Most useful NLog configurations

Question

What are the best or most useful configurations for logging with NLog   These can be simple or complex  as long as they re useful     I m thinking of examples like automatically rolling over log files at a certain size  changing the layout  log message  whether or not there is an exception  escalating the log level once an error has occurred  etc   Here are some links    NLog Demo Examples in the source

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Easier Way To Log each log level with a different layout using Conditional Layouts   lt variable name  VerboseLayout  value    level uppercase true     longdate      logger          when when level    LogLevel Trace inner MONITOR TRACE   message      when when level    LogLevel Debug inner MONITOR DEBUG   message      when when level    LogLevel Info inner MONITOR INFO   message      when when level    LogLevel Warn inner MONITOR WARN   message      when when level    LogLevel Error inner MONITOR ERROR   message      when when level    LogLevel Fatal inner MONITOR CRITICAL   message            exception format tostring      newline    newline     gt    See https   github com NLog NLog wiki When-Filter for syntax

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Log to Twitter  Based on this post about a log4net Twitter Appender  I thought I would try my hand at writing a NLog Twitter Target  using NLog 1 0 refresh  not 2 0    Alas  so far I have not been able to get a Tweet to actually post successfully   I don t know if it is something wrong in my code  Twitter  our company s internet connection firewall  or what   I am posting the code here in case someone is interested in trying it out   Note that there are three different  Post  methods   The first one that I tried is PostMessageToTwitter   PostMessageToTwitter is essentially the same as PostLoggingEvent in the orignal post   If I use that I get a 401 exception   PostMessageBasic gets the same exception   PostMessage  runs with no errors  but the message still does not make it up to Twitter   PostMessage and PostMessageBasic are based on examples that I found here on SO   FYI - I just now found a comment by  Jason Diller to an answer in this post that says that twitter is going to turn off basic authentication  next month    This was back in May 2010 and it is now December 2010  so I guess that could be why this is not working   using System  using System Collections Generic  using System Linq  using System Text  using System Net  using System Web  using System IO   using NLog  using NLog Targets  using NLog Config   namespace NLogExtensions      Target  TwitterTarget      public class TwitterTarget   TargetWithLayout         private const string REQUEST CONTENT TYPE    application x-www-form-urlencoded          private const string REQUEST METHOD    POST             The source attribute has been removed from the Twitter API           unless you re using OAuth           Even if you are using OAuth  there s still an approval process           Not worth it   API  will work for now           private const string TWITTER SOURCE NAME    Log4Net         private const string TWITTER UPDATE URL FORMAT    http   twitter com statuses update xml status  0            RequiredParameter      public string TwitterUserName   get  set          RequiredParameter      public string TwitterPassword   get  set         protected override void Write LogEventInfo logEvent              if  string IsNullOrWhiteSpace TwitterUserName     string IsNullOrWhiteSpace TwitterPassword   return         string msg   this CompiledLayout GetFormattedMessage logEvent          if  string IsNullOrWhiteSpace msg   return         try                   PostMessageToTwitter msg           PostMessageBasic msg                 catch  Exception ex                    Should probably do something here                        private void PostMessageBasic string msg                 Create a webclient with the twitter account credentials  which will be used to set the HTTP header for basic authentication        WebClient client   new WebClient   Credentials   new NetworkCredential   UserName   TwitterUserName  Password   TwitterPassword                Don t wait to receive a 100 Continue HTTP response from the server before sending out the message body        ServicePointManager Expect100Continue   false            Construct the message body        byte   messageBody   Encoding ASCII GetBytes  status     msg             Send the HTTP headers and message body  a k a  Post the data         client UploadData   http   twitter com statuses update xml   messageBody              private void PostMessage string msg              string user   Convert ToBase64String System Text Encoding UTF8 GetBytes TwitterUserName         TwitterPassword          byte    bytes   System Text Encoding UTF8 GetBytes  status     msg ToTweet           HttpWebRequest request    HttpWebRequest WebRequest Create  http   twitter com statuses update xml          request Method    POST         request ServicePoint Expect100Continue   false        request Headers Add  Authorization    Basic     user         request ContentType    application x-www-form-urlencoded         request ContentLength   bytes Length        Stream reqStream   request GetRequestStream          reqStream Write bytes  0  bytes Length         reqStream Close               private void PostMessageToTwitter string msg              var updateRequest   HttpWebRequest Create string Format TWITTER UPDATE URL FORMAT                                                  HttpUtility UrlEncode msg ToTweet      as HttpWebRequest        updateRequest ContentLength   0        updateRequest ContentType   REQUEST CONTENT TYPE        updateRequest Credentials   new NetworkCredential TwitterUserName  TwitterPassword         updateRequest Method   REQUEST METHOD         updateRequest ServicePoint Expect100Continue   false         var updateResponse   updateRequest GetResponse   as HttpWebResponse         if  updateResponse StatusCode    HttpStatusCode OK  amp  amp  updateResponse StatusCode    HttpStatusCode Continue                  throw new Exception string Format  An error occurred while invoking the Twitter REST API  Response Code   0     updateResponse StatusCode                         public static class Extensions         public static string ToTweet this string s              if  string IsNullOrEmpty s     s Length  lt  140                  return s                 return s Substring 0  137                         Configure it like this   Tell NLog the assembly containing the target    lt extensions gt     lt add assembly  NLogExtensions   gt   lt  extensions gt    Configure the target    lt targets gt       lt target name  twitter  type  TwitterTarget  TwitterUserName  yourtwittername  TwitterPassword  yourtwitterpassword  layout    longdate    logger    level    message     gt   lt  targets gt    If someone tries this out and has success  post back with your findings

