It missed to call the setup() method of its super class which prepares
the MockSystemReader

Change-Id: I39858749f8d0115fc6ac7edc8847ffb2bbc85c33
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

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>

Move the implementation of the static equals() method to a new method
and suppress the error. Deprecate the old method to signal that we
intend to remove it in the next major release.

See https://errorprone.info/bugpattern/AmbiguousMethodReference

Change-Id: I5e29c97f4db3e11770be589a6ccd785e2c9ac7f2
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,

  start
  create-file
  read-file (currentTime)
  end

which had the following timestamps:

  create-file 1564589081
  start 1564589082
  read 1564589082
  end 1564589082

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>

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.

Example:

[filesystem "AdoptOpenJDK|11.0.3|/dev/disk1s1"]
	timestampResolution = 7000 nanoseconds
	minRacyThreshold = 3440 microseconds

Change-Id: I22195e488453aae8d011b0a8e3276fe3d99deaea
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Also-By: Marc Strapetz <marc.strapetz@syntevo.com>

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>

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>

This should help to detect if measured fsTimeResolution is too small.

Change-Id: Id1f54dbdedb52b17859904e47776fa3a5887b8be
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

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>

This helps to avoid some time critical tests can't prepare the test
fixture intended since measuring timestamp resolution takes time.

Change-Id: Ib34023e682a106070ca97e98ef16789a4dfb97b4
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

- use Path instead of File
- create test directories, files and output stream using Files methods
- delete unused list "files"

Change-Id: I8c5c601eca9f613efb5618d33b262277df92a06a
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

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>

Add a unittest.

In commit I5485db55 ("Fix FileSnapshot's consideration of file size"),
the special casing of UNKNOWN_SIZE was forgotten.

This change, together with I493f3b57b ("Measure file timestamp
resolution used in FileSnapshot") introduced a regression that would
occasionally surface in Gerrit integration tests marked UseLocalDisk,
with the symptom that creating the Admin user in NoteDb failed with a
LOCK_FAILURE.

Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Change-Id: I7ffd972581f815c144f810481103c7985af5feb0

As reported by Error Prone:

An inner class should be static unless it references members of its
enclosing class. An inner class that is made non-static unnecessarily
uses more memory and does not make the intent of the class clear.

See https://errorprone.info/bugpattern/ClassCanBeStatic

Change-Id: Ib99d120532630dba63cf400cc1c61c318286fc41
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>
(cherry picked from commit ee40efcea4)

Change-Id: I0644690e93c19c224c1d896fe3593f8b38901cbc
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

The only remaining code where the return value is ignored is in tests.
Update them to store the value and perform a basic assertion.

Change-Id: I29ef5bd5dd0648aac3490f9e47ecc74544109652
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

Test that JGit detects that packfiles have changed even if they are
repacked multiple times in one tick of the filesystem timer.

Test that this detection works also when repacking doesn't change the
length or the filekey of the packfile. In this case where a modified
file can't be detected by looking at file metadata JGit should still
detect too fast modification by racy git checks and trigger rescanning
the pack list and consequently rereading of packfile content.

Change-Id: I67682cfb807c58afc6de9375224ff7489d6618fb
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

If the attributes of FileSnapshot don't detect modification of a
packfile read the packfile's checksum and compare it against the
checksum cached in the loaded packfile.

Since reading the checksum needs less IO than reloading the complete
packfile this may help to reduce the overhead to detect modficiation
when a gc completes while ObjectDirectory scans for packfiles in another
thread.

Bug: 546891
Change-Id: I9811b497eb11b8a85ae689081dc5d949ca8c4be5
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Change-Id: Ibcd76a5e6e4183ada0be1d4436ce957243f2094d
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

This allows to verify the expected behavior in
FileSnapshotTest#testSimulatePackfileReplacement and enables extending
FileSnapshot for packfiles to read the packfile's checksum as another
criterion to detect modifications without reading the full content.

Also add another field capturing the result of the last check if
lastModified was racily clean.

Remove unnecessary determination of raciness in the constructor. It was
determined twice in all relevant cases.

Change-Id: I100a2f49d7949693d7b72daa89437e166f1dc107
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

NTFS does not support FileKey hence ignore this test on Windows.

Change-Id: I7b53a591daa5e03eb5e401b5b26d612ab68ce10d
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

testNewFileNoWait() was identical to testNewFileWithWait() but claims it
doesn't wait at all. Hence remove the waits.

