Find answers, guides, and tutorials to supercharge your content delivery. Logs are a very useful aspect of web server administration and web development as they provide useful debugging information and allow you to analyze other aspects of your web server.

This article will go through the process of configuring both your Nginx error log and access log files as well as display a few ways to read each file directly from the terminal. Nginx error logs are used to log general error messages. If you experience an error in your web application, it is always good practice to check the Nginx error log file to see if there is any additional information as to why the error occurred.

The directive will be in the following format and can be specified within an http, server, or location block:. Therefore, an example of what the directive looks like when each portion is populated will resemble:. When defining the severity level, Nginx will log all errors that are equal to or above the defined level. The following is a list of all severity levels from low to high you may use along with a short description of each.

For instance, in the example above we defined the severity level as warn. Therefore, Nginx would include all warnerrorcritalertand emerg errors in the error log. The Nginx access log is similar to the error log in that it logs information, however the type of information that it logs is what differentiates it. Nginx writes information in the access log regarding each request made by a client.

Therefore, when defining each portion of the access log directive, it may resemble the following:. Using the cat command will display the complete access or error log file in your terminal window.

For example you could use the following to display the contents of each file:. Alternatively, you could use the tail -f command to display the 10 most recent lines of the file and monitor the file for any additional changes. Additionally, you may use an awk command to display the number of responses that returned a particular status code. For example:. As shown above, this can be one manually however you can also use tools such as GoAccess or Loggly to also monitor and analyze your Nginx logs.

Now that you have more information regarding what the Nginx error log and access logs are for, try using them the next time you need certain information regarding your web server. Support Find answers, guides, and tutorials to supercharge your content delivery.Nginx HTTP server has a phenomenal logging facility which is highly customizable.

In this article, we will explain how to configure you own formats for access and error logs for Nginx in Linux. The aim of this guide is to help you understand how logs are generated, so as to configure custom log formats for purposes of debugging, troubleshooting or analysis of what unfolds within your web server as well as web applications such as tracing requests. The log format is described by common variables, and variables that generated only at the time when a log is written.

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The following is another useful logging format which we use for tracing requests to our web applications using the some of the default variables, it most importantly has the request ID and logs client location details country, country code, region and city. The following are more advanced logging configurations examples, which are useful for log formats that contain compression-related variables and for creating compressed log files:.

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In case Nginx experiences any glitches, it records information concerning them in the error log. These issues fall under different severity levels: debuginfonoticewarnerror this is the default level and works globallycritalertor emerg. This will instruct Nginx to log all messages of type warn and more severe log level critalertand emerg messages.

nginx debug log

In the next example, messages of critalertand emerg levels will be logged. Consider the configuration below, here, we have defined error logging on different levels in the http and server context. In case of an error, the message is written to only one error log, the one closest to the level where the error has appeared.

In some cases, we may want Nginx to perform conditional logging of messages.

nginx debug log

Not every message has to be logged by Nginx, therefore we can ignore insignificant or less important log entries from our access logs for particular instances. The parameters inside a map block which should exist in the http content only specify a mapping between source and resulting values. This example excludes requests with HTTP status codes 2xx and 3xx. Here is another useful example for debugging a web application in a development phase. This will ignore all messages and only log debug information.

You can find out more information, including logging to syslog here. In this guide, we explained how to configure custom logging format for access and error logs in Nginx. Use the feedback form below to ask questions or share you thoughts about this article. TecMint is the fastest growing and most trusted community site for any kind of Linux Articles, Guides and Books on the web.

Millions of people visit TecMint! If you like what you are reading, please consider buying us a coffee or 2 as a token of appreciation. We are thankful for your never ending support. Tags: Nginx Tips.

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View all Posts. Aaron Kili is a Linux and F. S enthusiast, an upcoming Linux SysAdmin, web developer, and currently a content creator for TecMint who loves working with computers and strongly believes in sharing knowledge. Your name can also be listed here.If you prefer redirecting common Lua errors to the HTTP response body during Lua development, you can put a Lua pcall call on the top level of your Lua code to catch and redirect any Lua exceptions.

