Avoid having to scan over ALL loose refs to determine if the
name is nested within or is a container of an existing reference.
This can get really expensive if there are too many loose refs.
Instead use exactRef and getRefsByPrefix which scan based on a
prefix.
With a simple shell script(like below) using jgit client to create
1k refs in a new repository on NFS, this change brings down the time
from 12mins to 7mins.
for ref in $(seq 1 1000); do
jgit branch "$ref"
done
Here are few recorded elapsed times to create a new branch on NFS
based repositories with varying loose refs count. As we see here,
this change improves the name conflicting check from O(n^2) to O(1).
loose_refs_count with_change without_change
50 44 ms 164 ms
300 45 ms 1193 ms
1k 38 ms 2610 ms
2k 44 ms 6003 ms
9k 46 ms 27860 ms
20k 45 ms 48591 ms
50k 51 ms 135471 ms
110k 43 ms 294252 ms
160k 52 ms 430976 ms
Change-Id: Ie994fc184b8f82811bfb37b111eb9733dbe3e6e0
Signed-off-by: Kaushik Lingarkar <quic_kaushikl@quicinc.com>
Fix PackInvalidException when fetch and repack run concurrently
We are running several servers with jGit. We need to run repack from
time to time to keep the repos performant. I.e. after push we test how
many small packs are in the repo and when a threshold is reached we run
the repack.
After upgrading jGit version we've found that if someone does the clone
at the time repack is running the clone sometimes (not always) fails
because the repack removes .pack file used by the clone. Server
exception and client error attached.
I've tracked down the cause and it seems to be introduced between jGit
5.2 (which we upgraded from) and 5.3 and being caused by this commit:
Move throw of PackInvalidException outside the catch -
afef866a44
The problem is that when the throw was inside of the try block the last
catch block catched the exception and called openFailed(false) method.
It is true that it called it with invalidate = false, which is wrong.
The real problem though is that with the throw outside of the try block
the openFail is not called at all and the fields activeWindows and
activeCopyRawData are not set to 0. Which affects the later called tests
like: if (++activeCopyRawData == 1 && activeWindows == 0).
The fix for this is relatively simple keeping the throw outside of the
try block and still having the invalid field set to true. I did
exhaustive testing of the change running concurrent clones and pushes
indefinitely and with the patch applied it never fails while without the
patch it takes relatively short to get the error.
See: https://www.eclipse.org/lists/jgit-dev/msg04014.html
Bug: 569349
Change-Id: I9dbf8801c8d3131955ad7124f42b62095d96da54
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
GC#deleteOrphans: handle failure to list files in pack directory
- log an error
- either there is no list or it is incomplete hence return immediately
Change-Id: Ieee5378ca06304056b9ccc30c1acd5f52360052d
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
If pack or index files are guarded by a pack lock (.keep file)
deleteOrphans() should not touch the respective files protected by the
lock file. Otherwise it may interfere with PackInserter concurrently
inserting a new pack file and its index.
The problem was caused by the following race.
All mentioned files are located in "objects/pack/".
File endings relevant in "pack" dir:
.pack
.keep
.idx
.bitmap
When ReceivePack receives a pack file it executes the following steps:
ReceivePack.service():
receivePackAndCheckConnectivity():
receivePack():
receive the pack
parse the pack, returns packLock (.keep file)
PackInserter.flush():
write tmpPck file: "insert_<random>.pack"
write tmpIdx file: "insert_<random>.idx"
real pack name: "pack-<SHA1>.pack"
real index name: "pack-<SHA1>.idx"
atomic rename tmpPack to realPack
atomic rename tmpIdx to tmpIdx
execute commands
unlock pack by removing .keep file
trigger auto gc if enabled
When PackInserter.flush() renames the temporary pack to the final
"pack-xxx.pack" file the temporary pack index file "insert_xxx.idx"
has no matching .pack file with the same base name for a short interval.
If deleteOrphans() ran during that interval it deduced the pack index
file was orphaned. Subsequently the missing pack index caused
MissingObjectExceptions since objects contained in the pack couldn't be
looked up anymore.
Bug: https://bugs.chromium.org/p/gerrit/issues/detail?id=13544
Change-Id: I559c81e4b1d7c487f92a751bd78b987d32c98719
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
WindowCache: add metric for cached bytes per repository
Since ObjectDatabase and PackFile don't know their repository use the
packfile's grand-grand-parent directory as an identifier for the
repository the packfile resides in.
