apache/flink · error · IllegalArgumentException

The %s is not a directory.

Error message

The %s is not a directory.

What it means

The second validation in listFilesInDirectory: the path exists but Files.isDirectory(directory) is false, so the method throws IllegalArgumentException("The %s is not a directory."). A regular file (or special fs object) was passed where a traversable directory is required.

Source

Thrown at flink-core/src/main/java/org/apache/flink/util/FileUtils.java:576

     * fileFilter}.
     *
     * @param directory the directory to be listed
     * @param fileFilter a file filter
     * @return a collection of {@code File}s
     * @throws IOException if an I/O error occurs while listing the files in the given directory
     */
    public static Collection<java.nio.file.Path> listFilesInDirectory(
            final java.nio.file.Path directory, final Predicate<java.nio.file.Path> fileFilter)
            throws IOException {
        checkNotNull(directory, "directory");
        checkNotNull(fileFilter, "fileFilter");

        if (!Files.exists(directory)) {
            throw new IllegalArgumentException(
                    String.format("The directory %s dose not exist.", directory));
        }
        if (!Files.isDirectory(directory)) {
            throw new IllegalArgumentException(
                    String.format("The %s is not a directory.", directory));
        }

        final FilterFileVisitor filterFileVisitor = new FilterFileVisitor(fileFilter);

        Files.walkFileTree(
                directory,
                EnumSet.of(FileVisitOption.FOLLOW_LINKS),
                Integer.MAX_VALUE,
                filterFileVisitor);

        return filterFileVisitor.getFiles();
    }

    /**
     * Computes the sum of sizes of all files in the directory and it's subdirectories.
     *
     * @param path the root path from which to start the calculation.

View on GitHub (pinned to 2f3c205e92)

Solutions

1. Point the call at the containing directory, not at a file
2. Validate with Files.isDirectory(dir) and report the exact configured value in your own error message
3. Delete or rename the stale file that occupies the expected directory location

Example fix

// before
Path p = Paths.get(config.get("plugins.dir")); // user set plugins.dir=/opt/flink/lib/flink-connector.jar
FileUtils.listFilesInDirectory(p, JAR_FILTER);

// after
Path p = Paths.get(config.get("plugins.dir"));
if (!Files.isDirectory(p)) throw new IllegalStateException("plugins.dir must be a directory: " + p);

if (!Files.isDirectory(dir)) throw new IllegalStateException("Expected a directory but got a file: " + dir);

When it happens

Trigger: Calling listFilesInDirectory with a path that names a regular file — e.g. pointing a 'scan this directory' option directly at a jar/zip file instead of the folder containing it.

Common situations: Configuration mistakes where a *-dir option is given a file path; a symlinked path resolving to a file; a previous run leaving a file where a directory was expected.

Related errors

• Can not create a Path from an empty string
• tempDirectories contains null entries
• {directory} is not a directory but a regular file
• The directory %s dose not exist.
• Not allowed configuration change(s) were detected:\n - {erro

AI-assisted analysis of apache/flink@2f3c205e92 (2026-08-14). Data as JSON: /api/errors/6b38ba3be7e83913. Report an issue: GitHub.