forked from TrueCloudLab/neoneo-go
339 lines
11 KiB
Markdown
339 lines
11 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: none.
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* new transaction in the block
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Contents: transaction.
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Filters: type.
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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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## 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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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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No filter parameters defined.
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* `transaction_added`
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Filter: `type` as a string containing standard transaction types
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(MinerTransaction, InvocationTransaction, etc)
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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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### `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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* transactions contained don't have `net_fee` and `sys_fee` fields
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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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"jsonrpc" : "2.0",
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"method" : "block_added",
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"params" : [
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{
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"previousblockhash" : "0x33f3e0e24542b2ec3b6420e6881c31f6460a39a4e733d88f7557cbcc3b5ed560",
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"nextconsensus" : "AZ81H31DMWzbSnFDLFkzh9vHwaDLayV7fU",
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"index" : 205,
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"nonce" : "0000000000000457",
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"version" : 0,
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"tx" : [
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{
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"version" : 0,
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"attributes" : [],
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"txid" : "0xf9adfde059810f37b3d0686d67f6b29034e0c669537df7e59b40c14a0508b9ed",
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"size" : 10,
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"vin" : [],
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"type" : "MinerTransaction",
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"scripts" : [],
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"vout" : []
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},
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{
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"version" : 1,
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"txid" : "0x93670859cc8a42f6ea994869c944879678d33d7501d388f5a446a8c7de147df7",
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"attributes" : [],
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"size" : 60,
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"script" : "097465737476616c756507746573746b657952c103507574676f20ccfbd5f01d5b9633387428b8bab95a9e78c2",
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"vin" : [],
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"scripts" : [],
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"type" : "InvocationTransaction",
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"vout" : []
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}
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],
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"time" : 1586154525,
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"hash" : "0x48fba8aebf88278818a3dc0caecb230873d1d4ce1ea8bf473634317f94a609e5",
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"script" : {
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"invocation" : "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",
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"verification" : "532102103a7f7dd016558597f7960d27c516a4394fd968b9e65155eb4b013e4040406e2102a7bc55fe8684e0119768d104ba30795bdcc86619e864add26156723ed185cd622102b3622bf4017bdfe317c58aed5f4c753f206b7db896046fa7d774bbc4bf7f8dc22103d90c07df63e690ce77912e10ab51acc944b66860237b608c4f8f8309e71ee69954ae"
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},
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"merkleroot" : "0x9d922c5cfd4c8cd1da7a6b2265061998dc438bd0dea7145192e2858155e6c57a"
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}
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]
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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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* `net_fee` and `sys_fee` fields are always missing
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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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"params" : [
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{
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"vin" : [],
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"scripts" : [],
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"attributes" : [],
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"txid" : "0x93670859cc8a42f6ea994869c944879678d33d7501d388f5a446a8c7de147df7",
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"size" : 60,
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"vout" : [],
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"type" : "InvocationTransaction",
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"version" : 1,
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"script" : "097465737476616c756507746573746b657952c103507574676f20ccfbd5f01d5b9633387428b8bab95a9e78c2"
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}
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],
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"method" : "transaction_added",
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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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"method" : "notification_from_execution",
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"jsonrpc" : "2.0",
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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" : "ByteArray"
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},
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{
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"value" : "507574",
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"type" : "ByteArray"
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},
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{
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"value" : [
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{
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"type" : "ByteArray",
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"value" : "746573746b6579"
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},
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{
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"value" : "7465737476616c7565",
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"type" : "ByteArray"
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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" : "0xc2789e5ab9bab828743833965b1df0d5fbcc206f"
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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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"executions" : [
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{
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"vmstate" : "HALT",
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"contract" : "0x0000000000000000000000000000000000000000",
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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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"type" : "ByteArray",
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"value" : "636f6e74726163742063616c6c"
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},
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{
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"type" : "ByteArray",
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"value" : "507574"
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},
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{
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"value" : [
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{
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"value" : "746573746b6579",
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"type" : "ByteArray"
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},
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{
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"type" : "ByteArray",
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"value" : "7465737476616c7565"
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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" : "0xc2789e5ab9bab828743833965b1df0d5fbcc206f"
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}
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],
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"gas_consumed" : "1.048",
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"stack" : [
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{
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"type" : "Integer",
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"value" : "1"
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}
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],
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"trigger" : "Application"
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}
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],
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"txid" : "0x93670859cc8a42f6ea994869c944879678d33d7501d388f5a446a8c7de147df7"
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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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