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425 lines
15 KiB
Markdown
425 lines
15 KiB
Markdown
# Notification subsystem
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Original motivation, requirements and general solution strategy are described
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in the issue #895.
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This extension allows a websocket client to subscribe to various events and
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receive them as JSON-RPC notifications from the server.
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## Events
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Currently supported events:
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* new block added
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Contents: block.
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Filters: primary ID.
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* new transaction in the block
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Contents: transaction.
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Filters: sender and cosigner.
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* notification generated during execution
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Contents: container hash, contract script hash, stack item.
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Filters: contract script hash.
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* transaction executed
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Contents: application execution result.
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Filters: VM state.
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Filters use conjunctional logic.
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## Ordering and persistence guarantees
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* new block is only announced after its processing is complete and the chain
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is updated to the new height
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* no disk-level persistence guarantees are given
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* new in-block transaction is announced after block processing, but before
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announcing the block itself
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* transaction notifications are only announced for successful transactions
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* all announcements are being done in the same order they happen on the chain
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At first transaction execution is announced, then followed by notifications
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generated during this execution, then followed by transaction announcement.
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Transaction announcements are ordered the same way they're in the block.
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* unsubscription may not cancel pending, but not yet sent events
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## Subscription management
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To receive events clients need to subscribe to them first via `subscribe`
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method. Upon successful subscription clients receive subscription ID for
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subsequent management of this subscription. Subscription is only valid for
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connection lifetime, no long-term client identification is being made.
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Errors are not described down below, but they can be returned as standard
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JSON-RPC errors (most often caused by invalid parameters).
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### `subscribe` method
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Parameters: event stream name, stream-specific filter rules hash (can be
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omitted if empty).
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Recognized stream names:
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* `block_added`
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Filter: `primary` as an integer with primary (speaker) node index from
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ConsensusData.
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* `transaction_added`
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Filter: `sender` field containing string with hex-encoded Uint160 (LE
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representation) for transaction's `Sender` and/or `cosigner` in the same
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format for one of transaction's `Cosigners`.
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* `notification_from_execution`
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Filter: `contract` field containing string with hex-encoded Uint160 (LE
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representation).
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* `transaction_executed`
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Filter: `state` field containing `HALT` or `FAULT` string for successful
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and failed executions respectively.
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Response: returns subscription ID (string) as a result. This ID can be used to
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cancel this subscription and has no meaning other than that.
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Example request (subscribe to notifications from contract
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0x6293a440ed80a427038e175a507d3def1e04fb67 generated when executing
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transactions):
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```
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{
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"jsonrpc": "2.0",
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"method": "subscribe",
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"params": ["notification_from_execution", {"contract": "6293a440ed80a427038e175a507d3def1e04fb67"}],
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"id": 1
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}
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```
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Example response:
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```
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{
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"jsonrpc": "2.0",
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"id": 1,
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"result": "55aaff00"
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}
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```
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### `unsubscribe` method
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Parameters: subscription ID as a string.
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Response: boolean true.
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Example request (unsubscribe from "55aaff00"):
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```
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{
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"jsonrpc": "2.0",
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"method": "unsubscribe",
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"params": ["55aaff00"],
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"id": 1
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}
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```
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Example response:
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```
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{
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"jsonrpc": "2.0",
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"id": 1,
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"result": true
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}
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```
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## Events
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Events are sent as JSON-RPC notifications from the server with `method` field
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being used for notification names. Notification names are identical to stream
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names described for `subscribe` method with one important addition for
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`event_missed` which can be sent for any subscription to signify that some
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events were not delivered (usually when client isn't able to keep up with
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event flow).
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Verbose responses for various structures like blocks and transactions are used
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to simplify working with notifications on client side. Returned structures
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mostly follow the one used by standard Neo RPC calls, but may have some minor
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differences.
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If a server-side event matches several subscriptions from one client, it's
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only sent once.
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### `block_added` notification
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As a first parameter (`params` section) contains block converted to JSON
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structure which is similar to verbose `getblock` response but with the
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following differences:
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* it doesn't have `size` field (you can calculate it client-side)
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* it doesn't have `nextblockhash` field (it's supposed to be the latest one
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anyway)
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* it doesn't have `confirmations` field (see previous)
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No other parameters are sent.
