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Is the mempool stored on the blockchain? If it is, isn't it then easily possible to have all wallets scan the mempool in order to give immediate updates that a trx was actually sent? Just knowing that a trx is actually sent is a big deal for a receiver rather than have to wait for the tx to be included in a block first which can take some time if the mempool is congested, or if a block takes a long time to be mined.

Actual confirmations is another subject and not what I'm asking.

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The transaction pool is not stored on the blockchain: it is the set of transactions that are used to feed new blocks. Nodes store it in memory, and a poolstate.bin file when the node exits.

The wallet currently scans the txpool for new transactions. If you run show_transfers pool in monero-wallet-cli, you will see them, for example. I believe monero-wallet-gui also shows them, but I'm less sure about it.

A useful, but mostly unknown feature in monero-wallet-gui is incoming transaction tracking: in the Receive page, there is a "Tracking" line which will check the blockchain and txpool in realtime for transactions matching the settings (payment ID and optional amount) set above it. If you are on this screen while waiting for your transaction to arrive, you will see that line change as your transaction is seen in the txpool, then in the blockchain.

I'll quote the "Help" link's text here for more information:

This is a simple sales tracker:

Click Generate to create a random payment id for a new customer

Let your customer scan that QR code to make a payment (if that customer has software which supports QR code scanning).

This page will automatically scan the blockchain and the tx pool for incoming transactions using this QR code. If you input an amount, it will also check that incoming transactions total up to that amount.

It's up to you whether to accept unconfirmed transactions or not. It is likely they'll be confirmed in short order, but there is still a possibility they might not, so for larger values you may want to wait for one or more confirmation(s).

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I'm not sure about the cli wallet, but the the GUI wallet shows the tx's in mempool that belongs to you. It's a relatively new feature so to try it out you either need to build the GUI yourself or download one of the precompiled test builds from buildbot.

  • "Show unconfirmed transfers + num of confirmations #397" is very cool. When do you estimate release? – pl55 Jan 20 '17 at 12:38
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Is the mempool stored on the blockchain?

As the name suggests the mempool is the pool of transactions that exist in memory on one or more nodes in the network. Typically these are transactions that are waiting in line to get into a block.

Just knowing that a trx is actually sent is a big deal for a receiver rather than have to wait for the tx to be included in a block

What does it mean for a transaction to have been 'sent', though? Piped onto the network in a best effort manner? A confirmation of receipt from one of your peers? All of your peers?

In the end, there are no guarantees that everything went as you'd like until your transaction is included in a block (preferable several blocks down on the chain!). Until that happens, network partitions and hardware failures can cause all the nodes holding your transaction to fail.

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