Bounded, read-only access to the log files of a node - the web equivalent of observer_cli's log tail pane: read the last chunk of a logger file during an incident without flushing or locking anything.

Log sources are restricted to the file-backed :logger handlers configured on the target node (:logger.get_handler_config/0); free-form paths are never accepted from the caller, so the dashboard cannot be used to read arbitrary files.

The tail itself is a single stdlib-only RPC: a pre-parsed :erl_eval expression opens the file on the remote node, preads at most max_bytes from the end and closes it. Nothing is required on the target node beyond OTP itself, matching how ObserverWeb.SystemInfo keeps remote calls version-independent.

Making logs visible

Elixir applications log to the console by default, in which case there is nothing to tail. Add a file handler to the observed application (standard Elixir 1.15+ configuration):

# config/config.exs
config :my_app, :logger, [
  {:handler, :file_log, :logger_std_h,
   %{config: %{file: ~c"/var/log/my_app/my_app.log"}, formatter: Logger.Formatter.new()}}
]

# lib/my_app/application.ex - in start/2
Logger.add_handlers(:my_app)

Or attach one at runtime without restarting:

:logger.add_handler(:file_log, :logger_std_h, %{config: %{file: ~c"/var/log/my_app.log"}})

See the installation guide's "Logs" section for rotation options and Erlang release notes.