Matthias Sohn [Sat, 3 Aug 2019 10:02:34 +0000 (12:02 +0200)]
JMH benchmark for SimpleLruCache
See [1] for JMH documentation and [2] how to use JMH in Eclipse.
The benchmarks pom currently cannot use the JGit parent pom due to an
ecj bug [3] regarding annotation processing. Hence for now do not
inherit from the JGit parent pom and copy the compiler plugin
configuration for javac from the parent pom.
After running the Maven build the benchmark can be run using Maven:
Do not rely on ArrayIndexOutOfBoundsException to detect end of input
In the Config#StringReader we relied on ArrayIndexOutOfBoundsException
to detect the end of the input. Creation of exception with (deep) stack
trace can significantly degrade performance in case when we read
thousands of config files, like in the case when Gerrit reads all
external ids from the NoteDb.
Use the buf.length to detect the end of the input.
Thomas Wolf [Thu, 12 Sep 2019 19:05:19 +0000 (21:05 +0200)]
WorkingTreeIterator: handle different timestamp resolutions
Older JGit stored only milliseconds timestamps in the index. Newer
JGit may get finer timestamps from the file system. This leads to
slow index diffs when a new JGit runs against an index produced
by older JGit because many timestamps will differ and JGit will
then do many content checks. See [1].
Handle this migration case by only comparing milliseconds if the
index entry has only millisecond precision.
The inverse may also occur; also compare only milliseconds if the
file timestamp has only millisecond precision.
Do the same also for microsecond resolution. On Windows, NTFS may
provide 100ns resolution and may be used by external programs writing
the index, but Java's WindowsFileAttributes may provide only
microseconds.
File timestamp precision in Java depends not only on the Java APIs
used by different JGit versions but may also change when running the
same Java code on different VMs. And of course the resolution may
vary among operating and file systems. Moreover, timestamp precision
in the index depends on the program that wrote the index. Canonical
git may use a different resolution, maybe even different between git
versions.
Change-Id: Idfd08606c883cb98787b2138f9baf0cc89a57b56 Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch> Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Matthias Sohn [Tue, 10 Sep 2019 14:08:45 +0000 (16:08 +0200)]
Fix WorkingTreeIterator.compareMetadata() for CheckStat.MINIMAL
If CheckStat is MINIMAL or timestamps have no nanosecond part
WorkingTreeIterator.compareMetaData only checks the second part of
timestamps and ignores nanoseconds which may have ended up in the index
by using native git.
we currently proceed comparing fileLastModified and cacheLastModified
with full precision which is wrong since we determined that we detected
reduced timestamp resolution.
Fix this and also handle smudged index entries for CheckStat.MINIMAL.
Change-Id: I6149885903ac63d79b42d234cc02aa4e19578f3c Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
David Pursehouse [Wed, 10 Oct 2018 01:53:35 +0000 (10:53 +0900)]
Bazel: Require minimum bazel version 0.17.1
Check the bazel version using the checker from bazel_skylib, and
require at least version 0.17.1 which is the minimum version that
does not suffer from the Java API mismatch issue [1].
The implementation is borrowed from the Gerrit project.