Remove metric for a repository if the number of cached bytes for the
repository drops to 0 in order to ensure the map of cached bytes per
repository doesn't contain repositories which have no data cached in the
WindowCache.
Change-Id: I969ab8029db0a292e7585cbb36ca0baa797da20b
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
WindowCache: add option to use strong refs to reference ByteWindows
Java GC evicts all SoftReferences when the used heap size comes close to
the maximum heap size. This means peaks in heap memory consumption can
flush the complete WindowCache which was observed to have negative
impact on performance of upload-pack in Gerrit.
Hence add a boolean option core.packedGitUseStrongRefs to allow using
strong references to reference packfile pages cached in the WindowCache.
If this option is set to true Java gc can no longer flush the
WindowCache to free memory if the used heap comes close to the maximum
heap size. On the other hand this provides more predictable performance.
Bug: 553573
Change-Id: I9de406293087ab0fa61130c8e0829775762ece8d
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Add the following statistics
- cache hit count and hit ratio
- cache miss count and miss ratio
- count of successful and failed loads
- rate of failed loads
- load, eviction and request count
- average and total load time
Use LongAdder instead of AtomicLong to implement counters in order to
improve scalability.
Optionally expose these metrics via JMX, they are registered with the
platform MBean server if the config option jmx.WindowCacheStats = true
in the user or system level git config.
Bug: 553573
Change-Id: Ia2d5246ef69b9c2bd594a23934424bc5800774aa
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
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.
Bug: 548716
Change-Id: I613c8059964513ce2370543620725b540b3cb6d1
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
These warnings were missed to address in a0048208 which introduced them.
Change-Id: Ia2d15fdce72c10378d020682b80fe7fc548c0d4c
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
UploadPack: support custom packfile-to-URI mapping
Teach UploadPack to take a provider of URIs corresponding to cached
packs. When fetching, if the client supports the packfile-uri feature,
and if such a cached pack were to be streamed, instead send the
corresponding URI.
This packfile-uri feature is implemented in the jt/fetch-cdn-offload
branch of Git. There is interest in this feature [1], but it is not yet
merged.
[1] https://public-inbox.org/git/cover.1552073690.git.jonathantanmy@google.com/
Change-Id: I9a32dae131c9c56ad2ff4a8a9638ae3b5e44dc15
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Previously, the API did not enforce ordering of writes. Misuse of
this API would lead to data effectively being lost.
Guard against that with IllegalArgumentException, and add a test.
Change-Id: I04f55c481d60532fc64d35fa32c47037a03988ae
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
reftable: fix seeking to refs in reflog implementation
Small reftables omit the log index. Currently,
ReftableWriter#shouldHaveIndex does this if there is a single-block
log, but other writers could decide on different criteria.
In the case that the log index is missing, we have to linearly search
for the right block. It is never appropriate to use binary search on
blocks for log data, as the blocks are compressed and therefore
irregularly sized.
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Change-Id: Id59874edf6bf45c7dec502d9465888e077ffe198
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>
[error prone] suppress AmbiguousMethodReference in AnyObjectId
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>
Fix NarrowingCompoundAssignment warnings from Error Prone
Error Prone reports:
[NarrowingCompoundAssignment] Compound assignments from long to int
hide lossy casts
and
[NarrowingCompoundAssignment] Compound assignments from int to byte
hide lossy casts
See https://errorprone.info/bugpattern/NarrowingCompoundAssignment
Fix the warnings by adding explicit casts or changing types as
necessary.
Now that all occurrences of the warning are fixed, increase its
severity to ERROR.
Change-Id: Idb3670e6047b146ae37daee07212ff9455512623
Signed-off-by: David Pursehouse <david.pursehouse@gmail.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>
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>
Fix FileSnapshot#save(long) and FileSnapshot#save(Instant)
Use the fallback timestamp resolution as already described in the
javadoc of these methods. Using zero file timestamp resolution doesn't
make sense.
Change-Id: Iaad2a0f99c3be3678e94980a0a368181b6aed38c
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
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.
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>
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>
These are useful to avoid typos, and also for tab completion.
