How to access environment variables

This guide will show you how to grant access to environment variables to an Apibara indexer.

You script can access any environment variable with the Deno.env.get function. This function returns the value of the environment variable or an undefined value if the variable is not set.

const value = Deno.env.get("MY_VAR");

Usually, environment variables are used to configure and indexer for different deployments (e.g. testnet and mainnet). In this example we use environment variables to change the indexer's starting block.

indexer.ts

export const config = {
  streamUrl: "https://sepolia.starknet.a5a.ch",
  startingBlock: Number(Deno.env.get("STARTING_BLOCK") || 0),
  network: "starknet",
  filter: {
    header: { weak: false },
  },
  sinkType: "console",
  sinkOptions: {},
};

export default async function transform(_block) {
  return [];
}

If you run this example you will get an error like the following.

Terminal

apibara run indexer.ts -A dna_xxx

sink configuration error
├╴at /dna/sinks/sink-common/src/error.rs:142:14
├╴failed to load configuration from script
│
╰─▶ indexer script operation failed
    ├╴at /dna/script/src/script.rs:339:22
    ├╴failed to run indexer event loop
    ╰╴error: Error: Requires env access to "STARTING_BLOCK", run again with the --allow-env flag
          at Object.getEnv [as get] (ext:runtime/30_os.js:86:14)
          at file:///path/to/indexer.ts:3:34

Allow access to existing environment variables

The easiest way to solve this issue is by allowing the indexer to access existing environment variables.

First we set the STARTING_BLOCK variable in the current shell session.

Terminal

export STARTING_BLOCK=100000

Then we run the script again, this time with the --allow-env-from-env flag. This flag takes a comma-separated list of environment variables the indexer can access. Notice that the position of the flag is significant, it must come before the script name.

Terminal

apibara run --allow-env-from-env=STARTING_BLOCK indexer.ts -A dna_xxx

2024-02-13T13:33:32.619668Z  INFO acquiring persistence lock
2024-02-13T13:33:32.619718Z  INFO lock acquired
2024-02-13T13:33:32.634648Z  INFO status server listening on 0.0.0.0:32987
2024-02-13T13:33:33.005900Z  INFO handle block batch block=100000 status=finalized
2024-02-13T13:33:33.006784Z  INFO []
2024-02-13T13:33:33.006846Z  INFO handle block batch block=100001 status=finalized
2024-02-13T13:33:33.007102Z  INFO []

Using .env files

The Apibara CLI can load environment variables from .env files.

Create a testnet.env file with the following content.

testnet.env

STARTING_BLOCK=200000

Then run the CLI again, this time with the --allow-env flag. This flag accepts the path to a .env file. Like the previous flag, the position of the flag is significant, it must come before the script name.

Terminal

apibara run --allow-env=testnet.env indexer.ts -A dna_xxx

2024-02-13T13:40:21.053736Z  INFO acquiring persistence lock
2024-02-13T13:40:21.053781Z  INFO lock acquired
2024-02-13T13:40:21.067066Z  INFO status server listening on 0.0.0.0:43259
2024-02-13T13:40:21.474451Z  INFO handle block batch block=200000 status=finalized
2024-02-13T13:40:21.475397Z  INFO []
2024-02-13T13:40:21.475460Z  INFO handle block batch block=200001 status=finalized
2024-02-13T13:40:21.475715Z  INFO []