If you need to monitor your application’s health, troubleshoot issues quickly, and ensure compliance with various security policies, application logging is compulsory. Without proper logging, identifying the root cause of failures, tracking suspicious activity, or optimizing application performance will become significantly more challenging, if not impossible.
In this guide, we’ll go over some key best practices for application logging so you can increase visibility into your systems, improve the debugging process, and maintain reliable operations.
Topics covered in this article:
10 critical application logging best practices
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- Aggregate log data
- Carefully consider which events to log
- Include relevant details
- Exclude sensitive information
- Use the right format
- record-log-events-at-the-right-level>Record log events at the right level
- Separate your payload data and log messages
- Establish storage limits
- Store multiple copies of logs
- Use the right application logging tool
Logging for reliable and secure applications
What are application logs?
Application logs are records of events and activities occurring within an application. They have a structured format and can provide information on everything from user interactions and system performance to errors, warnings, and debugging details.
By analyzing application logs, teams can better identify patterns, track down the root causes of failures, and optimize performance. They are vital for troubleshooting and diagnosing issues because they provide a record of what happened before, during, and after an event, helping recreate the sequence of actions that led to the issue.
Application logs allow organizations to quickly detect suspicious activity that could signal a security breach. Application logs can help developers, system administrators, and security teams monitor application health and diagnose issues, all while ensuring compliance with industry and government regulatory requirements.
Application logging and debugging aren’t the same, though they are closely related. Debugging typically occurs during the application development process as developers pinpoint and resolve code issues. In contrast, application logging takes place in the background once the application is up and running, providing insights into its overall health and behavior over time.
Within each application log file, you can find valuable information that sheds some light on your application and its performance, including:
- Timestamps: The timestamp on an application log indicates when an event occurred, helping you understand the sequence of events. This can be crucial for pinpointing the root cause of a problem while also revealing broader patterns and trends over time.
- Context information: Context information includes key details about a logged event, such as the operation in progress at the time and the user associated with it. By providing this context, logs offer deeper insight into each event, helping you diagnose and resolve issues more efficiently.
- Log levels: Application logs also include log levels, which indicate the severity or importance of each log entry. These levels help filter and analyze log data, allowing you to identify and prioritize critical issues. You can also configure your application to record specific log levels based on its environment. For instance, during development, you might log all levels for comprehensive debugging, whereas in production, you may limit logging to more severe levels to reduce noise and optimize performance.
10 critical application logging best practices
1. Aggregate log data
One of the most crucial aspects of application logging is aggregating log data. This process involves collecting and summarizing logs to streamline analysis and provide a comprehensive view of system activity. Aggregating logs makes it easier to spot trends and patterns, helping you quickly diagnose performance bottlenecks, troubleshoot issues, and optimize your application. To ensure effective aggregation and analysis, be sure to standardize log formats—inconsistent logs can create unnecessary complexity and hinder insights.
2. Carefully consider which events to log
Log events provide valuable insights into your application and its behavior. However, you must log the right events to support the troubleshooting, security, auditing, testing, monitoring, and performance improvement efforts for your application. You will want to keep track of:
- Access logs: Access logs record every request made to your application, from page loads to file downloads. By analyzing these logs, you can gain deeper insights into user behavior while quickly identifying potential security vulnerabilities and threats.
- Authentication logs: These logs capture details of every application login attempt, including whether it was successful and which user attempted to gain access.
- Authorization logs: Authorization logs can inform you when users attempt to perform actions for which they don’t have the necessary permissions.
- Change logs: Change logs can shed light on the changes made to your application. For example, you can learn about source code modifications, database updates, and configuration setting adjustments through change logs.
- Error logs: These logs record errors or exceptions and are categorized by severity level. Error logs are particularly useful for debugging, allowing developers to quickly identify the root cause of issues.
- Availability logs: Reviewing availability logs helps gain insight into your application’s uptime and downtime. They provide information on when the crash occurred, how long the application was down, and the cause of the crash.
- Opt-ins: It’s also a good idea to log various opt-ins. For example, you might collect logs when users opt into your application’s terms of service, enable two-factor authentication, or agree to receive push notifications.
- Data imports and exports: Data imports and exports are higher-risk events as they involve transferring large volumes of information, which can lead to data corruption and loss or unauthorized access if not properly managed. That’s why it’s good practice to collect and analyze logs associated with data imports and exports.
3. Include relevant details
When logging application events, include details that provide meaningful context for troubleshooting and data analysis. However, avoid overloading logs with redundant or unnecessary information, as this can make them harder to parse and drive up storage costs.
4. Exclude sensitive information
While including relevant details in logs is essential, data privacy should always be a priority. Avoid logging sensitive information, such as personally identifiable information (PII) or encryption keys. Ensure your organization’s privacy policy extends to log data and all partners adhere to your compliance standards. To minimize the risk of accidental data exposure, closely follow organizational, industry, and government privacy regulations.
5. Use the right format
It’s a good idea to use human-readable logs. By using plain text or simple key-value pairs in your application logs, your developers and system administrators can quickly scan logs and identify issues without needing to resort to specialized tools. With easy-to-read logs, properly formatted timestamps, and clear, descriptive messages that don’t use overly technical jargon, you can reduce the time spent troubleshooting and debugging.
