In software engineering, tracing is a specialized use of logging to record information about a program's execution. Software engineering is the application of a systematic disciplined quantifiable approach to the development operation and maintenance of Software. Data logging is the practice of recording sequential Data, often chronologically. This information is typically used by programmers for debugging purposes, and additionally, depending on the type and detail of information contained in a trace log, by experienced system administrators or technical support personnel to diagnose common problems with software. A programmer is someone who writes Computer software. The term computer programmer can refer to a specialist in one area of computer programming or to a generalist A system administrator, systems administrator, or sysadmin, is a person employed to maintain and operate a Computer system and/or network. Technical support (also tech support) is a range of services providing assistance with technology products such as mobile phones televisions Computers Tracing is a cross-cutting concern. In Computer science, cross-cutting concerns are aspects of a program which affect (crosscut other concerns.
There is not always a clear distinction between tracing and other forms of logging, except that the term tracing is almost never applied to logging that is a functional requirement of a program (therefore excluding logging of data from an external source, such as data acquisition in a high-energy physics experiment, and write ahead logging). In Software engineering, a functional requirement defines a function of a Software system or its component Data acquisition is the sampling of the real world to generate data that can be manipulated by a computer Particle physics is a branch of Physics that studies the elementary constituents of Matter and Radiation, and the interactions between them In Computer science, write ahead logging (WAL is a family of techniques for providing atomicity and durability (two of the ACID properties Logs that record program usage (such as a server log) or operating system events primarily of interest to a system administrator (see for example Event Viewer) fall in a gray area with regards to terminology. A server log is a log file (or several files automatically created and maintained by a server of activity performed by it An operating system (commonly abbreviated OS and O/S) is the software component of a Computer system that is responsible for the management and coordination Event Viewer is a component of Microsoft 's Windows NT line of operating systems that lets administrators and users view the event logs on a local or This article deals with tracing that is primarily for debugging or diagnostic purposes.
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Event logging versus tracing
Difficulties in making a clear distinction between event logging and software tracing arise from the fact that the some of the same technologies can be used for both, and further because many of the criteria that distinguish between the two are continuous rather than discrete. The following table lists some important, but by no means precise or universal, distinctions that are used by developers to select technologies for each purpose, and that guide the separate development of new technologies in each area:
| Event logging | Software tracing |
|---|---|
| Consumed primarily by system administrators | Consumed primarily by developers |
| Logs "high level" information (e. g. failed installation of a program) | Logs "low level" information (e. g. a thrown exception) |
| Must not be too "noisy" (contain many duplicate events or information not helpful to its intended audience) | Can be noisy |
| A standards-based output format is often desirable, sometimes even required | Few limitations on output format |
| Event log messages are often localized | Localization is rarely a concern |
| Addition of new types of events, as well as new event messages, need not be agile | Addition of new tracing messages must be agile |
Event logging
Event logging provides system administrators with information useful for diagnostics and auditing. Exception handling is a programming language construct or computer hardware mechanism designed to handle the occurrence of a condition that changes the normal flow of execution Standardization (or standardisation) is the process of developing and agreeing upon technical standards. In Computing, Internationalization and localization (also spelled internationalisation and localisation, see spelling differences) are means of adapting The most general definition of an audit is an evaluation of a person organization system process project or product The different classes of events that will be logged, as well as what details will appear in the event messages, are often considered early in the development cycle. Many event logging technologies allow or even require each class of event to be assigned a unique "code", which is used by the event logging software or a separate viewer (e. g. , Event Viewer) to format and output a human-readable message. This facilitates localization and allows system administrators to more easily obtain information on problems that occur.
Because event logging is used to log high-level information (often failure information), performance of the logging implementation is often less important.
A special concern, preventing duplicate events from being recorded "too often" is taken care of through event throttling.
Software tracing
Software tracing provides developers with information useful for debugging. This information is used both during the development cycle and after the software is released. Unlike event logging, software tracing usually does not have the concept of a "class" of event or an "event code". Other reasons that event logging solutions based on event codes are inappropriate for software tracing include:
- Because software tracing is low-level, there are often many more types of messages that would need to be defined, many of which would only be used at one place in the code. The event code paradigm introduces significant development overhead for these "one-shot" messages.
- The types of messages that are logged are often less stable through the development cycle than for event logging.
- Because the tracing output is intended to be consumed by the developer, the messages don't need to be localized. Keeping tracing messages separate from other resources that need to be localized (such as event messages) is therefore important.
- There are messages that should never be seen. In Computer programming, an assertion is a predicate (ie a true–false statement placed in a program to indicate that the developer thinks that the
- Tracing messages should be kept in the code, because they can add to the readability of the code. This is not always possible or feasible with event logging solutions.
Another important consideration for software tracing is performance. Because software tracing is low-level, the possible volume of trace messages is much higher. To address performance concerns, it often must be possible for software tracing to be turned off, either at compile-time or run-time. A compiler is a Computer program (or set of programs that translates text written in a computer language (the source language) into another
Other special concerns:
- In proprietary software, tracing data may include sensitive information about the product's source code. Proprietary software is Computer software on which the producer has set restrictions on use private modification copying, or republishing. In Computer science, source code (commonly just source or code) is any sequence of statements or declarations written in some Human-readable
- If tracing is enabled or disabled at run-time, many methods of tracing require a significant amount of additional data be included in the binary, which can indirectly hurt performance even when tracing is disabled.
- If tracing is enabled or disabled at compile-time, getting trace data for a problem on a customer machine depends on the customer being willing and able to install a special, tracing-enabled version of your software and then duplicating the problem.
- Many uses of tracing have very stringent robustness requirements. Robustness is the quality of being able to withstand stresses pressures or changes in procedure or circumstance This is both in the robustness of the trace output but also in that the use-case being traced should not be disrupted.
- In operating systems, tracing is sometimes useful in situations (such as boot) where some of the technologies used to provide event logging may not be available. In Computing, booting ( booting up) is a bootstrapping process that starts Operating systems when the user turns on a Computer system
Technologies and techniques
Software tracing:
- Tracing macros
- Output to debugger (see for example [1])
- Aspect-oriented programming and related instrumentation techniques
- Windows software trace preprocessor (aka WPP)
- Linux system level and user level tracing with Kernel Markers and LTTng
Event logging:
- syslog (see article for specific implementations)
- Event Logging APIs for Microsoft Windows
- Windows Event Log (new for Windows Vista)
Appropriate for both:
- Apache logging
- Event Tracing for Windows
- Java logging APIs
- Visual Basic logging (for Visual Basic .NET)
- Logcheck: a free and open-source utility to manage logs
- LogMX: a universal log/trace viewer (commercial)
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