Change-Id: I0f2d267e46b36bc40297c9657c447f3fd8b9f831
Signed-off-by: David Turner <dturner@twosigma.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>
We should not use configuration when creating FileSnapshot when
accessing FileBasedConfig.
Change-Id: Ic521632870f18bb004751642b9d30648dd94049a
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
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>
Checking lastModified is time critical hence debug trace is the only way
to analyze issues since debugging is impractical.
Also add configuration for buffering of log4j output to reduce runtime
impact when debug trace is on. Limit buffer to 1MiB and comment this
configuration out since we may not always want to use buffering.
Change-Id: Ib1a0537b67c8dc3fac994a77b42badd974ce6c97
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Persist filesystem timestamp resolution and allow manual configuration
To enable persisting filesystem timestamp resolution per FileStore add a
new config section to the user global git configuration:
- Config section is "filesystem"
- Config subsection is concatenation of
- Java vendor (system property "java.vm.vendor")
- runtime version (system property "java.vm.version")
- FileStore's name
- separated by '|'
e.g.
"AdoptOpenJDK|1.8.0_212-b03|/dev/disk1s1"
The prefix is needed since some Java versions do not expose the full
timestamp resolution of the underlying filesystem. This may also
depend on the underlying operating system hence concrete key values
may not be portable.
- Config key for timestamp resolution is "timestampResolution" as a time
value, supported time units are those supported by
DefaultTypedConfigGetter#getTimeUnit
If timestamp resolution is already configured for a given FileStore
the configured value is used instead of measuring the resolution.
When timestamp resolution was measured it is persisted in the user
global git configuration.
Example:
[filesystem "AdoptOpenJDK|1.8.0_212-b03|/dev/disk1s1"]
timestampResolution = 1 seconds
If locking the git config file fails retry saving the resolution up to 5
times in order to workaround races with another thread.
In order to avoid stack overflow use the fallback filesystem timestamp
resolution when loading FileBasedConfig which creates itself a
FileSnapshot to help checking if the config changed.
Note:
- on some OSes Java 8,9 truncate to milliseconds or seconds, see
https://bugs.openjdk.java.net/browse/JDK-8177809, fixed in Java 10
- UnixFileAttributes up to Java 12 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 up to
Java 12
Hence do not attempt to manually configure a higher timestamp resolution
than supported by the Java version being used at runtime.
Bug: 546891
Bug: 548188
Change-Id: Iff91b8f9e6e5e2295e1463f87c8e95edf4abbcf8
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)
Error Prone: Increase severity of NonOverridingEquals to ERROR
Error Prone reports the warning on several classes:
[NonOverridingEquals] equals method doesn't override Object.equals;
if this is a type-specific helper for a method that does override
Object.equals, either inline it into the callers or rename it to
avoid ambiguity.
See https://errorprone.info/bugpattern/NonOverridingEquals
Most of these are in the public API, so we can't rename or inline them
without breaking the API. FileSnapshot is not part of the public API,
but clients may be using it anyway, so we also shouldn't change that.
Suppress all the warnings instead. Having the check at severity ERROR
will at least make sure we don't introduce any new occurrences.
Change-Id: I92345c11256f06b4fa03ccc13337f72af5a43591
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>
Reference comparison with EMPTY and MISSING_FILE is intended; these
are static instances used as markers, and will always be the same
instances.
Change-Id: Ic27f5b797bdb9370cf8f6b3b7bb3f1523d4a454c
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>
PackWriter: Prefer boolean operators over logical operators in comparisons
Using the | and & operators in boolean conditions results in a warning
from Error Prone:
[ShortCircuitBoolean]
Prefer the short-circuiting boolean operators && and || to & and |.
see https://errorprone.info/bugpattern/ShortCircuitBoolean
Change-Id: I4275c60306e43c74030c4465ba02cb853ad444e1
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>
Increase severity of OperatorPrecedence to ERROR, and fix instances
Fix all remaining instances of the OperatorPrededence warning, by adding
parentheses to make the precedence explicit.
Change-Id: Ib296dfed09f9be042d0ff0f7fad8214e4dd766b4
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>
The TODO comments say "in 5.0", but 5.0 was already released without
resolving them. Remove "in 5.0" on the assumption that the mentioned
improvements still need to be done at some point.
