Tracing Reference¶

New in version 3.0.

A reference for client tracing API.

Request life cycle¶

A request goes through the following stages and corresponding fallbacks.

Overview¶

Name	Description
start	on_request_start
redirect	on_request_redirect
acquire_connection	Connection acquiring
headers_received
exception	on_request_exception
end	on_request_end
headers_sent
chunk_sent	on_request_chunk_sent
chunk_received	on_response_chunk_received

Connection acquiring¶

Name	Description
begin
end
queued_start	on_connection_queued_start
create_start	on_connection_create_start
reuseconn	on_connection_reuseconn
queued_end	on_connection_queued_end
create_end	on_connection_create_end
exception	Exception raised
resolve_dns	DNS resolving
sock_connect	Connection establishment

DNS resolving¶

Name	Description
begin
end
exception	Exception raised
resolve_end	on_dns_resolvehost_end
resolve_start	on_dns_resolvehost_start
cache_hit	on_dns_cache_hit
cache_miss	on_dns_cache_miss

TraceConfig¶

class aiohttp.TraceConfig(trace_config_ctx_factory=SimpleNamespace)¶

Trace config is the configuration object used to trace requests launched by a ClientSession object using different events related to different parts of the request flow.

Parameters: trace_config_ctx_factory – factory used to create trace contexts, default class used types.SimpleNamespace

trace_config_ctx(trace_request_ctx=None)¶

Parameters: trace_request_ctx – Will be used to pass as a kw for the trace_config_ctx_factory.

Build a new trace context from the config.

Every signal handler should have the following signature:

async def on_signal(session, context, params): ...

where session is ClientSession instance, context is an object returned by trace_config_ctx() call and params is a data class with signal parameters. The type of params depends on subscribed signal and described below.

on_request_start¶

Property that gives access to the signals that will be executed when a request starts.

params is aiohttp.TraceRequestStartParams instance.

on_request_chunk_sent¶

Property that gives access to the signals that will be executed when a chunk of request body is sent.

params is aiohttp.TraceRequestChunkSentParams instance.

New in version 3.1.

on_response_chunk_received¶

Property that gives access to the signals that will be executed when a chunk of response body is received.

params is aiohttp.TraceResponseChunkReceivedParams instance.

New in version 3.1.

on_request_redirect¶

Property that gives access to the signals that will be executed when a redirect happens during a request flow.

params is aiohttp.TraceRequestRedirectParams instance.

on_request_end¶

Property that gives access to the signals that will be executed when a request ends.

params is aiohttp.TraceRequestEndParams instance.

on_request_exception¶

Property that gives access to the signals that will be executed when a request finishes with an exception.

params is aiohttp.TraceRequestExceptionParams instance.

on_connection_queued_start¶

Property that gives access to the signals that will be executed when a request has been queued waiting for an available connection.

params is aiohttp.TraceConnectionQueuedStartParams instance.

on_connection_queued_end¶

Property that gives access to the signals that will be executed when a request that was queued already has an available connection.

params is aiohttp.TraceConnectionQueuedEndParams instance.

on_connection_create_start¶

Property that gives access to the signals that will be executed when a request creates a new connection.

params is aiohttp.TraceConnectionCreateStartParams instance.

on_connection_create_end¶

Property that gives access to the signals that will be executed when a request that created a new connection finishes its creation.

params is aiohttp.TraceConnectionCreateEndParams instance.

on_connection_reuseconn¶

Property that gives access to the signals that will be executed when a request reuses a connection.

params is aiohttp.TraceConnectionReuseconnParams instance.

on_dns_resolvehost_start¶

Property that gives access to the signals that will be executed when a request starts to resolve the domain related with the request.

params is aiohttp.TraceDnsResolveHostStartParams instance.

on_dns_resolvehost_end¶

Property that gives access to the signals that will be executed when a request finishes to resolve the domain related with the request.

params is aiohttp.TraceDnsResolveHostEndParams instance.

on_dns_cache_hit¶

Property that gives access to the signals that will be executed when a request was able to use a cached DNS resolution for the domain related with the request.

params is aiohttp.TraceDnsCacheHitParams instance.

on_dns_cache_miss¶

Property that gives access to the signals that will be executed when a request was not able to use a cached DNS resolution for the domain related with the request.

params is aiohttp.TraceDnsCacheMissParams instance.