flask-watchlog-apm 1.1.0

Flask instrumentation for Watchlog APM with JSON OTLP export

flask_watchlog_apm

🔗 Website: https://watchlog.io

flask_watchlog_apm is a lightweight APM integration for Flask, built on OpenTelemetry. It provides:

• Auto-instrumentation for Flask routes and underlying HTTP calls
• Manual custom spans via the OpenTelemetry API
• JSON-over-HTTP exporter (OTLP) compatible with Watchlog Agent
• Environment detection (local vs in-cluster Kubernetes)
• Configurable sampling, error-only and slow-only span export

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Installation

Install from PyPI:

pip install flask_watchlog_apm

Or directly from GitHub:

pip install git+https://github.com/Watchlog-monitoring/flask_watchlog_apm.git

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Quick Start

Initialize the APM before registering any routes:

# main.py
from flask import Flask
from flask_watchlog_apm.instrument import instrument_app

app = Flask(__name__)

# 1) Initialize Watchlog APM
instrument_app(
    app,
    service_name="my-flask-service",   # your service name
    headers={"Authorization": "Bearer <token>"},
    sample_rate=0.5,                   # random sample rate (0.0–1.0, capped at 0.3)
    send_error_spans=True,             # always export error spans
    error_tps=10,                      # max 10 error spans per second
    slow_threshold_ms=100              # always export spans >100ms
)

# 2) Define your routes
@app.route("/")
def hello():
    return "Hello, Watchlog APM!"

# 3) Run your app
if __name__ == "__main__":
    app.run(host="0.0.0.0", port=6000, debug=True)

What happens?

1. Flask endpoints and outbound HTTP calls (via requests) are auto-instrumented.
2. Spans are batched and sent as JSON to your Watchlog Agent (local or in-cluster).
3. Configurable filters—sampling, error-only, slow-only—are applied.

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Configuration Options

Parameter	Type	Default	Description
service_name	str	required	Name of your Flask service
otlp_endpoint	str	http://localhost:3774/apm	Base OTLP URL (overrides auto-detection if different from default)
headers	dict	{}	Additional HTTP headers for OTLP requests
batch_max_size	int	200	Maximum spans per batch
batch_delay_ms	int	5000	Delay in milliseconds between batch exports
sample_rate	float	1.0	Random sampling rate (0.0–1.0, internal cap at 0.3)
send_error_spans	bool	False	If True, always export spans with non-OK status
error_tps	int	None	Max error spans to export per second (None = unlimited)
slow_threshold_ms	int	0	If >0, always export spans slower than this threshold (ms)
export_timeout	float	10.0	HTTP request timeout (seconds) for exporter POSTs

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Manual Custom Spans

Use the OpenTelemetry API to create custom spans:

from opentelemetry import trace

tracer = trace.get_tracer(__name__)

@app.route("/db")
def fetch_db():
    with tracer.start_as_current_span("db.query", attributes={"db.system":"postgresql"}):
        # your DB logic here
        return "db query done"

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Environment Detection

The package automatically detects the runtime environment:

• Local (non-K8s): sends to http://localhost:3774/apm
• Kubernetes (in-cluster): sends to http://watchlog-python-agent.monitoring.svc.cluster.local:3774/apm

Detection checks in order:

1. Existence of /var/run/secrets/kubernetes.io/serviceaccount/token
2. Presence of kubepods in /proc/1/cgroup
3. DNS lookup of kubernetes.default.svc.cluster.local

Manual Override: You can override the endpoint by passing otlp_endpoint option in instrument_app() function

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Docker Setup

When running your Flask app in Docker, you need to configure the correct agent endpoint.

Using otlp_endpoint Option (Recommended for Docker)

# main.py
from flask import Flask
from flask_watchlog_apm.instrument import instrument_app

app = Flask(__name__)

# Initialize Watchlog APM with explicit agent URL for Docker
instrument_app(
    app,
    service_name="my-flask-service",
    otlp_endpoint="http://watchlog-agent:3774/apm",  # Use container name
    sample_rate=0.5,
    send_error_spans=True,
    error_tps=10,
    slow_threshold_ms=100
)

@app.route("/")
def hello():
    return "Hello, Watchlog APM!"

if __name__ == "__main__":
    app.run(host="0.0.0.0", port=6000, debug=True)

Docker Compose Example:

version: '3.8'

services:
  watchlog-agent:
    image: watchlog/agent:latest
    container_name: watchlog-agent
    ports:
      - "3774:3774"
    environment:
      - WATCHLOG_APIKEY=your-api-key
      - WATCHLOG_SERVER=https://log.watchlog.ir
    networks:
      - app-network

  flask-app:
    build: .
    container_name: flask-app
    ports:
      - "6000:6000"
    environment:
      - FLASK_ENV=production
    depends_on:
      - watchlog-agent
    networks:
      - app-network

networks:
  app-network:
    driver: bridge

Docker Run Example:

# 1. Create network
docker network create app-network

# 2. Run Watchlog Agent
docker run -d \
  --name watchlog-agent \
  --network app-network \
  -p 3774:3774 \
  -e WATCHLOG_APIKEY="your-api-key" \
  -e WATCHLOG_SERVER="https://log.watchlog.ir" \
  watchlog/agent:latest

# 3. Run Flask app (make sure your code sets otlp_endpoint='http://watchlog-agent:3774/apm')
docker run -d \
  --name flask-app \
  --network app-network \
  -p 6000:6000 \
  my-flask-app

Important Notes:

• When using Docker, use the container name as the hostname (e.g., watchlog-agent)
• Both containers must be on the same Docker network
• The agent must be running before your app starts
• Set the otlp_endpoint option in your code to point to the agent container
• If otlp_endpoint is not provided (or set to default), auto-detection will be used

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License

MIT © Mohammadreza

Built for Watchlog.io