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NLog configuration with appsettings.json
NLog's Configuration have always been highly configurable through XML. It is now also possible to configure NLog to parse the configuration from other sources.
ℹ️ This will only work for ASP.NET Core and .NET Core applications, and it required the usage of NLog.Extensions.Logging or NLog.Web.AspNetCore
NLog.Extensions.Logging is now able to load NLog's Configuration from appsettings.json using Microsoft Extension ConfigurationSection.
Introduced with NLog.Extensions.Logging ver. 1.5.0
var config = new ConfigurationBuilder()
.SetBasePath(System.IO.Directory.GetCurrentDirectory())
.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
.Build();
NLog.LogManager.Configuration = new NLogLoggingConfiguration(config.GetSection("NLog"));Fluent API added with NLog.Web.AspNetCore ver. 4.9.3
Supports appsettings.json override by loading environment specific settings based on ASPNETCORE_ENVIRONMENT:
var logger = LogManager.Setup()
.LoadConfigurationFromAppSettings()
.GetCurrentClassLogger();Manual loading of appsettings.json with fluent API:
var config = new ConfigurationBuilder()
.SetBasePath(basePath ?? Directory.GetCurrentDirectory())
.AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
.AddJsonFile($"appsettings.{environment}.json", optional: true)
.AddEnvironmentVariables().Build();
var logger = LogManager.Setup()
.LoadConfigurationFromSection(config)
.GetCurrentClassLogger();{
"NLog": {
"throwConfigExceptions": true,
"targets": {
"async": true,
"logfile": {
"type": "File",
"fileName": "c:/temp/nlog-${shortdate}.log"
},
"logconsole": {
"type": "Console"
}
},
"rules": [
{
"logger": "*",
"minLevel": "Info",
"writeTo": "logconsole"
},
{
"logger": "*",
"minLevel": "Debug",
"writeTo": "logfile"
}
]
}
}JSON Schema is included in the official schema for appsettings.json files available at https://json.schemastore.org/appsettings.json.
Please note it has no auto-completion for the target properties
{
"Logging": {
"LogLevel": {
"Default": "Debug"
},
"NLog": {
"IncludeScopes": true
}
},
"NLog": {
"autoReload": true,
"throwConfigExceptions": true,
"internalLogLevel": "Info",
"internalLogFile": "${basedir}/internal-nlog.txt",
"extensions": [
{ "assembly": "NLog.Extensions.Logging" },
{ "assembly": "NLog.Web.AspNetCore" }
],
"variables": {
"var_logdir": "c:/temp"
},
"default-wrapper": {
"type": "AsyncWrapper",
"overflowAction": "Block"
},
"targets": {
"all-file": {
"type": "File",
"fileName": "${var_logdir}/nlog-all-${shortdate}.log",
"layout": {
"type": "JsonLayout",
"Attributes": [
{
"name": "timestamp",
"layout": "${date:format=o}"
},
{
"name": "level",
"layout": "${level}"
},
{
"name": "logger",
"layout": "${logger}"
},
{
"name": "message",
"layout": "${message:raw=true}"
},
{
"name": "properties",
"encode": false,
"layout": {
"type": "JsonLayout",
"includeallproperties": "true"
}
}
]
}
},
"own-console": {
"type": "LimitingWrapper",
"interval": "00:00:01",
"messageLimit": 100,
"target": {
"type": "ColoredConsole",
"layout": "${longdate}|${event-properties:item=EventId_Id:whenEmpty=0}|${uppercase:${level}}|${logger}|${message} ${exception:format=tostring}|${callsite}",
"rowHighlightingRules": [
{
"condition": "level == LogLevel.Error",
"foregroundColor": "Red"
},
{
"condition": "level == LogLevel.Fatal",
"foregroundColor": "Red",
"backgroundColor": "White"
}],
"wordHighlightingRules": [
{
"regex": "on|off",
"foregroundColor": "DarkGreen"
},
{
"condition": "level == LogLevel.Debug",
"text": "[TEST]",
"foregroundColor": "Blue"
}]
}
},
"database": {
"type": "Database",
"dbProvider": "System.Data.SqlClient",