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Logging different levels depending on whether or not there is an error  This example allows you to get more information when there is an error in your code  Basically  it buffers messages and only outputs those at a certain log level  e g  Warn  unless a certain condition is met  e g  there has been an error  so the log level is    Error   then it will output more info  e g  all messages from log levels    Trace   Because the messages are buffered  this lets you gather trace information about what happened before an Error or ErrorException was logged - very useful   I adapted this one from an example in the source code  I was thrown at first because I left out the AspNetBufferingWrapper  since mine isn t an ASP app  - it turns out that the PostFilteringWrapper requires some buffered target  Note that the target-ref element used in the above-linked example cannot be used in NLog 1 0  I am using 1 0 Refresh for a  NET 4 0 app   it is necessary to put your target inside the wrapper block  Also note that the logic syntax  i e  greater-than or less-than symbols   lt  and    has to use the symbols  not the XML escapes for those symbols  i e   amp gt  and  amp lt   or else NLog will error   app config    lt  xml version  1 0   gt   lt configuration gt       lt configSections gt           lt section name  nlog  type  NLog Config ConfigSectionHandler  NLog   gt       lt  configSections gt        lt nlog xmlns  http   www nlog-project org schemas NLog xsd  xmlns xsi  http   www w3 org 2001 XMLSchema-instance            throwExceptions  true  internalLogToConsole  true  internalLogLevel  Warn  internalLogFile  nlog log  gt           lt variable name  appTitle  value  My app   gt           lt variable name  csvPath  value    specialfolder folder Desktop file   appTitle  log csv    gt            lt targets async  true  gt               lt  --The following will keep the default number of log messages in a buffer and write out certain levels if there is an error and other levels if there is not  Messages that appeared before the error  in code  will be included  since they are buffered -- gt               lt wrapper-target xsi type  BufferingWrapper  name  smartLog  gt                   lt wrapper-target xsi type  PostFilteringWrapper  gt                       lt  -- lt target-ref name  fileAsCsv   gt -- gt                       lt target xsi type  File  fileName    csvPath                       archiveAboveSize  4194304  concurrentWrites  false  maxArchiveFiles  1  archiveNumbering  Sequence                       gt                           lt layout xsi type  CsvLayout  delimiter  Tab  withHeader  false  gt                               lt column name  time  layout    longdate     gt                               lt column name  level  layout    level upperCase true    gt                               lt column name  message  layout    message     gt                               lt column name  callsite  layout    callsite includeSourcePath true     gt                               lt column name  stacktrace  layout    stacktrace topFrames 10     gt                               lt column name  exception  layout    exception format ToString    gt                               lt  -- lt column name  logger  layout    logger    gt -- gt                           lt  layout gt                       lt  target gt                         lt  --during normal execution only log certain messages-- gt                        lt defaultFilter gt level  gt   LogLevel Warn lt  defaultFilter gt                         lt  --if there is at least one error  log everything from trace level-- gt                        lt when exists  level  gt   LogLevel Error  filter  level  gt   LogLevel Trace    gt                   lt  wrapper-target gt               lt  wrapper-target gt            lt  targets gt            lt rules gt               lt logger name     minlevel  Trace  writeTo  smartLog   gt           lt  rules gt       lt  nlog gt   lt  configuration gt

