mirror of
https://codeberg.org/anoncontributorxmr/monero.git
synced 2024-11-26 17:32:33 +00:00
62 lines
3 KiB
Markdown
62 lines
3 KiB
Markdown
|
# The Current/Future Status of ZMQ in Monero
|
||
|
|
|
||
|
|
## ZMQ Pub/Sub
|
||
|
|
Client `ZMQ_SUB` sockets must "subscribe" to topics before it receives any data.
|
||
|
|
This allows filtering on the server side, so network traffic is reduced. Monero
|
||
|
|
allows for filtering on: (1) format, (2) context, and (3) event.
|
||
|
|
|
||
|
|
* **format** refers to the _wire_ format (i.e. JSON) used to send event
|
||
|
|
information.
|
||
|
|
* **context** allows for a reduction in fields for the event, so the
|
||
|
|
daemon doesn't waste cycles serializing fields that get ignored.
|
||
|
|
* **event** refers to status changes occurring within the daemon (i.e. new
|
||
|
|
block to main chain).
|
||
|
|
|
||
|
|
* Formats:
|
||
|
|
* `json`
|
||
|
|
* Contexts:
|
||
|
|
* `full` - the entire block or transaction is transmitted (the hash can be
|
||
|
|
computed remotely).
|
||
|
|
* `minimal` - the bare minimum for a remote client to react to an event is
|
||
|
|
sent.
|
||
|
|
* Events:
|
||
|
|
* `chain_main` - changes to the primary/main blockchain.
|
||
|
|
* `txpool_add` - new _publicly visible_ transactions in the mempool.
|
||
|
|
Includes previously unseen transactions in a block but _not_ the
|
||
|
|
`miner_tx`. Does not "re-publish" after a reorg. Includes `do_not_relay`
|
||
|
|
transactions.
|
||
|
|
|
||
|
|
The subscription topics are formatted as `format-context-event`, with prefix
|
||
|
|
matching supported by both Monero and ZMQ. The `format`, `context` and `event`
|
||
|
|
will _never_ have hyphens or colons in their name. For example, subscribing to
|
||
|
|
`json-minimal-chain_main` will send minimal information in JSON when changes
|
||
|
|
to the main/primary blockchain occur. Whereas, subscribing to `json-minimal`
|
||
|
|
will send minimal information in JSON on all available events supported by the
|
||
|
|
daemon.
|
||
|
|
|
||
|
|
The Monero daemon will ensure that events prefixed by `chain` will be sent in
|
||
|
|
"chain-order" - the `prev_id` (hash) field will _always_ refer to a previous
|
||
|
|
block. On rollbacks/reorgs, the event will reference an earlier block in the
|
||
|
|
chain instead of the last block. The Monero daemon also ensures that
|
||
|
|
`txpool_add` events are sent before `chain_*` events - the `chain_*` messages
|
||
|
|
will only serialize miner transactions since the other transactions were
|
||
|
|
previously published via `txpool_add`. This prevents transactions from being
|
||
|
|
serialized twice, even when the transaction was first observed in a block.
|
||
|
|
|
||
|
|
ZMQ Pub/Sub will drop messages if the network is congested, so the above rules
|
||
|
|
for send order are used for detecting lost messages. A missing gap in `height`
|
||
|
|
or `prev_id` for `chain_*` events indicates a lost pub message. Missing
|
||
|
|
`txpool_add` messages can only be detected at the next `chain_` message.
|
||
|
|
|
||
|
|
Since blockchain events can be dropped, clients will likely want to have a
|
||
|
|
timeout against `chain_main` events. The `GetLastBlockHeader` RPC is useful
|
||
|
|
for checking the current chain state. Dropped messages should be rare in most
|
||
|
|
conditions.
|
||
|
|
|
||
|
|
The Monero daemon will send a `txpool_add` pub exactly once for each
|
||
|
|
transaction, even after a reorg or restarts. Clients should use the
|
||
|
|
`GetTransactionPool` after a reorg to get all transactions that have been put
|
||
|
|
back into the tx pool or been invalidated due to a double-spend.
|
||
|
|
|
||
|
|
|