SDK Clients without Credential Providers about aws-sdk-js-v3

[RanVaknin]

Hi @jd-carroll ,

Are you consuming the SDK through ES modules (i.e., using import instead of require)? Modern bundlers can be configured to include only the code that is actually used in your application, even if other modules are imported.

What is your bundler configuration?

Thanks,
Ran

[kuhe]

Mark those modules are external while bundling. Then they will sit in a split chunk that should never be imported if you are indeed providing credentials.

That reduces the size of the parsed and executed code. If you actually have a space limitation in the Lambda with regard to the 128kb, you can mark the external modules as empty, which varies depending on the bundler, so that they are split into a chunk and that chunk is deleted or empty.

[jd-carroll]

@kuhe - Right, that is currently the only way to accomplish this.

@RanVaknin - Of course, including setting mainFields to ['module', 'main']. Let me know if you need help with the esbuild command to bundle the demo lambda function below (you'll also need to make sure you are minimizing the code)

Here is a simple example:

import { AssumeRoleCommand, STSClient } from '@aws-sdk/client-sts';

export const handler = async () => {
  const client = new STSClient({
    region: 'us-west-2',
    credentials: {
      accessKeyId: 'fake-access-key-id',
      secretAccessKey: 'fake-secret-access-key'
    }
  });
  await client.send(
    new AssumeRoleCommand({ RoleArn: 'arn:aws:iam::123456789012:role/demo', RoleSessionName: 'session1' })
  );
};

The bundled lambda function from esbuild looks like:

If we look at just @aws-sdk/*, that has:

There are a couple of problems here

Problem 1: Non "excludable" code paths

The first problem is that bundler has no way of knowing that the credential providers are unneccessary. This boils down into two parts:

• credentialDefaultProvider is deprecated
  I believe the more appropriate use is credentials as I have in the example. You are also able to give a provider for credentials. However the issue is that the runtimeConfig for STSClient (and likely all clients) has:

export const getRuntimeConfig = (config) => {
    ...
    return {
        ...config,
        ...
        credentialDefaultProvider: config?.credentialDefaultProvider ?? credentialDefaultProvider,
        ...

So if you do not set credentialDefaultProvider there is a hard import of the @aws-sdk/credential-provider-node

• httpAuthSchemes always uses credentialDefaultProvider
  But even if you set the credentialDefaultProvider in the client config. The httpAuthSchemes always uses the credentialDefaultProvider from the import, i.e.:

import { defaultProvider as credentialDefaultProvider } from "@aws-sdk/credential-provider-node";

So you would also need to do something like:

  const client = new STSClient({
    region: 'us-west-2',
    credentials: {
      accessKeyId: 'fake-access-key-id',
      secretAccessKey: 'fake-secret-access-key'
    },
    credentialDefaultProvider: undefined,
    httpAuthSchemes: [
      {
        schemeId: 'aws.auth#sigv4',
        identityProvider: (ipc) =>
          ipc.getIdentityProvider('aws.auth#sigv4') ||
          (() => Promise.resolve({ expiration: new Date(Date.now() + 1000) })),
        signer: new AwsSdkSigV4Signer()
      },
      {
        schemeId: 'smithy.api#noAuth',
        identityProvider: (ipc) => ipc.getIdentityProvider('smithy.api#noAuth') || (async () => ({})),
        signer: new NoAuthSigner()
      }
    ]
  });

But even doing all that, doesn't seem to make any difference.

Only if I completely comment out the credentialDefaultProvider and httpAuthSchemes from the getRuntimeConfig will the @aws-sdk/credential-provider-node be treeshook from the bundle.

I tried a couple of different ways to add a default credentialDefaultProvider into the config while still allowing it to be tree shaken, but none seemed to work. My guess would be that it needs to be something more like:

    const combined = {
        ...clientSharedValues,
        ...config,
        runtime: "node",
        ...,
    };
    if (!combined.credentialDefaultProvider) {
      combined.credentialDefaultProvider = getCredentialDefaultProvider();
    }
    return result;

Where the import of @aws-sdk/credential-provider-node is moved one level deep into the getCredentialDefaultProvider method call. All that to say, the code flow is too complex for static analysis to identify that credentialDefaultProvider is not necessary.

Problem 2: Incorrect exports conditions

The other item you should notice is that not 100% of the code is ESM. And if we look at where the non-ESM code is coming from (by clicking on the percentages), some of it is coming from @aws-sdk

The issue is that the exports from @aws-sdk/core are setup incorrectly. For example, the "default" export from core looks like:

  "main": "./dist-cjs/index.js",
  "module": "./dist-es/index.js",
  "types": "./dist-types/index.d.ts",
  "exports": {
    ".": {
      "node": "./dist-cjs/index.js",
      "import": "./dist-es/index.js",
      "require": "./dist-cjs/index.js",
      "types": "./dist-types/index.d.ts"
    },

The problem is that bundlers will prefer "exports" over any top-level "mian" / "module" and when bundling for a lambda we are setting the platform to be node which forces the conditions ['node', 'default'] when evaluating the exports.

The result is that any ESM module importing core will only ever receive the cjs bundle.

The exports should be structured like:

  "main": "./dist-cjs/index.js",
  "module": "./dist-es/index.js",
  "types": "./dist-types/index.d.ts",
  "exports": {
    ".": {
      "node": {
        "import": "./dist-es/index.js",
        "require": "./dist-cjs/index.js"
      },
      "import": "./dist-es/index.js",
      "require": "./dist-cjs/index.js",
      "types": "./dist-types/index.d.ts"
    },

Or really, the node is probably unnecessary, so it should really just be:

  "main": "./dist-cjs/index.js",
  "module": "./dist-es/index.js",
  "types": "./dist-types/index.d.ts",
  "exports": {
    ".": {
      "import": "./dist-es/index.js",
      "require": "./dist-cjs/index.js",
      "types": "./dist-types/index.d.ts"
    },

The impact of including core as a CJS module is only minor, the real issue is @aws-sdk/credential-provider-node. Once these are resolved, it would be good to reach out to fast-xml-parser to see if they can release an ESM version of the module in addition to the CJS.

Going back to the first problem... I suspect that even the example solution I suggest may not be enough to indicate to the bundle that @aws-sdk/credential-provider-node can be treeshaken from the bundle (without significant code changes).

Which brings me back to my original suggestion in that there should be a new "Raw" client which has bare-bones configuration and requires the user to provide other necessary configuration details, such as credentials.

[kuhe]

Please make a pre-bundle build step that replaces the runtimeConfig.ts file with one that does not contain @aws-sdk/credential-provider-node if that is what you need.

The use-case is not common enough to provide an official variant from the AWS SDK.

---

Regarding exports:

  "exports": {
    ".": {
      "import": "./dist-es/index.js",
      "require": "./dist-cjs/index.js",
      "types": "./dist-types/index.d.ts"
    },

There is a reason the node exports overrides import.

We only offer our CJS distribution for Node.js because our ES distribution is not MJS compliant and It is only for bundlers. We have not analyzed what effect MJS compliance would have on web bundlers. The CJS distribution will likely remain the only or at least preferred Node.js offering for as long as our minimum Node.js version supports CJS-within-ESM but not ESM-within-CJS.

[jd-carroll]

Got it. That's unfortunate that we are required to exclude the unnecessary credential providers ourselves, because its a savings of >75kb minimized (so at scale would be pretty meaningful). But all good.

For the esbuild'ers, as @-kuhe mentioned above, the best/easist thing to do is drop all of those providers into the excludes of esbuild.

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