Make log functions exportable (#455)

* Make log functions exportable

To make it easier to switch to logger in kv_index_tictactree - export the log functions from leveled so that they can be reused

* Changes post review

Added brief description of the module to explain why the approach to logging is used.

* Result of log should be `ok`

src/leveled_log.erl

@@ -1,5 +1,24 @@
-%% Module to abstract from choice of logger, and allow use of logReferences
-%% for fast lookup
+%% -------- LOG ---------
+%%
+%% Centralised logging, to make it easier to change log implementation.
+%% 
+%% The use of a ?LOGBASE map is a personal preference.  With formatting of code
+%% using maximum column widths, I prefer not to have log text within the code
+%% itself, as there may be a temptation to make log text misleadingly terse to
+%% make the code more readable.
+%% 
+%% This means that using logger's capability to add actual code line references
+%% to the log becomes mute - as all logs log from the same code line.  However,
+%% the process does enforce the use of log references to provide a simple way
+%% to search the code and find where the log occurred.  This can be helpful
+%% when there are frequent code changes which may change line numbers between
+%% releases (whereas log references stay stable).  The log references
+%% themselves can be helpful when optimising query times in splunk-like log
+%% indexing tools.
+%% 
+%% There are overheads with the approach (e.g. the maps:get/2 call for each log
+%% ).  However, the eprof testing of leveled indicates that this is not a
+%% relatively significant overhead. 
 
 -module(leveled_log).
 
@@ -9,6 +28,8 @@
             log_timer/3,
             log_randomtimer/4]).
 
+-export([log/5, log_timer/6]).
+
 -export([set_loglevel/1, 
             set_databaseid/1,
             add_forcedlogs/1,
@@ -24,8 +45,9 @@
 
 -type log_level()  ::  debug | info | warning | error | critical.
 -type log_options() :: #log_options{}.
+-type log_base() :: #{atom() => {log_level(), binary()}}.
 
--export_type([log_options/0, log_level/0]).
+-export_type([log_options/0, log_level/0, log_base/0]).
 
 -define(LOG_LEVELS, [debug, info, warning, error, critical]).
 -define(DEFAULT_LOG_LEVEL, error).
@@ -273,7 +295,7 @@
         ic012 =>
             {warning, <<"Tag ~w not found in Strategy ~w - maybe corrupted">>},
         ic013 =>
-            {warning, "File with name ~s to be ignored in manifest as scanning for first key returned empty - maybe corrupted"},
+            {warning, <<"File with name ~s to be ignored in manifest as scanning for first key returned empty - maybe corrupted">>},
         ic014 =>
             {info, <<"Compaction to be run with strategy ~w and max_run_length ~w">>},
         cdb01 =>
@@ -390,12 +412,13 @@ return_settings() ->
 
 -spec log(atom(), list()) -> ok.
 log(LogReference, Subs) ->
-    log(LogReference, Subs, ?LOG_LEVELS).
+    log(LogReference, Subs, ?LOG_LEVELS, ?LOGBASE, backend).
 
-log(LogRef, Subs, SupportedLogLevels) ->
-    {LogLevel, Log} = maps:get(LogRef, ?LOGBASE),
+-spec log(atom(), list(), list(log_level()), log_base(), atom()) -> ok.
+log(LogRef, Subs, SupportedLevels, LogBase, Tag) ->
+    {LogLevel, Log} = maps:get(LogRef, LogBase),
     LogOpts = get_opts(),
-    case should_i_log(LogLevel, SupportedLogLevels, LogRef, LogOpts) of
+    case should_i_log(LogLevel, SupportedLevels, LogRef, LogOpts) of
         true ->
             DBid = LogOpts#log_options.database_id,
             Prefix =
@@ -405,7 +428,7 @@ log(LogRef, Subs, SupportedLogLevels) ->
                 LogLevel,
                 unicode:characters_to_list([Prefix, Log, Suffix]),
                 Subs,
-                #{log_type => backend}
+                #{log_type => Tag}
             );
         false ->
             ok
@@ -430,10 +453,13 @@ is_active_level([_|T], C, L) -> is_active_level(T, C, L).
 
 -spec log_timer(atom(), list(), erlang:timestamp()) -> ok.
 log_timer(LogReference, Subs, StartTime) ->
-    log_timer(LogReference, Subs, StartTime, ?LOG_LEVELS).
+    log_timer(LogReference, Subs, StartTime, ?LOG_LEVELS, ?LOGBASE, backend).
 
-log_timer(LogRef, Subs, StartTime, SupportedLevels) ->
-    {LogLevel, Log} = maps:get(LogRef, ?LOGBASE),
+-spec log_timer(
+    atom(), list(), erlang:timestamp(), list(log_level()), log_base(), atom())
+        -> ok.
+log_timer(LogRef, Subs, StartTime, SupportedLevels, LogBase, Tag) ->
+    {LogLevel, Log} = maps:get(LogRef, LogBase),
     LogOpts = get_opts(),
     case should_i_log(LogLevel, SupportedLevels, LogRef, LogOpts) of
         true ->
@@ -446,13 +472,13 @@ log_timer(LogRef, Subs, StartTime, SupportedLevels) ->
                 LogLevel,
                 unicode:characters_to_list([Prefix, Log, Duration, Suffix]),
                 Subs,
-                #{log_type => backend}
+                #{log_type => Tag}
             );
         false ->
             ok
     end.
 
--spec log_randomtimer(atom(), list(), erlang:timestamp(), float()) -> ok.
+-spec log_randomtimer(atom(), list(), erlang:timestamp(), float()) -> term().
 log_randomtimer(LogReference, Subs, StartTime, RandomProb) ->
     R = rand:uniform(),
     case R < RandomProb of
@@ -488,14 +514,27 @@ duration_text(StartTime) ->
 
 should_i_log(LogLevel, Levels, LogRef) ->
     should_i_log(LogLevel, Levels, LogRef, get_opts()).
-        
-log_test() ->
-    log(d0001, []),
-    log_timer(d0001, [], os:timestamp()).
 
 log_warning_test() ->
-    ok = log(g0001, [], [warning, error]),
-    ok = log_timer(g0001, [], os:timestamp(), [warning, error]).
+    ok = log(g0001, [], [warning, error], ?LOGBASE, backend),
+    ok =
+        log_timer(
+            g0001, [], os:timestamp(), [warning, error], ?LOGBASE, backend
+        ).
+
+log_wrongkey_test() ->
+    ?assertException(
+        error,
+        {badkey, wrong0001},
+        log(wrong0001, [],[warning, error], ?LOGBASE, backend)
+    ),
+    ?assertException(
+        error,
+        {badkey, wrong0001},
+        log_timer(
+            wrong0001, [], os:timestamp(), [warning, error], ?LOGBASE, backend
+        )
+    ).
 
 shouldilog_test() ->
     ok = set_loglevel(debug),