Add example about multi chain relayer + gas station

docs/2.develop/relayers/relayer-gas-example.md

@@ -0,0 +1,152 @@
+---
+id: relayer-gas-example
+title: Multichain Relayer and Gas Station example
+sidebar_label: Relayer + Gas Station
+---
+import {CodeTabs, Language, Github} from "@site/src/components/codetabs"
+import Tabs from '@theme/Tabs';
+import TabItem from '@theme/TabItem';
+
+In this article you'll learn how to run end-to-end tests on the entire Multichain Relayer system.  
+
+:::info Required tools
+
+For this tutorial, you'll need to have installed:
+
+ - [Multichain Relayer Server](https://github.com/near/multichain-relayer-server)
+ - [Gas Station Event indexer](https://github.com/near/gas-station-event-indexer)
+ - [NEAR CLI RS](https://github.com/near/near-cli-rs)
+
+:::
+
+## Setup
+
+Before you start testing, set up your local environment and install the Relayer server, the Event indexer and NEAR CLI.
+
+### Multichain Relayer server
+
+The main function of this server is interfacing with foreign chain RPCs sending both pre-signed funding transactions to cover gas and the actual pre-signed transaction once the funding is done.
+
+To run the [Multichain Relayer Server](https://github.com/near/multichain-relayer-server):
+
+1. Configure the Multichain Relayer by editing the [`config.toml`](https://github.com/near/multichain-relayer-server/blob/main/config.toml) file
+2. Start the multichain relayer server:
+   ```sh
+   cargo run
+   ```
+
+:::tip
+
+Find the Multichain Relayer server source code in [this GitHub repository](https://github.com/near/multichain-relayer-server).
+
+:::
+
+### Gas Station Event indexer
+
+The event indexer picks up events emitted from the [gas station contract](gas-station.md) used for generating signed foreign chain transactions and calls the multichain relayer `/send_funding_and_user_signed_txns` endpoint locally.
+
+To run the [Gas Station indexer](https://github.com/near/gas-station-event-indexer):
+
+1. Ensure you have the [Multichain Relayer Server](#multichain-relayer-server) running on `localhost:3030`
+2. Create and activate a Python virtual environment:
+   ```sh
+   pip install requirements.txt
+   ```
+
+3. Update the [`config.toml`](https://github.com/near/gas-station-event-indexer/blob/main/config.toml) configuration file with appropriate values
+   ```
+   network = "testnet"
+   # gas station contract account id
+   contract_id = "canhazgas.testnet"
+   ```
+
+4. Run the indexer:
+   ```sh
+   python3 gas-station-event-indexer.py
+   ```
+
+:::tip
+
+Find the Gas Station Event indexer source code in [this GitHub repository](https://github.com/near/gas-station-event-indexer).
+
+:::
+
+## Running tests
+
+1. Set the transaction details of the EVM transaction you want to send in [`generate_rlp_evm_txn.py`](https://github.com/near/multichain-relayer-server/blob/5b040611f2dc6c6b405b5ec00d5102e3cc27a65c/integration_tests/generate_rlp_evm_txn.py), run the script, and save the RLP hex string output.
+
+<CodeTabs>
+  <Language value="Python" language="python">
+    <Github fname="generate_rlp_evm_txn.py"
+        url="https://github.com/near/multichain-relayer-server/blob/5b040611f2dc6c6b405b5ec00d5102e3cc27a65c/integration_tests/generate_rlp_evm_txn.py"
+        start="7" end="13" />
+  </Language>
+  <Language value="Rust" language="rust">
+    <Github fname="test.rs"
+        url="https://github.com/near/multichain-relayer-server/blob/5b040611f2dc6c6b405b5ec00d5102e3cc27a65c/tests/tests.rs"
+        start="7" end="13" />
+  </Language>
+</CodeTabs>
+
+:::note
+
+If that doesn't work, try running the `generate_eip1559_rlp_hex()` test in [`tests/tests.rs`](https://github.com/near/multichain-relayer-server/blob/5b040611f2dc6c6b405b5ec00d5102e3cc27a65c/tests/tests.rs) (Python and Rust output different hex RLP encoded transactions)
+
+:::
+