Change-Id: I49b8ca5cb49a43c55fe61870c18c42f32fb4b74d
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Due to finite filesystem timestamp resolution the last modified
timestamp of files cannot detect file changes which happened in the
immediate past (less than one filesystem timer tick ago).

Some filesystems expose unique file identifiers, e.g. inodes in Posix
filesystems which are named filekeys in Java's BasicFileAttributes. Use
them as another means to detect file modifications based on stat
information.

Running git gc on a repository yields a new packfile with the same id as
a packfile which existed before the gc if these packfiles contain the
same set of objects. The content of the old and the new packfile might
differ if a different PackConfig was used when writing the packfile.
Considering filekeys in FileSnapshot may help to detect such packfile
modifications.

Bug: 546891
Change-Id: I711a80328c55e1a31171d540880b8e80ec1fe095
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Convert anonymous inner classes to lambda expressions or member
references

Bug: 545856
CQ: 19537
Change-Id: I621431c178e8b99316314602f7c66c9a36f9ae98
Signed-off-by: Carsten Hammer <carsten.hammer@t-online.de>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Change-Id: I1a9112e6a4f938638c599b489cb0858eca27ab91
Signed-off-by: Carsten Hammer <carsten.hammer@t-online.de>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Do not reload packfiles when their associated filesnapshot is not
modified on disk compared to the one currently stored in memory.

Fix the regression introduced by fef78212 which, in conjunction with
core.trustfolderstats = false, caused any lookup of objects inside
the packlist to loop forever when the object was not found in the pack
list.

Bug: 546190
Change-Id: I38d752ebe47cefc3299740aeba319a2641f19391
Signed-off-by: Luca Milanesio <luca.milanesio@gmail.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Add resolveTipSha1, an inverse of exactRef(String ...), to RefDatabase
and provide a default implementation that runs in O(n) time where n is
the number of refs. For RefTable, provide an implementation that runs
in O(log(n)) time.

[ifrade@google.com: with tests in InMemoryRepositoryTest to exercise
 the reftable code path, too]

Change-Id: I2811ccd0339cdc1c74b42cce2ea003f07a2ce9e1
Signed-off-by: Patrick Hiesel <hiesel@google.com>
Signed-off-by: Ivan Frade <ifrade@google.com>

The new references created in the peeling do not receive the update
index. In other words, the update index of a reference (if set) is lost
in the peeling.

Pass-through the update index to the newly created references.

Tested via InMemoryRepository, which uses DfsReftableDatabase.

Change-Id: I7ff7c737a9c3366fdec296a4d9b2e51d10227957
Signed-off-by: Ivan Frade <ifrade@google.com>

The prune method did not delete empty fanout directories when loose
objects moved to a new pack file but only when loose unreferenced
objects were pruned.

Change-Id: Ia068f4914c54d9cf9f40b75e8ea50759402b5000
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Due to finite filesystem timestamp resolution the last modified
timestamp of files cannot detect file changes which happened in the
immediate past (less than one filesystem timer tick ago).

Read and consider file size also, so that differing file size can help
to more accurately detect file changes without reading the file content.
Use bulk read to avoid multiple stat calls to retrieve file attributes.

Change-Id: I974288fff78ac78c52245d9218b5639603f67a46
Signed-off-by: Luca Milanesio <luca.milanesio@gmail.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

see
https://groups.google.com/d/msg/repo-discuss/oDB2rl3doDc/tFEh5Xt0CAAJ

Change-Id: Ia6d4631c64e065d8b9b09e0b45e7a9ea8ac3f41d
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
(cherry picked from commit 882fed0d96)

see
https://groups.google.com/d/msg/repo-discuss/oDB2rl3doDc/tFEh5Xt0CAAJ

Change-Id: Ia6d4631c64e065d8b9b09e0b45e7a9ea8ac3f41d
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Deprecate the method in favor of setEncoding(Charset).

Update the only caller in the code base that was still using
the deprecated variant.

Change-Id: I6357f2d0c727007013c72e9d5b7c72a3f5f3f2b1
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

Bug caused the pack to be 12 bytes short when cold cache.  Also added
test for copyPackAsIs method.