Matthias Sohn [Tue, 3 Sep 2019 14:02:44 +0000 (16:02 +0200)]
Merge branch 'stable-5.0' into stable-5.1
* stable-5.0:
Prepare 4.11.10-SNAPSHOT builds
JGit v4.11.9.201909030838-r
Bazel: Update bazlets to the latest master revision
Bazel: Remove FileTreeIteratorWithTimeControl from BUILD file
BatchRefUpdate: repro racy atomic update, and fix it
Delete unused FileTreeIteratorWithTimeControl
Fix RacyGitTests#testRacyGitDetection
Change RacyGitTests to create a racy git situation in a stable way
Silence API warnings
Change-Id: I172136a031ff0730e575327cafb3527c9650a71d Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Matthias Sohn [Tue, 3 Sep 2019 13:54:54 +0000 (15:54 +0200)]
Merge branch 'stable-4.11' into stable-5.0
* stable-4.11:
Prepare 4.11.10-SNAPSHOT builds
JGit v4.11.9.201909030838-r
Bazel: Update bazlets to the latest master revision
Bazel: Remove FileTreeIteratorWithTimeControl from BUILD file
BatchRefUpdate: repro racy atomic update, and fix it
Delete unused FileTreeIteratorWithTimeControl
Fix RacyGitTests#testRacyGitDetection
Change RacyGitTests to create a racy git situation in a stable way
Silence API warnings
Change-Id: Ifb6a4dbea2f48fd2ffa66eb737d61920aefedfbd Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Matthias Sohn [Tue, 3 Sep 2019 12:23:29 +0000 (14:23 +0200)]
Merge branch 'stable-4.10' into stable-4.11
* stable-4.10:
Bazel: Update bazlets to the latest master revision
Bazel: Remove FileTreeIteratorWithTimeControl from BUILD file
BatchRefUpdate: repro racy atomic update, and fix it
Delete unused FileTreeIteratorWithTimeControl
Fix RacyGitTests#testRacyGitDetection
Change RacyGitTests to create a racy git situation in a stable way
Silence API warnings
Change-Id: If672b4f0c350f4e8ff7e1e706485cffd8137236d Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Matthias Sohn [Tue, 3 Sep 2019 11:24:28 +0000 (13:24 +0200)]
Merge branch 'stable-4.9' into stable-4.10
* stable-4.9:
BatchRefUpdate: repro racy atomic update, and fix it
Delete unused FileTreeIteratorWithTimeControl
Fix RacyGitTests#testRacyGitDetection
Change RacyGitTests to create a racy git situation in a stable way
Silence API warnings
Change-Id: Id5bf44645655fca40ad22bb1f1ad20a7c2e8f6db Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Han-Wen Nienhuys [Sat, 31 Aug 2019 19:33:58 +0000 (21:33 +0200)]
BatchRefUpdate: repro racy atomic update, and fix it
PackedBatchRefUpdate was creating a new packed-refs list that was
potentially unsorted. This would be papered over when the list was
read back from disk in parsePackedRef, which detects unsorted ref
lists on reading, and sorts them. However, the BatchRefUpdate also
installed the new (unsorted) list in-memory in
RefDirectory#packedRefs.
With the timestamp granularity code committed to stable-5.1, we can
more often accurately decide that the packed-refs file is clean, and
will return the erroneous unsorted data more often. Unluckily timed
delays also cause the file to be clean, hence this problem was
exacerbated under load.
The symptom is that refs added by a BatchRefUpdate would stop being
visible directly after they were added. In particular, the Gerrit
integration tests uses BatchRefUpdate in its setup for creating the
Admin group, and then tries to read it out directly afterward.
The tests recreates one failure case. A better approach would be to
revise RefList.Builder, so it detects out-of-order lists and
automatically sorts them.
Fixes https://bugs.eclipse.org/bugs/show_bug.cgi?id=548716 and
https://bugs.chromium.org/p/gerrit/issues/detail?id=11373.
Matthias Sohn [Tue, 18 Jun 2019 09:32:59 +0000 (11:32 +0200)]
Fix RacyGitTests#testRacyGitDetection
This test case assumed file system timestamp resolution of 1 second. On
filesystems with a finer resolution this test fails since the index
entry is only smudged if the file index entry's lastModified and the
lastModified of the git index itself are within the same filesystem
timer tick. Fix this by ensuring that these timestamps are identical
which should work for any filesystem timer resolution.
Bug: 548188
Change-Id: Id84d59e1cfeb48fa008f8f27f2f892c4f73985de Signed-off-by: Matthias Sohn <matthias.sohn@sap.com> Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>
(cherry picked from commit 1159f9dd7c80a53c2509cd75d997a6afed37f9a6)
Matthias Sohn [Mon, 26 Aug 2019 20:43:11 +0000 (22:43 +0200)]
Return a new instance from openSystemConfig and openUserConfig
Move the handling of cached user and system config to getSystemConfig
and getUserConfig methods and revert the implementation of
openSystemConfig and openUserConfig to the old stateless
implementation.
This ensures the open methods respect the passed-in parent config, which
may be different on each invocation. Additionally, returning a new
instance matches the behavior of the previous implementation of the
default system reader, which downstream callers may be depending on.
