1 files changed, 341 insertions, 0 deletions
diff --git a/lib/kernel/src/group_history.erl b/lib/kernel/src/group_history.erl
new file mode 100644
index 0000000000..9745848992
--- /dev/null
+++ b/lib/kernel/src/group_history.erl
@@ -0,0 +1,341 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 2017-2018. All Rights Reserved.
+%%
+%% Licensed under the Apache License, Version 2.0 (the "License");
+%% you may not use this file except in compliance with the License.
+%% You may obtain a copy of the License at
+%%
+%%     http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS,
+%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%% See the License for the specific language governing permissions and
+%% limitations under the License.
+%%
+%% %CopyrightEnd%
+%%
+-module(group_history).
+-export([load/0, add/1]).
+
+%% Make a minimal size that should encompass set of lines and then make
+%% a file rotation for N files of this size.
+-define(DEFAULT_HISTORY_FILE, "erlang-shell-log").
+-define(MAX_HISTORY_FILES, 10).
+-define(DEFAULT_SIZE, 1024*512). % 512 kb total default
+-define(DEFAULT_STATUS, disabled).
+-define(MIN_HISTORY_SIZE, (50*1024)). % 50 kb, in bytes
+-define(DEFAULT_DROP, []).
+-define(DISK_LOG_FORMAT, internal). % since we want repairs
+-define(LOG_NAME, '$#group_history').
+-define(VSN, {0,1,0}).
+
+%%%%%%%%%%%%%%
+%%% PUBLIC %%%
+%%%%%%%%%%%%%%
+
+%% @doc Loads the shell history from memory. This function should only be
+%% called from group:server/3 to inject itself in the previous commands
+%% stack.
+-spec load() -> [string()].
+load() ->
+    wait_for_kernel_safe_sup(),
+    case history_status() of
+        enabled ->
+            case open_log() of
+                {ok, ?LOG_NAME} ->
+                    read_full_log(?LOG_NAME);
+                {repaired, ?LOG_NAME, {recovered, Good}, {badbytes, Bad}} ->
+                    report_repairs(?LOG_NAME, Good, Bad),
+                    read_full_log(?LOG_NAME);
+                {error, {need_repair, _FileName}} ->
+                    repair_log(?LOG_NAME);
+                {error, {arg_mismatch, repair, true, false}} ->
+                    repair_log(?LOG_NAME);
+                {error, {name_already_open, _}} ->
+                    show_rename_warning(),
+                    read_full_log(?LOG_NAME);
+                {error, {size_mismatch, Current, New}} ->
+                    show_size_warning(Current, New),
+                    resize_log(?LOG_NAME, Current, New),
+                    load();
+                {error, {invalid_header, {vsn, Version}}} ->
+                    upgrade_version(?LOG_NAME, Version),
+                    load();
+                {error, Reason} ->
+                    handle_open_error(Reason),
+                    disable_history(),
+                    []
+            end;
+        _ ->
+            []
+    end.
+
+%% @doc adds a log line to the erlang history log, if configured to do so.
+-spec add(iodata()) -> ok.
+add(Line) -> add(Line, history_status()).
+
+add(Line, enabled) ->
+    case lists:member(Line, to_drop()) of
+        false ->
+            case disk_log:log(?LOG_NAME, Line) of
+                ok ->
+                    ok;
+                {error, no_such_log} ->
+                    _ = open_log(), % a wild attempt we hope works!
+                    disk_log:log(?LOG_NAME, Line);
+                {error, _Other} ->
+                    % just ignore, we're too late
+                    ok
+            end;
+        true ->
+            ok
+    end;
+add(_Line, disabled) ->
+    ok.
+
+%%%%%%%%%%%%%%%
+%%% PRIVATE %%%
+%%%%%%%%%%%%%%%
+
+%% Because loading the shell happens really damn early, processes we depend on
+%% might not be there yet. Luckily, the load function is called from the shell
+%% after a new process has been spawned, so we can block in here
+wait_for_kernel_safe_sup() ->
+    case whereis(kernel_safe_sup) of
+        undefined ->
+            timer:sleep(50),
+            wait_for_kernel_safe_sup();
+        _ ->
+            ok
+    end.
