server: default rate limit

[xhebox]

Signed-off-by: xhe xw897002528@gmail.com

What problem does this PR solve?

Issue Number: close None

Problem Summary: To prevent too frequent API requests.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

while true; do
        echo "$(date)"
        i=0
        while [ "${i}" -lt "110" ]; do
                curl -Ls 127.0.0.1:3080/api/metrics > /dev/null
                i=$((i+1))
        done
        curl -Ls 127.0.0.1:3080/api/metrics | head -1 || true
done

• No code

Notable changes

• Has configuration change
• Has HTTP API interfaces change (Don't forget to add the declarative for API)
• Has tiproxyctl change
• Other user behavior changes

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None