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Example:
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```
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{
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"params" : [
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{
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"index" : 207,
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"time" : 1590006200,
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"nextconsensus" : "AXSvJVzydxXuL9da4GVwK25zdesCrVKkHL",
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"consensusdata" : {
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"primary" : 0,
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"nonce" : "0000000000000457"
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},
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"previousblockhash" : "0x04f7580b111ec75f0ce68d3a9fd70a0544b4521b4a98541694d8575c548b759e",
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"witnesses" : [
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{
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"invocation" : "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",
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"verification" : "130c2102103a7f7dd016558597f7960d27c516a4394fd968b9e65155eb4b013e4040406e0c2102a7bc55fe8684e0119768d104ba30795bdcc86619e864add26156723ed185cd620c2102b3622bf4017bdfe317c58aed5f4c753f206b7db896046fa7d774bbc4bf7f8dc20c2103d90c07df63e690ce77912e10ab51acc944b66860237b608c4f8f8309e71ee699140b413073b3bb"
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}
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],
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"version" : 0,
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"hash" : "0x239fea00c54c2f6812612874183b72bef4473fcdf68bf8da08d74fd5b6cab030",
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"tx" : [
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{
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"txid" : "0xf736cd91ab84062a21a09b424346b241987f6245ffe8c2b2db39d595c3c222f7",
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"witnesses" : [
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{
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"verification" : "0c2102b3622bf4017bdfe317c58aed5f4c753f206b7db896046fa7d774bbc4bf7f8dc20b410a906ad4",
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"invocation" : "0c4016e7a112742409cdfaad89dcdbcb52c94c5c1a69dfe5d8b999649eaaa787e31ca496d1734d6ea606c749ad36e9a88892240ae59e0efa7f544e0692124898d512"
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}
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],
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"vout" : [],
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"cosigners" : [],
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"validuntilblock" : 1200,
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"nonce" : 8,
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"netfee" : "0.0030421",
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"sender" : "ALHF9wsXZVEuCGgmDA6ZNsCLtrb4A1g4yG",
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"sysfee" : "0",
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"type" : "InvocationTransaction",
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"attributes" : [],
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"version" : 1,
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"vin" : [],
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"size" : 204,
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"script" : "10c00c04696e69740c14769162241eedf97c2481652adf1ba0f5bf57431b41627d5b52"
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},
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{
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"script" : "01e8030c14316e851039019d39dfc2c37d6c3fee19fd5809870c14769162241eedf97c2481652adf1ba0f5bf57431b13c00c087472616e736665720c14769162241eedf97c2481652adf1ba0f5bf57431b41627d5b5238",
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"size" : 277,
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"attributes" : [],
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"version" : 1,
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"vin" : [],
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"netfee" : "0.0037721",
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"sender" : "ALHF9wsXZVEuCGgmDA6ZNsCLtrb4A1g4yG",
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"sysfee" : "0",
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"type" : "InvocationTransaction",
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"nonce" : 9,
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"cosigners" : [
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{
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"scopes" : 1,
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"account" : "0x870958fd19ee3f6c7dc3c2df399d013910856e31"
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}
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],
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"validuntilblock" : 1200,
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"witnesses" : [
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{
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"invocation" : "0c4027727296b84853c5d9e07fb8a40e885246ae25641383b16eefbe92027ecb1635b794aacf6bbfc3e828c73829b14791c483d19eb758b57638e3191393dbf2d288",
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"verification" : "0c2102b3622bf4017bdfe317c58aed5f4c753f206b7db896046fa7d774bbc4bf7f8dc20b410a906ad4"
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}
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],
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"vout" : [],
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"txid" : "0xe1cd5e57e721d2a2e05fb1f08721b12057b25ab1dd7fd0f33ee1639932fdfad7"
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}
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],
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"merkleroot" : "0xb2c7230ebee4cb83bc03afadbba413e6bca8fcdeaf9c077bea060918da0e52a1"
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}
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],
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"jsonrpc" : "2.0",
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"method" : "block_added"
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}
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```
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### `transaction_added` notification
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In the first parameter (`params` section) contains transaction converted to
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JSON which is similar to verbose `getrawtransaction` response, but with the
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following differences:
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* block's metadata is missing (`blockhash`, `confirmations`, `blocktime`)
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No other parameters are sent.
