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File 0132-Add-persistence-to-history-of-the-non-legacy-shell.patch of Package erlang
From 4b9e1dd37f6e55ba1a04fad36d8ed3c0201b1942 Mon Sep 17 00:00:00 2001 From: Fred Hebert <mononcqc@ferd.ca> Date: Sat, 22 Apr 2017 17:39:08 -0400 Subject: [PATCH 2/2] Add persistence to history of the non-legacy shell This patch adds a mechanism by which shell history gets stored persistently on disk and gets loaded whenever a new shell session begins. The log files are added to the user's cache directory, with multiple files in it, although the location is configurable. All Erlang instances on a given host will share the same log file. There are two hook points in group.erl that are used: when instantiating the buffer, where we fetch from disk, and when adding a line to the buffer (gets stored). This allows all shell instances to use the same base set of lines when loaded, but to keep their history separate after the fact. As lines are added as you go, a new shell session (with ^G -> s -> c) will have access to previous sessions' lines. The implementation makes use of the disk_log library with a rotating log in order to store data, and allow automated repairs. By default, the feature is disabled and must be turned on through OTP environment variable part of the kernel application. The options include: | Option | Accepted values | Default | Description | | ------------------------ | ----------------- |---------- | -------------------- | | shell_history | enabled, disabled | disabled | turn feature on/off | | shell_history_path | any string | user cache| where to put files | | shell_history_file_bytes | 51200..N bytes | 512kb | max data size (>50kb)| | shell_history_drop | ["q().", ...] | [] | blacklisted lines | A version header is added to the disk_log configuration, allowing changes in the storage format to be enacted in the future (i.e. adding segmentation by node name in the same file, or encoding) without conflict. Log rotation is used with multiple log files to ensure proper enforcement of resizing without too much data loss. Because disk_log does not allow to just flush bits of content on rewrite (it truncates any full file), we instead use a wrap log and try to divide the configured size into up to 10 log files so that every time we rotate a log, we lose only 10% of the data. This remains true for corrupted files that cannot fully be repaired. This many-logs-based approach in turn forces the use of a minimal log size for the `shell_history_file_bytes` configuration, since it has to be divided by 10. The shell history is not loaded for the `user` process which, despite running the group.erl module, does not actually require history as it mostly just forwards IO protocol information. --- lib/kernel/doc/src/kernel_app.xml | 23 +++ lib/kernel/src/Makefile | 1 + lib/kernel/src/group.erl | 3 +- lib/kernel/src/group_history.erl | 341 ++++++++++++++++++++++++++++++++++++++ lib/kernel/src/kernel.app.src | 1 + 5 files changed, 368 insertions(+), 1 deletion(-) create mode 100644 lib/kernel/src/group_history.erl diff --git a/lib/kernel/doc/src/kernel_app.xml b/lib/kernel/doc/src/kernel_app.xml index 28af15549..9fccb4c7a 100644 --- a/lib/kernel/doc/src/kernel_app.xml +++ b/lib/kernel/doc/src/kernel_app.xml @@ -419,6 +419,29 @@ MaxT = TickTime + TickTime / 4</code> using this service.</p> <p>Defaults to <c>false</c>.</p> </item> + <tag><c>shell_history = enabled | disabled </c></tag> + <item> + <p>Specifies whether shell history should be logged to disk + between usages of <c>erl</c>.</p> + </item> + <tag><c>shell_history_drop = [string()]</c></tag> + <item> + <p>Specific log lines that should not be persisted. For + example <c>["q().", "init:stop()."]</c> will allow to + ignore commands that shut the node down. Defaults to + <c>[]</c>.</p> + </item> + <tag><c>shell_history_file_bytes = integer()</c></tag> + <item> + <p>how many bytes the shell should remember. By default, the + value is set to 512kb, and the minimal value is 50kb.</p> + </item> + <tag><c>shell_history_path = string()</c></tag> + <item> + <p>Specifies where the shell history files will be stored. + defaults to the user's cache directory as returned by + <c>filename:basedir(user_cache, "erlang-history")</c>.</p> + </item> <tag><c>shutdown_func = {Mod, Func}</c></tag> <item> <p>Where:</p> diff --git a/lib/kernel/src/Makefile b/lib/kernel/src/Makefile index 2a89faaf1..78aa6192a 100644 --- a/lib/kernel/src/Makefile +++ b/lib/kernel/src/Makefile @@ -85,6 +85,7 @@ MODULES = \ global_group \ global_search \ group \ + group_history \ heart \ hipe_unified_loader \ inet \ diff --git a/lib/kernel/src/group.erl b/lib/kernel/src/group.erl index b5e73117d..0eeaaad8d 100644 --- a/lib/kernel/src/group.erl +++ b/lib/kernel/src/group.erl @@ -33,7 +33,7 @@ start(Drv, Shell, Options) -> server(Drv, Shell, Options) -> process_flag(trap_exit, true), edlin:init(), - put(line_buffer, proplists:get_value(line_buffer, Options, [])), + put(line_buffer, proplists:get_value(line_buffer, Options, group_history:load())), put(read_mode, list), put(user_drv, Drv), put(expand_fun, @@ -783,6 +783,7 @@ save_line_buffer("\n", Lines) -> save_line_buffer(Line, [Line|_Lines]=Lines) -> save_line_buffer(Lines); save_line_buffer(Line, Lines) -> + group_history:add(Line), save_line_buffer([Line|Lines]). save_line_buffer(Lines) -> diff --git a/lib/kernel/src/group_history.erl b/lib/kernel/src/group_history.erl new file mode 100644 index 000000000..5ca5e2d1d --- /dev/null +++ b/lib/kernel/src/group_history.erl @@ -0,0 +1,341 @@ +%% +%% %CopyrightBegin% +%% +%% Copyright Ericsson AB 2017. 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 ~s. 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('$#erlang-history-invalid-file', + "Shell history expects to be able to use the file ~s " + "which currently exists and is not a file usable for " + "history logging purposes. History logging will be " + "disabled.~n", [FileName]). + +show_unexpected_warning({M,F,A}, Term) -> + show('$#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. diff --git a/lib/kernel/src/kernel.app.src b/lib/kernel/src/kernel.app.src index 25e4ddd95..1128ee3ec 100644 --- a/lib/kernel/src/kernel.app.src +++ b/lib/kernel/src/kernel.app.src @@ -44,6 +44,7 @@ global_group, global_search, group, + group_history, heart, hipe_unified_loader, inet6_tcp, -- 2.13.0
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