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Treating exceptions differently  We often want to get more information when there is an exception  The following configuration has two targets  a file and the console  which filter on whether or not there is any exception info   EDIT  Jarek has posted about a new method of doing this in vNext    The key is to have a wrapper target with xsi type  FilteringWrapper  condition  length    exception    gt 0    lt nlog xmlns  http   www nlog-project org schemas NLog mono2 xsd        xmlns xsi  http   www w3 org 2001 XMLSchema-instance        autoReload  true        internalLogLevel  Warn        internalLogFile  nlog log log         gt       lt variable name  VerboseLayout                 value    longdate    level upperCase true    message                           callsite includSourcePath true                 gt       lt variable name  ExceptionVerboseLayout                  value    VerboseLayout     stacktrace topFrames 10                            exception format ToString                      gt        lt targets async  true  gt           lt target name  file  xsi type  File  fileName  log log                  layout    VerboseLayout   gt           lt  target gt            lt target name  fileAsException                    xsi type  FilteringWrapper                   condition  length    exception    gt 0  gt               lt target xsi type  File                        fileName  log log                        layout    ExceptionVerboseLayout     gt           lt  target gt            lt target xsi type  ColoredConsole                  name  console                  layout    NormalLayout    gt            lt target xsi type  FilteringWrapper                    condition  length    exception    gt 0                    name  consoleException  gt               lt target xsi type  ColoredConsole                       layout    ExceptionVerboseLayout     gt           lt  target gt       lt  targets gt        lt rules gt           lt logger name     minlevel  Trace  writeTo  console consoleException    gt           lt logger name     minlevel  Warn  writeTo  file fileAsException    gt       lt  rules gt    lt  nlog gt

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Log from Silverlight  When using NLog with Silverlight you can send the trace to the server side via the provided web service   You can also write to a local file in the Isolated Storage  which come in handy if the web server is unavailable  See here for details  i e  use something like this to make yourself a target   namespace NLogTargets        Target  IsolatedStorageTarget        public sealed class IsolatedStorageTarget   TargetWithLayout               IsolatedStorageFile  storageFile   null          string  fileName    Nlog log      Default  Configurable through the  filename  attribute in nlog config          public IsolatedStorageTarget                                 IsolatedStorageTarget                         if   storageFile    null                                 storageFile Dispose                     storageFile   null                                   public string filename                       set                                fileName   value                             get                               return  fileName                                      protected override void Write LogEventInfo logEvent                        try                               writeToIsolatedStorage this Layout Render logEvent                              catch  Exception e                                   Not much to do about his                                      public void writeToIsolatedStorage string msg                        if   storageFile    null                   storageFile   IsolatedStorageFile GetUserStoreForApplication                using  IsolatedStorageFile isolatedStorage   IsolatedStorageFile GetUserStoreForApplication                                     The isolated storage is limited in size  So  when approaching the limit                    simply purge the log file   Yeah yeah  the file should be circular  I know                     if   storageFile AvailableFreeSpace  lt  msg Length   100                                        using  IsolatedStorageFileStream stream   new IsolatedStorageFileStream  fileName  FileMode Truncate  FileAccess Write  isolatedStorage                                                                Write to isolated storage                 using  IsolatedStorageFileStream stream   new IsolatedStorageFileStream  fileName  FileMode Append  FileAccess Write  isolatedStorage                                         using  TextWriter writer   new StreamWriter stream                                                 writer WriteLine msg

