Add /playground endpoint that serves an playground UI with support fo…

…r configuration and intermediate steps

.envrc

@@ -0,0 +1,3 @@
+export LANGCHAIN_TRACING_V2=true
+export LANGCHAIN_ENDPOINT=http://localhost:8000
+export OPENAI_API_KEY=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

examples/chain/server.py

@@ -1,18 +1,19 @@
 #!/usr/bin/env python
 """Example LangChain server exposes a chain composed of a prompt and an LLM."""
 from fastapi import FastAPI
+from fastapi.middleware.cors import CORSMiddleware
 from typing_extensions import TypedDict
 
 from langchain.chat_models import ChatOpenAI
 from langchain.prompts import PromptTemplate, ChatPromptTemplate
+from langchain.schema.output_parser import StrOutputParser
 from langchain.schema.runnable.utils import ConfigurableField
 from langserve import add_routes
 
-model = ChatOpenAI().configurable_alternatives(
+model = ChatOpenAI(temperature=0.5).configurable_alternatives(
     ConfigurableField(id="llm", name="LLM"),
     high_temp=ChatOpenAI(temperature=0.9),
     low_temp=ChatOpenAI(temperature=0.1, max_tokens=1),
-    mid_temp=ChatOpenAI(temperature=0.5),
 )
 
 # prompt = ChatPromptTemplate.from_messages(
@@ -24,18 +25,28 @@
     "tell me a joke about {topic}"
 ).configurable_fields(
     template=ConfigurableField(
-        id="topic", name="Topic", description="The topic of the joke"
+        id="prompt", name="Prompt", description="The prompt to use."
     )
 )
 
-chain = prompt | model
+chain = prompt | model | StrOutputParser()
 
 app = FastAPI(
     title="LangChain Server",
     version="1.0",
     description="Spin up a simple api server using Langchain's Runnable interfaces",
 )
 
+# Set all CORS enabled origins
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+    expose_headers=["*"],
+)
+
 
 # The input type is automatically inferred from the runnable
 # interface; however, if you want to override it, you can do so
@@ -56,4 +67,4 @@ class ChainInput(TypedDict):
 if __name__ == "__main__":
     import uvicorn
 
-    uvicorn.run(app, host="localhost", port=8000)
+    uvicorn.run(app, host="localhost", port=8003)

langserve-playground/.eslintrc.cjs

@@ -0,0 +1,18 @@
+module.exports = {
+  root: true,
+  env: { browser: true, es2020: true },
+  extends: [
+    'eslint:recommended',
+    'plugin:@typescript-eslint/recommended',
+    'plugin:react-hooks/recommended',
+  ],
+  ignorePatterns: ['dist', '.eslintrc.cjs'],
+  parser: '@typescript-eslint/parser',
+  plugins: ['react-refresh'],
+  rules: {
+    'react-refresh/only-export-components': [
+      'warn',
+      { allowConstantExport: true },
+    ],
+  },
+}

langserve-playground/.gitignore

@@ -0,0 +1,24 @@
+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+pnpm-debug.log*
+lerna-debug.log*
+
+node_modules
+dist
+dist-ssr
+*.local
+
+# Editor directories and files
+.vscode/*
+!.vscode/extensions.json
+.idea
+.DS_Store
+*.suo
+*.ntvs*
+*.njsproj
+*.sln
+*.sw?

langserve-playground/README.md

@@ -0,0 +1,27 @@
+# React + TypeScript + Vite
+
+This template provides a minimal setup to get React working in Vite with HMR and some ESLint rules.
+
+Currently, two official plugins are available:
+
+- [@vitejs/plugin-react](https://github.com/vitejs/vite-plugin-react/blob/main/packages/plugin-react/README.md) uses [Babel](https://babeljs.io/) for Fast Refresh
+- [@vitejs/plugin-react-swc](https://github.com/vitejs/vite-plugin-react-swc) uses [SWC](https://swc.rs/) for Fast Refresh
+
+## Expanding the ESLint configuration
+
+If you are developing a production application, we recommend updating the configuration to enable type aware lint rules:
+
+- Configure the top-level `parserOptions` property like this:
+
+```js
+   parserOptions: {
+    ecmaVersion: 'latest',
+    sourceType: 'module',
+    project: ['./tsconfig.json', './tsconfig.node.json'],
+    tsconfigRootDir: __dirname,
+   },
+```
+
+- Replace `plugin:@typescript-eslint/recommended` to `plugin:@typescript-eslint/recommended-type-checked` or `plugin:@typescript-eslint/strict-type-checked`
+- Optionally add `plugin:@typescript-eslint/stylistic-type-checked`
+- Install [eslint-plugin-react](https://github.com/jsx-eslint/eslint-plugin-react) and add `plugin:react/recommended` & `plugin:react/jsx-runtime` to the `extends` list

langserve-playground/index.html

@@ -0,0 +1,21 @@
+<!doctype html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <link rel="icon" type="image/svg+xml" href="/vite.svg" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>Playground</title>
+  </head>
+  <body>
+    <div id="root"></div>
+    <script>
+      try {
+        window.CONFIG_SCHEMA = ____LANGSERVE_CONFIG_SCHEMA
+        window.INPUT_SCHEMA = ____LANGSERVE_INPUT_SCHEMA
+      } catch (error) {
+        // pass
+      }
+    </script>
+    <script type="module" src="/src/main.tsx"></script>
+  </body>
+</html>