Change-Id: Idf8fb0e50d1215245d4b032e2e00df4b218c115f
Signed-off-by: Minh Thai <mthai@google.com>

This method tried to iterate spurious files which may exist in the
.git/refs folder, e.g. on Mac a .DS_Store may have been created there by
inspecting the folder using the finder application. This led to a
NotDirectoryException when deleteEmptyRefsFolders tried to create an
iterator for such a file entry. Skip files contained in the refs folder
to ensure the method only tries to iterate contained folders but not
files.

Change-Id: I5f31e733072a35db1e93908a9c69a8891ae5c206
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Change-Id: Ia4202c860b851bef5db72ea6781b3e6a32484e08
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

Change-Id: I22a244114ef973b3801cf3b639ff782f21c02f98
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Its implementation contains

		} catch (IOException e) {
			// Legacy API, assume error means "no"
			return false;
		}

Better to use ObjectDatabase#has, which throws IOException to report
errors.

Change-Id: I7de02f7ceb8f57b2a8ebdb16d2aa4376775ff933
Signed-off-by: Jonathan Nieder <jrn@google.com>

Psuedorefs like FETCH_HEAD and MERGE_HEAD are supposed to be directly
under the .git directory, not in other locations in the SEARCH_PATH
like refs/ and refs/heads/.  Use exactRef to access them.

Change-Id: Iab8ac47008822fa78fc0691e239e518c34d7a98e
Signed-off-by: Jonathan Nieder <jrn@google.com>

Now the reference carries its updateIndex, so the cursor doesn't need
to expose it.

Change-Id: Icbfca46f92a13f3d8215ad10b2a166a6f40b0b0f
Signed-off-by: Ivan Frade <ifrade@google.com>

In DFS implementations the reference table can fall out of sync, but
it is not possible to check this situation in the current API.

Add a property to the Refs indicating the order of its updates.  This
version is set only by RefDatabase implementations that support
versioning (e.g reftable based).

Caller is responsible to check if the reference db creates versioned
refs before accessing getUpdateIndex(). E.g:

   Ref ref = refdb.exactRef(...);
   if (refdb.hasVersioning()) {
       ref.getUpdateIndex();
   }

Change-Id: I0d5ec8e8df47c730301b2e12851a6bf3dac9d120
Signed-off-by: Ivan Frade <ifrade@google.com>

Change-Id: I0fdf595cba93f5a5cdd0496cee07ac91db304532
Signed-off-by: Mincong Huang <mincong.h@gmail.com>

Previous commits block the addition to the repo of dangerous .gitmodules
files, but some could have been committed before those safeguards where
in place.

Add a check in DfsFsck to validate the .gitmodules files in the repo.
Use the same validation than the ReceivePack, translating the
results to FsckErrors.

Note that *all* .gitmodules files in the storage will be checked, not
only the latest version.

Change-Id: I040cf1f31a779419aad0292ba5e6e76eb7f32b66
Signed-off-by: Ivan Frade <ifrade@google.com>

Change-Id: Ie1631784b5eba04edb21f66df284f9e279fd2ec0
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

The BufferedWriter is opened in a try-with-resource and thus will be
automatically closed.

Presumably the close was added to make sure it is closed before the
subsequent test statements are executed. Instead of explicitly closing
it, let the try-with-resource automatically close it, and move the
subsequent statements out of the try-block.

Change-Id: If5fada2f580ef9cbaad3a0b9216b5200b917781a
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

Replace explicit construction of FileWriter with calls to the
utility method Files.newBufferedWriter, which allows to specify
the charset.

Also convert to try-with-resource.

Change-Id: I9fa3f612b9b2fc5ac12cd79d6e61ca181120dbf5
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

Change-Id: Ie492406005be56ccaf4dfb385ae376636404816d
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

Change-Id: Ie9a9f917503019e7fa51ccbc11a5a3518b74434b
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

As reported by Error Prone:

An inner class should be static unless it references members of its
enclosing class. An inner class that is made non-static unnecessarily
uses more memory and does not make the intent of the class clear.

See https://errorprone.info/bugpattern/ClassCanBeStatic

Change-Id: Ib99d120532630dba63cf400cc1c61c318286fc41
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

There should only be one statement after the expect(...) method.

Any additional statements after the statement that is expected to
throw will never be executed in a passing test. This can lead to
inappropriately passing tests where later incorrect assertions are
skipped by the thrown exception.

See https://errorprone.info/bugpattern/ExpectedExceptionChecker

Change-Id: I20fecf8fb7a243e9da097e6d03fbf8cd69151bf0
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>