Substreams-powered subgraphs

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Substreams is a new framework for processing blockchain data, developed by StreamingFast for The Graph Network. A substreams modules can output entity changes, which are compatible with Subgraph entities. A subgraph can use such a Substreams module as a data source, bringing the indexing speed and additional data of Substreams to subgraph developers.

This cookbook requires yarn, the dependencies necessary for local Substreams development, and the latest version of Graph CLI (>=0.52.0):

npm install -g @graphprotocol/graph-cli

graph init --from-example substreams-powered-subgraph

A Substreams package is composed of types (defined as Protocol Buffers), modules (written in Rust), and a substreams.yaml file which references the types, and specifies how modules are triggered. Visit the Substreams documentation to learn more about Substreams development, and check out awesome-substreams and the Substreams cookbook for more examples.

The Substreams package in question detects contract deployments on Mainnet Ethereum, tracking the creation block and timestamp for all newly deployed contracts. To do this, there is a dedicated Contract type in /proto/example.proto (learn more about defining Protocol Buffers):

syntax = "proto3";

package example;

message Contracts {
  repeated Contract contracts = 1;
}

message Contract {
    string address = 1;
    uint64 blockNumber = 2;
    string timestamp = 3;
    uint64 ordinal = 4;
}

The core logic of the Substreams package is a map_contract module in lib.rs, which processes every block, filtering for Create calls which did not revert, returning Contracts:

#[substreams::handlers::map]
fn map_contract(block: eth::v2::Block) -> Result<Contracts, substreams::errors::Error> {
    let contracts = block
        .transactions()
        .flat_map(|tx| {
            tx.calls
                .iter()
                .filter(|call| !call.state_reverted)
                .filter(|call| call.call_type == eth::v2::CallType::Create as i32)
                .map(|call| Contract {
                    address: format!("0x{}", Hex(&call.address)),
                    block_number: block.number,
                    timestamp: block.timestamp_seconds().to_string(),
                    ordinal: tx.begin_ordinal,
                })
        })
        .collect();
    Ok(Contracts { contracts })
}

A Substreams package can be used by a subgraph as long as it has a module which outputs compatible entity changes. The example Substreams package has an additional graph_out module in lib.rs which returns a substreams_entity_change::pb::entity::EntityChanges output, which can be processed by Graph Node.

#[substreams::handlers::map]
pub fn graph_out(contracts: Contracts) -> Result<EntityChanges, substreams::errors::Error> {
    // hash map of name to a table
    let mut tables = Tables::new();

    for contract in contracts.contracts.into_iter() {
        tables
            .create_row("Contract", contract.address)
            .set("timestamp", contract.timestamp)
            .set("blockNumber", contract.block_number);
    }

    Ok(tables.to_entity_changes())
}

These types and modules are pulled together in substreams.yaml:

specVersion: v0.1.0
package:
  name: 'substreams_test' # the name to be used in the .spkg
  version: v1.0.1 # the version to use when creating the .spkg

imports: # dependencies
  entity: https://github.com/streamingfast/substreams-entity-change/releases/download/v0.2.1/substreams-entity-change-v0.2.1.spkg

protobuf: # specifies custom types for use by Substreams modules
  files:
    - example.proto
  importPaths:
    - ./proto

binaries:
  default:
    type: wasm/rust-v1
    file: ./target/wasm32-unknown-unknown/release/substreams.wasm

modules: # specify modules with their inputs and outputs.
  - name: map_contract
    kind: map
    inputs:
      - source: sf.ethereum.type.v2.Block
    output:
      type: proto:test.Contracts

  - name: graph_out
    kind: map
    inputs:
      - map: map_contract
    output:
      type: proto:substreams.entity.v1.EntityChanges # this type can be consumed by Graph Node

You can check the overall "flow" from a Block, to map_contract to graph_out by running substreams graph:

To prepare this Substreams package for consumption by a subgraph, you must run the following commands:

yarn substreams:protogen # generates types in /src/pb
yarn substreams:build # builds the substreams
yarn substreams:package # packages the substreams in a .spkg file

# alternatively, yarn substreams:prepare calls all of the above commands

This generates a spkg file based on the package name and version from substreams.yaml. The spkg file has all the information which Graph Node needs to ingest this Substreams package.

Substreams-powered subgraphs introduce a new kind of data source, "substreams". Such subgraphs can only have one data source.

This data source must specify the indexed network, the Substreams package (spkg) as a relative file location, and the module within that Substreams package which produces subgraph-compatible entity changes (in this case map_entity_changes, from the Substreams package above). The mapping is specified, but simply identifies the mapping kind ("substreams/graph-entities") and the apiVersion.

specVersion: 0.0.4
description: Ethereum Contract Tracking Subgraph (powered by Substreams)
repository: https://github.com/graphprotocol/graph-tooling
schema:
  file: schema.graphql
dataSources:
  - kind: substreams
    name: substream_test
    network: mainnet
    source:
      package:
        moduleName: graph_out
        file: substreams-test-v1.0.1.spkg
    mapping:
      kind: substreams/graph-entities
      apiVersion: 0.0.5

The subgraph.yaml also references a schema file. The requirements for this file are unchanged, but the entities specified must be compatible with the entity changes produced by the Substreams module referenced in the subgraph.yaml.

type Contract @entity {
  id: ID!

  "The timestamp when the contract was deployed"
  timestamp: String!

  "The block number of the contract deployment"
  blockNumber: BigInt!
}

Given the above, subgraph developers can use Graph CLI to deploy this Substreams-powered subgraph.

yarn install # install graph-cli
yarn subgraph:build # build the subgraph
yarn subgraph:deploy # deploy the subgraph

That's it! You have built and deployed a Substreams-powered subgraph.

In order to serve Substreams-powered subgraphs, Graph Node must be configured with a Substreams provider for the relevant network, as well as a Firehose or RPC to track the chain head. These providers can be configured via a config.toml file:

[chains.mainnet]
shard = "main"
protocol = "ethereum"
provider = [
  { label = "substreams-provider-mainnet",
    details = { type = "substreams",
    url = "https://mainnet-substreams-url.grpc.substreams.io/",
    token = "exampletokenhere" }},
  { label = "firehose-provider-mainnet",
    details = { type = "firehose",
    url = "https://mainnet-firehose-url.grpc.firehose.io/",
    token = "exampletokenhere" }},
]