main.py

# Copyright 2021 Google LLC

# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at

#     https://www.apache.org/licenses/LICENSE-2.0

# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# [START monitoring_sli_metrics_prometheus_setup]
import random
import time

from flask import Flask

from prometheus_client import (
    Counter,
    generate_latest,
    Histogram,
    REGISTRY,
)

# [END monitoring_sli_metrics_prometheus_setup]

app = Flask(__name__)
# [START monitoring_sli_metrics_prometheus_create_metrics]
PYTHON_REQUESTS_COUNTER = Counter("python_requests", "total requests")
PYTHON_FAILED_REQUESTS_COUNTER = Counter("python_failed_requests", "failed requests")
PYTHON_LATENCIES_HISTOGRAM = Histogram(
    "python_request_latency", "request latency by path"
)
# [END monitoring_sli_metrics_prometheus_create_metrics]


@app.route("/")
# [START monitoring_sli_metrics_prometheus_latency]
@PYTHON_LATENCIES_HISTOGRAM.time()
# [END monitoring_sli_metrics_prometheus_latency]
def homePage():
    # count request
    # [START monitoring_sli_metrics_prometheus_counts]
    PYTHON_REQUESTS_COUNTER.inc()
    # fail 10% of the time
    if random.randint(0, 100) > 90:
        PYTHON_FAILED_REQUESTS_COUNTER.inc()
        # [END monitoring_sli_metrics_prometheus_counts]
        return ("error!", 500)
    else:
        random_delay = random.randint(0, 5000) / 1000
        # delay for a bit to vary latency measurement
        time.sleep(random_delay)
        return "home page"


# [START monitoring_sli_metrics_prometheus_metrics_endpoint]
@app.route("/metrics", methods=["GET"])
def stats():
    return generate_latest(REGISTRY), 200


# [END monitoring_sli_metrics_prometheus_metrics_endpoint]


if __name__ == "__main__":
    app.run(debug=True, host="0.0.0.0", port=8080)