Automate mining based on a trigger in Geth

Question

Currently, I am manually running the miner.start() function every time I want to mine in geth. How can I add a trigger in such a way that mining takes place automatically when there are 5 transactions pending?

Answer 1

Add --preload "mine_on_demand.js" to your geth command. Add this js file to the folder where the geth is located.

mine_on_demand.js:

function checkWork() {
    if (eth.getBlock("pending").transactions.length > 4) {
        if (eth.mining) return;
        console.log("Pending transactions! Mining...");
        miner.start(1);
    } else {
        miner.stop();
        console.log("No transactions! Mining stopped.");
    }
}

eth.filter("latest", function(err, block) { checkWork(); });
eth.filter("pending", function(err, block) { checkWork(); });

checkWork();