Move the implementation of the new caching methods getSystemConfig and
getUserConfig up to SystemReader. This avoids that we break the ABI for
subclasses of SystemReader.
Also see [1] which fixed a similar problem with Gerrit's custom
SystemReader.
Matthias Sohn [Tue, 20 Aug 2019 22:29:45 +0000 (00:29 +0200)]
Avoid sign extension when comparing mtime with Instant#getEpochSecond
Ensure we use the same type when comparing seconds since the epoch.
This does not prevent that in 2038 timestamps in seconds since the epoch
stored in a 32 bit integer will overflow. Integer.MAX_VALUE translates
to 2038-01-19T03:14:07Z. After this date we'll have an issue since we
store seconds since the epoch in a 32 bit integer in some places.
Bug: 319142
Change-Id: If0c03003d40b480f044686e2f7a2f62c9f4e2fe1 Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Michael Keppler [Tue, 20 Aug 2019 14:09:12 +0000 (16:09 +0200)]
Fix deprecation in DirCache caused by Instant based DirCacheEntry
Replace the two int variables smudge_s and smudge_ns by an Instant and
use the new method DirCacheEntry.mightBeRacilyClean(Instant).
Change-Id: Id70adbb0856a64909617acf65da1bae8e2ae934a Signed-off-by: Michael Keppler <Michael.Keppler@gmx.de> Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Matthias Sohn [Wed, 14 Aug 2019 23:25:28 +0000 (01:25 +0200)]
Cache user global and system-wide git configurations
So far the git configuration and the system wide git configuration were
always reloaded when jgit accessed these global configuration files to
access global configuration options which are not in the context of a
single git repository. Cache these configurations in SystemReader and
only reload them if their file metadata observed using FileSnapshot
indicates a modification.
Change-Id: I092fe11a5d95f1c5799273cacfc7a415d0b7786c Signed-off-by: Matthias Sohn <matthias.sohn@sap.com> Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>
Matthias Sohn [Sun, 11 Aug 2019 00:43:02 +0000 (02:43 +0200)]
Avoid setup and saving FileStoreAttributes compete for ~/.gitconfig lock
FS determines FileStore attributes in a background thread and tries to
save the results to the global git configuration. This competed with
LocalDiskRepositoryTestCase#setup trying to save changes to the same
file requiring the same lock. This frequently led to one of the threads
failing to acquire the lock.
Fix this by first initiating determination of FileStore attributes which
then uses a MockSystemReader not using a userConfig stored to disk which
avoids this race for the lock.
Change-Id: I30fcd96bc15100f8ef9b2a9eb3320bb5ace97c67 Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Matthias Sohn [Mon, 12 Aug 2019 15:40:39 +0000 (17:40 +0200)]
Improve retry handling when saving FileStoreAttributes fails
- fix handling of interrupts in FileStoreAttributes#saveToConfig
- increase retry wait time to 100ms
- don't wait after last retry
- dont retry if failure is caused by another exception than
LockFailedException
Change-Id: I108c012717d2bcce71f2c6cb9cf0879de704ebc2 Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Make supportsAtomicCreateNewFile return true as default
The method org.eclipse.jgit.util.FS.supportsAtomicCreateNewFile()
should default to true as mentioned in docs [1]
org.eclipse.jgit.util.FS_POSIX.supportsAtomicCreateNewFile() method
will set the value to false if the git config
core.supportsatomiccreatenewfile is not set.
It should default to true if the configuration is undefined.
Matthias Sohn [Mon, 12 Aug 2019 10:02:59 +0000 (12:02 +0200)]
Update orbit to R20190602212107-2019-06 to enable backports from master
update
- org.apache.httpcomponents.httpclient to 4.5.6.v20190503-0009
- org.apache.httpcomponents.httpcore to 4.4.10.v20190123-2214
- com.jcraft.jsch" version to 0.1.55.v20190404-1902
- org.mockito to 2.23.0.v20190527-1420
add its dependencies
- net.bytebuddy.byte-buddy 1.9.0.v20181107-1410
- net.bytebuddy.byte-buddy-agent 1.9.0.v20181106-1534
- org.objenesis to 2.6.0.v20180420-1519
FS#getFileStoreAttributes used the real userConfig and not the mocked
one. This led to test errors when running tests with Bazel since it
sandboxes tests which prevents they can write to ~/.gitconfig.
