Light Log Manual

Light logs are based on RSyslog and used for debugging. Light logs should be disabled when using Light for high performance.

Setup

(1) Create log directory

cd /var/log
mkdir light
sudo chown -R syslog:adm light # The group and user have to be changed

(2) Modify RSyslog config file

Open /etc/rsyslog.conf and add the following content:

local7.debug			/var/log/light/light.log
local7.info			/var/log/light/light_info.log
local7.warn			/var/log/light/light_warn.log
local7.err			/var/log/light/light_err.log

Every file includes the logs at the same and higher severity levels.

(3) Restart RSyslog

sudo service rsyslog restart

Configuration

The Light stack and application can create logs, and we can configure the log severity level.

There are 6 levels (from 0 to 5), i.e. LIGHT_LOG_DEBUG, LIGHT_LOG_INFO, LIGHT_LOG_WARNING, LIGHT_LOG_ERR, LIGHT_LOG_CRIT, LIGHT_LOG_NONE.

(1) Log level of Light

Change the log_level parameter in the shell scripts of Light, such as startFirstCore.sh. If the log_level is 2, the Light logs whose level are equal or higher than LIGHT_LOG_WARNING are enabled. If the log_level is 5, all Light logs are disabled.

(2) Log level of applications

Change the APP_LOG_LEVEL value in light_h.c. If the APP_LOG_LEVEL is 2, the application logs whose level are equal or higher than LIGHT_LOG_WARNING are enabled. If the APP_LOG_LEVEL is 5, all application logs are disabled.

Then re-compile the Light FM:

sudo ./build_light_module.sh

APIs

(1) light_log_init()

Set the output location of logs, i.e. STDOUT and SYSLOG.

void light_log_init(int loc)

Parameter:

loc: the output location of logs. The value could be LOG_TO_STDOUT or LOG_TO_SYSLOG.

(2) light_log()

Add a log at a specific log level.

inline void light_log(int level, const char* format, ...)

Parameter:

level: log level.

format, …: log content.

Example:

Add an info-level log “LOG_CONTENT”.

light_log(LIGHT_LOG_INFO, "LOG_CONTENT\n");