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Client Logger
Desktop Viewer



NSLogger is a high perfomance logging utility which displays traces emitted by client applications running on Mac OS X or iOS (iPhone OS). It replaces your usual NSLog()-based traces and provides powerful additions like display filtering, image and binary logging, traces buffering, timing information, etc.

NSLogger feature summary:

  • View logs using the Mac OS X desktop viewer
  • Online (application running and connected to NSLogger) and offline (saved logs) log viewing
  • Buffer all traces in memory or in a file, send them over to viewer when a connection is acquired
  • View logs from client applications on the local network, or remotely over the internet
  • Save viewer logs to share them and/or review them later
  • Export logs to text files
  • Open raw buffered traces files that you brought back from client applications not directly connected to the log viewer

You'll find instructions for use in the NSLogger wiki.

Your application emits traces using the NSLogger trace APIs. The desktop viewer application (running on Mac OS X 10.6 or later) displays them.

Clients automatically find the logger application running on Mac OS X via Bonjour networking, and can optionally connect to a specific remote host / port. You have no setup to do: just start the logger on your Mac, launch your iOS or Mac OS X application then when your app emits traces, they will automatically show up in NSLogger if the viewer is running locally on your network. Until a logger is found, logs are buffered on the client so you don't lose anything.

Desktop Viewer (main window)

One-step setup

All you have to do is add LoggerClient.h, LoggerClient.m and LoggerCommon.h (as well as add the CFNetwork.framework and SystemConfiguration.framework frameworks) to your iOS or Mac OS X application, then replace your NSLog() calls with LogMessageCompat() calls. We recommend using a macro, so you can turn off logs when building the distribution version of your application.

Using the desktop logger

Start the NSLogger application on Mac OS X. Your client app must run on a device that is on the same network as your Mac. When it starts logging traces, it will automatically (by default) look for the desktop NSLogger using Bonjour. As soon as traces start coming, a new window will open on your Mac. Advanced users can setup a Remote Host / Port to log from a client to a specific host).

You can create custom filters to quickly switch between different views of your logs.

Evolved logging facility

It's very easy to log binary data or images using NSLogger. Use the LogData() and LogImage() calls in your application, and you're done. Advanced users can also enable remote logging to have logs sent directly from remote devices running at distant locations, or have logs be directed to a file that can later be sent to a remote server.

Powerful desktop viewer

The desktop viewer application provides tools like:

  • Filters (with regular expression matching) that let your perform data mining in your logs
  • Timing information: each message displays the time elapsed since the previous message in the filtered display, so you can get a sense of time between events in your application.
  • Image and binary data display directly in the log window
  • Markers (when a client is connected, place a marker at the end of a log to clearly see what happens afterwards, for example place a marker before pressing a button in your application)
  • Fast navigation in your logs
  • Display and export all your logs as text

Your logs can be saved to a .nsloggerdata file, and reloaded later. When logging to a file, name your log file with extension .rawnsloggerdata so NSLogger can reopen and process it. You can have clients remotely generating raw logger data files, then send them to you so you can investigate post-mortem.

Note that the NSLogger Mac OS X viewer requires Mac OS X 10.6 or later.

Filter Editor

High performance, low overhead

NSLogger runs in its own thread in your application. It tries hard to consume as few CPU and memory as possible. If the desktop viewer has not been found yet, your traces can be buffered in memory until a connection is acquired. This allows for tracing in difficult situations, for example device wakeup times when the network connection is not up and running.

NSLogger can be used for low-level code in situations where only CoreFoundation can be called. Disable the ALLOW_COCOA flag in LoggerClient.h to prevent any use of Cocoa code.

Work in progress - Current status

This tool comes from a personal need for a more powerful logger. There are more features planned for inclusion, here is a quick list of what I'm thinking of. Requests and suggestions are welcome.

  • Remember last filter set used per application name / identifier
  • Turn SSL on for remote logging (currently being worked on, checkout the ssl branch to test it)
  • For multiple subsequent connections by the same client (multiple app runs), reuse the same window much like Instruments does
  • Log entry colorization
  • Search and search term highlight in Details window
  • Support time-based filtering (filter clause based on the time lapse between a previous trace)
  • Pause (buffer logs) and resume sending logs to the logger, in order to eliminate NSLogger's network load from the equation when testing networking code

You'll find documentation in the NSLogger Wiki

NSLogger uses Brandon Walkin's BWToolkit. The source tree for BWToolkit is currently included here because I suck at Git.

NSLogger is Copyright (c) 2010 Florent Pillet, All Rights Reserved. Released under the New BSD Licence.

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