alibaba/Sentinel · error · IllegalStateException

Size of file < > exceeds the bufSize ( )

Error message

Size of file <%s> exceeds the bufSize (%d): %d

What it means

FileInJarReadableDataSource.readSource() opens the jar entry and checks inputStream.available() against the fixed buffer allocated at construction. If the in-jar file is larger than bufSize, reading it into the single buffer would truncate the config, so it throws IllegalStateException naming the file, buffer size, and actual size.

Solutions

1. Increase bufSize at construction to at least the largest expected file size (bounded by MAX_SIZE).
2. Or use the default constructor size (1 MB) which covers most rule files.
3. Verify the actual in-jar file size: unzip -l app.jar | grep <fileInJarName> and compare with bufSize in the error message.

Example fix

// before
new FileInJarReadableDataSource<>(jar, name, parser, 4096, charset);
// rules.json grew past 4KB -> IllegalStateException on readSource

// after
new FileInJarReadableDataSource<>(jar, name, parser, 1024 * 1024, charset);

// Size the buffer from the actual entry before constructing
try (JarFile jf = new JarFile(new File(jarName))) {
    int size = (int) jf.getInputStream(jf.getJarEntry(fileInJarName)).available();
    bufSize = Math.max(size, 4096);
} // then construct with bufSize (<= MAX_SIZE)

try {
    return ds.readSource();
} catch (IllegalStateException e) {
    if (e.getMessage() != null && e.getMessage().contains("exceeds the bufSize")) {
        // rebuild datasource with larger bufSize (file grew in new build)
        ds = rebuildWithLargerBuffer();
        return ds.readSource();
    }
    throw e;
}

When it happens

Trigger: readSource()/firstLoad() when the target file inside the jar grew beyond bufSize — typical after a jar rebuild added more rules, while the datasource was constructed with a small explicit bufSize or after fat-jar repackaging.

Common situations: Constructing with a tight bufSize (e.g. 4 KB) that fit at first, then the config file grows in a later release; misjudging available() semantics for compressed jar entries (it can under-report but the check still fires when over).

Related errors

• bufSize must between
• file size= , is bigger than bufSize= . Can't read
• Bad argument: groupId=
• Bad argument: ruleKey=
• Bad argument: serverAddr=

AI-assisted analysis of alibaba/Sentinel@a3f40ba8e9 (2026-08-14). Data as JSON: /api/errors/d7196708c8444727. Report an issue: GitHub.

Appendix: source

Thrown at sentinel-extension/sentinel-datasource-extension/src/main/java/com/alibaba/csp/sentinel/datasource/FileInJarReadableDataSource.java:100

        }
        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) {
                throw new IllegalStateException(String.format("Size of file <%s> exceeds the bufSize (%d): %d",
                    jarFile.getName(), buf.length, inputStream.available()));
            }
            int len = inputStream.read(buf);
            return new String(buf, 0, len, charset);
        }
    }

    private void firstLoad() {
        try {
            T newValue = loadConfig();
            getProperty().updateValue(newValue);
        } catch (Throwable e) {
            RecordLog.warn("[FileInJarReadableDataSource] Error when loading config", e);
        }
    }

    @Override
    public void close() throws Exception {

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