ObserverWeb.Tracer (Observer Web v0.2.8)

This module provides Tracer context

Summary

Functions

get_default_functions_matchspecs()

This function retrieves all match specs available in the Tracing page's match-spec picker.

get_module_functions_info(node \\ Node.self(), module)

This function retrieves all functions within the passed node and module

get_modules(node \\ Node.self())

This function retrieves all modules within the passed node

get_tool_functions_matchspecs()

Match specs forced in by the Profiling tools (see ObserverWeb.Tracer.Tool.forced_match_spec_keys/1), kept separate from get_default_functions_matchspecs/0 so they don't show up as user-facing options in the Tracing page's match-spec picker - capture_args is redundant there (the display tool already traces full argument values) and call_seq's captured arguments would be mislabeled as the caller by the display decoding.

start_trace(functions, attrs \\ %{})

This function starts the trace for the passed module/functions

state()

This function returns the current trace server state

stop_trace(session_id)

This function stops the trace for the passed session ID

Types

t()

@type t() :: %ObserverWeb.Tracer{
  functions_by_node: map(),
  max_messages: non_neg_integer(),
  request_pid: pid() | nil,
  session_id: binary() | nil,
  session_timeout_ms: non_neg_integer(),
  status: :idle | :running,
  tool: ObserverWeb.Tracer.Tool.t(),
  tool_opts: map(),
  tool_state: term()
}

Functions

get_default_functions_matchspecs()

@spec get_default_functions_matchspecs() :: map()

This function retrieves all match specs available in the Tracing page's match-spec picker.

NOTE: ObserverWeb.Tracer.Server concatenates the patterns of every selected key into separate match-spec clauses (not a single clause with combined actions), and Erlang match specs only run the first clause whose head matches - since every clause here matches on _, selecting more than one key at once means only the first selected key's actions actually run.

get_module_functions_info(node \\ Node.self(), module)

@spec get_module_functions_info(node :: atom(), module :: atom()) :: %{
  functions: map(),
  module: atom(),
  node: atom()
}

This function retrieves all functions within the passed node and module

get_modules(node \\ Node.self())

@spec get_modules(node :: atom()) :: list()

This function retrieves all modules within the passed node

get_tool_functions_matchspecs()

@spec get_tool_functions_matchspecs() :: map()

call_seq combines return_trace() and argument capture in a single clause because of the first-matching-clause limitation described in get_default_functions_matchspecs/0 - forcing return_trace + capture_args as two clauses would only ever run the first one.

start_trace(functions, attrs \\ %{})

@spec start_trace(functions :: list(), attrs :: map()) ::
  {:ok, t()} | {:error, :already_started}

This function starts the trace for the passed module/functions

Accepts an optional :tool attr (any ObserverWeb.Tracer.Tool.t(): :display - the default - :count, :duration, :call_seq or :flame_graph) selecting how trace events are reported back: :display streams each event as a {:new_trace_message, ...} message like today, other tools instead accumulate events and report a single {:tool_report, session_id, report} message when the session ends. :tool_opts passes per-tool options, e.g. %{aggregation: :avg} for :duration.

state()

@spec state() :: map()

This function returns the current trace server state

stop_trace(session_id)

@spec stop_trace(binary()) :: :ok

This function stops the trace for the passed session ID