To keep your logs detailed yet efficient, consider using a structured format—especially if your application generates a large amount of data. Standard formats such as JSON or XML ensure every log captures key details, including timestamps, security levels, system states, and user actions. This makes it easier to spot issues, troubleshoot problems, and monitor security without drowning in data. Plus, a standardized format helps streamline log analysis and integration with management tools, saving time and effort.
6. Record log events at the right level
It’s also important to record events at the correct log level. This way, your logs will remain well-organized, making it easier to filter, search, and analyze relevant data without being overwhelmed by unnecessary details.
Log levels include:
- TRACE: At the TRACE log level, logs cover events in the step-by-step execution of your code. Compared to other log levels, TRACE logs are incredibly verbose and contain a high amount of detail. As a result, they are typically used only during debugging or development to track the exact flow of execution. It is best to avoid using TRACE logs once your application has been launched, as this can lead to excessive log noise and storage costs.
- DEBUG: DEBUG logs are useful during the software debugging process, as they capture more details than INFO logs, yet less than TRACE logs. DEBUG logs contain more information than you typically need in everyday use, but they can provide valuable insights when troubleshooting your application or diagnosing issues within your test environment.
- INFO: This log level is for events that don’t impact operations. Essentially, INFO logs provide general updates on the normal functioning of your application, covering activities such as configuration changes, system events, and authorization requests. Generally, you can ignore INFO logs while your application is functioning normally. However, if something goes wrong, you may need to dig into your INFO logs to trace the sequence of events leading up to the issue and gain additional context for troubleshooting.
- WARN: At the WARN log level, you can find logs that highlight potential issues that aren’t currently causing failures but could lead to problems down the line. WARN logs indicate unexpected application behavior that hasn’t yet impacted operations. By closely monitoring WARN logs, your team can address potential risks before they escalate into critical failures.
- ERROR: The ERROR logging level indicates significant issues with your application that impact its functionality but will not necessarily cause the system to crash. ERROR logs can capture failed transactions, service disruptions, and exceptions that require attention to maintain application stability and operation.
- FATAL: This is the highest, most severe log level. It is used for severe issues that can cause system crashes, data loss, or major failures and require immediate intervention.
To ensure you’re logging events at the right level, review your logging framework settings. Pay close attention to exceptions—determine whether they should be logged at the INFO or ERROR level—and verify that all log messages align with their intended severity. For example, status updates should fall under INFO, while unexpected failures or critical bugs requiring immediate attention should be categorized as ERROR, FATAL, or CRITICAL.
7. Separate your payload data and log messages
Keep your payload data and log messages separate to improve readability and analysis. Payload data captures details about your application processes, while log messages describe what your application is doing. Mixing them can make logs harder to interpret and manage. Separating them not only keeps logs more organized but also enhances security by allowing you to store sensitive payload data in a more secure location than general log messages.
8. Establish storage limits
It’s also important to create storage limits early on, as your application will generate hundreds to millions of logs daily. As a result, log data will accumulate rapidly and consume a significant amount of your disk space. If you don’t have proper storage limits in advance, your application may experience major performance issues or crash.
Setting storage limits helps you retain relevant, recent log data while archiving or deleting older logs that are no longer useful. This frees up disk space and ensures your application and systems run smoothly. Plus, storage limits make resource management more efficient, allowing you to allocate space based on the importance and volume of your log data.
9. Store multiple copies of logs
Redundancy is vital, so make sure you store multiple copies of your log data in different systems or locations. Having sufficient log redundancy can help ensure your log data is always available and maintains its integrity.
By storing several copies of your log files in various locations, you can restore your application and systems to their previous state in the event of system failures, data loss, or security breaches. Losing critical log data could hinder your ability to investigate issues, track security incidents, or maintain compliance.
To maximize reliability, consider using a combination of on-premises storage, cloud-based solutions, and external backups. Implement automated backups and regularly verify their integrity to ensure logs remain accessible when needed.
10. Use the right application logging tool
Instead of manually reviewing application logs, use an application logging tool or an observability platform to simplify the process. These tools can collect, parse, and analyze logs on your behalf, allowing you to quickly identify patterns, troubleshoot issues, and monitor system performance in real time. Many include easy-to-read dashboards that allow you to understand your application and its performance at a glance, providing real-time alerts so you can proactively address potential issues before they escalate.
The right application logging tool should support structured logging, provide powerful search and filtering capabilities, and integrate seamlessly with your existing infrastructure. Features such as automated alerts, anomaly detection, and visualization dashboards can further enhance log analysis and security monitoring.
By leveraging a reliable logging solution, you can reduce the time spent on manual log reviews, minimize the risk of overlooking critical events, and improve the overall efficiency of your network operations.
Logging for reliable and secure applications
Effective application logging is crucial for maintaining system health, efficiently troubleshooting issues, and ensuring compliance with security policies. By following these application logging best practices, you can enhance observability, streamline debugging, and improve overall system performance. Leveraging the right logging tools and strategies will not only simplify log management but also help proactively optimize your application’s performance and resolve issues before they worsen.
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