Can't seem to get PostgresSaver to work. Data is still getting saved in the local docker instance in development

[maheshj567]

Hello all. I've been trying to setup a custom checkpointer using an external Postegres DB. Here's what I'm doing...

const checkpointer = PostgresSaver.fromConnString(process.env.POSTGRES_URI!);

async function setupCheckpointer() {
  console.log("Setting up checkpointer");

  // examples show the await being called directly without a function wrapper like this, but calling await requires an async function. Hence this setup
  await checkpointer.setup();
}

setupCheckpointer();

//...graph setup code

export const graph = workflow.compile({ checkpointer });

When I run it using npx @langchain/langgraph-cli dev, it stores the checkpoint information in the .langgraph_api folder. I tried npx @langchain/langgraph-cli up and it stores the info in the Postgres instance inside the docker container.

I can't seem to get it to store the information in the external DB defined by process.env.POSTGRES_URI. Am I missing something here? Would really appreciate any help that I can get. Thank you.

[hinthornw]

That's because langgraph platform uses its own managed persistence layer, and custom checkpointers are not yet supported.

dev uses an in-memory one
up uses a postgres one and you can configure the URL and other things via env vars

[hinthornw]

That's how it works! In the open source library.

If you use the platform, it's all configured and optimized for you, so you don't need to construct all of that.

[maheshj567]

Ok, but I'm not referring to the platform. I'm trying to make it work in the open-source library in my local development. Isn't PostgresSaver supposed to let me save checkpoint info to a custom DB instance (not docker or in-memory) when run locally?

[ncrmro]

@maheshj567 @hinthornw is there any plan to support custom checkpointers? I tried to look at the source code for @langchain/langgraph-cli but I could not find it, is it opensource?

[ncrmro]

Found it here

[ncrmro]

• It looks like the nodejs langchain server doesn't actually support postgres/redis
• It looks like the cli up command bring up the python based version of the image which I'm not sure quite sure atm how interfaces with the js based code
• it looks like up also won't start without a license key...