Is this the best way?
There are several ways to set the MIME type, better explained and discussed in this StackOverflow question. Your way works fine and gets the job done.
What is the difference between returning a String and returning plain text?
If you return a string Flask will automatically handle some of the Response logic for you. This means using some default values. If you set up two different endpoints you'll see that the difference turns out to be that your code returns the following header:
Content-Type:"text/plain; charset=utf-8"
While just returning a string (and default MIME type) would return the following header:
Content-Type:"text/html; charset=utf-8"
Why do I need the mimetype?
You might say that it is technically more correct, given that your response is simply plain text, and not HTML. However, a more forcing reason for needing it would be that a third party system you are using (Prometheus) relies on or cares about the contents of the "Content-Type" header. If they do, then you must set it for them to accept it.
Example code
For the Content-Type header demonstration I used the following example Python code:
from flask import Flask, make_response
app = Flask(__name__)
def generateMetrics():
return "hello world"
@app.route('/metrics')
def metrics():
response = make_response(generateMetrics(), 200)
response.mimetype = "text/plain"
return response
@app.route('/metrics2')
def metrics2():
return generateMetrics()
I then viewed the returned body and headers using Postman.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…