Add no_proxy support

[arthurpassos]

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• New Feature

Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):

Allow proxy to be bypassed for hosts specified in no_proxy env variable and ClickHouse proxy configuration.

Documentation entry for user-facing changes

• [ X ] Documentation is written (mandatory for new features)

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[alexey-milovidov]

Missing escaping.

[alexey-milovidov]

This feature looks too ad-hoc. Missing motivation about use cases. Why environment variables?

[arthurpassos]

This feature looks too ad-hoc. Missing motivation about use cases.

Consider the scenario where a ClickHouse instance uses two different S3 installations: AWS and a private one. For the AWS one, the user wants all requests to go through their proxy, while for the private one, no. With the current implementation, there is no way to achieve this.

Why environment variables?

ClickHouse currently supports proxy configuration in two different places: env variables and configuration files. This PR will add the functionality to both, but I haven't had the time to implement for configuration files yet. Plus, it's pretty standard to support NO_PROXY through environment variables.

[filimonov]

Why environment variables?

Not invited by us, just most tools in linux support that.

https://stackoverflow.com/questions/62632642/how-to-use-no-proxy-on-linux-machines-wildcards-leading-dots
https://stackoverflow.com/questions/13559377/curl-bypass-proxy-for-localhost

You
Looking for some documentation about NO_PROXY env variable, and who support that.

ChatGPT
The NO_PROXY environment variable is used to specify a list of domain names, IP addresses, or subnets that should be excluded from proxying. When using a proxy server, all traffic is generally redirected through the proxy unless specified otherwise in NO_PROXY. This is particularly useful in environments where you want to avoid the overhead of proxying local or intranet communications.

How NO_PROXY Works:

• Format: The NO_PROXY variable is a comma-separated list of domains and IP addresses that should bypass the proxy. For example: NO_PROXY=localhost,127.0.0.1,example.com,*.mycompany.com.
• Wildcards: You can use an asterisk (*) as a wildcard to match any subdomain. For example, *.example.com would apply to subdomain.example.com, another.example.com, etc.
• Ports: You can specify ports in NO_PROXY to exclude specific port traffic from being proxied. For example: example.com:8080.

Support for NO_PROXY:

• Operating Systems: Most Unix-like operating systems, including Linux and macOS, support the NO_PROXY variable natively. Windows also supports environment variables for proxy settings, though the behavior can vary slightly depending on the implementation.
• Programming Languages: Many programming languages and their standard libraries respect the NO_PROXY setting. For instance:
  • Python: The urllib library respects NO_PROXY.
  • Node.js: The request module and others respect NO_PROXY.
• Tools and Applications: Most command-line tools and applications that use network requests support NO_PROXY. This includes tools like curl, wget, and many others.

Documentation and Standards:

While there isn't a formal RFC that defines the behavior of NO_PROXY, its usage is largely consistent across different environments due to convention. The best place to find documentation on how NO_PROXY is implemented in a specific tool or library is typically the official documentation for that tool or library.

If you're using a specific tool or programming environment and need to know how it handles NO_PROXY, it would be a good idea to look at the official documentation or the configuration settings related to proxy handling in that environment.

Curl: https://curl.se/libcurl/c/CURLOPT_NOPROXY.html
wget: https://www.gnu.org/software/wget/manual/html_node/Proxies.html
etc.

Discussion about standardizing that.

https://about.gitlab.com/blog/2021/01/27/we-need-to-talk-no-proxy/

[arthurpassos]

@alexey-milovidov can you enable CI?

[arthurpassos]

We should merge #63427 first

[robot-ch-test-poll]

This is an automated comment for commit 48de600 with description of existing statuses. It's updated for the latest CI running

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[arthurpassos]

@evillique can you also enable ci on #63427? That pr needs to be merged before this one

[CheSema]

This list is constructed from env. It is immutable for the rest of the program live.

Why we copy it to each connection?
Why do we leave it in raw format and parse each time?

[arthurpassos]

hm... if I had to argue, I would say simplicity and consistency with other types of resolvers that do not rely on environment variables. They always read stuff on the fly and generate a new configuration.

It is not a strong argument, tho. I could introduce some sort of static variable in EnvironmentProxyConfigurationResolver so that it reads only once from the environment and always returns that.

As for the native format, mostly because DB::ProxyConfiguration is 3rd party agnostic. Meaning it has no dependencies on Poco or AWS SDK. In any case, I am fine with converting it only once and storing the poco format in DB::ProxyConfiguration. If the need to abstract that ever appears, we can do it. For now, we can make this change.

What do you think?

[arthurpassos]

The last commit is a possible implementation of the above idea, please take a look: 3ae8176.