Messenger

What is messenger

Messenger is an independent inter-chain program. It works for MAP Omnichain Service.

Messenger listens to relevant events as preset in the program and builds a proof on the ledger of the source chain; then transmit the message of the event and proof to Vault or Data on the destination chain.

The flexibility of applications opens up many possibilities for Messenger, where applications can charge cross-chain users flexible transaction fees and reward Messenger accordingly.

Messenger SDK

As a main component of MAP Omnichain Services, Messenger SDK will be open to Dapp developers.

Quick Start

the recommanded way to get the executable is to download it from the release page.

if you want to build it from the source code,check the building section below.

2. Prepare the accounts for each chain

fund some accounts in order to send txs on each chain, you want to provice crosse-chain service. the esaiest way is to using the same one address for every chain.

after that we need to import the account into the keystore of compass. using the private key is the simplest way,run the following command in terminal:

compass accounts import --privateKey '********** your private key **********'

during the process of importing, you will be asked to input a password. the password is used to encrypt your keystore.you have to input it when unlocking your account.

to list the imported keys in the keystore, using the command below:

compass accounts list

3. Modify the configuration file

copy a example configure file from

{
  "mapchain": {
    "id": "212",
    "endpoint": "http://18.142.54.137:7445",
    "from": "0xE0DC8D7f134d0A79019BEF9C2fd4b2013a64fCD6",
    "opts": {
      "mcs": "0x0ac4611305254cdd257beC56CB79CBeC720Cd02D",
      "lightnode": "0x000068656164657273746F726541646472657373",
      "http": "true",
      "gasLimit": "4000000000000",
      "maxGasPrice": "2000000000000",
      "syncIdList": "[34434]"
    }
  },
  "chains": [
    {
      "name": "pri-eth",
      "type": "ethereum",
      "id": "34434",
      "endpoint": "http://18.138.248.113:8545",
      "from": "0xE0DC8D7f134d0A79019BEF9C2fd4b2013a64fCD6",
      "opts": {
        "mcs": "0xcfc80beddb70f12af6da768fc30e396889dfce26",
        "lightnode": "0x80Be41aEBFdaDBD58a65aa549cB266dAFb6b8304",
        "http": "true",
        "gasLimit": "400000000000",
        "maxGasPrice": "200000000000",
        "syncToMap": "true"
      }
    }
  ]
}

modify the configuration accordingly. fill the accounts for each chain.

4. Running the executable

lauch and keep the executable runing simply by run:

compass messenger --blockstore ./block-eth-map --config ./config-mcs-erh-map.json

you will be asked to input the password to unlock your account.(which you have inputed at step 2) if everything runs smoothly. it's all set

Building

Building compass requires a Go compiler(version 1.16 or later)

under the root directory of the repo

make build: Builds compass in ./build. make install: Uses go install to add compass to your GOBIN.

Start with the following command:

compass messenger --blockstore ./block-eth-map --config ./config.json

Configuration

the configuration file is a small JSON file.

{
  "mapchain": {
        "id": "0",                          // Chain ID of the MAP chain
        "endpoint": "ws://<host>:<port>",   // Node endpoint
        "from": "0xff93...",                // MAP chain address of maintainer
        "opts": {}                          // MAP Chain configuration options (see below)
    },
  "chains": []                              // List of Chain configurations
}

A chain configurations take this form:

{
    "name": "eth",                      // Human-readable name
    "type": "ethereum",                 // Chain type (Please see the following cousin for details)
    "id": "0",                          // Chain ID
    "endpoint": "ws://<host>:<port>",   // Node endpoint
    "from": "0xff93...",                // On-chain address of maintainer
    "keystorePath" : "/you/path/",      // 
    "opts": {},                         // Chain-specific configuration options (see below)
}

chain	type
ethereum	ethereum
bsc	bsc
goerli	eth2
polygon	matic
near	near
klaytn	klaytn

chain

type

ethereum

bsc

goerli

eth2

polygon

matic

near

klaytn

Options

Since MAP is also a EVM based chain, so the opts of the mapchain is following the options below as well Ethereum chains support the following additional options:

{
    "mcs": "0x12345...",                                    // Address of the bridge contract (required)
    "maxGasPrice": "0x1234",                                // Gas price for transactions (default: 20000000000)
    "gasLimit": "0x1234",                                   // Gas limit for transactions (default: 6721975)
    "gasMultiplier": "1.25",                                // Multiplies the gas price by the supplied value (default: 1)
    "http": "true",                                         // Whether the chain connection is ws or http (default: false)
    "startBlock": "1234",                                   // The block to start processing events from (default: 0)
    "blockConfirmations": "10"                              // Number of blocks to wait before processing a block
    "egsApiKey": "xxx..."                                   // API key for Eth Gas Station (https://www.ethgasstation.info/)
    "egsSpeed": "fast"                                      // Desired speed for gas price selection, the options are: "average", "fast", "fastest"
    "lightnode": "0x12345...",                              // the lightnode to sync header
    "syncToMap": "true",                                    // Whether sync blockchain headers to Map
    "syncIdList": "[214]"                                   // Those chain ids are synchronized to the map，and This configuration can only be used in mapchain
    "event": "mapTransferOut(...)|depositOutToken(...)",    // MCS events monitored by the program, multiple with | interval，
                                                            // Here we give the events that need to be monitored，Map:mapTransferOut(bytes,bytes,bytes32,uint256,uint256,bytes,uint256,bytes) Near: 2ef1cdf83614a69568ed2c96a275dd7fb2e63a464aa3a0ffe79f55d538c8b3b5|150bd848adaf4e3e699dcac82d75f111c078ce893375373593cc1b9208998377
    "waterLine": "5000000000000000000",                     // If the user balance is lower than, an alarm will be triggered, unit ：wei
    "alarmSecond": "3000",                                  // How long does the user balance remain unchanged, triggering the alarm, unit ：seconds                                              
}

Blockstore

The blockstore is used to record the last block the maintainer processed, so it can pick up where it left off.

To disable loading from the chunk library, specify the "--fresh" flag. Add the fresh flag, and the program will execute from height 0，

In addition, the configuration file provides the "startBlock" option, and the program will execute from the startBlock

Keystore

Compass requires keys to sign and submit transactions, and to identify each bridge node on chain.

To use secure keys, see compass accounts --help. The keystore password can be supplied with the KEYSTORE_PASSWORD environment variable.

To import external ethereum keys, such as those generated with geth, use compass accounts import --ethereum /path/to/key.

To import private keys as keystores, use compass accounts import --privateKey key.

Chain Implementations

Ethereum (Solidity): contracts The Solidity contracts required for compass. Includes scripts for deployment.

Near

If you need to synchronize the near block, please install the near cli first. Here is a simple tutorial. For more information,

please check Near cli installation tutorial

First, install npm. Depending on the system, the running command is different. The following is an example of the installation command in

the ubuntu system. Use the apt install npm command to run npm install -g near cli,

After installation, use 'near -- version' to check whether the installation is successful

Configure the environment you need, for example:

` export NEAR_CLI_LOCALNET_RPC_SERVER_URL=https://archival-rpc.testnet.near.org

export NEAR_ENV=testnet `

Use the 'near login' command , Creates a key pair locally in .near-credentials with an implicit account as the accountId. (hash representation of the public key)

And record the directory to the keystorePath option in the configuration file

In addition, another program needs to be run for near messenger. Please check near-lake-s3