transaction are still pending

Question

in ethereum based private network, transaction are still pending. why this transaction does not complete ? below is information dumped from the console.

txpool.inspect
{
  pending: {
    0x5Cf70Fa5984683659dd661A4408C807a02C318C1: {
      0: "0x960b8fEc9f9C909878aC651113f833E99242338f: 50000000000000000000 wei + 121000 gas × 18000000000 wei"
    }
  },
  queued: {}
}

txpool.content
0: {
        blockHash: "0x0000000000000000000000000000000000000000000000000000000000000000",
        blockNumber: null,
        from: "0x5cf70fa5984683659dd661a4408c807a02c318c1",
        gas: "0x1d8a8",
        gasPrice: "0x430e23400",
        hash: "0xae26b46b73a0f9ee1da088bc66dc092a297584302a40cc3d2cf33e23b0833cee",
        input: "0x",
        nonce: "0x0",
        r: "0x9bdeaddaf2056a886b66b62e388cb1f3935c9cf4f003516607676681bc17caa4",
        s: "0x250109163780fd123258f20068f6f1a98224802f16b64585832aa6e5d83ad0",
        to: "0x960b8fec9f9c909878ac651113f833e99242338f",
        transactionIndex: "0x0",
        v: "0x3c30",
        value: "0x2b5e3af16b1880000"
      },

Answer 1

This is porbably due to nonce problems and synchronization between the RPC caller and the geth node. If you are trying to send many transactions in a short time, this is likely to happen.

EDIT :

If you try and send many transactions without managing nonce yourself in a short amount of time, it is possible that a transaction gets sent with the same , higher or less nonce as a previous one which will cause the previous transaction to stay in the tx pool for ever or get refuted. The miss calculation of nonce is due to web3 nonce guessing mechanism or any other framework that does that.

An other point : If you don't run any miner ( or any kind of block maker ) node within your network, you will not be able to make any blocks. So the transactions stay in the txpool untill they get mined ( when a miner or maker node joins in )