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I provided a couple of reasonably interesting answers to this question   Nlog - Generating Header Section for a log file  Adding a Header   The question wanted to know how to add a header to the log file   Using config entries like this allow you to define the header format separately from the format of the rest of the log entries   Use a single logger  perhaps called  headerlogger  to log a single message at the start of the application and you get your header   Define the header and file layouts      lt variable name  HeaderLayout  value  This is the header   Start time     longdate  Machine     machinename  Product version     gdc item version    gt     lt variable name  FileLayout  value    longdate      logger      level      message     gt    Define the targets using the layouts    lt target name  fileHeader  xsi type  File  fileName  xxx log  layout    HeaderLayout     gt   lt target name  file  xsi type  File  fileName  xxx log  layout    InfoLayout     gt    Define the loggers    lt rules gt     lt logger name  headerlogger  minlevel  Trace  writeTo  fileHeader  final  true    gt     lt logger name     minlevel  Trace  writeTo  file    gt   lt  rules gt    Write the header  probably early in the program     GlobalDiagnosticsContext Set  version    01 00 00 25       LogManager GetLogger  headerlogger   Info  It doesn t matter what this is because the header format does not include the message  although it could      This is largely just another version of the  Treating exceptions differently  idea   Log each log level with a different layout  Similarly  the poster wanted to know how to change the format per logging level   It wasn t clear to me what the end goal was  and whether it could be achieved in a  better  way   but I was able to provide a configuration that did what he asked      lt variable name  TraceLayout  value  This is a TRACE -   longdate      logger      level      message    gt      lt variable name  DebugLayout  value  This is a DEBUG -   longdate      logger      level      message    gt      lt variable name  InfoLayout  value  This is an INFO -   longdate      logger      level      message    gt      lt variable name  WarnLayout  value  This is a WARN -   longdate      logger      level      message    gt      lt variable name  ErrorLayout  value  This is an ERROR -   longdate      logger      level      message    gt      lt variable name  FatalLayout  value  This is a FATAL -   longdate      logger      level      message    gt      lt targets gt        lt target name  fileAsTrace  xsi type  FilteringWrapper  condition  level  LogLevel Trace  gt          lt target xsi type  File  fileName  xxx log  layout    TraceLayout     gt        lt  target gt        lt target name  fileAsDebug  xsi type  FilteringWrapper  condition  level  LogLevel Debug  gt          lt target xsi type  File  fileName  xxx log  layout    DebugLayout     gt        lt  target gt        lt target name  fileAsInfo  xsi type  FilteringWrapper  condition  level  LogLevel Info  gt          lt target xsi type  File  fileName  xxx log  layout    InfoLayout     gt        lt  target gt        lt target name  fileAsWarn  xsi type  FilteringWrapper  condition  level  LogLevel Warn  gt          lt target xsi type  File  fileName  xxx log  layout    WarnLayout     gt        lt  target gt        lt target name  fileAsError  xsi type  FilteringWrapper  condition  level  LogLevel Error  gt          lt target xsi type  File  fileName  xxx log  layout    ErrorLayout     gt        lt  target gt        lt target name  fileAsFatal  xsi type  FilteringWrapper  condition  level  LogLevel Fatal  gt          lt target xsi type  File  fileName  xxx log  layout    FatalLayout     gt        lt  target gt      lt  targets gt          lt rules gt          lt logger name     minlevel  Trace  writeTo  fileAsTrace fileAsDebug fileAsInfo fileAsWarn fileAsError fileAsFatal    gt          lt logger name     minlevel  Info  writeTo  dbg    gt        lt  rules gt     Again  very similar to Treating exceptions differently

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Configure NLog via XML  but Programmatically  What   Did you know that you can specify the NLog XML directly to NLog from your app  as opposed to having NLog read it from the config file   Well  you can   Let s say that you have a distributed app and you want to use the same configuration everywhere   You could keep a config file in each location and maintain it separately  you could maintain one in a central location and push it out to the satellite locations  or you could probably do a lot of other things   Or  you could store your XML in a database  get it at app startup  and configure NLog directly with that XML  maybe checking back periodically to see if it had changed      string xml      lt nlog gt                      lt targets gt                        lt target name  console  type  Console  layout    message     gt                      lt  targets gt                       lt rules gt                        lt logger name     minlevel  Error  writeTo  console    gt                      lt  rules gt                    lt  nlog gt       StringReader sr   new StringReader xml     XmlReader xr   XmlReader Create sr     XmlLoggingConfiguration config   new XmlLoggingConfiguration xr  null     LogManager Configuration   config      NLog is now configured just as if the XML above had been in NLog config or app config    logger Trace  Hello - Trace      Won t log   logger Debug  Hello - Debug      Won t log   logger Info  Hello - Info        Won t log   logger Warn  Hello - Warn        Won t log   logger Error  Hello - Error      Will log   logger Fatal  Hello - Fatal      Will log      Now let s change the config  the root logging level        string xml2      lt nlog gt                     lt targets gt                        lt target name  console  type  Console  layout    message     gt                      lt  targets gt                       lt rules gt                        lt logger name     minlevel  Trace  writeTo  console    gt                      lt  rules gt                    lt  nlog gt       StringReader sr2   new StringReader xml2     XmlReader xr2   XmlReader Create sr2     XmlLoggingConfiguration config2   new XmlLoggingConfiguration xr2  null     LogManager Configuration   config2     logger Trace  Hello - Trace      Will log   logger Debug  Hello - Debug      Will log   logger Info  Hello - Info        Will log   logger Warn  Hello - Warn        Will log   logger Error  Hello - Error      Will log   logger Fatal  Hello - Fatal      Will log   I m not sure how robust this is  but this example provides a useful starting point for people that might want to try configuring like this

