTRY-1827
Project: Sentry
Issue Type: Improvement
Affects Versions: 1.8.0, sentry-ha-redesign
Reporter: Misha Dmitriev
Assignee: Misha Dmitriev
Fix For: 1.8.0, sentry-ha-redesign
We obtained a heap dump taken from the JVM running Hive Metastore at the time
when Sentry HDFS sync operation was performed. I've analyzed this dump with
jxray (www.jxray.com) and found that more than 19% of memory is wasted due to
empty or suboptimally-sized Java collections:
{code}
9. BAD COLLECTIONS
Total collections: 54,057,249 Bad collections: 31,569,606 Overhead:
5,292,821K (19.3%)
{code}
Most of these collections come from thrift classes used by the Sentry plugin,
see below. The associated memory waste can be significantly reduced or
eliminated if these collections were allocated lazily and then with the initial
capacity smaller than the default 16 elements for HashMap/HashSet.
{code}
1,869,023K (6.8%): j.u.HashSet: 3388670 of 1-elem 979,537K (3.6%), 5897806 of
empty 552,919K (2.0%), 1010321 of small 336,566K (1.2%)
<-- org.apache.sentry.hdfs.service.thrift.TPathEntry.children <--
{j.u.HashMap}.values <--
org.apache.sentry.hdfs.service.thrift.TPathsDump.nodeMap <--
org.apache.sentry.hdfs.service.thrift.TPathsUpdate.pathsDump <-- Java
Local@7fea0851c360 (org.apache.sentry.hdfs.service.thrift.TPathsUpdate)
1,190,050K (4.3%): j.u.HashMap: 3382765 of 1-elem 898,546K (3.3%), 1005341 of
small 291,503K (1.1%)
<-- org.apache.sentry.hdfs.HMSPaths$Entry.children <--
org.apache.sentry.hdfs.HMSPaths$Entry.{parent} <-- {j.u.HashSet} <--
{j.u.TreeMap}.values <-- org.apache.sentry.hdfs.HMSPaths.authzObjToPath <--
org.apache.sentry.hdfs.UpdateableAuthzPaths.paths <--
org.apache.sentry.hdfs.MetastorePlugin.authzPaths <-- Java Local@7fe4fe84e030
(org.apache.sentry.hdfs.MetastorePlugin)
969,442K (3.5%): j.u.TreeSet: 5907188 of 1-elem 969,148K (3.5%)
<-- org.apache.sentry.hdfs.service.thrift.TPathEntry.authzObjs <--
{j.u.HashMap}.values <--
org.apache.sentry.hdfs.service.thrift.TPathsDump.nodeMap <--
org.apache.sentry.hdfs.service.thrift.TPathsUpdate.pathsDump <-- Java
Local@7fea0851c360 (org.apache.sentry.hdfs.service.thrift.TPathsUpdate)
487,690K (1.8%): j.u.TreeSet: 4801877 of empty 487,690K (1.8%)
<-- org.apache.sentry.hdfs.HMSPaths$Entry.authzObjs <--
org.apache.sentry.hdfs.HMSPaths$Entry.{parent} <-- {j.u.HashSet} <--
{j.u.TreeMap}.values <-- org.apache.sentry.hdfs.HMSPaths.authzObjToPath <--
org.apache.sentry.hdfs.UpdateableAuthzPaths.paths <--
org.apache.sentry.hdfs.MetastorePlugin.authzPaths <-- Java Local@7fe4fe84e030
(org.apache.sentry.hdfs.MetastorePlugin)
415,064K (1.5%): j.u.HashMap: 5897806 of empty 414,689K (1.5%)
<-- org.apache.sentry.hdfs.HMSPaths$Entry.children <-- {j.u.HashSet} <--
{j.u.TreeMap}.values <-- org.apache.sentry.hdfs.HMSPaths.authzObjToPath <--
org.apache.sentry.hdfs.UpdateableAuthzPaths.paths <--
org.apache.sentry.hdfs.MetastorePlugin.authzPaths <-- Java Local@7fe4fe84e030
(org.apache.sentry.hdfs.MetastorePlugin)
{code}
Additionally, a significant percentage of memory is wasted due to duplicate
strings:
{code}
7. DUPLICATE STRINGS
Total strings: 29,986,017 Unique strings: 9,640,413 Duplicate values:
4,897,743 Overhead: 2,570,746K (9.4%)
{code}
Of them, more than 1/3 come from sentry:
{code}
917,331K (3.3%), 10517636 dup strings (498477 unique), 10517636 dup backing
arrays:
<-- org.apache.sentry.hdfs.service.thrift.TPathEntry.pathElement <--
{j.u.HashMap}.values <-- org.apache.sen
try.hdfs.service.thrift.TPathsDump.nodeMap <--
org.apache.sentry.hdfs.service.thrift.TPathsUpdate.pathsDump <-- Ja
va Local@7fea0851c360 (org.apache.sentry.hdfs.service.thrift.TPathsUpdate)
{code}
These can be eliminated by inserting String.intern() calls in the appropriate
places.
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