alibaba/arthas · error · IllegalArgumentException

Time fragment index is expected, please type -i to specify

Error message

Time fragment index is expected, please type -i to specify

What it means

Thrown by checkArguments() in the `tt` command when a delete (-d) or play/replay (-p) action is requested but no time fragment index (-i) is supplied. Each recorded time fragment is identified by an integer index; you must specify which one to delete or replay.

Source

Thrown at core/src/main/java/com/taobao/arthas/core/command/monitor200/TimeTunnelCommand.java:255

    static String validateSizeLimit(Integer sizeLimit) {
        if (sizeLimit != null && sizeLimit.intValue() <= 0) {
            return "sizeLimit must be greater than 0.";
        }
        return null;
    }

    /**
     * 检查参数是否合法
     */
    private void checkArguments() {
        String validateError = validateSizeLimit(sizeLimit);
        if (validateError != null) {
            throw new IllegalArgumentException(validateError);
        }

        // 检查d/p参数是否有i参数配套
        if ((isDelete || isPlay) && null == index) {
            throw new IllegalArgumentException("Time fragment index is expected, please type -i to specify");
        }

        // 在t参数下class-pattern,method-pattern
        if (isTimeTunnel) {
            if (StringUtils.isEmpty(classPattern)) {
                throw new IllegalArgumentException("Class-pattern is expected, please type the wildcard expression to match");
            }
            if (StringUtils.isEmpty(methodPattern)) {
                throw new IllegalArgumentException("Method-pattern is expected, please type the wildcard expression to match");
            }
        }

        // 一个参数都没有是不行滴
        if (null == index && !isTimeTunnel && !isDeleteAll && StringUtils.isEmpty(watchExpress)
                && !isList && StringUtils.isEmpty(searchExpress)) {
            throw new IllegalArgumentException("Argument(s) is/are expected, type 'help tt' to read usage");
        }
    }

View on GitHub (pinned to 21cf2e9ba5)

Solutions

Add `-i <index>` where <index> is the time fragment id shown by `tt -l`.
Run `tt -l` first to list recorded fragments and their indices.
To delete all fragments use the delete-all option instead of -d.

Example fix

// before
tt -d
// after
tt -i 1000 -d

Defensive patterns

Strategy: validation

Validate before calling

if ((isDelete || isPlay) && index == null) {
    fail("-d/-p require -i <index>");
}

Type guard

null

Try / catch

null

Prevention

Always pair -d/-p with -i <index>.
List fragments first with `tt -l` to find the index.

When it happens

Trigger: Running `tt -d` or `tt -p` without `-i <index>`, e.g. `tt -d` alone, or `tt -p --replay-times 2` without the index.

Common situations: Forgetting the -i index; assuming -d deletes all (use -D/--delete-all for that); index variable left null in a script.

Related errors

AI-assisted analysis of alibaba/arthas@21cf2e9ba5 (2026-08-14). Data as JSON: /api/errors/fa4d0513f7736276. Report an issue: GitHub.