Name
cowboy_tracer_h - Tracer stream handler
Description
The module cowboy_tracer_h
can be used to conditionally trace streams based on information found in the request. Trace messages are given to the configured callback.
Options
opts() :: #{
tracer_callback => Callback,
tracer_flags => [atom()],
tracer_match_specs => [MatchSpec]
}
Callback :: fun((init | terminate | tuple(), State) -> State)
MatchSpec :: MatchPredicate
| {method, binary()}
| {host, binary()}
| {path, binary()}
| {path_start, binary()}
| {header, binary()}
| {header, binary(), binary()}
| {peer_ip, inet:ip_address()}
MatchPredicate :: fun((cowboy_stream:streamid(),
cowboy_req:req(),
cowboy:opts()) -> boolean())
}
Configuration for the tracer stream handler.
This module will not set trace patterns. Those must be set by the user directly, either from the callback's init
or, preferably, in advance.
- tracer_callback
The function that will be called for each trace events. It will also be called before any trace event with an argument init
, and when the stream is terminated with an argument terminate
.
This option is required for tracing to be enabled. The tracer stream handler does nothing otherwise.
- tracer_flags
Trace flags to enable. See the documentation of erlang:trace/3
for details. Note that all trace flags are allowed except for the tracer
flag.
- tracer_match_specs
A list of match conditions that must all be fulfilled for the stream to be traced. Cowboy will compare these with the information found in the request and only enable tracing if all matches succeed.
This option is required for tracing to be enabled. The tracer stream handler does nothing otherwise.
Events
The tracer stream handler does not produce any event.
Changelog
See also
cowboy(7), cowboy_stream(3), cowboy_compress_h(3), cowboy_metrics_h(3), cowboy_stream_h(3)
Cowboy
2.8
Function Reference
Navigation
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