+2. Ensure the [Multichain Relayer server](#multichain-relayer-server) is configured correctly and running.
+
+3. Ensure the [Gas Station indexer](#gas-station-event-indexer) is running locally.
+
+4. Construct the signed transaction using the [near-cli-rs](https://github.com/near/near-cli-rs).
+   The receiver account ID should be the gas station contract.
+   You will need 2 actions if you want the gas station to cover your gas cost on the foreign chain:
+    - 1 action to send the NEAR equivalent
+    - 1 function call to the gas station.
+
+   You should transfer the amount of `NEAR` that's needed to cover gas both on NEAR and on the foreign chain.
+   You also need to paste in the RLP generated hex for the EVM transaction you want on the other chain generated in step 1.
+
+   When it asks you to _send_ or _display_, choose <kbd>send</kbd>.
+   Example below:
+   ```sh
+   near contract call-function as-transaction canhazgas.testnet create_transaction json-args '{"transaction_rlp_hex":"eb80851bf08eb000825208947b965bdb7f0464843572eb2b8c17bdf27b720b14872386f26fc1000080808080","use_paymaster":true}' prepaid-gas '100.000 TeraGas' attached-deposit '0.5 NEAR' sign-as nomnomnom.testnet network-config testnet sign-with-keychain send
+   ```
+
+5. Get the `"id"` from the receipts from the call in step 4, and use that to call `sign_next` twice:
+   ```sh
+    near contract call-function as-transaction canhazgas.testnet sign_next json-args '{"id":"16"}' prepaid-gas '300.0 Tgas' attached-deposit '0 NEAR' sign-as nomnomnom.testnet network-config testnet sign-with-keychain send
+   ```
+
+## Options for testing purposes
+
+Instead of creating a signed transaction and calling the gas station contract to sign it, you can get the recently signed transactions by calling the contract while replacing the `blockheight` with a more recent block height:
+
+```sh
+near contract call-function as-read-only canhazgas.testnet list_signed_transaction_sequences_after json-args '{"block_height":"157111000"}' network-config testnet now
+```
+
+This will return something like the output below. Take an individual entry in the list of JSONs and send that as the payload of a `POST` request to the `/send_funding_and_user_signed_txns` endpoint:
+
+```jsx
+[
+  {
+    "created_by_account_id": "b807806adcb73f6aecb5ed98bb8bd7bbe7bbf8ed342596ab700ef6b050abc4c3",
+    "foreign_chain_id": "97",
+    "signed_transactions": [
+      "0x02f873610385174876e80085174876e80082520894c89663ac6d169bc3e2e0a99d9fe96f2e82bcc307870eebe0b40e800080c080a0712d44ba4cd7567764231e21f054c5e7d008055222820e9d5ba148ede48755f7a06e8b812d37047593fc51fce7254ea7aef89927cada729bc903cd36fa9659dce4",
+      "0x02f873618085174876e80085174876e80082520894ef55a8bdf4498ea0af88bc54efb29608bb25e130872aa1efb94e000080c080a017d7024fe9e32ad8da1181729fac7e6a45311c47bf59f2b5a8b5e9fe002c0617a04ad725b362cf12c6e066c5b0b7ecbbf08f5e4d0a240337e6ddc8076f0528e3e5"
+    ]
+  },
+...
+  {
+    "created_by_account_id": "b807806adcb73f6aecb5ed98bb8bd7bbe7bbf8ed342596ab700ef6b050abc4c3",
+    "foreign_chain_id": "97",
+    "signed_transactions": [
+      "0x02f873610185174876e80085174876e80082520894c89663ac6d169bc3e2e0a99d9fe96f2e82bcc307870eebe0b40e800080c001a0ff19fe769246de8483b986e5aeaa3360bfb74f238e2a91ea353dac9aad9e24a0a020485dcd2c64172b9bc058b7813646dafbf2f27d51aae388b074e514fdb6de05",
+      "0x02f873618085174876e80085174876e80082520894ef55a8bdf4498ea0af88bc54efb29608bb25e130872e2f6e5e14800080c001a0dac67c383e8de3211f3c5d360cc2e9a21d160711fc3f80113ac525169317e2eca07140a1d0d1528b6eaf9fac4bb1bd44c1c4f63bb956292b0211a0dad1748e2eea"
+    ]
+  }
+]
+```
+

website/sidebars.js

@@ -147,6 +147,7 @@ const sidebar = {
           "Multichain Gas Relayer": [
             "develop/relayers/multichain-server",
             "develop/relayers/gas-station",
+            "develop/relayers/relayer-gas-example",
           ]
         },
       ]