But keep in mind, not all errors can be captured this way because you could have errors when sending out the response, then it is impossible to put such errors into the response body. During Lua code development, you can disable the Lua code cache temporarily so that you do not have to reload the Nginx server for your external Lua code changes to take effect.

Also, it is strongly recommended to follow the test-driven development workflow. If you are on Linux, there are quite many real-time analysing tools based on systemtapwhich can be used to inspect a running Nginx worker process in various ways:.

These tools can not only debug functional problems, but also profile online servers to find performance bottlenecks.

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In very rare use cases, standard OpenResty components may incur memory issues as well. To debug such memory issues which lead to either segmentation faults or weird nondeterminism in software behaviors due to memory corruptions, we can use Valgrind to reliably find the real culprit when the issues can be relatively easy to reproduce. To simplify the special build settings for Valgrind usage, OpenResty provides the openresty-valgrind pre-built Linux packages for various common Linux distributions:.

If your Linux system is not supported in the pre-built package repositories yet, you can build your own openresty-valgrind by following the steps in the openresty-valgrind's RPM spec file.

Among other things, remember to configure the following lines in your nginx. OpenResty's Test::Nginx test scaffold has provide builtin support for running tests with Valgrind, which is referred to as the "Valgrind test mode". You can find detailed documentation with examples in the "Programming OpenResty" book online:. One limitation with Valgrind When your OpenResty application requires nontrivial load of real traffic to reproduce or you have to enable special nginx child processes like worker processes and cache manager processes to reproduce the issue, then you can consider rebuilding your OpenResty with clang or gcc's AddressSanitizer ASAN tool, which also gives much better performance.

We will provide the openresty-asan package in our official OpenResty Linux package repositories in the near future to make this easier. Debugging memory issues 3rd-party Lua libraries or 3rd-party NGINX C modules that are not maintained by OpenResty might be subject to memory issues since they might not go through the same careful testing of the standard OpenResty components.We can control many aspects about error logging which will help us debug our Nginx configuration.

I believe, we never break something that we never code!

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So before you copy-paste any Nginx config, make sure you remove unwanted codes. You might end up fixing your problem using them alone.

Most of the time, you will be needing this only. Specially when you are seeing or unexpected pages. You can find other possible values here. You can find your public IP here. You can find more details on this here. You need to recompile Nginx to use this. For Ubuntu users, there is a launchpad repo.

I recently came across this and I am yet to use it for debugging on a project. When I will do it, I will post details about it. There is a Nginx module for Perl language and one for Lua language. As I am very bad at learning new languages, chances are less that I will ever write more on this. Skip to content. Before we proceed… I believe, we never break something that we never code! Like this: Like Loading Sorry, your blog cannot share posts by email.I love Nginx for its revery proxy capabilities and ease of configuration.

When proxying a request to another server, you may or may not have access to log of the server. So it is important to be able to debug, where the problem lies when an issue occurs.

Common problems that you may face when proxying request are below. These techniques will be applicable to other servers like Gunicorn, uwsgi, or other sites as well. The above config passes all php scripts to the running php-fpm server listening on And anything other than php is denied.

Now this error does indicate that there is an issue with the headers that were sent back.

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In our demo case there is just one file to check, but in a real project there would be multiple files and it becomes hard to say where the error might be coming from. Socat is a command line based utility that establishes two bidirectional byte streams and transfers data between them.

Install socat based on the package manager you have on your OS. One of the below commands should do. Once installed we need to run socat to listen on a port different than and pass the data to port. So we will run a socat in a new terminal or screen or tmux.

The communication transfer between the two ports will only happen till socat is running. The command is self explanatory.

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It is to listen on and pass traffic bidirectionaly between the two The -v is for verbose output, it helps us print the traffic. Note: You will need to make sure the user has access to the socket.

