cloudflare_kv.ts

import type { KVNamespace } from "@cloudflare/workers-types";

import {
  BaseCache,
  getCacheKey,
  serializeGeneration,
  deserializeStoredGeneration,
} from "@langchain/core/caches";
import { Generation } from "@langchain/core/outputs";

/**
 * @deprecated Install and import from "@langchain/cloudflare" instead.
 *
 * Represents a specific implementation of a caching mechanism using Cloudflare KV
 * as the underlying storage system. It extends the `BaseCache` class and
 * overrides its methods to provide the Cloudflare KV-specific logic.
 * @example
 * ```typescript
 * // Example of using OpenAI with Cloudflare KV as cache in a Cloudflare Worker
 * const cache = new CloudflareKVCache(env.KV_NAMESPACE);
 * const model = new ChatAnthropic({
 *   cache,
 * });
 * const response = await model.invoke("How are you today?");
 * return new Response(JSON.stringify(response), {
 *   headers: { "content-type": "application/json" },
 * });
 *
 * ```
 */
export class CloudflareKVCache extends BaseCache {
  private binding: KVNamespace;

  constructor(binding: KVNamespace) {
    super();
    this.binding = binding;
  }

  /**
   * Retrieves data from the cache. It constructs a cache key from the given
   * `prompt` and `llmKey`, and retrieves the corresponding value from the
   * Cloudflare KV namespace.
   * @param prompt The prompt used to construct the cache key.
   * @param llmKey The LLM key used to construct the cache key.
   * @returns An array of Generations if found, null otherwise.
   */
  public async lookup(prompt: string, llmKey: string) {
    let idx = 0;
    let key = getCacheKey(prompt, llmKey, String(idx));
    let value = await this.binding.get(key);
    const generations: Generation[] = [];

    while (value) {
      generations.push(deserializeStoredGeneration(JSON.parse(value)));
      idx += 1;
      key = getCacheKey(prompt, llmKey, String(idx));
      value = await this.binding.get(key);
    }

    return generations.length > 0 ? generations : null;
  }

  /**
   * Updates the cache with new data. It constructs a cache key from the
   * given `prompt` and `llmKey`, and stores the `value` in the Cloudflare KV
   * namespace.
   * @param prompt The prompt used to construct the cache key.
   * @param llmKey The LLM key used to construct the cache key.
   * @param value The value to be stored in the cache.
   */
  public async update(prompt: string, llmKey: string, value: Generation[]) {
    for (let i = 0; i < value.length; i += 1) {
      const key = getCacheKey(prompt, llmKey, String(i));
      await this.binding.put(
        key,
        JSON.stringify(serializeGeneration(value[i]))
      );
    }
  }
}