The `Http` provider establishes an Http connection with a node, allowing you to send RPC requests to the node to fetch data, simulate calls, send transactions and much more.
## Initializing an Http Provider
Lets take a quick look at few ways to create a new `Http` provider. Since the `Http` provider implements the [`FromStr`](https://doc.rust-lang.org/std/str/trait.FromStr.html) one of the easiest ways to initialize a new provider is by using the `from_str()` method.
```rust
use ethers::providers::{Http, Middleware, Provider};
#[tokio::main]
async fn main() -> eyre::Result<()> {
// Initialize a new Http provider
let rpc_url = "https://mainnet.infura.io/v3/c60b0bb42f8a4c6481ecd229eddaca27";
let provider = Provider::try_from(rpc_url)?;
Ok(())
}
```
The `Http` provider also supplies a way to initialize a new authorized connection.
```rust
// Initializes a new HTTP Client with authentication
use ethers::providers::{Authorization, Http};
use url::Url;
#[tokio::main]
async fn main() -> eyre::Result<()> {
let url = Url::parse("http://localhost:8545")?;
let provider = Http::new_with_auth(url, Authorization::basic("admin", "good_password"));
Ok(())
}
```
Additionally, you can initialize a new provider with your own custom `reqwest::Client`.
```rust
use ethers::providers::Http;
use url::Url;
#[tokio::main]
async fn main() -> eyre::Result<()> {
let url = Url::parse("http://localhost:8545")?;
let client = reqwest::Client::builder().build()?;
let provider = Http::new_with_client(url, client);
Ok(())
}
```
## Basic Usage
Now that you have successfully established an Http connection with the node, you can use any of the methods provided by the `Middleware` trait. In the code snippet below, the provider is used to get the chain id, current block number and the content of the node's mempool.
```rust
use ethers::providers::{Http, Middleware, Provider};
#[tokio::main]
async fn main() -> eyre::Result<()> {
let rpc_url = "https://mainnet.infura.io/v3/c60b0bb42f8a4c6481ecd229eddaca27";
let provider = Provider::try_from(rpc_url)?;
let chain_id = provider.get_chainid().await?;
let block_number = provider.get_block_number().await?;
let tx_pool_content = provider.txpool_content().await?;
Ok(())
}
```
You can also use the provider to interact with smart contracts. The snippet below uses the provider to establish a new instance of a UniswapV2Pool and uses the `get_reserves()` method from the smart contract to fetch the current state of the pool's reserves.
let rpc_url = "https://mainnet.infura.io/v3/c60b0bb42f8a4c6481ecd229eddaca27";
let provider = Arc::new(Provider::try_from(rpc_url)?);
// Initialize a new instance of the Weth/Dai Uniswap V2 pair contract
let pair_address = H160::from_str("0xA478c2975Ab1Ea89e8196811F51A7B7Ade33eB11")?;
let uniswap_v2_pair = IUniswapV2Pair::new(pair_address, provider);
// Use the get_reserves() function to fetch the pool reserves
let (reserve_0, reserve_1, block_timestamp_last) =
uniswap_v2_pair.get_reserves().call().await?;
Ok(())
}
```
This example is a little more complicated, so lets walk through what is going on. The `IUniswapV2Pair` is a struct that is generated from the `abigen!()` macro. The `IUniswapV2Pair::new()` function is used to create a new instance of the contract, taking in an `Address` and an `Arc<M>` as arguments, where `M` is any type that implements the `Middleware` trait. Note that the provider is wrapped in an [`Arc`](https://doc.rust-lang.org/std/sync/struct.Arc.html) when being passed into the `new()` function.
It is very common to wrap a provider in an `Arc` to share the provider across threads. Lets look at another example where the provider is used asynchronously across two tokio threads. In the next example, a new provider is initialized and used to asynchronously fetch the number of Ommer blocks from the most recent block, as well as the previous block.
// Spin up a new thread to get the uncle count of the previous block
let task_1 = tokio::spawn(async move { provider.get_uncle_count(prev_block_number).await });
// Wait for the tasks to finish
for task in [task_0, task_1] {
if let Ok(uncle_count) = task.await? {
println!("Success!");
}
}
Ok(())
}
```
<br>
Before heading to the next chapter, feel free to check out the docs for the [`Http` provider](https://docs.rs/ethers/latest/ethers/providers/struct.Http.html). Keep in mind that we will cover advanced usage of providers at the end of this chapter. Now that we have the basics covered, lets move on to the next Provider, Websockets!