langserve-playground/package.json

@@ -0,0 +1,39 @@
+{
+  "name": "langserve-playground",
+  "private": true,
+  "version": "0.0.0",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "tsc && vite build",
+    "lint": "eslint . --ext ts,tsx --report-unused-disable-directives --max-warnings 0",
+    "preview": "vite preview"
+  },
+  "dependencies": {
+    "@emotion/react": "^11.11.1",
+    "@emotion/styled": "^11.11.0",
+    "@jsonforms/core": "^3.1.0",
+    "@jsonforms/material-renderers": "^3.1.0",
+    "@jsonforms/react": "^3.1.0",
+    "@microsoft/fetch-event-source": "^2.0.1",
+    "@mui/icons-material": "^5.14.11",
+    "@mui/material": "^5.14.11",
+    "@mui/x-date-pickers": "^6.16.0",
+    "fast-json-patch": "^3.1.1",
+    "json-schema-defaults": "^0.4.0",
+    "react": "^18.2.0",
+    "react-dom": "^18.2.0"
+  },
+  "devDependencies": {
+    "@types/react": "^18.2.15",
+    "@types/react-dom": "^18.2.7",
+    "@typescript-eslint/eslint-plugin": "^6.0.0",
+    "@typescript-eslint/parser": "^6.0.0",
+    "@vitejs/plugin-react": "^4.0.3",
+    "eslint": "^8.45.0",
+    "eslint-plugin-react-hooks": "^4.6.0",
+    "eslint-plugin-react-refresh": "^0.4.3",
+    "typescript": "^5.0.2",
+    "vite": "^4.4.5"
+  }
+}

langserve-playground/src/App.css

@@ -0,0 +1,5 @@
+#root {
+  max-width: 1280px;
+  margin: 0 auto;
+  padding: 2rem;
+}

langserve-playground/src/App.tsx

@@ -0,0 +1,127 @@
+import React, { useEffect, useState } from "react";
+import { Card, Button, Stack } from "@mui/material";
+import defaults from "json-schema-defaults";
+import { JsonForms } from "@jsonforms/react";
+import {
+  materialRenderers,
+  materialCells,
+} from "@jsonforms/material-renderers";
+
+import { useSchemas } from "./useSchemas";
+import "./App.css";
+import { useStreamLog } from "./useStreamLog";
+import { JsonFormsCore } from "@jsonforms/core";
+
+function str(o: unknown): React.ReactNode {
+  return typeof o === "object"
+    ? JSON.stringify(o, null, 2)
+    : (o as React.ReactNode);
+}
+
+function App() {
+  // store form state
+  const [configData, setConfigData] = useState<
+    Pick<JsonFormsCore, "data" | "errors">
+  >({ data: {}, errors: [] });
+  const [inputData, setInputData] = useState<
+    Pick<JsonFormsCore, "data" | "errors">
+  >({ data: {}, errors: [] });
+  // fetch input and config schemas from the server
+  const schemas = useSchemas();
+  // apply defaults defined in each schema
+  useEffect(() => {
+    if (schemas.config) {
+      setConfigData({ data: defaults(schemas.config), errors: [] });
+      setInputData({ data: defaults(schemas.input), errors: [] });
+    }
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [schemas.config]);
+  // the runner
+  const { startStream, stopStream, latest } = useStreamLog();
+
+  return schemas.config && schemas.input ? (
+    <>
+      <h1>Playground</h1>
+      <Card sx={{ padding: 2 }}>
+        <h2>Configuration</h2>
+        <JsonForms
+          schema={schemas.config}
+          data={configData.data}
+          renderers={materialRenderers}
+          cells={materialCells}
+          onChange={({ data, errors }) =>
+            data ? setConfigData({ data, errors }) : undefined
+          }
+        />
+        {!!configData.errors?.length && (
+          <>
+            <h3>Validation Errors</h3>
+            {configData.errors?.map((e, i) => (
+              <p key={i}>{e.message}</p>
+            ))}
+          </>
+        )}
+      </Card>
+      <Card sx={{ marginTop: 2, padding: 2 }}>
+        <h2>Inputs</h2>
+        <JsonForms
+          schema={schemas.input}
+          data={inputData.data}
+          renderers={materialRenderers}
+          cells={materialCells}
+          onChange={({ data, errors }) => setInputData({ data, errors })}
+        />
+        {!!inputData.errors?.length && (
+          <>
+            <h3>Validation Errors</h3>
+            {inputData.errors?.map((e, i) => (
+              <p key={i}>{e.message}</p>
+            ))}
+          </>
+        )}
+      </Card>
+      <Stack direction="row" spacing={2} sx={{ marginTop: 2 }}>
+        <Button
+          disabled={
+            !!inputData.errors?.length ||
+            !!configData.errors?.length ||
+            !!stopStream
+          }
+          variant="contained"
+          color="primary"
+          onClick={() => startStream(inputData.data, configData.data)}
+        >
+          {stopStream ? "Running..." : "Run"}
+        </Button>
+        <Button
+          disabled={!stopStream}
+          variant="contained"
+          color="secondary"
+          onClick={stopStream}
+        >
+          Stop
+        </Button>
+      </Stack>
+      {latest && (
+        <Card sx={{ marginTop: 2, padding: 2 }}>
+          <h2>Output</h2>
+          {latest.streamed_output.map(str).join("") ?? "..."}
+        </Card>
+      )}
+      {latest && (
+        <Card sx={{ marginTop: 2, padding: 2 }}>
+          <h2>Intermediate Steps</h2>
+          {Object.values(latest.logs).map((log) => (
+            <div key={log.id}>
+              <h3>{log.name}</h3>
+              <p>{log.start_time}</p>
+              <pre>{str(log.final_output) ?? "..."}</pre>
+            </div>
+          ))}
+        </Card>
+      )}
+    </>
+  ) : null;
+}
+
+export default App;