Fix this by first preparing the MockedSystemReader and the mocked config
before calling FS#getFileStoreAttributes.
Also fix ConfigTest which broke due to this change since it inherits
from LocalDiskRepositoryTestCase and calls its setup method which was
changed here. We can no longer assert by comparing plain text since FS
adds FileStoreAttributes to the mocked userConfig. Also the default
options seen by this test changed since we now use a mocked config.
Change-Id: I76bc7c94953fe979266147d3b309a68dda9d4dfe Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Matthias Sohn [Sat, 10 Aug 2019 21:34:58 +0000 (23:34 +0200)]
Ensure we use MockSystemReader in tests
If we use the default system reader FileStoreAttributes cannot persist
attributes in userConfig when tests run in Bazel due to sandboxing.
Hence we need to ensure that all tests use MockSystemReader (and
especially a mocked userConfig).
Change-Id: Ic1ad8e2ec5a150c5433434a5f6667d6c4674c87d Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Matthias Sohn [Sat, 10 Aug 2019 21:28:07 +0000 (23:28 +0200)]
Remove FileBasedConfig.load(boolean) introduced in d45219ba
We can't add this method to the super class StoredConfig since that
abstracts from filesystem storage. MockSystemReader.MockConfig is a
StoredConfig and is also used by tests for dfs based storage. Hence
remove this leaky abstraction.
This implies we always use the fallback FileStoreAttributes which means
a config file modification is considered racy within the first 2
seconds. This should not be an issue since typically configs change
rarely and re-reading a config within the racy period is relatively
cheap since configs are small.
Change-Id: Ia2615addc24a7cadf3c566ee842c6f4f07e159a5 Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Matthias Sohn [Thu, 8 Aug 2019 08:10:12 +0000 (10:10 +0200)]
Fix OpenSshConfigTest#config
- use FS.DETECTED instead of db.getFS() since the ssh config is
typically in a different place than the repository, the same is used in
OpenSshConfig
- reduce unnecessary repeated writes by introducing wait for one tick of
the file time resolution
Change-Id: Ifac915e97ff420ec5cf8e2f162e351f9f51b6b14 Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Increase the safety factor to 2.5x for extra safety if max of measured
timestamp resolution and measured minimal racy threshold is < 100ms, use
1.25 otherwise since for large filesystem resolution values the
influence of finite resolution of the system clock should be negligible.
Before, not yet using the newly introduced minRacyThreshold measurement,
the threshold was 1.1x FS resolution, and we could issue the
following sequence of events,
In this case, the difference between create-file and read is 5ms,
which exceeded the 4ms FS resolution, even though the events together
took just 2ms of runtime.
Reproduce with:
bazel test --runs_per_test=100 \
//org.eclipse.jgit.test:org_eclipse_jgit_internal_storage_file_FileSnapshotTest
The file system timestamp resolution is 4ms in this case.
This code assumes that the kernel and the JVM use the same clock that
is synchronized with the file system clock. This seems plausible,
given the resolution of System.currentTimeMillis() and the latency for
a gettimeofday system call (typically ~1us), but it would be good to
justify this with specifications.
Also cover a source of flakiness: if the test runs under extreme load,
then we could have
start
create-file
<long delay>
read
end
which would register as an unmodified file. Avoid this by skipping the
test if end-start is too big.
[msohn]:
- downported from master to stable-5.1
- skip test if resolution is below 10ms
- adjust safety factor to 1.25 for resolutions above 100ms
Change-Id: I87d2cf035e01c44b7ba8364c410a860aa8e312ef Signed-off-by: Han-Wen Nienhuys <hanwen@google.com> Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Matthias Sohn [Mon, 5 Aug 2019 16:00:35 +0000 (18:00 +0200)]
In LockFile#waitForStatChange wait in units of file time resolution
Since we now measure file time resolution we can use it to replace the
hard coded wait time of 25ms. FileSnapshot#equals will return true until
the mtime of the old (o) and the new FileSnapshot (n) differ by at least
one file time resolution.
