[Tarantool-patches] [PATCH v4 7/8] lua/log: allow to configure logging without a box

[Cyrill Gorcunov <gorcunov@gmail.com>]

In the commit we allow to configure logger without
calling box.cfg{}.

Fixes #689

@TarantoolBot document
Title: Module log

Module log allows to setup logger early without calling ``box.cfg()``.
Configuration parameters are same as in ``box.cfg()`` call.

Example
```
> log = require('log')
> log.cfg({log='filename', log_format='plain', log_level=6})
...
> log.cfg({log_format='json', log_level=5})
```

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
---
 src/box/lua/load_cfg.lua |  13 +++--
 src/lua/log.lua          | 117 +++++++++++++++++++++++++++++++++++++--
 2 files changed, 119 insertions(+), 11 deletions(-)

diff --git a/src/box/lua/load_cfg.lua b/src/box/lua/load_cfg.lua
index 9aef12840..00e424156 100644
--- a/src/box/lua/load_cfg.lua
+++ b/src/box/lua/load_cfg.lua
@@ -471,11 +471,13 @@ end
 local function apply_default_modules_cfg(cfg)
     --
     -- logging
-    for k,v in pairs(log.box_api.cfg) do
-        if cfg[k] == nil then
-            cfg[k] = v
-        end
-    end
+    log.box_api.cfg_apply_default(cfg)
+end
+
+local function update_modules_cfg(cfg)
+    --
+    -- logging
+    log.box_api.cfg_update(cfg)
 end
 
 -- Return true if two configurations are equivalent.
@@ -597,6 +599,7 @@ local function load_cfg(cfg)
             end
         end
     end
+    update_modules_cfg(cfg)
     if not box.cfg.read_only and not box.cfg.replication then
         box.schema.upgrade{auto = true}
     end
diff --git a/src/lua/log.lua b/src/lua/log.lua
index ce546f21e..31a80e18a 100644
--- a/src/lua/log.lua
+++ b/src/lua/log.lua
@@ -97,6 +97,14 @@ local fmt_str2num = {
     ["json"]            = ffi.C.SF_JSON,
 }
 
+local function fmt_list()
+    local keyset = {}
+    for k in pairs(fmt_str2num) do
+        keyset[#keyset + 1] = k
+    end
+    return table.concat(keyset, ',')
+end
+
 --
 -- Default options. The keys are part of
 -- user API, so change with caution.
@@ -162,18 +170,17 @@ local function log_rotate()
 end
 
 local function log_level(level)
+    if type(level) ~= 'number' then
+        error("log: 'level' (or 'log_level' option) expects a number")
+    end
     ffi.C.say_set_log_level(level)
     rawset(log_cfg, 'log_level', level)
 end
 
 local function log_format(name)
     if not fmt_str2num[name] then
-        local keyset = {}
-        for k in pairs(fmt_str2num) do
-            keyset[#keyset + 1] = k
-        end
         local m = "log_format: expected %s"
-        error(m:format(table.concat(keyset, ',')))
+        error(m:format(fmt_list()))
     end
 
     if fmt_str2num[name] == ffi.C.SF_JSON then
@@ -194,6 +201,100 @@ local function log_pid()
     return tonumber(ffi.C.log_pid)
 end
 
+local cfg_params_once = {
+    'log',
+    'log_nonblock',
+}
+
+--
+-- Setup dynamic parameters.
+local function dynamic_cfg(cfg)
+
+    for _, k in pairs(cfg_params_once) do
+        if cfg[k] ~= nil and cfg[k] ~= log_cfg[k] then
+            local m = "log: '%s' can't be set dynamically"
+            error(m:format(k))
+        end
+    end
+
+    if cfg.log_level ~= nil then
+        log_level(cfg.log_level)
+    end
+
+    if cfg.log_format ~= nil then
+        log_format(cfg.log_format)
+    end
+end
+
+--
+-- Load or reload configuration via log.cfg({})
+--
+-- The syntax is the same as for box.cfg({}).
+local function load_cfg(oldcfg, cfg)
+    cfg = cfg or {}
+
+    if cfg.log_format ~= nil then
+        if fmt_str2num[cfg.log_format] == nil then
+            local m = "log: 'log_format' must be %s"
+            error(m:format(fmt_list()))
+        end
+    end
+
+    if cfg.log_level ~= nil then
+        if type(cfg.log_level) ~= 'number' then
+            error("log: 'log_level' option must be a number")
+        end
+    end
+
+    if cfg.log_nonblock ~= nil then
+        if type(cfg.log_nonblock) ~= 'boolean' then
+            error("log: 'log_nonblock' option must be 'true' or 'false'")
+        end
+    end
+
+    if ffi.C.say_logger_initialized() == true then
+        return dynamic_cfg(cfg)
+    end
+
+    cfg.log_level = cfg.log_level or log_cfg.log_level
+    cfg.log_format = cfg.log_format or log_cfg.log_format
+    cfg.log_nonblock = cfg.log_nonblock or (log_cfg.log_nonblock or false)
+
+    --
+    -- We never allow confgure the logger in background
+    -- mode since we don't know how the box will be configured
+    -- later.
+    ffi.C.say_logger_init(cfg.log, cfg.log_level,
+                          cfg.log_nonblock, cfg.log_format, 0)
+
+    --
+    -- Update log_cfg vars to show them in module
+    -- configuration output.
+    rawset(log_cfg, 'log', cfg.log)
+    rawset(log_cfg, 'log_level', cfg.log_level)
+    rawset(log_cfg, 'log_nonblock', cfg.log_nonblock)
+    rawset(log_cfg, 'log_format', cfg.log_format)
+end
+
+--
+-- Apply defaut config to the box module
+local function box_cfg_apply_default(box_cfg)
+    for k, v in pairs(log_cfg) do
+        if box_cfg[k] == nil then
+            box_cfg[k] = v
+        end
+    end
+end
+
+--
+-- Reflect the changes made by box.cfg interface
+local function box_cfg_update(box_cfg)
+    rawset(log_cfg, 'log', box_cfg.log)
+    rawset(log_cfg, 'log_level', box_cfg.log_level)
+    rawset(log_cfg, 'log_nonblock', box_cfg.log_nonblock)
+    rawset(log_cfg, 'log_format', box_cfg.log_format)
+end
+
 local compat_warning_said = false
 local compat_v16 = {
     logger_pid = function()
@@ -215,17 +316,21 @@ local log = {
     pid = log_pid,
     level = log_level,
     log_format = log_format,
+    cfg = setmetatable(log_cfg, {
+        __call = load_cfg,
+    }),
     --
     -- Internal API to box module, not for users,
     -- names can be changed.
     box_api = {
-        cfg = log_cfg,
         set_log_level = function()
             log_level(box.cfg.log_level)
         end,
         set_log_format = function()
             log_format(box.cfg.log_format)
         end,
+        cfg_apply_default = box_cfg_apply_default,
+        cfg_update = box_cfg_update,
     },
 }
 
-- 
2.26.2