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Some of these fall into the category of general NLog  or logging  tips rather than strictly configuration suggestions   Here are some general logging links from here at SO  you might have seen some or all of these already    log4net vs  Nlog  Logging best practices  What  39 s the point of a logging facade   Why do loggers recommend using a logger per class   Use the common pattern of naming your logger based on the class Logger logger   LogManager GetCurrentClassLogger     This gives you a high degree of granularity in your loggers and gives you great flexibility in the configuration of the loggers  control globally  by namespace  by specific logger name  etc    Use non-classname-based loggers where appropriate   Maybe you have one function for which you really want to control the logging separately   Maybe you have some cross-cutting logging concerns  performance logging    If you don t use classname-based logging  consider naming your loggers in some kind of hierarchical structure  maybe by functional area  so that you can maintain greater flexibility in your configuration   For example  you might have a  database  functional area  an  analysis  FA  and a  ui  FA   Each of these might have sub-areas   So  you might request loggers like this   Logger logger   LogManager GetLogger  Database Connect    Logger logger   LogManager GetLogger  Database Query    Logger logger   LogManager GetLogger  Database SQL    Logger logger   LogManager GetLogger  Analysis Financial    Logger logger   LogManager GetLogger  Analysis Personnel    Logger logger   LogManager GetLogger  Analysis Inventory      And so on   With hierarchical loggers  you can configure logging globally  the     or root logger   by FA  Database  Analysis  UI   or by subarea  Database Connect  etc    Loggers have many configuration options    lt logger name  Name Space Class1  minlevel  Debug  writeTo  f1    gt    lt logger name  Name Space Class1  levels  Debug Error  writeTo  f1    gt    lt logger name  Name Space    writeTo  f3 f4    gt   lt logger name  Name Space    minlevel  Debug  maxlevel  Error  final  true    gt     See the NLog help for more info on exactly what each of the options means   Probably the most notable items here are the ability to wildcard logger rules  the concept that multiple logger rules can  execute  for a single logging statement  and that a logger rule can be marked as  final  so subsequent rules will not execute for a given logging statement   Use the GlobalDiagnosticContext  MappedDiagnosticContext  and NestedDiagnosticContext to add additional context to your output   Use  variable  in your config file to simplify   For example  you might define variables for your layouts and then reference the variable in the target configuration rather than specify the layout directly        lt variable name  brief  value    longdate      level      logger      message    gt     lt variable name  verbose  value    longdate      machinename      processid      processname      level      logger      message    gt     lt targets gt       lt target name  file  xsi type  File  layout    verbose   fileName    basedir    shortdate  log    gt       lt target name  console  xsi type  ColoredConsole  layout    brief     gt     lt  targets gt    Or  you could create a  custom  set of properties to add to a layout      lt variable name  mycontext  value    gdc item appname      mdc item threadprop    gt     lt variable name  fmt1withcontext  value    longdate      level      logger       mycontext      message    gt     lt variable name  fmt2withcontext  value    shortdate      level      logger       mycontext      message    gt    Or  you can do stuff like create  day  or  month  layout renderers strictly via configuration      lt variable name  day  value    date format dddd    gt     lt variable name  month  value    date format MMMM    gt     lt variable name  fmt  value    longdate      level      logger      day      month      message    