Prevent multiple async-profiler library deployments

[aleks-p]

If we try to load the async-profiler library from multiple processes at the same time, loading can fail because we are trying to deploy the app multiple times.

One case where this can happen is when the SDK is used in concurrently executed unit tests.

Caused by: java.nio.file.FileAlreadyExistsException: /var/folders/rl/p7hzvh8943v6xf55qksjjc240000gn/T/redacted-pyroscope/libasyncProfiler-redacted-6bf68b96dcb6e8ec20caa84e1e69e6659f17f5.so
	at java.base/sun.nio.fs.UnixException.translateToIOException(UnixException.java:94)
	at java.base/sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:106)
	at java.base/sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:111)
	at java.base/sun.nio.fs.UnixFileSystemProvider.newByteChannel(UnixFileSystemProvider.java:262)
	at java.base/java.nio.file.spi.FileSystemProvider.newOutputStream(FileSystemProvider.java:482)
	at java.base/java.nio.file.Files.newOutputStream(Files.java:228)
	at java.base/java.nio.file.Files.copy(Files.java:3164)
	at io.pyroscope.labels.io.pyroscope.PyroscopeAsyncProfiler.deployLibrary(PyroscopeAsyncProfiler.java:54)
	at io.pyroscope.labels.io.pyroscope.PyroscopeAsyncProfiler.<clinit>(PyroscopeAsyncProfiler.java:25)

An alternative approach is to use Files.createTempDirectory which will result in separate deployments for each process, though in the case of unit testing this can be wasteful.

[korniltsev]

Can the current implementation still trigger a race? For example one process is created and in the process of copying the library and the other process already see the library exists and tries to load it while it is still being copied?

[aleks-p]

Can the current implementation still trigger a race? For example one process is created and in the process of copying the library and the other process already see the library exists and tries to load it while it is still being copied?

You are right, I've switched to the alternative mentioned above - creating a unique temp directory.