Server Timing

A Server-Timing response header on every request to a Pocker instance: how long the instance's own handler took, and how long it took to wake the instance for the request. Your browser's dev tools show it in the request's Timing tab.

Server-Timing: origin;dur=12.4, wake;dur=0.0

Install · Configure · Use · Integrations · Example

Install

Server Timing is built into pocketone and on whenever it serves many instances with provider: pocker. There's nothing to install. It isn't used for a single app or under provider: docker.

In your own Pocker build, list it first among the extensions, so its header covers every other hop:

srv := &pocker.Server{Config: cfg, Extensions: []pocker.Extension{servertiming.New() /*, other extensions */}}

The module is github.com/pockethost/pocketone/ext/multisite-servertiming. It works the same in pocker.Provider{Extensions: ...}.

Configure

There's nothing to configure: no pocketone.yaml section, flag or settings screen.

Use

Open your browser's dev tools, pick a request to an instance and look at its timing, or read the header with curl:

curl -s -D - -o /dev/null http://alpha.localhost:8090/api/health | grep -i server-timing

Entry	What it measures
`origin`	The instance's own handler: from handing it the request until it sent its response headers.
`wake`	Starting the instance for this request. `0` when it was already running.

Each value is in milliseconds, one decimal, up to the response headers (time to first byte). The innermost hop comes first; values a server in front already sent are kept, and this host's entries are added after them.

Integrations

Pocker registers origin and wake for every request it hands to an instance.
Add your own entries. Host code and other extensions call pocker.Timing(ctx, fn) during a request; fn returns []pocker.TimingEntry{{Name, Dur, Desc}} and runs when the headers go out. Only extensions listed after Server Timing are covered. Put names in Desc, never addresses.
Go API. FormatTiming, AppendServerTiming and WithServerTiming render entries, append them to a header and wrap a response writer, for a server that isn't a Pocker extension.

Example

There's no example/main.go. See it used in examples/pocketone/multi.go, which lists it first in the pocketone binary's Pocker extensions.

How it works

It's a Pocker wrapper (Wrap(http.Handler)). For each request it starts collecting timing entries in the request's context, then stamps them into the Server-Timing header just before the response headers go out (not on interim 1xx responses). Flush, Hijack and http.ResponseController keep working through its writer.

License

MIT