Using Access Log to Troubleshoot Web Server Issues

Using Access Log to Troubleshoot Web Server Issues

Every click or swipe leaves behind a digital trail that’s stored in logs – for instance, firewall logs track attacks while web server access logs monitor user activity.

Access logs provide valuable data regarding when, who and how a file was accessed – information which is invaluable when troubleshooting performance issues and detecting security threats.


Access logs provide security professionals with an invaluable set of data points that can be used to identify security threats. For instance, an access log indicating that someone attempted to gain entry where they weren’t supposed to could indicate brute force attacks or other suspicious activity on your site; similarly, logs can detect when attackers attempt to launch DDoS attacks against it.

Filtering an access log may appear complex at first, but you’ll soon learn it’s simple to hone in on specific types of information. For instance, you could set the filtering to look only for requests coming from certain IP addresses or file types to gain a clear picture of what’s going on with your servers and identify potential issues that arise.

Analyzing access logs can also be helpful when troubleshooting web errors. If, for instance, your server experiences an unusually large number of HTTP errors (404), this could indicate it has some issues that need addressing and can give us insight into what might be causing these issues – potentially giving us enough data to address and remedy them quickly and effectively.

Access logs are an integral component of endpoint detection and response (EDR). EDR solutions use monitoring endpoints such as desktops, laptops, smartphones, printers and printers to identify and block malware or threats from entering networks; EDR solutions may also detect file transfers to removable drives which attackers could use to install malware or exfiltrate sensitive information from removable disk drives; EDR solutions use access log data collected to quickly detect these attacks ensuring compliance with regulations such as PCI-DSS or HIPAA regulations and ensure protection from unauthorized access or exfiltrate sensitive data being compromised while maintaining compliance with regulations such as PCI-DSS and HIPAA regulations.


While access logs provide valuable security information, they also reveal performance metrics that can help organizations optimize web server configuration and applications. This data can provide opportunities to enhance user experience, optimize search engine optimization (SEO), increase website speed and security and decrease website downtime.

An increase in HTTP Error 404s may signal internal website problems, so studying your logs will allow you to identify and resolve these more quickly.

Filtering data when analyzing an access log allows you to focus on specific types of requests or conditions, like request types, gRPC status codes, tracing parameters, health check statuses or response flags. Furthermore, multiple filters can be combined together using Boolean operations like OR and AND.

The access log format can be customized using the config directive, using either strings or format dictionaries as its output format. Strings provide simple text strings that can be used to insert various types of data points (including user-defined variables). Format dictionaries use command operators to evaluate values and produce structured output that can produce numeric, boolean, or list values nesting for easy production of meaningful reports.

Additionally, the config directive allows you to provide both a fileNamePattern and symlink name for the active log file. When rotating logs take place, this symlink will point directly to the new log file instead of being automatically deleted like some web servers do – instead it is placed into an archive directory for safekeeping.

Log data management can be both time-consuming and complex. By connecting your web server with Sumo Logic’s log management solution, you can streamline the collection and analysis of Apache access logs – saving valuable time while developing an in-depth knowledge of your website’s performance.


Troubleshooting issues effectively requires having access to the appropriate tools; which is why Access Log provides numerous debugging features to assist in pinpointing any potential issues.

These include:.

Debug Messages
Debug EXEC commands can help capture diagnostic messages that provide information about router operations and status. They’re helpful when troubleshooting network connectivity or performance issues, though you should seek guidance from Cisco technical support before employing these commands as they could disrupt normal routing operations and even lead to its crash.

Debugging mode can be enabled by adding the debug=True flag to any page in your configuration file. When enabled, an embedded debug report will be generated with links that provide details and trace of requests that caused errors or problems. By default, this report opens in a new tab or window but there’s also the option from a drop down menu for it to open within its parent error message as a frame.

CustomLog allows you to set the location and content of your access log file. With LogFormat you can also filter and format log entries using keywords or wildcards; field names in LogFormat include tag, package message line or even regular expression filters based on negative words like MyTag which filter out those that do not match MyTag based filters (e.g -tag:MyTag will only return entries where MyTag doesn’t match).

Debugging features of great benefit include viewing full raw logging data for specific IP addresses. This is useful if your web server serves multiple customers simultaneously. Likewise, the Headers directive allows you to customize what headers appear in log files, while you can choose to have it automatically roll over after a specified amount of time has elapsed between when it was last written and now being written over again – an invaluable feature for protecting important logging data!


Access logs provide invaluable insight when troubleshooting issues on your site. For instance, an increase in HTTP error 404 errors could indicate that users are trying to visit pages that no longer exist and you can use an access log’s information to quickly address these requests by quickly locating their source.

A high number of 5xx errors may be an indicator that your server is experiencing internal problems, with accompanying error codes helping identify their root causes.

Your Nginx server configuration determines the information contained in an access log. You can customize its contents using the CustomLog directive and the LogFormat variable; an access log entry typically contains timestamp in local time, client address information, request method (HTTP verb), and requested page name as data points.

By default, Nginx stores the access logs in a central repository at /var/log/nginx/access. However, you can configure your system to automatically roll over this log file when its maximum size has been reached, providing for unlimited amounts of data storage.

Utilizing a log management tool like Sumo Logic to collect and analyze your access logs makes it much simpler to identify patterns that could indicate issues on your website, for instance an increase in 404 errors could indicate that one or more pages on your site has been deleted, or its URL incorrect.

Drill down into any particular user agent or browser within an access log entry to gain more detailed information. For instance, to see which files were accessed by ZmEu user agent from an access log entry, use the search box located on the left sidebar of Sumo Logic WAF console to search.

Additionally to examining an access log, you can also view the status codes returned by an Nginx server. These “return codes” help developers and testers assess how well an application is functioning.

Mark Funk
Mark Funk is an experienced information security specialist who works with enterprises to mature and improve their enterprise security programs. Previously, he worked as a security news reporter.