User Guide: SDKs > Volt MX Iris SDK > Using Log SDK

Volt MX Logger

Introduction

Volt MX Logger is introduced to persist logs based on six log levels:

• Trace
• Debug
• Info
• Warn
• Error
• Fatal

The logger feature provides three ways of providing logs to output: console, file and network. The logger feature is defined in the namespace voltmx.logger. Each log will be printed as per the below syntax:

 [LoggerInstanceName][AppID AppVersion][TimestampTimeZone][LogLevel][SessionID][ThreadInformation][DeviceId][DeviceOSInfo][FileName][ClassName][MethodName][LineNo]Message

Scope

The Volt MX Logger feature is available for Volt MX Iris, Android, iOS, and Windows 10.

Properties

voltmx.logger exposes the below properties:

currentLogLevel

currentLogLevel sets the log level of the logger to any of the six mentioned levels. setting to a certain level will allow the logs of that level and above to be persisted. For instance, if the currentLogLevel is set to Error, only the error and fatal log statements are printed.

APIs

Multiple instances of the logger can be created using APIs. The console and the file can be activated as a part of the configuration, if required. The below APIs are introduced to create logger, activate persistors and generate the logs.

createFilePersistor()

The createFilePersistor() API is used to create the configuration for the file persistor. This configuration can be used with the loggerConfig object (For more information, refer addPersistor API).

Note: In Iris Android, if you want activate file persistor and view the logs in the file, you need to add WRITE_EXTERNAL_STORAGE under Permissions tab.

maxFileSize

The maxFileSize API is used to define the maximum size of the files created in bytes.

maxNumberOfLogFiles

To define the maxNumberOfLogFiles the app can have at a maximum during any instant. The filePersistor is a rolling file appender i.e. the data of latest configured files is preserved.

createLoggerConfig()

CreateLoggerConfig() is used to create the configuration object for the logger. This object is used in the createNewLogger() API. The object has various properties exposed to define our configuration. To apply the configuration, you need to use setConfig() API . When you pass the object through createNewLogger() API , configuration object is immediately applied .

bytesLimit

The console logs will be printed as soon as the logging methods are invoked. It is performance intensive to persist the logs one by one on the file. The bytesLimit can be used to accumulate the logs until the bytesLimit is reached and then flushed onto the file.

statementsLimit

The console logs will be printed as soon as the logging methods are invoked. It is performance intensive to persist the logs one by one on the file. The statementsLimit can be used to accumulate the logs until the specified number of statements are reached and then flushed onto the file.

timeFormat

Each log is printed in a specified format. The format includes the timestamp. This property is used to specify the syntax of the timeFormat.

timeZone

Each log is printed in a specified format. The format includes the timestamp. This property is used to specify the syntax of the timeZone.

overrideConfig

All the properties are exposed by loggerConfig. Changing the property and using setConfig() API will affect all the logger instances created. overrideConfig is used to specify if the configuration should override the existing configuration.

logLevel

The logLevel property works similar to currentLogLevel property. There are six log levels in the logLevel property.

addPersistor

The property can be used to add file persistor through loggerConfig object.

createNewLogger() API

activatePersistors()

Unless we activate persistors, logs will not be pushed to the corresponding persistors. This is a mandatory step and no persistor is activated by default.

Note: Console Persistor logs will not be available in Iris Windows 10 and Native Windows 10.

deactivatePersistors()

If you want to make sure the logs are not pushed to a corresponding persistor or any combination of them, use deactivatePersistors() API.

trace() API

The trace() API is used to trace log level messages.

debug() API

The debug() API is used to log the debug level messages:

info() API

The info() API is used to log the info level messages.

error() API

The error() API is used to log the error messages:

warn() API

The warn() API is used to log the warning messages:

fatal() API

The fatal() API is used to log the fatal messages:

flush() API

The flush() API is used to flush all the statements onto the activated persistors regardless whether the bytesLimit or statementsLimit are met.

setconfig() API

The setconfig() API is a convenience API used to set LoggerConfig (mentioned earlier). Since loggerConfig is a singleton, If you set the loggerConfig once, it is applied across all the logger objects.

setPersistConfig()

The setPersistConfig() API is used to change persistorConfig or set it to fresh, when it is not set through loggerConfig. As the persistors are singletons, they will have impact on all loggerObjects when set.

App Logger

The default logger Instance created can be used to write log statements. If the user wants to create additional logger instances he is free to do so. The logger name used for appLogger is voltmxLogger.

Usage

 voltmx.logger.appLogger.error("Message to be logged at error log level");
voltmx.logger.appLogger.debug("Message to be logged at error log level");
voltmx.logger.appLogger.trace("Message to be logged at error log level");

Usage Guidelines/Restrictions/Examples

 //Create Logger Configuration
var lConfig = new voltmx.logger.createLoggerConfig();
//Create FilePersistor
Var persistor1 = new voltmx.logger.createFilePersistor();
//Add Persistor to the loggerConfig  
lConfig.addPersistor(persistor1);
//Create Logger Object  
loggerObj = new voltmx.logger.createNewLogger("UserLogs", lConfig);
voltmx.logger.activatePersistors(voltmx.logger.consolePersistor);
voltmx.logger.activatePersistors(voltmx.logger.filePersistor);
voltmx.logger.currentLogLevel = voltmx.logger.logLevel.INFO;
//Print Statements  
for(var i=0;i<20;i++){
var msg = "statement" + i;
loggerObj.debug("Message in debug level" + msg);
loggerObj.trace("Message in trace level" + msg);
loggerObj.fatal("Message in Fatal level" + msg);
loggerObj.info("Message in Info level" + msg);
loggerObj.warn("Message in warn level" + msg);
loggerObj.error("Message in error level" + msg);
}

Note:

• Unlike the file and console persistors, the network persistor is always enabled and can be managed from Volt MX Foundry Admin Console. Do not create/activate/deactivate the network persistor from the client application code. For more details on configuring Network Persistor, refer to the Log Level by Client Filters section in the Standard Logs doc.
• To manage middleware logs, refer to App Services > Logs.
• Running the logger on Android devices that run on Android Lollipop or earlier versions with less than 1GB RAM may cause memory issues. These memory issues are at the Android OS level and have been declared obsolete by Google. For more information, refer to the Issue Tracker.