Add FastAPI app to communicate with LangGraph Server

api/Dockerfile

@@ -0,0 +1,12 @@
+FROM python:3.12
+
+WORKDIR /code
+COPY ./pyproject.toml /code/pyproject.toml
+# Get files required by hatch to create the environment
+COPY ./src/chatbot/__about__.py /code/src/chatbot/__about__.py
+COPY ./README.md /code/README.md
+RUN python -m pip install --upgrade pip && pip install hatch
+RUN hatch env create
+COPY ./api /code/api
+
+CMD ["hatch", "run", "uvicorn", "api.main:app", "--host", "0.0.0.0", "--port", "8080"]

api/main.py

@@ -0,0 +1,93 @@
+from fastapi import FastAPI
+from langgraph_sdk import get_client
+from pydantic import BaseModel
+
+app = FastAPI()
+
+langgraph_client = get_client(url="http://langgraph-api:8000")
+
+
+class ChatMessage(BaseModel):
+    text: str
+    model_config = {
+        "json_schema_extra": {
+            "examples": [
+                {
+                    "text": "Hello",
+                }
+            ]
+        }
+    }
+
+
+class HumanReview(BaseModel):
+    action: str
+    data: str
+    model_config = {
+        "json_schema_extra": {
+            "examples": [
+                {
+                    "action": "feedback",
+                    "data": "That's not what I meant! Please try again.",
+                },
+                {
+                    "action": "continue",
+                    "data": "",
+                },
+            ]
+        }
+    }
+
+
+@app.get("/")
+async def read_main():
+    return {"msg": "Hello! Welcome to the LangGraph Chat API"}
+
+
+@app.get("/chat")
+async def list_chat_threads():
+    """
+    List all chat threads.
+    """
+    return await langgraph_client.threads.search(
+        metadata={"graph_id": "chat"},
+    )
+
+
+@app.get("/chat/{thread_id}")
+async def get_chat_history(thread_id: str):
+    """
+    Get the chat history for the given thread.
+    """
+    return await langgraph_client.threads.get(thread_id=thread_id)
+
+
+@app.post("/chat/{thread_id}")
+async def chat_with_thread(thread_id: str, message: ChatMessage):
+    """
+    Take message from user and return response from chatbot.
+    If chat thread does not exist, create a new thread.
+    """
+    return await langgraph_client.runs.wait(
+        thread_id=thread_id,
+        assistant_id="chat",
+        input={"messages": [{"role": "user", "content": message.text}]},
+        if_not_exists="create",
+    )
+
+
+@app.post("/chat/{thread_id}/human_review")
+async def human_review(thread_id: str, review: HumanReview):
+    """
+    Submit human review to resume interrupted thread.
+    """
+    return await langgraph_client.runs.wait(
+        thread_id=thread_id,
+        assistant_id="chat",
+        command={
+            "resume": {
+                "action": review.action,
+                "data": review.data,
+            }
+        },
+    )

api/test_main.py

@@ -0,0 +1,11 @@
+from fastapi.testclient import TestClient
+
+from .main import app
+
+client = TestClient(app)
+
+
+def test_read_main():
+    response = client.get("/")
+    assert response.status_code == 200
+    assert response.json() == {"msg": "Hello! Welcome to the LangGraph Chat API"}

compose.yaml

@@ -39,3 +39,7 @@ services:
     environment:
       REDIS_URI: redis://langgraph-redis:6379
       POSTGRES_URI: postgres://postgres:postgres@langgraph-postgres:5432/postgres?sslmode=disable
+  api:
+    image: chatbot-api:latest
+    ports:
+      - "8080:8080"

pyproject.toml

@@ -30,7 +30,9 @@ dependencies = [
   "pydantic",
   "python-dotenv",
   "langchain-tavily",
-  "grandalf"
+  "grandalf",
+  "fastapi[standard]",
+  "uvicorn[standard]",
 ]
 
 [project.urls]
@@ -66,7 +68,7 @@ lint.ignore = ["E501"]
 exclude = ["__pycache__", "build", "dist", ".venv"]
 
 [tool.coverage.run]
-source_pkgs = ["chatbot", "tests"]
+source_pkgs = ["chatbot", "tests", "api"]
 branch = true
 parallel = true
 omit = [
@@ -76,6 +78,7 @@ omit = [
 [tool.coverage.paths]
 chatbot = ["src/chatbot", "*/chatbot/src/chatbot"]
 tests = ["tests", "*/chatbot/tests"]
+api = ["api", "*/chatbot/api"]
 
 [tool.coverage.report]
 exclude_lines = [

src/chatbot/__about__.py

@@ -1,4 +1,4 @@
 # SPDX-FileCopyrightText: 2025-present Nam Le <lehainam2371999@gmail.com>
 #
 # SPDX-License-Identifier: MIT
-__version__ = "0.0.5"
+__version__ = "0.0.6"

src/chatbot/graph.py

@@ -2,7 +2,6 @@
 
 from dotenv import load_dotenv
 from langchain_core.messages import AIMessage
-from langgraph.checkpoint.memory import MemorySaver
 from langgraph.graph import END, START, StateGraph
 
 from chatbot.utils.nodes.human_review import human_review_node
@@ -42,8 +41,6 @@ def route_after_chatbot(state: State) -> Literal[END, "human_review", "tools"]:
 )
 graph_builder.add_edge("tools", "chatbot")
 
-memory = MemorySaver()
-# graph = graph_builder.compile(checkpointer=memory)  # In memory saver should not be used when deployed using LangGraph
 graph = graph_builder.compile()
 
 graph.get_graph().print_ascii()