+
+%% Repair the log out of band
+repair_log(Name) ->
+    Opts = lists:keydelete(size, 1, log_options()),
+    case disk_log:open(Opts) of
+        {repaired, ?LOG_NAME, {recovered, Good}, {badbytes, Bad}} ->
+            report_repairs(?LOG_NAME, Good, Bad);
+        _ ->
+            ok
+    end,
+    _ = disk_log:close(Name),
+    load().
+
+%% Return whether the shell history is enabled or not
+-spec history_status() -> enabled | disabled.
+history_status() ->
+    case is_user() orelse application:get_env(kernel, shell_history) of
+        true -> disabled; % don't run for user proc
+        {ok, enabled} -> enabled;
+        undefined -> ?DEFAULT_STATUS;
+        _ -> disabled
+    end.
+
+%% Return whether the user process is running this
+-spec is_user() -> boolean().
+is_user() ->
+    case process_info(self(), registered_name) of
+        {registered_name, user} -> true;
+        _ -> false
+    end.
+
+%% Open a disk_log file while ensuring the required path is there.
+open_log() ->
+    Opts = log_options(),
+    _ = ensure_path(Opts),
+    disk_log:open(Opts).
+
+%% Return logger options
+log_options() ->
+    Path = find_path(),
+    File = filename:join([Path, ?DEFAULT_HISTORY_FILE]),
+    Size = find_wrap_values(),
+    [{name, ?LOG_NAME},
+     {file, File},
+     {repair, true},
+     {format, internal},
+     {type, wrap},
+     {size, Size},
+     {distributed, []},
+     {notify, false},
+     {head, {vsn, ?VSN}},
+     {quiet, true},
+     {mode, read_write}].
+
+-spec ensure_path([{file, string()} | {atom(), _}, ...]) -> ok | {error, term()}.
+ensure_path(Opts) ->
+    {file, Path} = lists:keyfind(file, 1, Opts),
+    filelib:ensure_dir(Path).
+
+%% @private read the logs from an already open file. Treat closed files
+%% as wrong and returns an empty list to avoid crash loops in the shell.
+-spec read_full_log(term()) -> [string()].
+read_full_log(Name) ->
+    case disk_log:chunk(Name, start) of
+        {error, no_such_log} ->
+            show_unexpected_close_warning(),
+            [];
+        eof ->
+            [];
+        {Cont, Logs} ->
+            lists:reverse(maybe_drop_header(Logs) ++ read_full_log(Name, Cont))
+    end.
+
+read_full_log(Name, Cont) ->
+    case disk_log:chunk(Name, Cont) of
+        {error, no_such_log} ->
+            show_unexpected_close_warning(),
+            [];
+        eof ->
+            [];
+        {NextCont, Logs} ->
+            maybe_drop_header(Logs) ++ read_full_log(Name, NextCont)
+    end.
+
+maybe_drop_header([{vsn, _} | Rest]) -> Rest;
+maybe_drop_header(Logs) -> Logs.
+
+-spec handle_open_error(_) -> ok.
+handle_open_error({arg_mismatch, OptName, CurrentVal, NewVal}) ->
+    show('$#erlang-history-arg-mismatch',
+         "Log file argument ~p changed value from ~p to ~p "
+         "and cannot be automatically updated. Please clear the "
+         "history files and try again.~n",
+         [OptName, CurrentVal, NewVal]);
+handle_open_error({not_a_log_file, FileName}) ->
+    show_invalid_file_warning(FileName);
+handle_open_error({invalid_index_file, FileName}) ->
+    show_invalid_file_warning(FileName);
+handle_open_error({invalid_header, Term}) ->
+    show('$#erlang-history-invalid-header',
+         "Shell history expects to be able to use the log files "
+         "which currently have unknown headers (~p) and may belong to "
+         "another mechanism. History logging will be "
+         "disabled.~n",
+         [Term]);
+handle_open_error({file_error, FileName, Reason}) ->
+    show('$#erlang-history-file-error',
+         "Error handling File ~ts. Reason: ~p~n"
+         "History logging will be disabled.~n",
+         [FileName, Reason]);
+handle_open_error(Err) ->
+    show_unexpected_warning({disk_log, open, 1}, Err).
