aiohttp instrumentation: span for DNS resolution

[dacevedo12]

What problem do you want to solve?

aiohttp has hooks that would allow this instrumentation to report spans and/or dns related metrics.

this is useful to identify dns issues or bottlenecks on cluster instances

https://docs.aiohttp.org/en/stable/tracing_reference.html

Describe the solution you'd like

I'd like to have visibility over dns resolution for my http calls

Describe alternatives you've considered

extend the instrumentation in my own codebase

Additional Context

No response

Would you like to implement a fix?

None

[dacevedo12]

In the meantime

from types import SimpleNamespace
from typing import Any

import aiohttp
from opentelemetry import context, trace
from opentelemetry.instrumentation.aiohttp_client import AioHttpClientInstrumentor
from opentelemetry.instrumentation.utils import is_instrumentation_enabled
from opentelemetry.trace import SpanKind, get_tracer


class AioHTTPInstrumentor(AioHttpClientInstrumentor):
    def _instrument(self, **kwargs: Any) -> None:
        tracer = get_tracer(__name__)

        async def on_dns_resolvehost_start(
            _session: aiohttp.ClientSession,
            trace_config_ctx: SimpleNamespace,
            params: aiohttp.TraceDnsResolveHostStartParams,
        ) -> None:
            if not is_instrumentation_enabled():
                trace_config_ctx.span = None
                return
            trace_config_ctx.span = tracer.start_span(
                "dns_resolvehost", kind=SpanKind.CLIENT, attributes={"host": params.host}
            )
            trace_config_ctx.token = context.attach(
                trace.set_span_in_context(trace_config_ctx.span)
            )

        async def on_dns_resolvehost_end(
            _session: aiohttp.ClientSession,
            trace_config_ctx: SimpleNamespace,
            _params: aiohttp.TraceDnsResolveHostEndParams,
        ) -> None:
            if trace_config_ctx.span is None:
                return
            context.detach(trace_config_ctx.token)
            trace_config_ctx.span.end()

        trace_config = aiohttp.TraceConfig()
        trace_config.on_dns_resolvehost_start.append(on_dns_resolvehost_start)
        trace_config.on_dns_resolvehost_end.append(on_dns_resolvehost_end)
        super()._instrument(**kwargs, trace_configs=[trace_config])