Database replication

<div class="demo"><div class="head"><b>REPLICATION LOG</b><span id="lag">lag 2</span></div><div class="stage repl"><div class="server">primary<div class="cell">LSN 104</div></div><div class="wire">→</div><div class="server">replica<div class="cell" id="replica">LSN 102</div></div></div><div class="foot"><span id="replstatus">replaying log</span><span>async copy</span></div></div>

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let n=0;function tick(){let l=[102,103,104][n];document.getElementById('replica').textContent='LSN '+l;document.getElementById('replica').classList.toggle('on',n===2);document.getElementById('lag').textContent='lag '+(104-l);document.getElementById('replstatus').textContent=n===2?'caught up':'replaying log';n=(n+1)%3}tick();const t=setInterval(tick,900);document.querySelector('.demo').onclick=()=>{clearInterval(t);tick()}