Query the Hosted Service
Prerequisites
Install Rust and Cargo, the Rust package manager
Open your Terminal application then run the following command
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
Overview
The Graph is a decentralized protocol that enables developers to query data from blockchains using GraphQL. In this lesson, we will use Rust to submit a GraphQL query to the graph-network-mainnet
subgraph on The Graph’s Hosted Service. This hands-on lesson will provide you with the practical experience needed to interface with The Graph's ecosystem, and moreover, demonstrate the immense potential of leveraging Rust to interact with decentralized data networks. Let's dig in and uncover the incredible possibilities that await us in the realm of Rust, GraphQL, and The Graph's Hosted Service!
GraphQL query
To start, let's discuss the subgraph and GraphQL query we're submitting. The graph-network-mainnet
subgraph extracts data from the protocol's smart contracts and makes it accessible via GraphQL queries. Indexers are the node operators of the protocol and allocate GRT tokens to subgraphs as part of their operations.
In this lesson, we're requesting data about indexers that is defined in the protocol's smart contracts. Our query is filtering results to the first 10 indexers who have allocated at least 1 GRT token to any subgraph in the protocol. Finally we're narrowing down the returned fields to id
, defaultDisplayName
, and stakedTokens
.
Table 1. Subgraph field descriptions
id
the Ethereum address of the Indexer
defaultDisplayName
the current default display name of the Indexer. Potentially null
and used to filter queries
stakedTokens
current tokens staked in The Graph protocol
Figure 1. Subgraph query
query indexers {
indexers(first:10, where: {allocatedTokens_gt: "0"}) {
id
defaultDisplayName
stakedTokens
}
}
Getting started with Rust
Coming soon
Create a new cargo project
Open your Terminal application and change to your home directory
cd ~
Create a new directory called
rohr
and change into it
mkdir -p rohr && cd rohr
Create a new
cargo
project calledindexer_subgraph_query
cargo new indexer_subgraph_query
Change into the new
indexer_subgraph_query
directory
cd indexer_subgraph_query
Add dependencies to your project
Open
Cargo.toml
withnano
nano Cargo.toml
serde = { version = "1.0.149", features = ["derive"] }
reqwest = { version = "0.11", features = ["json"]}
tokio = { version = "1.23.0", features = ["full"] }
Save your changes to
Cargo.toml
and exitnano
ctrl + x
y
Write Rust code
structs.rs
Create a new file called
structs.rs
in thesrc
directory
nano src/structs.rs
Add the following use declarations to
src/structs.rs
use std::string::String;
use serde::Deserialize;
Next define a few
struct
statements insrc/structs.rs
#[allow(non_snake_case)]
#[derive(Debug, Deserialize, PartialEq)]
pub struct Indexer {
pub id: String,
pub defaultDisplayName: Option<String>,
pub stakedTokens: Option<String>,
}
#[derive(Debug, Deserialize, PartialEq)]
pub struct IndexerData {
pub indexers: Vec<Indexer>
}
#[derive(Debug, Deserialize, PartialEq)]
pub struct IndexerResponse {
pub data: IndexerData
}
Notice that we created three structs:
IndexerResponse
: the highest-level struct in the hierarchy. It defines the response format from thePOST
request sent to The Graph's Hosted ServiceIndexerData
andIndexer
: nested structs which define data returned in theIndexerResponse
Each Indexer in The Graph protocol would theoretically be assigned to an Indexer
struct, with the IndexerData
struct containing all Indexer
structs (or a subset based on the query filter submitted, i.e. first 10).
Finally, IndexerData
is the value of the IndexerResponse
data
field.
Save your changes to
src/structs.rs
and exitnano
ctrl + x
y
Your file structs.rs
will look something like this
use std::string::String;
use serde::Deserialize;
#[allow(non_snake_case)]
#[derive(Debug, Deserialize, PartialEq)]
pub struct Indexer {
pub id: String,
pub defaultDisplayName: Option<String>,
pub stakedTokens: Option<String>,
}
#[derive(Debug, Deserialize, PartialEq)]
pub struct IndexerData {
pub indexers: Vec<Indexer>
}
#[derive(Debug, Deserialize, PartialEq)]
pub struct IndexerResponse {
pub data: IndexerData
}
main.rs
Open
src/main.rs
withnano
nano src/main.rs
Delete all existing lines in the file
ctrl + shift + k
Add the following user declarations to the top of
src/main.rs
use std::collections::HashMap;
mod structs;
use crate::structs::*;
Run your program
From your terminal, use cargo
to compile and run your Rust program
cargo run
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