Some sockets run with permissions and the owners are different than root or your current user. So you would need to change the owner of these socket or chmod them to for your testing. From this we can easily see that X-MY-Header is coming with large data and after reading bytes that is 8KB of headers, nginx just leaves it and fails the request. So it becomes easy to understand what values the backend is getting and why it is not working. So we update our config to. As we can see the url is now corrected.

But we still have a This could be because of Host: So we should set the host name also with our request. Note: This is only needed because we are sending the proxy to socat listener on localhost.There are many ways to troubleshoot the ingress-controller.

The following are basic troubleshooting methods to obtain more information. This is performed by editing the deployment. A number of components are involved in the authentication process and the first step is to narrow down the source of the problem, namely whether it is a problem with service authentication or with the kubeconfig file.

The Ingress controller needs information from apiserver. Therefore, authentication is required, which can be achieved in two different ways:. Service Account: This is recommended, because nothing has to be configured. The Ingress controller will use information provided by the system to communicate with the API server.

See 'Service Account' section for details. Kubeconfig file: In some Kubernetes environments service accounts are not available. In this case a manual configuration is required. The Ingress controller binary can be started with the --kubeconfig flag. The value of the flag is a path to a file specifying how to connect to the API server.

Using the --kubeconfig does not requires the flag --apiserver-host. See 'kubeconfig' section for details. Please do not use this approach in production. In the diagram below you can see the full authentication flow with all options, starting with the browser on the lower left hand side.

nginx debug log

It provides a secret token that is required to authenticate with the API server. The contents of the tokens are invalid. It will automatically be recreated. You have a non-standard Kubernetes installation and the file containing the token may not be present. If you experience this error, verify that your API server is using the ServiceAccount admission controller. If you are configuring the API server by hand, you can set this with the --admission-control parameter.

Note that you should use other admission controllers as well. Before configuring this option, you should read about admission controllers. Gdb can be used to with nginx to perform a configuration dump. This allows us to see which configuration is being used, as well as older configurations. Note: The below is based on the nginx documentation.

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nginx debug log

Welcome Deployment User guide Examples.Logs are very useful to monitor activities of any application apart from providing you with valuable information while you troubleshoot it.

Like any other application, NGINX also records events like visitors to your site, issues it encountered and more to log files. This information enables you to take preemptive measures in case you notice some serious discrepancies in the log events.

This article will guide you in details about how to configure NGINX logging so that you have a better insight into its activities. Let us find out more about NGINX access log, error log and how to enable them if you have not done it earlier. Here you can find which files are accessed, how NGINX responded to a request, what browser a client is using, IP address of clients and more. It is possible to use the information from the access log to analyze the traffic to find sites usages over time.

Further, by monitoring the access logs properly, one can find out if a user is sending some unusual request for finding flaws in the deployed web application. This may happen if there is some error in the configuration file.

Nginx Web Server configuration with Examples

Therefore if NGINX is unable to start or abruptly stopped running then you should check the error logs to find more details.

You may also find few warnings in the error log but it does not indicate that a problem has occurred but the event may pose a serious issue in the near future.

That means access log of all the virtual host will be recorded in the same file. It is always better to segregate the access logs of all the virtual hosts by recording them in a separate file. To view the access logs for the domain domain1.

The default log format used to record an event in the access log is combined log format. The following example defines a custom log format by extending the predefined combined format with the value of gzip compression ratio of the response. Now tail the access log to find the gzip ratio at the end of the log event.

Debugging Nginx Configuration

For example, the following example sets the severity level of error messages to be logged to crit. All the examples described above records the log events to a file. In some situation, you might want to disable the error log.

There are many types of log levels that are associated with a log event and with a different priority.

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All the log levels are listed below. In the following log levels, debug has top priority and includes the rest of the levels too.

For example, if you specify error as a log level, then it will also capture log events those are labeled as crit, alert and emergency. The access and error logs in NGINX will not only keep a tab on users activity but also save your time and effort in the process of debugging.

Further, you can also customize the access log if you need more information at your disposal. It is always better to enable access and error logs because these two files contain all the clues for better maintenance of the NGINX server. Your email address will not be published.