gt     lt targets gt       lt target name  console  xsi type  ColoredConsole  layout    fmt     gt     lt  targets gt    You can also use layout renders to define your filename      lt variable name  day  value    date format dddd    gt     lt targets gt       lt target name  file  xsi type  File  layout    verbose   fileName    basedir    day  log    gt     lt  targets gt    If you roll your file daily  each file could be named  Monday log    Tuesday log   etc   Don t be afraid to write your own layout renderer   It is easy and allows you to add your own context information to the log file via configuration   For example  here is a layout renderer  based on NLog 1 x  not 2 0  that can add the Trace CorrelationManager ActivityId to the log      LayoutRenderer  ActivityId      class ActivityIdLayoutRenderer   LayoutRenderer         int estimatedSize   Guid Empty ToString   Length       protected override void Append StringBuilder builder  LogEventInfo logEvent              builder Append Trace CorrelationManager ActivityId              protected override int GetEstimatedBufferSize LogEventInfo logEvent              return estimatedSize              Tell NLog where your NLog extensions  what assembly  like this      lt extensions gt       lt add assembly  MyNLogExtensions   gt     lt  extensions gt    Use the custom layout renderer like this      lt variable name  fmt  value    longdate      ActivityId      message    gt    Use async targets    lt nlog gt     lt targets async  true  gt       lt  -- all targets in this section will automatically be asynchronous -- gt     lt  targets gt   lt  nlog gt    And default target wrappers    lt nlog gt       lt targets gt         lt default-wrapper xsi type  BufferingWrapper  bufferSize  100   gt         lt target name  f1  xsi type  File  fileName  f1 txt   gt         lt target name  f2  xsi type  File  fileName  f2 txt   gt       lt  targets gt       lt targets gt         lt default-wrapper xsi type  AsyncWrapper  gt           lt wrapper xsi type  RetryingWrapper   gt         lt  default-wrapper gt         lt target name  n1  xsi type  Network  address  tcp   localhost 4001   gt         lt target name  n2  xsi type  Network  address  tcp   localhost 4002   gt         lt target name  n3  xsi type  Network  address  tcp   localhost 4003   gt       lt  targets gt     lt  nlog gt    where appropriate   See the NLog docs for more info on those   Tell NLog to watch and automatically reload the configuration if it changes    lt nlog autoReload  true    gt     There are several configuration options to help with troubleshooting NLog   lt nlog throwExceptions  true    gt   lt nlog internalLogFile  file txt    gt   lt nlog internalLogLevel  Trace Debug Info Warn Error Fatal    gt   lt nlog internalLogToConsole  false true    gt   lt nlog internalLogToConsoleError  false true    gt    See NLog Help for more info   NLog 2 0 adds LayoutRenderer wrappers that allow additional processing to be performed on the output of a layout renderer  such as trimming whitespace  uppercasing  lowercasing  etc    Don t be afraid to wrap the logger if you want insulate your code from a hard dependency on NLog  but wrap correctly   There are examples of how to wrap in the NLog s github repository   Another reason to wrap might be that you want to automatically add specific context information to each logged message  by putting it into LogEventInfo Context    There are pros and cons to wrapping  or abstracting  NLog  or any other logging framework for that matter    With a little effort  you can find plenty of info here on SO presenting both sides   If you are considering wrapping  consider using Common Logging   It works pretty well and allows you to easily switch to another logging framework if you desire to do so   Also if you are considering wrapping  think about how you will handle the context objects  GDC  MDC  NDC    Common Logging does not currently support an abstraction for them  but it is supposedly in the queue of capabilities to add

