8d728b91创建于 2023年11月15日历史提交

Log Management

Overview

Function Introduction

Basic functions of a log include recording key nodes and troubleshooting faults during the init startup process.

Logs help troubleshoot faults, check the startup duration of each subsystem, command execution duration, and more.
Log tags (including param, uevent, and module) for different modules can be viewed.
Logs can be printed for key phases, for example, the startup of the first phase, a required partition and its device node, uevent creation, service startup, and more.
Log levels are configurable. Available log levels include INIT_DEBUG, INIT_INFO, INIT_WARN, INIT_ERROR, and INIT_FATAL.

Basic Concepts

The implementation of the init log function varies according to the OpenHarmony version.

OpenHarmony standard system: The init log function is implemented via dmesg log of the Linux kernel.
For the OpenHarmony LiteOS small system, the init log function is implemented by using the hilog API.
For the OpenHarmony LiteOS mini system, the init log function is implemented by using the printf API.

Log Type

init logs are classified into hilog and demsg logs. The hilog log records information related to system service processes, and the demsg log records information related to the kernel.

Log Level

init logs are classified into five levels, which can be set by the (INIT_DEBUG_LEVEL)persist.init.debug.loglevel parameter.

InitLogLevel:
  INIT_DEBUG = 0,
  INIT_INFO,
  INIT_WARN,
  INIT_ERROR,
  INIT_FATAL

Kmsg log level. The options are as follows:

"<7>" =====> "DEBUG"
"<6>" =====> "INFO"
"<4>" =====> "WARNING"
"<3>" =====> "ERROR"
"<3>" =====> "FATAL"

Key Macros for Log Control

INIT_DMESG specifies whether to record kernel logs in /dev/kmsg. INIT_FILE specifies whether to write log information to the /data/init_agent/begetctl.log file. INIT_AGENT specifies whether to use hilog to record log information.

Key APIs:

  void EnableInitLog (InitLogLevel level) Enables the init log function.

  void SetInitLogLevel(InitLogLevel level) Sets the log level to control log output.

  void StartupLog(InitLogLevel logLevel, uint32_t domain, const char *tag, const char *fmt, ...) Provides an entry to the init log function.

STARTUP_LOGI is a macro defined for StartupLog, which is defined in the /base/startup/init/interfaces/innerkits/include/beget_ext.h file. Other logs are redefined based on the STARTUP_LOGI macro.

deviceInfo module (init/device_info/idevice_info.h):

  DINFO_LOGI
  DINFO_LOGE
  DINFO_LOGV

Param JS API module (init/interfaces/kits/jskits/src/native_parameters_js.h):

  PARAM_JS_LOGI
  PARAM_JS_LOGE
  PARAM_JS_LOGV
  PARAM_JS_LOGW

Shell module (init/services/begetctl/shell/shell_utils.h):

  BSH_LOGI
  BSH_LOGE
  BSH_LOGV

LoopEvent module (init/services/loopevent/utils/le_utils.h):

  LE_LOGI
  LE_LOGE
  LE_LOGV

Plug-in module (init/services/modules/plugin_adapter.h):

  PLUGIN_LOGI
  PLUGIN_LOGE
  PLUGIN_LOGV
  PLUGIN_LOGW

Param module (init/services/param/include/param_utils.h):

  PARAM_LOGI
  PARAM_LOGE
  PARAM_LOGV
  PARAM_LOGW

ParamWatcher module (init/services/param/watcher/include/watcher_utils.h):

  WATCHER_LOGI
  WATCHER_LOGE
  WATCHER_LOGV

init log module implemented based on the macros defined by StartupLog (init/services/log/init_log.h)

  INIT_LOGV
  INIT_LOGI
  INIT_LOGW
  INIT_LOGE
  INIT_LOGF

Constraints

N/A

How to Develop

Use Cases

init logs are mainly used to start modules (like param, ueventd, and module) during init startup, and are used in the open API begetutils.

Available APIs

Table 1 Log APIs

API	Format and Example	Description
INIT_LOGV	INIT_LOGV("Add %s to job %s", service->name, jobName);	Prints the log of the DEBUG level.
INIT_LOGI	INIT_LOGI("Start init first stage.");	Prints the log of the INFO level.
INIT_LOGW	INIT_LOGW("initialize signal handler failed");	Prints the log of the WARN level.
INIT_LOGE	INIT_LOGE("Failed to format other opt");	Prints the log of the ERROR level.
INIT_LOGF	INIT_LOGF("Failed to init system");	Prints the log of the FATAL level.
INIT_ERROR_CHECK	INIT_ERROR_CHECK(ctx != NULL, return NULL, "Failed to get cmd args ");	Prints a log and executes return NULL when ctx != NULL is not true.
INIT_INFO_CHECK	INIT_INFO_CHECK(sockopt != NULL, return SERVICE_FAILURE, "Failed to malloc for service %s", service->name);	Prints a log and executes return SERVICE_FAILURE when sockopt != NULL is not true.
INIT_WARNING_CHECK	INIT_WARNING_CHECK(argsCount <= SPACES_CNT_IN_CMD_MAX, argsCount = SPACES_CNT_IN_CMD_MAX, "Too much arguments for command, max number is %d", SPACES_CNT_IN_CMD_MAX);	Prints a log and executes argsCount = SPACES_CNT_IN_CMD_MAX when argsCount <= SPACES_CNT_IN_CMD_MAX is not true.
INIT_CHECK	INIT_CHECK(arg != NULL, return NULL);	Executes return NULL when arg != NULL is not true.
INIT_CHECK_RETURN_VALUE	INIT_CHECK_RETURN_VALUE(errno == 0, -1);	Executes return -1 when errno == 0 is not true.
INIT_CHECK_ONLY_RETURN	INIT_CHECK_ONLY_RETURN(cmd != NULL);	Executes return when cmd != NULL is not true.
INIT_CHECK_ONLY_ELOG	INIT_CHECK_ONLY_ELOG(execv(argv[0], argv) == 0, "execv %s failed! err %d.", argv[0], errno);	Prints only log "execv %s failed! err %d." when execv(argv[0], argv) == 0 is not true.

Development Example

Call an API to print the log.

For example, call INIT_LOGI("Start init first stage.") in //base/startup/init/services/init/standard/init.c to print the log.

void SystemPrepare(void)
{
   MountBasicFs();
   CreateDeviceNode();
   LogInit();
   // Make sure init log always output to /dev/kmsg.
   EnableDevKmsg();
   INIT_LOGI("Start init first stage.");
   // Only ohos normal system support
   // two stages of init.
   // If we are in updater mode, only one stage of init.
   if (InUpdaterMode() == 0) {
       StartInitSecondStage();
   }
}

Run dmesg to check the printed log Start init first stage.

Set the log level by running the begetctl setloglevel level command.

In the command, set level to one of the following log levels: 0 (INIT_DEBUG), 1 (INIT_INFO), 2 (INIT_WARN), 3 (INIT_ERROR), and 4 (INIT_FATAL).

After the setting is complete, the level set via g_logLevel of init takes effect immediately, and log APIs can print logs only when their log levels are higher than or equal to this level. For example, begetctl setloglevel 3 sets the log level to INIT_ERROR. In this case, only INIT_LOGE and INIT_LOGF will print logs.

After the system is restarted, the configured log level will take effect after the load_persist_params command in the init.cfg file is executed.