如何设置 NLOG 以使用多个数据库

Question

In MVC project, have 5 separate areas. and other two separate projects in same solution.

there needs to have, three MVC areas to use NLOG with one database and other two areas to use NLOG with other database. Also, other two projects in same solution those also needs to use NLOG with different database.

So, as a solution, I am going to create separate project of NLOG in SLN and needs to setup separate NLOG project to allow different database to log based on request coming from related MVC areas or project.

How to accomplish this ?

Thanks

Answer 1

It is possible with NLogs default behaviour. We have to take quick a look at NLog:

How does NLog log?

Logger

NLog defines Loggers by Names. If a Logger has to write a log-message, NLog checks which rules should be applied.

Rule

For every log-message all rules are checked. If the Logger -Name and the minimum LogLevel is matching, the log-message will be written to the Target .

Target

Targets can be Log-Files, Databases or something else where the log-messages are persisted.

1. How do you use NLog?

Typically you create your Logger by requesting the DefaultClassLogger from the LogManager . This will create a Logger with the name "Namespace.SubnameSpace.ClassName". Alternatively you can request a Logger with a customname by calling LogManager.GetLogger("YourLoggerName") .

How to use two Targets?

If you want to log to two Targets at the same LogLevel you have to use two Loggers with different names. Those are only defined within you rules.

1. Setup two Rules with logger-names according to you classes or you customnames. Use ' * ' as wildcard: 'NameSpace1.*'
2. Request the correct Loggers from the LogManager

Examples

Example-config:

<?xml version="1.0" encoding="utf-8"?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

  <targets>
    <target name="logfile1" xsi:type="File" fileName="file1.txt" />
    <target name="logfile2" xsi:type="File" fileName="file2.txt" />
    <target name="logfileAllLogs" xsi:type="File" fileName="fileAllLogs.txt" />
  </targets>

  <rules>
    <logger name="Logger1" minlevel="Info" writeTo="logfile1" />
    <logger name="Logger2" minlevel="Info" writeTo="logfile2" />
    <logger name="*" minlevel="Info" writeTo="logfileAllLogs" /> <!-- Will be asked for all names because of the wildcard '*' -->
  </rules>
</nlog>

Programmatically

// Create your targets
FileTarget fileTarget1 = new FileTarget() { FileName = "file1.txt", Name = "logfile1" };
FileTarget fileTarget2 = new FileTarget() { FileName = "file2.txt", Name = "logfile2" };
FileTarget fileTargetAll = new FileTarget() { FileName = "fileAll.txt", Name = "logfileAll" };

// Create your rules
LoggingRule rule1 = new LoggingRule("Logger1", LogLevel.Info, fileTarget1); // This will be used only Logged to Loggers with the name "Logger1". Attention: Case-sensitive!
LoggingRule rule2 = new LoggingRule("Logger2", LogLevel.Info, fileTarget2);
LoggingRule ruleAll = new LoggingRule("*", LogLevel.Info, fileTargetAll); // This will be used by all existing loggers, because of the wildcard "*"

// create a configuration to introduce the rules and targets to the LogManager.
LoggingConfiguration config = new LoggingConfiguration();

// Add targets to the config
config.AddTarget(fileTarget1.Name, fileTarget1); // don't know why i have to give the name separately
config.AddTarget(fileTarget2.Name, fileTarget2);
config.AddTarget(fileTargetAll.Name, fileTargetAll);

// Add rules to the config
config.LoggingRules.Add(rule1);
config.LoggingRules.Add(rule2);
config.LoggingRules.Add(ruleAll);

// Set the config as current config
LogManager.Configuration = config;

// Let's log.. Get your loggers..
Logger logger1 = LogManager.GetLogger("Logger1");
Logger logger2 = LogManager.GetLogger("Logger2");

// Log something..
logger1.Error("Test Logger1a");
logger2.Error("Test Logger2a");
logger1.Error("Test Logger1b");
logger2.Error("Test Logger2b");

Example logging:

Logger logger1 = LogManager.GetLogger("Logger1");
Logger logger2 = LogManager.GetLogger("Logger2");

logger1.Error("Test Logger1a");
logger2.Error("Test Logger2a");
logger1.Error("Test Logger1b");
logger2.Error("Test Logger2b");

Expceted result:

// ---------- file1.txt ----------
// Test Logger1a
// Test Logger1b
// -------------------------------
//
// ---------- file2.txt ----------
// Test Logger2a
// Test Logger2b
// -------------------------------
//
// ---------- fileAll.txt ----------
// Test Logger1a
// Test Logger2a
// Test Logger1b
// Test Logger2b
// -------------------------------

In your example you propably got two DLLs with different namespaces. Something like Db1Lib.MyClass and Db2Lib.MyClass . If you want to set up your Loggers to log each DLL into an dedicated db, you should name your first Logger "Db1Lib*" and you second one "Db2Lib*". This way LogManager.GetCurrentClassLogger() will Name the Loggers correct. But this only works if your dbs are in different namespaces/classes.