Change-Id: Icb713a80ce9eb929242ed083406bfb6650c72223 Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Matthias Sohn [Fri, 19 Jul 2019 15:35:27 +0000 (17:35 +0200)]
Cache FileStoreAttributeCache per directory
Cache FileStoreAttributeCache entries since looking up FileStore for a
file may be expensive on some platforms.
Implement a simple LRU cache based on ConcurrentHashMap using a simple
long counter to order access to cache entries.
Change-Id: I4881fa938ad2f17712c05da857838073a2fc4ddb Signed-off-by: Matthias Sohn <matthias.sohn@sap.com> Signed-off-by: Marc Strapetz <marc.strapetz@syntevo.com> Also-By: Marc Strapetz <marc.strapetz@syntevo.com>
Matthias Sohn [Wed, 17 Jul 2019 14:31:42 +0000 (16:31 +0200)]
Persist minimal racy threshold and allow manual configuration
To enable persisting the minimal racy threshold per FileStore add a
new config option to the user global git configuration:
- Config section is "filesystem"
- Config subsection is concatenation of
- Java vendor (system property "java.vendor")
- Java version (system property "java.version")
- FileStore's name, on Windows we use the attribute volume:vsn instead
since the name is not necessarily unique.
- separated by '|'
e.g.
"AdoptOpenJDK|1.8.0_212-b03|/dev/disk1s1"
The same prefix is used as for filesystem timestamp resolution, so
both values are stored in the same config section
- The config key for minmal racy threshold is "minRacyThreshold" as a
time value, supported time units are those supported by
DefaultTypedConfigGetter#getTimeUnit
- measure for 3 seconds to limit runtime which depends on hardware, OS
and Java version being used
If the minimal racy threshold is configured for a given FileStore the
configured value is used instead of measuring it.
When the minimal racy threshold was measured it is persisted in the user
global git configuration.
Rename FileStoreAttributeCache to FileStoreAttributes since this class
is now declared public in order to enable exposing all attributes in one
object.
Change-Id: I22195e488453aae8d011b0a8e3276fe3d99deaea Signed-off-by: Matthias Sohn <matthias.sohn@sap.com> Also-By: Marc Strapetz <marc.strapetz@syntevo.com>
Matthias Sohn [Mon, 15 Jul 2019 13:00:09 +0000 (15:00 +0200)]
Measure minimum racy interval to auto-configure FileSnapshot
By running FileSnapshotTest#detectFileModified we found that the sum of
measured filesystem timestamp resolution and measured clock resolution
may yield a too small interval after a file has been modified which we
need to consider racily clean. In our tests we didn't find this behavior
on all systems we tested on, e.g. on MacOS using APFS and Java 8 and 11
this effect was not observed.
On Linux (SLES 15, kernel 4.12.14-150.22-default) we collected the
following test results using Java 8 and 11:
In 23-98% of 10000 test runs (depending on filesystem type and Java
version) the test failed, which means the effective interval which needs
to be considered racily clean after a file was modified is larger than
the measured file timestamp resolution.
"delta" is the observed interval after a file has been modified but
FileSnapshot did not yet detect the modification:
"resolution" is the measured sum of file timestamp resolution and clock
resolution seen in Java.
Java version filesystem failures resolution min delta max delta
1.8.0_212-b04 btrfs 98.6% 1 ms 3.6 ms 6.6 ms
1.8.0_212-b04 ext4 82.6% 3 ms 1.1 ms 4.1 ms
1.8.0_212-b04 xfs 23.8% 4 ms 3.7 ms 3.9 ms
1.8.0_212-b04 zfs 23.1% 3 ms 4.8 ms 5.0 ms
11.0.3+7 btrfs 98.1% 3 us 0.7 ms 4.7 ms
11.0.3+7 ext4 98.1% 6 us 0.7 ms 4.7 ms
11.0.3+7 xfs 98.5% 7 us 0.1 ms 8.0 ms
11.0.3+7 zfs 98.4% 7 us 0.7 ms 5.2 ms
Mac OS
1.8.0_212 APFS 0% 1 s
11.0.3+7 APFS 0% 6 us
The observed delta is not distributed according to a normal gaussian
distribution but rather random in the observed range between "min delta"
and "max delta".
