Add opentelemetry_resource_attr

[yuriolisa]

• Add opentelemetry_resource_attr

• Resolves: nginx: Configure custom resource attributes #232

[yuriolisa]

@open-telemetry/cpp-contrib-approvers, would it be possible to re-run only the failed jobs?

[lalitb]

@seemk @tobiasstadler - Can someone review this. thanks.

[Copilot]

Pull Request Overview

This PR adds support for custom resource attributes in the OpenTelemetry nginx instrumentation by introducing the opentelemetry_resource_attr configuration directive. This enhancement allows users to add custom resource attributes like service version and deployment environment to their traces.

• Adds opentelemetry_resource_attr directive to set custom resource attributes
• Updates the tracer provider initialization to use custom resource attributes instead of hardcoded service.name
• Preserves backward compatibility by defaulting service.name if not provided via resource attributes

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
instrumentation/nginx/src/agent_config.h	Adds resourceAttributes map to store custom resource attributes
instrumentation/nginx/src/otel_ngx_module.cpp	Implements the new directive handler and updates tracer provider initialization logic
instrumentation/nginx/test/conf/nginx.conf	Adds test configuration with sample resource attributes
instrumentation/nginx/test/instrumentation/test/instrumentation_test.exs	Adds test assertions for the new resource attributes
instrumentation/nginx/README.md	Documents the new opentelemetry_resource_attr directive

[Copilot]

The function should validate that exactly 2 arguments are provided (key and value). Currently, if fewer than 2 arguments are passed, accessing values[2] could cause undefined behavior.

Suggested change

	if (cf->args->nelts < 3) {
	ngx_log_error(NGX_LOG_ERR, cf->log, 0, "opentelemetry: invalid number of arguments for resource attribute. Expected 2 arguments (key and value).");
	return (char*)NGX_CONF_ERROR;
	}

[Copilot]

The key and value strings are constructed without null-termination validation. If key->data or value->data are not null-terminated within the specified length, this could lead to buffer overruns when used elsewhere.

Suggested change

	std::string strKey((const char*)key->data, key->len);
	std::string strValue((const char*)value->data, value->len);
	std::string strKey;
	std::string strValue;
	{
	std::vector<char> keyBuffer(key->data, key->data + key->len);
	keyBuffer.push_back('\0'); // Ensure null-termination
	strKey = std::string(keyBuffer.data());
	}
	{
	std::vector<char> valueBuffer(value->data, value->data + value->len);
	valueBuffer.push_back('\0'); // Ensure null-termination
	strValue = std::string(valueBuffer.data());
	}

[Copilot]

This appears to be an unrelated formatting fix (adding missing semicolon) that should be mentioned in the PR description or handled in a separate commit.

[yuriolisa]

It's also related to the #404.

[yuriolisa]

@lalitb, I've implemented the changes suggested by Copilot, and I believe the PR is now ready to go.