hooks.md

Hooks

A hook is a task that will be executed for each block. It receives data directly from the rule engine that filters blocks and transactions according to the all rules available.

## Available hooks

Tronhook comes with some default hooks that you can use right away.

Notification hook

NotificationHook lets you receive notifications (via HTTP or WS) when the rules have matching facts (block or transactions)

• http notification: you must provide a callback url that will be use to make a POST request with all the rules that were 'true' as well as the associated facts data (blocks or transactions)

Configuration to add in application.[env].conf

#Use notification hook
hook="org.tronhook.hook.NotificationHook"

NotificationHook{
	protocol=ws # choose protocol to use : http or ws
	httpcallbackurl="<http_url>" # when protocol = http will be used for callback

    #Websocket server configuration
	ws{
		host="localhost"
		port=7272
	}
}

Sample of notification body

The notification request body is a json payload structured as followed:

{
'ruleId':[list of facts matching this rule]
}

Example:

{
    "contract_trigger": [
        {
            "hash": "97f2947ca4b1c0f688625cf35035d21a9387ed84b1951bd0b8375d3beb29b8d1",
            "block": 5068245,
            "contract": {
                "from": "TSV5n6u5CcaT2K1c6WbWuqBZXDgUddnn9N",
                "contractAddress": "TEEXEWrkMFKapSMJ6mErg39ELFKDqEs6w3",
                "callValue": 0,
                "data": null,
                "callTokenValue": 45000000,
                "tokenId": 0
            },
            "from": "TSV5n6u5CcaT2K1c6WbWuqBZXDgUddnn9N",
            "to": null,
            "timestamp": 1545206664000,
            "type": 31,
            "data": null,
            "size": 216
        }
    ]
}

Block synchronization hook

Synchronizes the blocks into an elasticsearch database

Configuration to add in application.[env].conf

hook="org.tronhook.hook.elastic.BlockSyncHook"

BlockSyncES{
	soliditynode=${tron.soliditynode} #solidity node to use (only used if node type is set to solidity)
	fetchFee=false #should tx fees be retrieved while processing transactions ? (only used if node type is set to solidity)
	elasticsearch{
		host="<HOST>"
		port=<PORT>
		scheme=[http|https]
	}
}

Writing your own Hook

Writing a hook only consist of extending a class that will receive the filtered blocks.

class MyHook extends TronHook {

    // The field TRON_HOOK_ID is mandatory and will be used 
    // as configuration name
	public static final String TRON_HOOK_ID = "MyHook";
	

    // Hook receives configuration in constructor
	public MyHook(Config config) {
		super(config);
		
	}

    /**
    * Called on node start
    **/
    onStart(){
        // useful for initializing resources like db  ...
    }

    /**
    * Called on node stop
    **/
    onStop(){
        // useful for closing resources like db  ...
    }

    /**
    * Receives filtered blocks / transactions
    **/
    processBlocks(List<BlockModel> blocks) throws TronHookException{

        // itereate over blocks, transactions ...

        // hook configuration can be retrieve with following method
        getConfig.getIntValue('myhook_config')

    }

}