How does Cloud Trace decide which requests to trace?

[PK]

I spent some time tonight with Cloud Trace. It seems very promising but I could not find certain requests. Does it sample requests or is supposed to capture all of them? Is there a way to ensure that a certain request is captured?

Thanks,
PK

p...@gae123.com

[Zeehad (Cloud Platform Support)]

Hello,

Cloud trace captures all requests to application URIs. If you cannot see the request in the overview, find the trace by choosing the appropriate parameters. You can also create analysis reports for specific URIs.

I hope it helps. Cheers!

[Brad Abrams]

Thanks Zeehad...   That is correct!  Our engineering lead for Cloud Trace responded to PK off thread and I think her response might be helpful or at least interesting to others.

    The requests are sampled at a rate of 0.1 request per second for each app engine instance you have.

    If you want to force a request to be traced, add X-Cloud-Trace-Context header to your request. The trace header specification in rfc7230 syntax is as below:

trace-context := “X-Cloud-Trace-Context” “:” trace-id  “/” span-id[ “;” “o” “=” trace_options ] *( “;” key “=” value)

trace-id := 1*( HEXDIG) ; hex representation of a 128 bit value

span-id := 1*(DIGIT) ; decimal representation of a 64 bit value

trace-option := 1*(DIGIT) ; decimal representation of a 32 bit value

Trace-id is required to be a 32 char hex value representing a 128 bit number. It should be unique between your requests unless you intentionally want to bundle them together. You can use UUIDs.

Span-id is better to be set to "0" if this is the root of your trace. Unless you have mobile clients that send in trace data (which is unlikely since you just discovered the feature), I'd suggest you use "0"

trace-option: set to 1 if you want to trace this request. 0 if you don't want to trace the request

 Here is an example to show how to force tracing via curl:

curl "http://<your.apps.url>" --header "X-Cloud-Trace-Context: <trace-id>/0;o=1"

example trace-id: 105445aa7843bc8bf206b120001000

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