RFR: 8344911: Introduce test utility for asserting file open status

[Eirik Bjørsnøs]

On Sat, 23 Nov 2024 15:47:53 GMT, Eirik Bjørsnøs <eirbjo at openjdk.org> wrote:

> Please review this PR which  adds a utility API in the test libraries to assert whether a file is currently open.
> 
> Several OpenJDK  tests currently rely on approximations to check this, including deletion (fails only on Windows), or checking `/proc/<pid>/fd` (Works only on Linux). These approximations are blunt instruments, it would be better to have an exact cross platform solution for this need to check if a file is open or closed.
> 
> Initial support includes:
> 
> * `FileInputStream`, `FileOutputStream` and `RandomAccessFile` from `java.io`
> * `FileChannelImpl` from `java.nio`, meaning we can check synchronous NIO APIs such as `Files.newInputStream`, `Files.newOutputStream`, `Files.newByteChannel` and `FileChannel.open`
> 
> This allows testing of many (most?) JDK APIs such as `ZipFile`, `JarFile`, `JarURLConnection`, `FileURLConnection` etc.
> 
> Tests use the following configuration to enable  instrumentation of file access APIs:
> 
> 
> * @library /test/lib
> * @run driver jdk.test.lib.util.OpenFilesAgent
> * @run junit/othervm -javaagent:OpenFilesAgent.jar OpenFilesTest
> 
> 
> Also provided is an assertion API to verify whether files are open or not:
> 
> 
> Path file = Files.createFile(Path.of("file.txt"));
> assertClosed(file);
> try (var is = Files.newInputStream(file)) {
>     assertOpen(file);
> }
> assertClosed(file);
> ``` 
> 
> A failed `assertClosed` shows the stack trace for whatever action opened the file:
> 
> 
> Caused by: java.lang.Throwable: Opening stack trace of jdk/build/macosx-x86_64-server-release/JTwork/scratch/file.txt
> 	at jdk.test.lib.util.OpenFiles.openFile(OpenFiles.java:59)
> 	at java.base/java.nio.file.Files.newByteChannel(Files.java:357)
> 	at java.base/java.nio.file.Files.newByteChannel(Files.java:399)
> 	at java.base/java.nio.file.spi.FileSystemProvider.newInputStream(FileSystemProvider.java:371)
> 	at java.base/java.nio.file.Files.newInputStream(Files.java:154)
> 	at OpenFilesTest.sample(OpenFilesTest.java:81)
> 
> 
> See the library implementation test `OpenFilesTest` for samples.
> 
> Verification:
> With `OpenFilesTest` temporarily in tier1, GHA completed successfully across platforms.

Moving details out of the PR description to reduce mail noise:

Initial support includes:

* `FileInputStream`, `FileOutputStream` and `RandomAccessFile` from `java.io`
* `FileChannelImpl` from `java.nio`, meaning we can check synchronous NIO APIs such as `Files.newInputStream`, `Files.newOutputStream`, `Files.newByteChannel` and `FileChannel.open`

This allows testing of many (most?) JDK APIs such as `ZipFile`, `JarFile`, `JarURLConnection`, `FileURLConnection` etc.

Tests use the following configuration to enable  instrumentation of file access APIs:


* @library /test/lib
* @run driver jdk.test.lib.util.OpenFilesAgent
* @run junit/othervm -javaagent:OpenFilesAgent.jar OpenFilesTest


Also provided is an assertion API to verify whether files are open or not:


Path file = Files.createFile(Path.of("file.txt"));
assertClosed(file);
try (var is = Files.newInputStream(file)) {
    assertOpen(file);
}
assertClosed(file);
``` 

A failed `assertClosed` shows the stack trace for whatever action opened the file:


Caused by: java.lang.Throwable: Opening stack trace of jdk/build/macosx-x86_64-server-release/JTwork/scratch/file.txt
	at jdk.test.lib.util.OpenFiles.openFile(OpenFiles.java:59)
	at java.base/java.nio.file.Files.newByteChannel(Files.java:357)
	at java.base/java.nio.file.Files.newByteChannel(Files.java:399)
	at java.base/java.nio.file.spi.FileSystemProvider.newInputStream(FileSystemProvider.java:371)
	at java.base/java.nio.file.Files.newInputStream(Files.java:154)
	at OpenFilesTest.sample(OpenFilesTest.java:81)


See the library implementation test `OpenFilesTest` for samples.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/22343#issuecomment-2498571155