alibaba/Sentinel · error · IllegalArgumentException

bufSize must between (0, ${MAX_SIZE}], but ${bufSize} get

Error message

bufSize must between (0, ${MAX_SIZE}], but ${bufSize} get

What it means

FileInJarReadableDataSource reads a config file packaged inside a jar into a fixed byte buffer. bufSize must satisfy 0 < bufSize <= MAX_SIZE (DEFAULT_BUF_SIZE = 1024 * 1024 if you use the convenience constructor); values outside that range throw IllegalArgumentException because the single read cannot handle empty or oversized buffers.

Source

Thrown at sentinel-extension/sentinel-datasource-extension/src/main/java/com/alibaba/csp/sentinel/datasource/FileInJarReadableDataSource.java:81

    }

    public FileInJarReadableDataSource(String jarName, String fileInJarName, Converter<String, T> configParser,
                                       int bufSize) throws IOException {
        this(jarName, fileInJarName, configParser, bufSize, DEFAULT_CHARSET);
    }

    public FileInJarReadableDataSource(String jarName, String fileInJarName, Converter<String, T> configParser,
                                       Charset charset) throws IOException {
        this(jarName, fileInJarName, configParser, DEFAULT_BUF_SIZE, charset);
    }

    public FileInJarReadableDataSource(String jarName, String fileInJarName, Converter<String, T> configParser,
                                       int bufSize, Charset charset) throws IOException {
        super(configParser);
        AssertUtil.assertNotBlank(jarName, "jarName cannot be blank");
        AssertUtil.assertNotBlank(fileInJarName, "fileInJarName cannot be blank");
        if (bufSize <= 0 || bufSize > MAX_SIZE) {
            throw new IllegalArgumentException("bufSize must between (0, " + MAX_SIZE + "], but " + bufSize + " get");
        }
        AssertUtil.notNull(charset, "charset can't be null");
        this.buf = new byte[bufSize];
        this.charset = charset;
        this.jarName = jarName;
        this.fileInJarName = fileInJarName;
        initializeJar();
        firstLoad();
    }

    @Override
    public String readSource() throws Exception {
        if (null == jarEntry) {
            // Will throw FileNotFoundException later.
            RecordLog.warn(String.format("[FileInJarReadableDataSource] File does not exist: %s", jarFile.getName()));
        }
        try (InputStream inputStream = jarFile.getInputStream(jarEntry)) {
            if (inputStream.available() > buf.length) {

View on GitHub (pinned to a3f40ba8e9)

Solutions

  1. Use a positive bufSize no greater than FileInJarReadableDataSource.MAX_SIZE.
  2. Simplest: drop the bufSize argument and use the constructor defaulting to DEFAULT_BUF_SIZE (1 MB).
  3. If the in-jar file truly exceeds MAX_SIZE, that file cannot be loaded by this datasource — split it or raise bufSize only up to MAX_SIZE.

Example fix

// before
new FileInJarReadableDataSource<>(jar, name, parser, 0, charset);

// after
new FileInJarReadableDataSource<>(jar, name, parser, charset); // 1MB default
// or an explicit in-range size:
new FileInJarReadableDataSource<>(jar, name, parser, 64 * 1024, charset);
Defensive patterns

Strategy: validation

Validate before calling

int bufSize = Math.min(Math.max(requestedBufSize, 1), FileInJarReadableDataSource.DEFAULT_BUF_SIZE);
new FileInJarReadableDataSource<>(jarName, fileInJarName, parser, bufSize, charset);

Type guard

boolean isValidBufSize(int bufSize) {
    return bufSize > 0 && bufSize <= FileInJarReadableDataSource.DEFAULT_BUF_SIZE /* MAX_SIZE */;
}

Prevention

When it happens

Trigger: new FileInJarReadableDataSource(jarName, fileInJarName, parser, bufSize, charset) with bufSize <= 0 or bufSize > MAX_SIZE (the constructor asserts jarName/fileInJarName non-blank first).

Common situations: Sizing the buffer from the actual file length without bounds (a file bigger than MAX_SIZE), passing 0 by default, or computing bufSize from a config property that is unset.

Related errors

AI-assisted analysis of alibaba/Sentinel@a3f40ba8e9 (2026-08-14). Data as JSON: /api/errors/68a1a809bb024cdf. Report an issue: GitHub.