Run this test after measuring file timestamp resolution in
FS.FileAttributeCache to auto-configure JGit since it's unclear what
mechanism is causing this effect.
In FileSnapshot#isRacyClean use the maximum of the measured timestamp
resolution and the measured "delta" as explained above to decide if a
given FileSnapshot is to be considered racily clean. Add a 30% safety
margin to ensure we are on the safe side.
Change-Id: I1c8bb59f6486f174b7bbdc63072777ddbe06694d Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Matthias Sohn [Fri, 12 Jul 2019 07:49:13 +0000 (09:49 +0200)]
Add test for racy git detection in FileSnapshot
Repeat the test 10000 times to get statistics if measured
fsTimestampResolution is working in practice to detect racy git
situations.
Add a class to compute statistics for this test. Log delta between
lastModified and time when FileSnapshot failed to detect modification.
This happens if the racy git limit determined by measuring filesystem
timestamp resolution and clock resolution is too small. If it would be
correct FileSnapshot would always detect modification or mark it
modified if time since modification is smaller than the racy git limit.
Change-Id: Iabe7af1a7211ca58480f8902d4fa4e366932fc77 Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Matthias Sohn [Fri, 12 Jul 2019 07:45:09 +0000 (09:45 +0200)]
Enhance RepeatRule to report number of failures at the end
In order to enable counting how frequently a test fails if repeated add
option abortOnFailure. If it is true the test aborts on the first
failure. Otherwise it runs the configured number of repetitions and, if
there was any failure, throws a RepeatException reporting how many of
the test repetitions failed.
Change-Id: Ic47de44d4a6273fddf04b9993ad989903efb40c3 Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Matthias Sohn [Wed, 10 Jul 2019 14:17:21 +0000 (16:17 +0200)]
Fix FileSnapshotTests for filesystem with high timestamp resolution
When filesystem timestamp resolution is very high some tests don't work
since runtime of the test setup is too long to reach a racily clean
FileSnapshot. Hence skip these tests when timestamp resolution is higher
than 10 millisecond.
Change-Id: Ie47dd10eda22037b5c1ebff6b6becce0654ea807 Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Matthias Sohn [Mon, 8 Jul 2019 08:20:16 +0000 (10:20 +0200)]
Measure stored timestamp resolution instead of time to touch file
Measure granularity of timestamps stored in the filesystem by setting
and then getting lastModified timestamp until the read value changed.
Increase increment exponentially to limit number of iterations starting
with 1 microsecond since Java's FileTime (up to Java 12) truncates
timestamps to 1 microsecond resolution. The chosen algorithm yields 2000
steps between 1 ms and 2.5 s.
Also measure clock resolution and add that for the total timestamp
resolution. This avoids systematic measurement errors introduced by
doing IO to touch a file.
Change-Id: I9b37138619422452373e298d9d8c7cb2c384db3f Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Matthias Sohn [Tue, 2 Jul 2019 23:07:14 +0000 (01:07 +0200)]
Use Instant instead of milliseconds for filesystem timestamp handling
This enables higher file timestamp resolution on filesystems like ext4,
Mac APFS (1ns) or NTFS (100ns) providing high timestamp resolution on
filesystem level.
Note:
- on some OSes Java 8,9 truncate milliseconds, see
https://bugs.openjdk.java.net/browse/JDK-8177809, fixed in Java 10
- UnixFileAttributes truncates timestamp resolution to microseconds when
converting the internal representation to FileTime exposed in the API,
see https://bugs.openjdk.java.net/browse/JDK-8181493
- WindowsFileAttributes also provides only microsecond resolution
Change-Id: I25ffff31a3c6f725fc345d4ddc2f26da3b88f6f2 Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Matthias Sohn [Wed, 26 Jun 2019 07:10:31 +0000 (09:10 +0200)]
FS: ignore AccessDeniedException when measuring timestamp resolution
It seems on cygwin creating a file under a writable directory can fail
with AccessDeniedException. Log a warning in this case and fallback to
worst case timestamp resolution of 2 seconds.
Bug: 548648
Change-Id: Ic50c31ce9dc9ccadd4db5247df929418ac62d45c Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
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