Middleware

Step I. Connect to your TigerGraph Cloud Solution

Perfect! Now we’re ready to integrate pyTigerGraph into our API. Open main.py in your editor of choice and import pyTigerGraph.

import pyTigerGraph as tg

To make this safer, create a configs.py file and import the credentials from there.

touch config.py

In config.py:

HOST='https://covid-fullstack.i.tgcloud.io'
USERNAME='tigergraph'
PASSWORD='tigergraph'
GRAPHNAME='MyGraph'

Let's come back to main.py, create a connection to your TigerGraph Cloud server.

import config as Credential
conn = tg.TigerGraphConnection(host=Credential.HOST, username=Credential.USERNAME, password=Credential.PASSWORD, graphname=Credential.GRAPHNAME)
conn.apiToken = conn.getToken(conn.createSecret())

If this runs successfully, then you’re connected to TigerGraph Cloud! Congrats!

Step II. Establish the Cross-Origin Resource Sharing (CORS)

Since the communication between front and middleware don't specify a port, it is essential configure the CORS.

Let's import CORSMiddleware in main.py

from fastapi.middleware.cors import CORSMiddleware

Create a list of allowed origins (as strings).

origins = [
    "http://localhost:3000",
    "https://localhost:3000",
]

Specify the middleware allows:

• Credentials (Authorization headers, Cookies, etc).
  
• Specific HTTP methods (POST, PUT) or all of them with the wildcard "*".
• Specific HTTP headers or all of them with the wildcard "*".

app.add_middleware(
    CORSMiddleware,
    allow_origins=origins,
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

Step III. Create Query Endpoints

Let’s first run TigerGraph queries with FastAPI, starting with listPatients_Infected_By.

@app.get("/listPatients_Infected_By")
def readListPatients_Infected_By():
    gQuery = conn.runInstalledQuery("listPatients_Infected_By", {"p":2000000205})[0]['Infected_Patients']
    return gQuery

Break this down, we're running the listPatients_Infected_By query that is installed in GraphStudio. As the query parameter takes the Patient Vertex ID, the output return a list of infected Patients' ID.

If you haven’t already, run the file. Open http://127.0.0.1:8000/listPatients_Infected_By to run the query.

Awesome! Now, the data need to be transform into nested tree json format with keys like name (String), id (String), and children (list of objects).

After adding the data transformation, the GET method of listPatients_Infected_By would look like this

@app.get("/listPatients_Infected_By")
def readListPatients_Infected_By():
    gQuery = conn.runInstalledQuery("listPatients_Infected_By", {"p":2000000205})[0]['Infected_Patients']
    count = 0
    children = []
    for p in gQuery:
        children.append({
        "children": [],
        "collapsed": True,
        "id": str(count),
        "name": p[-3:] + "Patient",

        })
        count+=1

    result = {
        "name": "205 ROOT",
        "id": "root",
        "children": children,
        "style": {
            "fill": "#FFDBD9",
            "stroke":  "#FF6D67"
        }
    }
    return result

If you open the endpoint http://127.0.0.1:8000/listPatients_Infected_By, again.
You will see this!

You have transform the data, and the data is ready for the frontend and AntV G6.

👏 Great job! 👏 You have create a GET method API using TigerGraph Cloud and FastAPI & pyTigerGraph!

Below is the entire code from main.py

from typing import Optional
from fastapi import FastAPI
import config as Credential
from fastapi.middleware.cors import CORSMiddleware
import pyTigerGraph as tg

conn = tg.TigerGraphConnection(host=Credential.HOST, username=Credential.USERNAME, password=Credential.PASSWORD, graphname=Credential.GRAPHNAME)
conn.apiToken = conn.getToken(conn.createSecret())
app = FastAPI()

origins = [
    "http://localhost:3000",
    "https://localhost:3000",
]

app.add_middleware(
    CORSMiddleware,
    allow_origins=origins,
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

@app.get("/listPatients_Infected_By")
def readListPatients_Infected_By():
    gQuery = conn.runInstalledQuery("listPatients_Infected_By", {"p":2000000205})[0]['Infected_Patients']
    count = 0
    children = []
    for p in gQuery:
        children.append({
        "children": [],
        "collapsed": True,
        "id": str(count),
        "name": p[-3:] + "Patient",

        })
        count+=1

    result = {
        "name": "205 ROOT",
        "id": "root",
        "children": children,
        "style": {
            "fill": "#FFDBD9",
            "stroke":  "#FF6D67"
        }
    }
    return result