昨天我們試過了OpenTelemetry可以在functions內透過trace id和span id來追蹤。今天我們來用flask加上opentelemetry 追蹤我一些數值。

下面這邊截自 CNCF 在4/22好的一篇發文，有興趣的可以看看裡面有很詳細的說明 OpenTelemetry and Python: A complete instrumentation guide

那下面我們就來看一段flask + opentelemetry可以做到什麼

首先創造一個venv然後我們安裝flask和opentelemtry

pip install flask
pip install opentelemetry-distro

接下來我們寫一個app.py

from opentelemetry import trace
from opentelemetry.sdk.resources import Resource
from opentelemetry.sdk.trace import TracerProvider
from opentelemetry.sdk.trace.export import BatchSpanProcessor
from opentelemetry.sdk.trace.export import ConsoleSpanExporter

provider = TracerProvider()
processor = BatchSpanProcessor(ConsoleSpanExporter())
provider.add_span_processor(processor)
trace.set_tracer_provider(provider)
tracer = trace.get_tracer(__name__)

前面我們設置一些opentelemetry 的provider processor和 trace
接下來就可以在code裡面加上

from random import randint
from flask import Flask, request

app = Flask(__name__)

@app.route("/roll")
def roll():
    with tracer.start_as_current_span(
        "server_request",
        attributes={ "endpoint": "/roll" }
    ):

        sides = int(request.args.get('sides'))
        rolls = int(request.args.get('rolls'))
        return roll_sum(sides,rolls)

def roll_sum(sides, rolls):
    span = trace.get_current_span()
    sum = 0
    for r in range(0,rolls):
        result = randint(1,sides)
        span.add_event( "log", {
            "roll.sides": sides,
            "roll.result": result,
        })
        sum += result
    return  str(sum)

使用 trace.start_as_current_span 和 trace.get_current_span()來讓process 輸出到console上

接下來可以使用

flask run

來執行
然後我們做個curl

curl 'http://127.0.0.1:5000/roll?sides=10&rolls=1'

10面骰子骰一次
從flask console就可以看到

127.0.0.1 - - [06/Oct/2022 21:07:27] "GET /roll?sides=10&rolls=1 HTTP/1.1" 200 -
{
    "name": "server_request",
    "context": {
        "trace_id": "0xc58684710f70860f47fb9a45614c9be8",
        "span_id": "0x25b0982d63012c4b",
        "trace_state": "[]"
    },
    "kind": "SpanKind.INTERNAL",
    "parent_id": null,
    "start_time": "2022-10-06T13:07:27.033325Z",
    "end_time": "2022-10-06T13:07:27.033540Z",
    "status": {
        "status_code": "UNSET"
    },
    "attributes": {
        "endpoint": "/roll"
    },
    "events": [
        {
            "name": "log",
            "timestamp": "2022-10-06T13:07:27.033472Z",
            "attributes": {
                "roll.sides": 10,
                "roll.result": 3
            }
        }
    ],
    "links": [],
    "resource": {
        "attributes": {
            "telemetry.sdk.language": "python",
            "telemetry.sdk.name": "opentelemetry",
            "telemetry.sdk.version": "1.13.0",
            "service.name": "unknown_service"
        },
        "schema_url": ""
    }
}

裡面包含著各種擲骰子的參數

    "events": [
        {
            "name": "log",
            "timestamp": "2022-10-06T13:07:27.033472Z",
            "attributes": {
                "roll.sides": 10,
                "roll.result": 3
            }
        }
    ],

這樣每次在call /roll這個api我們就可以做追蹤了