"connectionString": "Data Source=database server;Initial Catalog=database;Trusted_Connection=False;User Id=AppUser;Password=AppUserPassword;",
"keepConnection": "true",
"commandText": "insert into dbo.log (Timestamp,Level,Message,Logger,Callsite,Exception) values (@Timestamp, @Level, @Message, @Logger, @Callsite, @Exception);",
"parameters": [
{
"name": "@Timestamp",
"layout": "${date:format=o}",
"dbType": "DbType.DateTime"
},
{
"name": "@Level",
"layout": "${level}"
},
{
"name": "@Message",
"layout": "${message}"
},
{
"name": "@Logger",
"layout": "${logger}"
},
{
"name": "@Callsite",
"layout": "${callsite}"
},
{
"name": "@Exception",
"layout": "${exception:tostring}"
}
]
},
"webFallback": {
"type": "FallbackGroup",
"returnToFirstOnSuccess": true,
"targets": {
"webPrimary": {
"type": "WebService",
"url": "http://localhost:1234/API/Post",
"protocol": "JsonPost",
"parameters": [
{
"name": "",
"layout": {
"type": "JsonLayout",
"includeallproperties": "true"
}
}]
},
"fileFallback": {
"type": "File",
"fileName": "${basedir}/logs/webfallback-${shortdate}.log"
}
}
}
},
"rules": [
{
"logger": "*",
"minLevel": "Trace",
"writeTo": "all-file"
},
{
"logger": "Microsoft.*",
"maxLevel": "Info",
"final": true
},
{
"logger": "*",
"minLevel": "Debug",
"writeTo": "own-console",
"filters": {
"whenRepeated": {
"layout": "${message}",
"action": "Ignore"
}
}
},
{
"logger": "*",
"minLevel": "Debug",
"writeTo": "database"
}
]
}
}ASP.NET Core uses the environment variable ASPNETCORE_ENVIRONMENT to configures app behavior based on the runtime environment. It also allows one to override appsettings for an environment:
- appsettings.json - Default settings
- appsettings.Production.json - Production specific settings.
- appsettings.Development.json - Development specific settings.
This can also be used for the NLog-config, so one can have special NLog targets for a certain environment
It is also possible to adjust environment variables using launchsettings.json. Ex: "environmentVariables": { "NLOG_RULES_0_MINLEVEL": "Info" }
Example of how one can override logging-rule "1" and introduce an additional logging-rule "99":
appsettings.json
"rules": {
"0": {
"logger": "Microsoft.*",
"maxLevel": "Error",
"final": true
},
"1": {
"logger": "*",
"minLevel": "Error",
"writeTo": "errorFile,errorEmail"
},
"2": {
"logger": "*",
"minLevel": "Debug",
"writeTo": "debugFile"
}
}appsettings.development.json
"rules": {
"1": {
"logger": "*",
"minLevel": "Error",
"writeTo": "errorFile"
},
"99": {
"logger": "*",
"minLevel": "Debug",
"writeTo": "debugConsole"
}
}Note one can also use more readable names instead of "0". Ex. call them "01_ErrorLog", "02_DebugFile". It is important to keep the numeric-prefix because the order of NLog Logging Rules are important (Ex. final-rules). For catch-all wildcard rules (Ex. logger: "*") then consider using a high value like "99_DebugConsole" to ensure it is sorted after more specific rules. Be aware that the readable name is case-sensitive when doing override.
While the ASP.NET Core configuration system is not case sensitive, you must be aware that in some cases NLog is case sensitive. For example, if you wanted to use an environment variable to override the var_logdir NLog variable in the configuration example above, you might be tempted to name the environment variable NLOG__VARIABLES__VAR_LOGDIR. This variable will result in an NLog configuration error, because NLog is looking for a variable named var_logdir. In order to work, your environment variable would need to be named NLOG__VARIABLES__var_logdir.
The SplitGroup-target-wrapper can be used to introduce extra NLog-target output without changing logging-rules.