Does IOUtils.copy block until writing is finished?

Question

Here's my situation: I'm using `IOUtils` to copy a file. The next thing I do is send a JSON message to another program to say, "You can download the copy". The problem is about 25% of the time the other program gets an error saying "Received unexpected EOF downloading artifact". Every time this error occurs, if I try again manually, the error doesn't occur. My theory is that `IOUtils.copy` doesn't block and the OS is still writing the file to the FS while the other program tries to download it. Is there a way to force `IOUtils.copy` or other functionally equivalent code to block until the OS has finished writing the file? Or is my theory incorrect? Here's the code I'm using: ``` private boolean archiveArtifact(String archivePath, String deployId, Artifact artifact) { InputStream inputStream = null; FileOutputStream fileOutputStream = null; boolean successful = true; try { File archiveDir = new File(archivePath); File deployDir = new File(archiveDir, deployId); if (!deployDir.exists())…

Accepted Answer

Your current code only ensures that the file content is passed to the operating system for writing; it does not guarantee that it is actually written to a the disk.

To be certain that the file is actually written to disk you can call `sync()` on the `FileDescriptor`:

```
fileOutputStream.flush();
fileOutputStream.getFD().sync();
```

Does IOUtils.copy block until writing is finished?

Solution

Problem