GetStartBlockHeimdallSpanID - Polygon gRPC

Example code for the GetStartBlockHeimdallSpanID grpc method. Сomplete guide on how to use GetStartBlockHeimdallSpanID grpc in GetBlock.io Web3 documentation.

Maps a Bor start block to its corresponding Heimdall span ID. Given a Bor block number, returns which Heimdall span that block belongs to — spans are ~6400-block windows during which a specific validator subset is authorized to produce blocks. Used by Heimdall to correlate Bor block ranges with span metadata (validator sets, producer selection).

Request Parameters

Parameter	Type	Required	Description
StartBlock	uint64	Yes	Bor start block number

Request Example

grpcurl

grpcurl -H 'x-access-token: <ACCESS-TOKEN>' \
        -d '{"StartBlock": "76540000"}' \
        shared.ap-southeast-1.getblock.io:443 \
        bor.BorApi/GetStartBlockHeimdallSpanID

JavaScript (Node.js)

import * as grpc from '@grpc/grpc-js';
import protoLoader from '@grpc/proto-loader';

const GRPC_TARGET = 'shared.ap-southeast-1.getblock.io:443';
const ACCESS_TOKEN = '<ACCESS-TOKEN>';
const PROTO_PATH = './protos/bor/bor.proto';

const packageDefinition = protoLoader.loadSync(PROTO_PATH, {
    keepCase: true,
    longs: String,
    enums: String,
    defaults: true,
    oneofs: true,
    includeDirs: ['./protos'],
});
const proto = grpc.loadPackageDefinition(packageDefinition);
const BorApiClient = proto.bor.BorApi;
const client = new BorApiClient(GRPC_TARGET, grpc.credentials.createSsl());

const metadata = new grpc.Metadata();
metadata.add('x-access-token', ACCESS_TOKEN);

const request = {
    "StartBlock": "76540000"
};

client.GetStartBlockHeimdallSpanID(request, metadata, (err, response) => {
    if (err) {
        console.error('gRPC error:', err.code, err.message);
        return;
    }
    console.log(JSON.stringify(response, null, 2));
});

Python

import grpc
from google.protobuf.json_format import MessageToJson

from bor import bor_pb2, bor_pb2_grpc

GRPC_TARGET = "shared.ap-southeast-1.getblock.io:443"
ACCESS_TOKEN = "<ACCESS-TOKEN>"

credentials = grpc.ssl_channel_credentials()
channel = grpc.secure_channel(GRPC_TARGET, credentials)
stub = bor_pb2_grpc.BorApiStub(channel)

metadata = [("x-access-token", ACCESS_TOKEN)]

request = bor_pb2.GetStartBlockHeimdallSpanIDRequest(
    StartBlock="76540000",
)
response = stub.GetStartBlockHeimdallSpanID(request, metadata=metadata)

print(MessageToJson(response, indent=2))

Go

package main

import (
    "context"
    "crypto/tls"
    "encoding/json"
    "fmt"
    "log"
    "time"

    "google.golang.org/grpc"
    "google.golang.org/grpc/credentials"
    "google.golang.org/grpc/metadata"

    "github.com/0xPolygon/polyproto/bor"
)

func main() {
    target := "shared.ap-southeast-1.getblock.io:443"
    accessToken := "<ACCESS-TOKEN>"

    creds := credentials.NewTLS(&tls.Config{})
    conn, err := grpc.Dial(target, grpc.WithTransportCredentials(creds))
    if err != nil {
        log.Fatalf("dial: %v", err)
    }
    defer conn.Close()

    client := bor.NewBorApiClient(conn)

    ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
    defer cancel()
    ctx = metadata.AppendToOutgoingContext(ctx, "x-access-token", accessToken)

    req := &bor.GetStartBlockHeimdallSpanIDRequest{
        StartBlock: "76540000",
    }
    resp, err := client.GetStartBlockHeimdallSpanID(ctx, req)
    if err != nil {
        log.Fatalf("rpc: %v", err)
    }

    j, _ := json.MarshalIndent(resp, "", "  ")
    fmt.Println(string(j))
}

Response Example

{
    "StartBlock": "76540000",
    "HeimdallSpanID": "6543"
}

H160 and H256 encoding. In JSON representations of protobuf messages, common.H160 (20-byte addresses) and common.H256 (32-byte hashes) are shown here as hex strings for readability. The actual JSON wire format from grpcurl or MessageToJson reflects the message structure defined in common/common.proto — typically a nested object encoding. Applications using the typed generated clients receive H160/H256 as strongly-typed message objects, not strings.