Change-Id: I3eb429803e2266de3fc490e1f3912991c08aa1ad
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>
When Error Prone checks are enabled, the "ClassCanBeStatic" warning is
triggered:
Inner class is non-static but does not reference enclosing class
see https://errorprone.info/bugpattern/ClassCanBeStatic
Change-Id: I5a0e3bf0cf8c28176d9c98914c1c0dfab9c5736f
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>
Repository: Add getIdentifier() method to avoid instanceof operator
This change is needed to implement permission aware ref database in
Gerrit: [1], that is a pre-requisite to re-enable Git v2 protocol in
Gerrit: [2].
Background: Last year Git v2 protocol was enabled in Gerrit. The fact,
that JGit layer was not calling ref advertise filter for Git v2
protocol, introduced security vulnerability.
The lesson learned from this security incident: Gerrit should not rely
on ref advertise filter being called by JGit to implement crictical
security checks. Instead, the idea is to use the same approach as
currently used by Google's internal code on googlesource.com that
didn't suffer from this vulnerability: provide a custom repository to
JGit. The repository provides a RefDatabase that is permission-aware
and will only ever return refs that the user has access to.
However, due to hard coded instanceof operator usages in JGit code
base, some tests in Gerrit are failing with: [1] in place. This change
addresses this problem.
[1] https://gerrit-review.googlesource.com/c/gerrit/+/212874
[2] https://gerrit-review.googlesource.com/c/gerrit/+/226754
Change-Id: I67c0f53ca33b149442e7ee3e51910d19e3f348d5
Signed-off-by: David Ostrovsky <david@ostrovsky.org>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Extend FileSnapshot for packfiles to also use checksum to detect changes
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>
Wait opening new packfile until it can't be racy anymore
If
- pack.waitPreventRacyPack = true (default is false)
- packfile size > pack.minSizePreventRacyPack (default is 100 MB)
wait after a new packfile was written and before it is opened until it
cannot be racy anymore.
If a new packfile is accessed while it's still racy at least the pack's
index will be reread by ObjectDirectory.scanPacksImpl(). Hence it may
save resources to wait one tick of the file system timer to avoid this
reloading. On filesystems with a coarse timestamp resolution it may be
beneficial to skip this wait for small packfiles.
Bug: 546891
Change-Id: I0e8bf3d7677a025edd2e397dd2c9134ba59b1a18
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Initialize it using the repository's config already in the constructor.
Change-Id: I4ea620a7db72956e7109f739990f09644640206b
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Capture reason for result of FileSnapshot#isModified
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>
This resolves a regression introduced in fef78212.
Change-Id: Ibb4521635a87012520566efc70870c59d11be874
Signed-off-by: Marc Strapetz <marc.strapetz@syntevo.com>
Include filekey file attribute when comparing FileSnapshots
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>
Measure file timestamp resolution used in FileSnapshot
FileSnapshot.notRacyClean() assumed a worst case filesystem timestamp
resolution of 2.5 sec (FAT has a resolution of 2 sec). Instead measure
timestamp resolution to avoid unnecessary IO caused by false positives
in detecting the racy git problem caused by finite filesystem timestamp
resolution [1].
Cache the measured resolution per FileStore since timestamp resolution
depends on the respective filesystem type. If timestamp resolution
cannot be measured or fails due to an exception fallback to the worst
case FAT timestamp resolution and avoid caching this value.
Add a 10% safety margin in FileSnapshot.notRacyClean(), though running
FsTest.testFsTimestampResolution() 1000 times which is not using a
safety margin didn't fail on Mac using APFS and Java 8, 11, 12.
Measured Java file timestamp resolution: [2]
[1] https://github.com/git/git/blob/master/Documentation/technical/racy-git.txt
[2] https://docs.google.com/spreadsheets/d/1imy0y6WmRqBf0kjCxzxj2X7M50eIVfa7oaUIzEOHmjo
Bug: 546891
Change-Id: I493f3b57b6b306285ffa7d392339d253e5966ab8
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
* fix equals() and hashCode() methods to consider size
* fix toString() to show size
Change-Id: I5485db55eda5110121efd65d86c7166b3b2e93d0
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Kaushik Lingarkar
Petr Hrebejk
Matthias Sohn
Han-Wen Nienhuys
Jonathan Tan
David Pursehouse
David Turner
David Ostrovsky
Marc Strapetz