Vercel KV

This example demonstrates how to setup chat history storage using the VercelKVStore BaseStore integration.

Setup

npm

npm install @langchain/community @langchain/core @vercel/kv

Yarn

yarn add @langchain/community @langchain/core @vercel/kv

pnpm

pnpm add @langchain/community @langchain/core @vercel/kv

Usage

import { createClient } from "@vercel/kv";
import { VercelKVStore } from "@langchain/community/storage/vercel_kv";
import { AIMessage, HumanMessage } from "@langchain/core/messages";

// Pro tip: define a helper function for getting your client
// along with handling the case where your environment variables
// are not set.
const getClient = () => {
  if (!process.env.VERCEL_KV_API_URL || !process.env.VERCEL_KV_API_TOKEN) {
    throw new Error(
      "VERCEL_KV_API_URL and VERCEL_KV_API_TOKEN must be set in the environment"
    );
  }
  const client = createClient({
    url: process.env.VERCEL_KV_API_URL,
    token: process.env.VERCEL_KV_API_TOKEN,
  });
  return client;
};

// Define the client and store
const client = getClient();
const store = new VercelKVStore({
  client,
});
// Define our encoder/decoder for converting between strings and Uint8Arrays
const encoder = new TextEncoder();
const decoder = new TextDecoder();
/**
 * Here you would define your LLM and chat chain, call
 * the LLM and eventually get a list of messages.
 * For this example, we'll assume we already have a list.
 */
const messages = Array.from({ length: 5 }).map((_, index) => {
  if (index % 2 === 0) {
    return new AIMessage("ai stuff...");
  }
  return new HumanMessage("human stuff...");
});
// Set your messages in the store
// The key will be prefixed with `message:id:` and end
// with the index.
await store.mset(
  messages.map((message, index) => [
    `message:id:${index}`,
    encoder.encode(JSON.stringify(message)),
  ])
);
// Now you can get your messages from the store
const retrievedMessages = await store.mget(["message:id:0", "message:id:1"]);
// Make sure to decode the values
console.log(retrievedMessages.map((v) => decoder.decode(v)));
/**
[
  '{"id":["langchain","AIMessage"],"kwargs":{"content":"ai stuff..."}}',
  '{"id":["langchain","HumanMessage"],"kwargs":{"content":"human stuff..."}}'
]
 */
// Or, if you want to get back all the keys you can call
// the `yieldKeys` method.
// Optionally, you can pass a key prefix to only get back
// keys which match that prefix.
const yieldedKeys = [];
for await (const key of store.yieldKeys("message:id:")) {
  yieldedKeys.push(key);
}
// The keys are not encoded, so no decoding is necessary
console.log(yieldedKeys);
/**
[
  'message:id:2',
  'message:id:1',
  'message:id:3',
  'message:id:0',
  'message:id:4'
]
 */
// Finally, let's delete the keys from the store
await store.mdelete(yieldedKeys);

API Reference:

• VercelKVStore from @langchain/community/storage/vercel_kv
• AIMessage from @langchain/core/messages
• HumanMessage from @langchain/core/messages

Related

• Key-value store conceptual guide