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Example:
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```
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{
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"method" : "transaction_added",
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"params" : [
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{
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"validuntilblock" : 1200,
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"version" : 1,
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"txid" : "0xe1cd5e57e721d2a2e05fb1f08721b12057b25ab1dd7fd0f33ee1639932fdfad7",
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"witnesses" : [
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{
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"invocation" : "0c4027727296b84853c5d9e07fb8a40e885246ae25641383b16eefbe92027ecb1635b794aacf6bbfc3e828c73829b14791c483d19eb758b57638e3191393dbf2d288",
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"verification" : "0c2102b3622bf4017bdfe317c58aed5f4c753f206b7db896046fa7d774bbc4bf7f8dc20b410a906ad4"
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}
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],
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"sysfee" : "0",
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"sender" : "ALHF9wsXZVEuCGgmDA6ZNsCLtrb4A1g4yG",
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"vout" : [],
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"netfee" : "0.0037721",
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"size" : 277,
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"attributes" : [],
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"script" : "01e8030c14316e851039019d39dfc2c37d6c3fee19fd5809870c14769162241eedf97c2481652adf1ba0f5bf57431b13c00c087472616e736665720c14769162241eedf97c2481652adf1ba0f5bf57431b41627d5b5238",
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"nonce" : 9,
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"vin" : [],
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"type" : "InvocationTransaction",
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"cosigners" : [
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{
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"account" : "0x870958fd19ee3f6c7dc3c2df399d013910856e31",
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"scopes" : 1
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}
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]
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}
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],
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"jsonrpc" : "2.0"
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}
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```
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### `notification_from_execution` notification
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Contains three parameters: container hash (hex-encoded LE Uint256 in a
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string), contract script hash (hex-encoded LE Uint160 in a string) and stack
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item (encoded the same way as `state` field contents for notifications from
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`getapplicationlog` response).
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Example:
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```
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{
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"jsonrpc" : "2.0",
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"method" : "notification_from_execution",
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"params" : [
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{
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"state" : {
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"value" : [
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{
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"value" : "636f6e74726163742063616c6c",
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"type" : "ByteString"
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},
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{
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"value" : "7472616e73666572",
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"type" : "ByteString"
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},
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{
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"value" : [
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{
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"value" : "769162241eedf97c2481652adf1ba0f5bf57431b",
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"type" : "ByteString"
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},
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{
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"value" : "316e851039019d39dfc2c37d6c3fee19fd580987",
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"type" : "ByteString"
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},
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{
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"value" : "1000",
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"type" : "Integer"
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}
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],
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"type" : "Array"
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}
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],
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"type" : "Array"
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},
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"contract" : "0x1b4357bff5a01bdf2a6581247cf9ed1e24629176"
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}
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]
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}
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```
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### `transaction_executed` notification
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Contains the same result as from `getapplicationlog` method in the first
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parameter and no other parameters. One difference from `getapplicationlog` is
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that it always contains zero in the `contract` field.
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Example:
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```
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{
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"method" : "transaction_executed",
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"params" : [
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{
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"txid" : "0xe1cd5e57e721d2a2e05fb1f08721b12057b25ab1dd7fd0f33ee1639932fdfad7",
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"executions" : [
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{
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"trigger" : "Application",
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"gasconsumed" : "2.291",
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"contract" : "0x0000000000000000000000000000000000000000",
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"stack" : [],
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"notifications" : [
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{
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"state" : {
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"type" : "Array",
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"value" : [
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{
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"value" : "636f6e74726163742063616c6c",
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"type" : "ByteString"
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},
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{
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"type" : "ByteString",
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"value" : "7472616e73666572"
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},
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{
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"value" : [
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{
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"value" : "769162241eedf97c2481652adf1ba0f5bf57431b",
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"type" : "ByteString"
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},
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{
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"type" : "ByteString",
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"value" : "316e851039019d39dfc2c37d6c3fee19fd580987"
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},
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{
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"value" : "1000",
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"type" : "Integer"
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}
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],
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"type" : "Array"
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}
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]
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},
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"contract" : "0x1b4357bff5a01bdf2a6581247cf9ed1e24629176"
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},
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{
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"contract" : "0x1b4357bff5a01bdf2a6581247cf9ed1e24629176",
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"state" : {
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"value" : [
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{
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"value" : "7472616e73666572",
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"type" : "ByteString"
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},
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{
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"value" : "769162241eedf97c2481652adf1ba0f5bf57431b",
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"type" : "ByteString"
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},
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{
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"value" : "316e851039019d39dfc2c37d6c3fee19fd580987",
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"type" : "ByteString"
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},
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{
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"value" : "1000",
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"type" : "Integer"
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}
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],
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"type" : "Array"
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}
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}
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],
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"vmstate" : "HALT"
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}
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]
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}
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],
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"jsonrpc" : "2.0"
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}
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```
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### `event_missed` notification
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Never has any parameters. Example:
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```
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{
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"jsonrpc": "2.0",
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"method": "event_missed",
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"params": []
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}
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```
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