5911521ba6
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> |
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| .. | ||
| META-INF/services | ||
| org/eclipse/jgit | ||
| jgit-s3-config.disabled.properties | ||
| jgit-s3-config.policy.bucket.json | ||
| jgit-s3-config.policy.user.json | ||
| jgit-s3-connection-v-0.properties | ||
| jgit-s3-connection-v-1.properties | ||
| jgit-s3-connection-v-2.properties | ||
| log4j.properties | ||