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Apparently  you can now use NLog with Growl for Windows    lt  xml version  1 0  encoding  utf-8    gt   lt nlog xmlns  http   www nlog-project org schemas NLog xsd        xmlns xsi  http   www w3 org 2001 XMLSchema-instance  gt        lt extensions gt           lt add assembly  NLog Targets GrowlNotify    gt       lt  extensions gt        lt targets gt           lt target name  growl  type  GrowlNotify  password    host    port      gt       lt  targets gt        lt rules gt           lt logger name     minLevel  Trace  appendTo  growl   gt       lt  rules gt    lt  nlog gt

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Reporting to an external website database  I wanted a way to simply and automatically report errors  since users often don t  from our applications  The easiest solution I could come up with was a public URL - a web page which could take input and store it to a database - that is sent data upon an application error   The database could then be checked by a dev or a script to know if there are new errors    I wrote the web page in PHP and created a mysql database  user  and table to store the data  I decided on four user variables  an id  and a timestamp  The possible variables  either included in the URL or as POST data  are    app  application name  msg  message - e g  Exception occurred      dev  developer - e g  Pat  src  source - this would come from a variable pertaining to the machine on which the app was running  e g  Environment MachineName or some such  log  a log file or verbose message     All of the variables are optional  but nothing is reported if none of them are set - so if you just visit the website URL nothing is sent to the db    To send the data to the URL  I used NLog s WebService target   Note  I had a few problems with this target at first  It wasn t until I looked at the source that I figured out that my url could not end with a      All in all  it s not a bad system for keeping tabs on external apps   Of course  the polite thing to do is to inform your users that you will be reporting possibly sensitive data and to give them a way to opt in out    MySQL stuff   The db user has only INSERT privileges on this one table in its own database    CREATE TABLE  reports       id  int 10  unsigned NOT NULL AUTO INCREMENT     ts  timestamp NULL DEFAULT CURRENT TIMESTAMP     applicationName  text     message  text     developer  text     source  text     logData  longtext    PRIMARY KEY   id     ENGINE InnoDB AUTO INCREMENT 2 DEFAULT CHARSET utf8 COMMENT  storage place for reports from external applications    Website code   PHP 5 3 or 5 2 with PDO enabled  file is index php in  report folder    lt  php  app     REQUEST  app     msg     REQUEST  msg     dev     REQUEST  dev     src     REQUEST  src     log     REQUEST  log      dbData       array     app    gt   app                msg    gt   msg                dev    gt   dev                src    gt   src                log    gt   log          print r  dbData      For debugging only  This could allow XSS attacks  if isEmpty  dbData   die  No data provided     try    db   new PDO  mysql host  host dbname reporting    reporter    pass  array      PDO  ATTR PERSISTENT   gt  true      s    db- gt prepare  INSERT INTO reporting reports            applicationName       message       developer       source       logData           VALUES            app        msg        dev        src        log                 s- gt execute  dbData   print  Added report to database     catch  PDOException  e       Sensitive information can be displayed if this exception isn t handled   print  Error        e- gt getMessage       lt br  gt    die  PDO error       function isEmpty  array   array          foreach   array as  element            if   empty  element                 return false                      return true      gt    App code  NLog config file    lt nlog xmlns  http   www nlog-project org schemas NLog xsd  xmlns xsi  http   www w3 org 2001 XMLSchema-instance        throwExceptions  true  internalLogToConsole  true  internalLogLevel  Warn  internalLogFile  nlog log  gt       lt variable name  appTitle  value  My External App   gt       lt variable name  csvPath  value    specialfolder folder Desktop file   appTitle  log csv    gt       lt variable name  developer  value  Pat   gt        lt targets async  true  gt           lt  --The following will keep the default number of log messages in a buffer and write out certain levels if there is an error and other levels if there is not  Messages that appeared before the error  in code  will be included  since they are buffered -- gt           lt wrapper-target xsi type  BufferingWrapper  name  smartLog  gt               lt wrapper-target xsi type  PostFilteringWrapper  gt                   lt target xsi type  File  fileName    csvPath                   archiveAboveSize  4194304  concurrentWrites  false  maxArchiveFiles  1  archiveNumbering  Sequence                   gt                       lt layout xsi type  CsvLayout  delimiter  Comma  withHeader  false  gt                           lt column name  time  layout    longdate     gt                           lt column name  level  layout    level upperCase true    gt                           lt column name  message  layout    message     gt                           lt column name  callsite  layout    callsite includeSourcePath true     gt                           lt column name  stacktrace  layout    stacktrace topFrames 10     gt                           lt column name  exception  layout    exception format ToString    gt                           lt  -- lt column name  logger  layout    logger    gt -- gt                       lt  layout gt                   lt  target gt                     lt  --during normal execution only log certain messages-- gt                    lt defaultFilter gt level  gt   LogLevel Warn lt  defaultFilter gt                     lt  --if there is at least one error  log everything from trace level-- gt                    lt when exists  level  gt   LogLevel Error  filter  level  gt   LogLevel Trace    gt               lt  wrapper-target gt           lt  wrapper-target gt            lt target xsi type  WebService  name  web                  url  http   example com report                   methodName                    namespace                    protocol  HttpPost                   gt               lt parameter name  app  layout    appTitle    gt               lt parameter name  msg  layout    message    gt               lt parameter name  dev  layout    developer    gt               lt parameter name  src  layout    environment variable UserName     windows-identity   on   machinename  running os   environment variable OSVersion  with CLR v  environment variable Version    gt               lt parameter name  log  layout    file-contents fileName   csvPath     gt           lt  target gt        lt  targets gt        lt rules gt           lt logger name     minlevel  Trace  writeTo  smartLog   gt           lt logger name     minlevel  Error  writeTo  web   gt       lt  rules gt   lt  nlog gt    Note  there may be some issues with the size of the log file  but I haven t figured out a simple way to truncate it  e g  a la  nix s tail command

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