apache/cassandra · error · IllegalStateException

Cannot read from an empty path

Error message

Cannot read from an empty path

What it means

Thrown by File.toPathForRead() when a read operation is attempted on a File whose internal path is null. The Cassandra I/O File wrapper requires a non-null path to resolve to a java.nio.file.Path for reading. It indicates the File object was constructed without a path (e.g. via a null-argument constructor path) and is unusable for reads.

Source

Thrown at src/java/org/apache/cassandra/io/util/File.java:800

    public File withSuffix(String suffix)
    {
        if (path == null)
            throw new IllegalStateException("Cannot suffix an empty path");
        return new File(path.getParent().resolve(path.getFileName().toString() + suffix));
    }

    private Path toPathForWrite()
    {
        if (path == null)
            throw new IllegalStateException("Cannot write to an empty path");
        return path;
    }

    private Path toPathForRead()
    {
        if (path == null)
            throw new IllegalStateException("Cannot read from an empty path");
        return path;
    }

    @VisibleForTesting
    public static FileSystem unsafeGetFilesystem()
    {
        return filesystem;
    }

    public static void unsafeSetFilesystem(FileSystem fs)
    {
        filesystem = fs;
    }
}

View on GitHub (pinned to 88fd0f6a0e)

Solutions

1. Find where the File was constructed and fix the null path source (check config/env for the path value).
2. Validate the path string is non-null/non-empty before constructing File.
3. Use File.isEmpty() or similar check to guard read calls.

Example fix

// before
File f = new File(config.commitLogDir); // config value null
f.newInputStream();

// after
if (config.commitLogDir == null || config.commitLogDir.isEmpty())
    throw new IllegalStateException("commitLogDir must be configured");
File f = new File(config.commitLogDir);
f.newInputStream();

if (path == null || path.isEmpty()) throw new IllegalArgumentException("path must be configured");

boolean isReadable(File f) { return f != null && !f.isEmpty(); }

try { file.newInputStream(); } catch (IllegalStateException e) { /* handle null path */ }

When it happens

Trigger: Calling any read-oriented method (e.g. newInputStream, toPathForRead-backed APIs) on org.apache.cassandra.io.util.File whose `path` field is null — typically a File built from a null String or null parent.

Common situations: Passing null configuration values (data/saved-caches paths) into file APIs; deserializing or programmatically constructing a File without validating the path; API migration where callers previously used java.io.File (which tolerated null less strictly at a later stage).

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• Cannot suffix an empty path
• Cannot write to an empty path
• Can't open %r for reading: %s
• Corrupt flags value for clustering prefix (isStatic flag set
• Corrupted sstable. Invalid flags found deserializing Deletio

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/9a88fc8f752e0b9f. Report an issue: GitHub.