et_selector(3)

👑 NAME 👑

et_selector — define event transforms and trace patterns 💅

(yeah bestie, this is et_selector(3), straight out of your Erlang Module Definition era ✨)

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🦋 DESCRIPTION 🦋

okay so real talk: this DESCRIPTION section is literally empty in the source — the manual just drops you straight into the data types and the functions. no lore, no backstory, just pure API. iconic honestly. moving on 🫶

🌸 DATA TYPES 🌸

• event() :: #event{}. — an event record, that's the whole vibe 💫
• level() :: 0..100. — a detail level, a number that lives anywhere from 0 to 100 inclusive, no cap 🔥

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💖 FUNCTIONS 💖

🎀 change_pattern/1

change_pattern({Mod :: module(), Pattern}) -> ok
                           when
                               Pattern ::
                                   DetailLevel | TracePattern |
                                   EmptyTracePattern,
                               DetailLevel :: level(),
                               TracePattern ::
                                   [{[term()] | '_' | atom(),
                                     [term()],
                                     [term()]}],
                               EmptyTracePattern :: [].

this one turns tracing on or off by swapping out the current trace pattern. it's giving "main character flips the switch" energy ✨

here's how the detail level call goes down:

• min detail level → deactivates tracing of calls to et:trace_me/4,5 🙈
• max detail level → activates tracing of all calls to et:trace_me/4,5 👑
• integer(X) detail level → activates tracing of all calls to et:trace_me/4,5 whose detail level argument is lesser than X 💫
• an empty match spec → deactivates tracing of calls to et:trace_me/4,5 💀
• other match specs → activates tracing of calls to et:trace_me/4,5 accordingly with erlang:trace_pattern/2 🔥

🧚 make_pattern/1

make_pattern({Mod :: module(), RawPattern}) ->
                        {Mod :: module(), TracePattern}
                        when
                            RawPattern :: level(),
                            TracePattern ::
                                [{[term()] | '_' | atom(),
                                  [term()],
                                  [term()]}].

this one bakes a trace pattern that's suitable to feed straight into change_pattern/1 🍓

same detail level rules, same energy:

• Min detail level → deactivates tracing of calls to et:trace_me/4,5 🙈
• Max detail level → activates tracing of all calls to et:trace_me/4,5 👑
• integer(X) detail level → activates tracing of all calls to et:trace_me/4,5 whose detail level argument is lesser than X 💫

also, go peek at erlang:trace_pattern/2 if you want more info about its match_spec() — iykyk 🌈

🌈 parse_event/2

parse_event(Mod, ValidTraceData) -> boolean | {true, event()}
                       when
                           Mod :: module(),
                           ValidTraceData :: ErlangTraceData | event(),
                           ErlangTraceData ::
                               {trace, pid(), atom(), term()} |
                               {trace, pid(), atom(), term(), term()} |
                               {trace_ts,
                                pid(),
                                atom(),
                                term(),
                                TS :: {integer(), integer(), integer()}} |
                               {trace_ts,
                                pid(),
                                atom(),
                                term(),
                                term(),
                                TS :: {integer(), integer(), integer()}} |
                               {seq_trace, atom(), term()} |
                               {seq_trace,
                                atom(),
                                term(),
                                TS :: {integer(), integer(), integer()}} |
                               {drop, integer()}.

this is the glow-up function: it transforms trace data and makes an event record out of it 💅✨

if you want the semantics of that trace data, erlang:trace/3 is where the lore lives 📖

an event record is made of these fields, bestie:

• detail_level — noise has a high level as opposed to essentials 🌊
• trace_ts — time when the trace was generated. same as event_ts if omitted in trace data ⏰
• event_ts — time when the event record was created 🕰️
• from — from actor, such as sender of a message 📨
• to — to actor, such as receiver of message 🫶
• label — label intended to provide a brief event summary 🏷️
• contents — all nitty gritty details of the event 🧐

oh and go check et:trace_me/4 and et:trace_me/5 for the details 👀

and here's what it hands back to you:

• {true, Event} — where Event is an #event{} record representing the trace data ✨
• true — means the trace data already is an event record and it's valid exactly as it is. no transformation needed, it ate and left no crumbs 👑
• false — means the trace data is uninteresting and should be dropped 💀

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that's the whole page, babe 🎀 brought to you by Ericsson AB, living in et version 1.8, forever known as et_selector(3) — stan a trace-pattern icon 💖✨