Response Fields

Field	Type	Description
StartBlock	uint64	Echo of the input StartBlock (helps clients confirm the query was interpreted correctly)
HeimdallSpanID	uint64	The Heimdall span ID that contains this Bor block

Use Cases

• Reconstructing which validator subset was authorized during a specific Bor block range

• Historical span analysis for producer performance metrics

• Cross-referencing Bor block production against Heimdall's span records

Error Handling

gRPC Status (Code)	Message	Cause
UNAUTHENTICATED (16)	missing or invalid x-access-token	Access token missing from x-access-token gRPC metadata or invalid
PERMISSION_DENIED (7)	access denied	Access token doesn't have permission for this method or endpoint
INVALID_ARGUMENT (3)	invalid request	Request message is malformed or fails validation (e.g. invalid block number tag)
INTERNAL (13)	internal error	Server-side error while processing the request
UNAVAILABLE (14)	service unavailable	Bor node is temporarily unavailable (syncing, restart, or overload)
DEADLINE_EXCEEDED (4)	deadline exceeded	Request took longer than the client-configured timeout
RESOURCE_EXHAUSTED (8)	rate limit exceeded	Rate limit exceeded for your plan

SDK Integration

TypeScript (ts-proto)

// 1. Vendor polyproto and generate typed clients with ts-proto:
//    git clone https://github.com/0xPolygon/polyproto
//    npx protoc \
//      --plugin=./node_modules/.bin/protoc-gen-ts_proto \
//      --ts_proto_out=./src/generated \
//      --ts_proto_opt=outputServices=grpc-js \
//      -I ./polyproto \
//      polyproto/bor/bor.proto polyproto/common/common.proto
//
// 2. Use the generated typed client:

import * as grpc from '@grpc/grpc-js';
import { BorApiClient } from './generated/bor/bor';

const client = new BorApiClient('shared.ap-southeast-1.getblock.io:443', grpc.credentials.createSsl());
const metadata = new grpc.Metadata();
metadata.add('x-access-token', '<ACCESS-TOKEN>');

const request = {
    "StartBlock": "76540000"
};
const response = await new Promise((resolve, reject) => {
    client.GetStartBlockHeimdallSpanID(request, metadata, (err, res) => err ? reject(err) : resolve(res));
});
console.log(response);

Rust (tonic)

// 1. Vendor polyproto and add tonic-build to build.rs:
//    tonic_build::configure()
//        .compile(&["polyproto/bor/bor.proto"], &["polyproto"])?;
//
// 2. Use the generated typed client:

use tonic::{transport::{Channel, ClientTlsConfig}, Request};

pub mod bor {
    tonic::include_proto!("bor");
}
use bor::bor_api_client::BorApiClient;
use bor::GetStartBlockHeimdallSpanIDRequest;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let tls = ClientTlsConfig::new();
    let channel = Channel::from_static("https://shared.ap-southeast-1.getblock.io")
        .tls_config(tls)?
        .connect()
        .await?;

    let mut client = BorApiClient::with_interceptor(channel, |mut req: Request<()>| {
        req.metadata_mut().insert(
            "x-access-token",
            "<ACCESS-TOKEN>".parse().unwrap(),
        );
        Ok(req)
    });

    let request = tonic::Request::new(GetStartBlockHeimdallSpanIDRequest { /* fields */ });
    let response = client.get_start_block_heimdall_span_i_d(request).await?;
    println!("{:?}", response);
    Ok(())
}