nacos-serving-python v0.1.3

Overview

nacos-serving-python focuses on seamless Service Registration & Discovery plus Config access for Python web apps and HTTP clients.

Core capabilities:

1. Auto register Flask / Django / FastAPI in three ways: a) CLI (module run)
   b) Import-triggered
   c) WSGI middleware injection
2. Built‑in service discovery for urllib / requests / httpx / aiohttp so you can call http://<service-name>/path directly.

Built atop the async Nacos v2 SDK (gRPC push + structured params).

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Installation & Usage

# 1. install the library
pip install nacos-serving-python

# 2. cd to your project root and run

# 3. run the auto-registration CLI
python -m nacos.auto.registration --nacos-server 127.0.0.1:8848 --service-name demoservice app.py

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Quick Start (Conceptual)

1. Build a client config (server address, namespace, credentials)
2. Create Config & Naming services (async)
3. Optionally: auto register your web service (one of 3 methods)
4. Use logical hostnames via adapters (urllib / requests / httpx / aiohttp)
5. Graceful shutdown: deregister ephemeral instance

(Full code samples removed for brevity—see demo/ & Chinese README.)

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Auto Registration (3 Methods)

Method	How	Use Case	Intrusive
CLI	python -m nacos.auto.registration app.py ...	Zero code change	None
Import	import nacos.auto.registration.enabled	Simple & explicit	Low
WSGI Middleware	from nacos.auto.middleware.wsgi import inject_wsgi_middleware then inject_wsgi_middleware(app)	Custom lifecycle / delayed	Low

Example (Import Trigger – Flask)

import nacos.auto.registration.enabled
from flask import Flask
app = Flask(__name__)

@app.route("/health")
def health(): return "OK"

if __name__ == "__main__":
    app.run(host="0.0.0.0", port=5001)

Example (WSGI Middleware – Flask)

from flask import Flask
from nacos.auto.middleware.wsgi import inject_wsgi_middleware
app = Flask(__name__)
inject_wsgi_middleware(app)
app.run()

Configuration File (nacos.yaml)

Placed at project root (nacos.yaml or application.yaml). See demo/*/nacos.yaml.

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CLI Startup Parameters

Invoke:

python -m nacos.auto.registration app.py [options]

Parameter	Example	Meaning
--nacos-server	127.0.0.1:8848	Nacos server address (host:port[,host:port...])
--namespace	public	Namespace ID
--service-name	demo.api	Logical service name
--service-port	8000	Explicit service port (auto-detect if omitted)
--service-ip	192.168.1.10	Explicit bind IP (auto-detect if omitted)
--service-group	DEFAULT_GROUP	Service group
--service-cluster	default	Cluster name (topology segmentation)
--service-weight	1.0	Load balancing weight
--metadata key=val	version=1.0.0	Repeatable: attach metadata entries
--register-on-startup	(flag)	Register immediately at startup
--register-on-request	(flag)	Lazy register on first request
--no-auto-register	(flag)	Disable auto registration (override defaults)
--retry-times	3	Registration retry count
--retry-interval	2	Retry interval seconds
--heartbeat-interval	5	Heartbeat interval seconds
--heartbeat-timeout	5	Heartbeat timeout seconds
--graceful-shutdown	(flag)	Enable graceful shutdown
--shutdown-timeout	10	Graceful shutdown max wait seconds
--deregister-on-exit	(flag)	Explicitly deregister on exit
--log-level	INFO	Logging level
--log-file	/path/file.log	Custom log file path
--empty-protection	true/false	Keep previous instance list when NACOS returns empty
--help		Show full help

Environment variables may override core fields (examples):

Env	Maps To
NACOS_SERVER	--nacos-server
NACOS_NAMESPACE	--namespace
NACOS_SERVICE_NAME	--service-name
NACOS_SERVICE_PORT	--service-port
NACOS_SERVICE_IP	--service-ip

If both CLI and env present: CLI takes precedence.

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Service Discovery (HTTP Clients)

Adapters allow logical hostname usage:

• urllib: from nacos.auto.discovery.ext.urllib import urlopen
• requests: from nacos.auto.discovery.ext import requests as nacos_requests
• httpx: from nacos.auto.discovery.ext.httpx import AsyncClient
• aiohttp: from nacos.auto.discovery.ext.aiohttp import get_session

Fallback steps (manual):

1. List healthy instances
2. Pick one (LB strategy)
3. Compose http://ip:port/path

Load Balancing & Resilience:

• Strategy: round-robin or random (implementation)
• Filters: healthy + enabled
• Retry: next instance on failure
• Cache: subscription-driven updates
• Empty protection: optional guard against transient zero instance returns

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Configuration Field Summary (nacos.yaml)

Section	Key	Description
nacos	server	Nacos server address list
nacos	namespace	Namespace ID
service	name	Logical service name
service	ip / port	Explicit service endpoint (auto-detected if omitted)
service	group	Service group (default DEFAULT_GROUP)
service	cluster	Cluster name
service	weight	Load balancing weight
service	metadata	Arbitrary key-value routing tags
registration	auto_register	Enable auto registration driver
registration	register_on_startup	Register immediately at startup
registration	register_on_request	Lazy register on first request
registration	retry_times / retry_interval	Retry strategy
discovery	empty_protection	Keep last snapshot if server returns empty
heartbeat	interval / timeout	Ephemeral heartbeat config
shutdown	graceful / timeout / deregister	Graceful exit behavior
logging	level / file	Logging control

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Migration (Legacy SDK → This)

Legacy	New	Change
Sync calls	Async await	Non-blocking
Flat params	Data classes	Structured
Polling	gRPC push	Lower latency
Custom discovery	Built-in adapters	Less boilerplate
Manual heartbeat	Managed ephemeral	Simplified lifecycle

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Best Practices

Scenario	Recommendation
Env isolation	Use namespaces per env
Canary / gray	Route via metadata.version
Security	Enable TLS + external credential store
Fallback	Cache last good instance
Heavy callbacks	Offload to queues / thread pools
Observability	Track resolution latency & errors

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Troubleshooting

Symptom	Cause	Action
No auto registration	Trigger not used	Use CLI/import/middleware
404 logical hostname	Adapter not imported	Import adapter module
Empty instance list	All offline or perms	Check Nacos console & creds
Config not updating	Listener missing	Register listener early
Residual instance	No graceful shutdown	Enable deregister-on-exit

Enable debug:

ClientConfigBuilder().log_level("DEBUG")

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Versioning

0.x = rapid iteration (breaking possible).
Pin dependency: nacos-serving-python>=0.1.0,<1.0.0.

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Contributing

Fork → Branch → Code / Tests → Docs → PR (with context & rollback plan).