How to Define a Logging Strategy for Mule

Defining a robust logging strategy for MuleSoft is essential to ensure that your applications are secure, reliable, and easy to maintain. A well-thought-out logging strategy helps in monitoring application performance, troubleshooting issues, and complying with regulatory requirements.

In the last few years, I’ve seen some customers implementing their integration projects with a wrong or non existing logging strategy.
A logging strategy is not just defining where we will put our logs or logging as much info as we can. It’s much more than that

In this series of posts, we are going to see, step by step, everything we need to define to properly define our Logging Strategy for Mule.
We are going to do that by answering these 5 questions: Why, When, What, Where and How.

Why?

The first and foremost question we need to answer is Why we are building a Logging Strategy? What are we trying to achieve with the info in our logs? One might think of common goals like improving the debugging or troubleshooting of our mule apps but there are many other aspects on which this information can be really helpful to improve other not so obvious operations of our mule platform.

In the post - Why Logging? The importance of having a clear Logging Strategy for Mule we will see up to 20 different goals that you can define for your logging strategy.

Having clear objectives for your Logging Strategy is going to be key to answer the rest of questions. We can’t really define what information we need to log if we don’t know exactly why we need that information. Nor we can decide when we should log that information if we don’t understand what aspect of our Operations we are trying to improve with that log info.

When?

We normally log information in our mule apps when there’s something important we want to record in the running history of the app. It could be something that has happened (an error, a completion of a task), it could be a informative message to understand what’s going on in the running flow or it could be a message for auditing or compliance (authenticated users, violated policies).

Whatever the situation is, we need to identify when exactly we want our applications to write to the log in order to achieve the goals that we defined in our previous step.
We can’t just leave it to the common sense of our developers. For different reasons:

First, because there would be as many criteria or common senses as developers. We need to log consistently, following the same guidelines for ALL of our mule apps. That will help a lot the Operator that would be analyzing and searching in our logs, because he/she will know what to expect, when he/she is expecting to find log info. The more predictable our logs are the better.
Secondly, because we need to avoid overlogging. Logging excessive information can create more problems, as it might obscure important information and mislead the person going through our logs. Finding the right amount of information that we need to log in our mule apps is key for our logging strategy.
And lastly, compliance and security - The information in our logs can be used for compliance and auditing purposes so we need to make sure our mule apps log the required information at the time needed.

In the post When to Log in our Mule Apps, we’ll cover in detail this. We will see a great amount of situations in which it will be convenient to log information, from different points of view.

What?

Once that we know what we want to achieve with our logs and when we are going to log, the next question we need to answer is what - What information should we include in our log messages?

And again, the answer cannot be as much info as we can, because, as we mentioned earlier, that might make it harder and misleading for the person analyzing our logs.

There’s much more information that we can add to a log other than the message we include in the logger. Things like the timestamp, the name and version of our app or the correlation ID are sometimes more important than the message itself

In the post What Information Should We Log in our Mule Apps? we’ll see all of these aspects so that we can create a standard set of fields/attributes that we want to see in our logs. This, as mentioned above, will make our logs predictable and concrete, which is incredibly helpful for the Operator reading our logs.

Where?

If you made it to this point your Logging Strategy would be looking very good. But it’s not complete. The next step is to define where we are going to write this information and where we are going to store (and implicitly who will have access to that).

The location for our logs is very important. Not just for the location itself, inside or outside mulesoft, but also because our log destination should give us the ability to visualize properly this information. So, things like aggregation, filtering or a proper search engine would be something that we would have to look into for our mule logs.

If we deploy to Cloudhub, Mulesoft will provide us with a log console for each app with some search functionalities but depending on what your goals are that might not be enough. If you’re deploying to standalone runtimes or Runtime Fabric you definitely need to think of a proper repository for our logs

There will be also other aspects for you to decide the right logs repository like retention policies or storage limitations. We will see all of that in these posts:

How?

Last but not least, how to do that? And this is when, for us Mulesoft Architects and Developers, the fun begins. For many people this is the most challenging question. I disagree. If we’ve been able to answer the previous 4 questions we’ve got a very good understanding of what we want to do with our logging, the rest is just a technical matter. This question is about how to provide a technical solution, with the functionalities included in our systems, to the requirements defined.

For this one, we can’t really summarize how to do everything about logging in one post. But what we’ll do is to keep a list of all the How To’s articles in this post so that we get you covered in as many technical challenges as you might face.

Here’s the list of Articles related to Logging in Mule: