Create/modify events not emitted if file is locked by another process
chromy96 opened this issue · 4 comments
DirectoryWatcher is trying to calculate the hash of every created/modified file when the event is emitted. Because of it, if the file is locked by the process writting to it, it can happen that some create/modify events are not emitted.
The error happens in PathUtils.hash(Path file) method. If you enable logging in catch clause, you will see that sometimes hash calculation fails with the following exception:
[ForkJoinPool.commonPool-worker-9] ERROR io.methvin.watcher.PathUtils - Exception when calculating hash
java.io.IOException: The process cannot access the file because it is being used by another process
at java.base/java.io.FileInputStream.readBytes(Native Method)
at java.base/java.io.FileInputStream.read(FileInputStream.java:258)
at com.google.common.io.ByteStreams.copy(ByteStreams.java:106)
at com.google.common.io.ByteSource.copyTo(ByteSource.java:246)
at com.google.common.io.ByteSource.hash(ByteSource.java:326)
at io.methvin.watcher.PathUtils.hash(PathUtils.java:49)
at io.methvin.watcher.DirectoryWatcher.notifyCreateEvent(DirectoryWatcher.java:257)
at io.methvin.watcher.DirectoryWatcher.watch(DirectoryWatcher.java:162)
at io.methvin.watcher.DirectoryWatcher.lambda$watchAsync$0(DirectoryWatcher.java:100)
at java.base/java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1700)
at java.base/java.util.concurrent.CompletableFuture$AsyncSupply.exec(CompletableFuture.java:1692)
at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:290)
at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1603)
at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:177)
My question is: Is it necessary to calculate the hash of the files at all? Would it be enough to keep only directories in hash map and emit all the events for the files as they happen?
Here's the gist with the test case that reproduces the issue for create event: https://gist.github.com/chromy96/def29f4e9a0430e90f9ae28434fcc0f7
Option for disabling hashing files woud be a great addition. I can provide the first implementation if you're busy right now.
A pull request would be great, or else I'll probably look at implementing it sometime the next month or so.