+
+find_wrap_values() ->
+    ConfSize = case application:get_env(kernel, shell_history_file_bytes) of
+        undefined -> ?DEFAULT_SIZE;
+        {ok, S} -> S
+    end,
+    SizePerFile = max(?MIN_HISTORY_SIZE, ConfSize div ?MAX_HISTORY_FILES),
+    FileCount = if SizePerFile > ?MIN_HISTORY_SIZE ->
+                       ?MAX_HISTORY_FILES
+                 ; SizePerFile =< ?MIN_HISTORY_SIZE ->
+                       max(1, ConfSize div SizePerFile)
+                end,
+    {SizePerFile, FileCount}.
+
+report_repairs(_, _, 0) ->
+    %% just a regular close repair
+    ok;
+report_repairs(_, Good, Bad) ->
+    show('$#erlang-history-report-repairs',
+         "The shell history log file was corrupted and was repaired. "
+         "~p bytes were recovered and ~p were lost.~n", [Good, Bad]).
+
+resize_log(Name, _OldSize, NewSize) ->
+    show('$#erlang-history-resize-attempt',
+         "Attempting to resize the log history file to ~p...", [NewSize]),
+    Opts = lists:keydelete(size, 1, log_options()),
+    _ = case disk_log:open(Opts) of
+        {error, {need_repair, _}} ->
+            _ = repair_log(Name),
+            disk_log:open(Opts);
+        _ ->
+            ok
+    end,
+    case disk_log:change_size(Name, NewSize) of
+        ok ->
+            show('$#erlang-history-resize-result',
+                 "ok~n", []);
+        {error, {new_size_too_small, _, _}} ->
+            show('$#erlang-history-resize-result',
+                 "failed (new size is too small)~n", []),
+            disable_history();
+        {error, Reason} ->
+            show('$#erlang-history-resize-result',
+                 "failed (~p)~n", [Reason]),
+            disable_history()
+    end.
+
+upgrade_version(_Name, Unsupported) ->
+    %% We only know of one version and can't support a newer one
+    show('$#erlang-history-upgrade',
+         "The version for the shell logs found on disk (~p) is "
+         "not supported by the current version (~p)~n",
+         [Unsupported, ?VSN]),
+    disable_history().
+
+disable_history() ->
+    show('$#erlang-history-disable', "Disabling shell history logging.~n", []),
+    application:set_env(kernel, shell_history, force_disabled).
+
+find_path() ->
+    case application:get_env(kernel, shell_history_path) of
+        undefined -> filename:basedir(user_cache, "erlang-history");
+        {ok, Path} -> Path
+    end.
+
+to_drop() ->
+    case application:get_env(kernel, shell_history_drop) of
+        undefined ->
+            application:set_env(kernel, shell_history_drop, ?DEFAULT_DROP),
+            ?DEFAULT_DROP;
+        {ok, V} when is_list(V) -> [Ln++"\n" || Ln <- V];
+        {ok, _} -> ?DEFAULT_DROP
+    end.
+
+%%%%%%%%%%%%%%%%%%%%%%%%
+%%% Output functions %%%
+%%%%%%%%%%%%%%%%%%%%%%%%
+show_rename_warning() ->
+    show('$#erlang-history-rename-warn',
+         "A history file with a different path has already "
+         "been started for the shell of this node. The old "
+         "name will keep being used for this session.~n",
+         []).
+
+show_invalid_file_warning(FileName) ->
+    show('$#erlang-history-invalid-file',
+         "Shell history expects to be able to use the file ~ts "
+         "which currently exists and is not a file usable for "
+         "history logging purposes. History logging will be "
+         "disabled.~n", [FileName]).
+
+show_unexpected_warning({M,F,A}, Term) ->
+    show('$#erlang-history-unexpected-return',
+         "unexpected return value from ~p:~p/~p: ~p~n"
+         "shell history will be disabled for this session.~n",
+         [M,F,A,Term]).
+
+show_unexpected_close_warning() ->
+    show('$#erlang-history-unexpected-close',
+         "The shell log file has mysteriousy closed. Ignoring "
+         "currently unread history.~n", []).
+
+show_size_warning(_Current, _New) ->
+    show('$#erlang-history-size',
+         "The configured log history file size is different from "
+         "the size of the log file on disk.~n", []).
+
+show(Key, Format, Args) ->
+    case get(Key) of
+        undefined ->
+            io:format(standard_error, Format, Args),
+            put(Key, true),
+            ok;
+        true ->
+            ok
+    end.