Guard MetricNode.fromThinString against lines with fewer than 7 fields

[vasiliy-mikhailov]

Problem

MetricNode.fromThinString splits the line on | and then reads strs[0] through strs[6] unconditionally:

String[] strs = line.split("\\|");
node.setTimestamp(Long.parseLong(strs[0]));
...
node.setRt(Long.parseLong(strs[6]));
if (strs.length >= 8) {            // trailing fields are already guarded
    node.setOccupiedPassQps(Long.parseLong(strs[7]));
}

A line with fewer than seven fields (a short or truncated metric line) throws ArrayIndexOutOfBoundsException, even though the optional trailing fields are already protected with length checks.

Fix

Apply the same length guard to the leading fields, so a short line is parsed defensively (populating the fields that are present) instead of crashing — consistent with the existing handling of strs[7]/strs[8].

Test

Adds testFromThinStringShortInput to MetricNodeTest with a 3-field line. It fails on 1.8 (ArrayIndexOutOfBoundsException: Index 3 out of bounds for length 3) and passes with this change.

AI assistance disclosure

This contribution was produced with the help of an AI pipeline. The pipeline processed a large amount of source code to surface suspected bugs, reproduced a subset of them with failing unit tests and generated candidate fixes, and prepared pull requests from the ones that held up. Each PR was then reviewed and verified by a human before being opened: the fix and test were checked by hand and the test was confirmed to fail before the change and pass after.