apache/seatunnel · error · IllegalArgumentException

input.multiline.match must be "after" or "before".

Error message

input.multiline.match must be "after" or "before".

What it means

input.multiline.match decides whether lines matching multiline.pattern are appended after or before the previous line. FileCollectConfig.validateMultilineMatch accepts only "after" or "before" (case-insensitive) and throws this IllegalArgumentException otherwise.

Source

Thrown at seatunnel-edge-agent/seatunnel-edge-agent-connector/src/main/java/org/apache/seatunnel/edge/agent/connector/config/FileCollectConfig.java:141

    }

    public boolean isJsonOutput() {
        return "json".equalsIgnoreCase(outputType);
    }

    public boolean isSkipOnError() {
        return !"fail".equalsIgnoreCase(onError);
    }

    private static void validateOnError(String value) {
        if (!value.equalsIgnoreCase("skip") && !value.equalsIgnoreCase("fail")) {
            throw new IllegalArgumentException("input.on-error must be \"skip\" or \"fail\".");
        }
    }

    private static void validateMultilineMatch(String value) {
        if (!value.equalsIgnoreCase("after") && !value.equalsIgnoreCase("before")) {
            throw new IllegalArgumentException(
                    "input.multiline.match must be \"after\" or \"before\".");
        }
    }

    private static void validateOutputType(String value) {
        if (!value.equalsIgnoreCase("line") && !value.equalsIgnoreCase("json")) {
            throw new IllegalArgumentException(
                    "input.output-format.type must be \"line\" or \"json\".");
        }
    }

    private static Charset resolveCharset(String encodingName, String inputId) {
        try {
            return Charset.forName(encodingName);
        } catch (IllegalCharsetNameException | UnsupportedCharsetException e) {
            throw new IllegalArgumentException(
                    "input.encoding is not supported: "
                            + encodingName

View on GitHub (pinned to cf67b549a7)

Solutions

1. Set input.multiline.match to "after" (pattern lines belong to the previous event) or "before" (pattern lines start a new event)
2. Verify the pattern/match pair semantics against your log format
3. Check that template rendering is not producing an empty match value

Example fix

# before
multiline.match = "forward"
# after
multiline.match = "after"

String match = cfg.get(FileCollectOptions.MULTILINE_MATCH);
if (!"after".equalsIgnoreCase(match) && !"before".equalsIgnoreCase(match)) { throw new IllegalArgumentException("multiline.match must be after or before"); }

try { FileCollectConfig.from(config); } catch (IllegalArgumentException e) { log.error("multiline.match invalid: {}", e.getMessage()); }

When it happens

Trigger: Setting input.multiline.match to values like "next", "previous", "forward", "backward", or an empty string.

Common situations: Confusion with other multiline implementations that use 'before/previous' style vocabularies, or truncated templated configs.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• Unknown format type:
• Unknown ftp connection mode: ${mode}
• input.multiline.flush-idle-timeout-ms must be > 0 when multi
• input.on-error must be "skip" or "fail".
• input.output-format.type must be "line" or "json".

AI-assisted analysis of apache/seatunnel@cf67b549a7 (2026-09-10). Data as JSON: /api/errors/c13ea5611ee0bc4e. Report an issue: GitHub.