A hotfix is a quickly prepared, deployed and delivered software update consisting of a targeted fix for a specific bug or vulnerability. Hotfixes usually require minimal or no downtime of the updated system.
The history of the term “hotfix”
Ages ago, the word “patch” was used in engineering for patchboards, where patches referred to “temporary” connections (compared to properly wired ones).
Later on, when punched cards were used to program computers around the 1950s, when a hole was punched by mistake, a simple tape was used to cover the undesired hole, and this piece of tape was called a “patch.” The “temporary” nature of such a fix remained.
As computing progressed beyond the use of punched cards, the meaning of the word “patch” as a temporary, targeted fix for a specific bug or even a vulnerability persisted:
1. n. A temporary addition to a piece of code, usually as a quick-and-dirty remedy to an existing bug or misfeature. A patch may or may not work, and may or may not eventually be incorporated permanently into the program.
2. v. To insert a patch into a piece of code.
With time, software grew more complex, and patches gradually evolved into what were essentially regular updates. Microsoft played a significant role in this change, as they became known for regularly releasing patches for Windows and the Microsoft Office suite. Users didn’t need to redownload and reinstall Windows or Office software; instead, the OS would automatically download an update package and install patches as soon as they were released and tested. These patches were usually well-tested and soon lost the “temporary” and “quick-and-dirty” fixes notion.
As the meaning of the word “patch” became less distinct, the term “hotfix” emerged, carrying the original sense of the word patch — a quick fix for a vulnerability or defect.
I believe the term “hot” refers to the fact that the application is still running (the computer is “hot” from the load), and the fix is applied with minimal or no downtime.
Hotfix vs coldfix vs bugfix
As defined above, hotfix is an urgent or critical fix for a software bug or security vulnerability that is applied quickly, often while the system is still running. Hotfixes are usually applied when the risk of the defect remaining in the system is higher than the risk that a quick-and-dirty hotfix can introduce.
A good example of a hotfix would be a quickly released update to fix the recent Crowdstrike incident: when the computer stalled, the company should have quickly updated their systems to restore the functionality. However, in this particular case the update itself caused the damage since it didn’t go through proper software testing.
A coldfix refers to fixes that are applied when the system is not actively running. These typically require the system to be stopped or rebooted, often during scheduled maintenance windows. The term is used to emphasize that the fix is applied in a controlled environment with no urgency to keep the system running.
We might use a coldfix if we find out that a certain Nginx binary module has a bug, and we need to update it. We have to stop the Nginx server, recompile the module, and then start Nginx back again. This update procedure will usually imply certain downtime. Coldfixes are usually tested more thoroughly than hotfixes.
A bugfix is a general term for a software update correcting any bug. The urgency can vary, with some bugfixes being critical and needing immediate attention, while others can be scheduled for future updates. Bugfixes can be implemented through regular updates, hotfixes, or coldfixes, depending on the severity and impact of the bug.
How to apply a hotfix
All systems are different, so the exact mechanics of applying a hotfix will vary greatly. However, certain steps are more or less universal.
First, you need to identify the issue, whether it’s a security vulnerability, a critical bug, or a system malfunction. Assess the severity of the issue to ensure that applying a hotfix is the best approach rather than waiting for the next regular update. Usually hotfixes are introduced when the risk of the defect or vulnerability is so severe that the proper cycle of development and testing isn’t an option.
Second, debug the problem and develop a quick solution to address this specific issue. The fix should be as targeted as possible to avoid introducing new issues.
Before deployment, test the hotfix in a staging or test environment that closely mirrors the production environment. This testing should focus on ensuring the fix resolves the issue without causing additional problems, although extensive testing may be limited due to the urgency.
Before applying the hotfix, back up the current system state, including configurations, databases, and other critical components. Communicate with relevant stakeholders, such as IT teams and end-users, about the impending hotfix, particularly if there’s a risk of minor disruption.
Then, deploy the hotfix in a way that minimizes downtime. If possible, apply the fix while the system is still running. For instance, update a configuration file or deploy a code change without stopping services. For systems with multiple servers, consider using a rolling deployment to apply the hotfix to one server at a time, reducing the overall impact.
After applying the hotfix, monitor the system closely for any unexpected behavior or issues. Check logs and alerts to ensure that the hotfix has been applied successfully and that the issue has been resolved.
When you’re certain the hotfix is working fine, document the hotfix details, including what was changed, why it was necessary, and any potential side effects. This documentation will assist in future troubleshooting and ensure the fix can be properly integrated into the main codebase later.
Upon completing the documentation, investigate the potential reasons for the defect and develop a proper permanent solution.
Benefits of hotfixes
Hotfixes as a measure allow you to quickly address critical issues and defects while minimizing downtime. The one and only benefit of a hotfix is reducing harm and damage from a found defect or vulnerability in your product. While the human factor is unremovable from development and there’s always a chance of a mistake, the QA and Information Security bodies of knowledge are well developed and provide multiple ways to assure quality and provide security.
Drawbacks of hotfixes
Hotfixes are firefighting. When a house catches fire, you pour the water until it stops, reducing the risk of the whole house burning down. However, water also introduces damage.
Hotfixes are urgent by nature. When in a rush to fix something, there’s always a higher risk of introducing other defects and vulnerabilities. Also, any urgent fix introduces additional complexity to the system since there’s not enough time for proper technical design and testing.
If your product is on fire all the time, find and fire the arsonists and employ TQM.
When to deploy a hotfix
First, it’s essential to assess the severity of the issue at hand. Critical issues, such as those affecting core functionality, causing significant disruptions, or introducing security vulnerabilities, often warrant a hotfix. For example, if a bug is causing system downtime, leading to data loss, or exposing the system to potential exploits, immediate action is necessary to mitigate these risks. In such cases, waiting for the next scheduled release could result in greater damage, more extensive downtime, or compromised security, making a hotfix the prudent choice.
The impact on users is another crucial factor to consider. If the bug is causing widespread problems that prevent users from accessing key features or performing essential tasks, the user experience is being significantly degraded. This can lead to frustration, loss of trust, and potential harm to the organization’s reputation. In these situations, a hotfix can quickly restore functionality and maintain user satisfaction. On the other hand, if the issue is minor, affecting only a small subset of users or causing minimal inconvenience, it might be more reasonable to address it in the next regular release rather than rushing a hotfix.
The decision also depends on the complexity and risk associated with deploying a hotfix. Hotfixes, by their nature, are developed and deployed rapidly, which can sometimes lead to insufficient testing. This introduces the risk of unintended side effects or new issues being introduced into the system. Therefore, it’s important to weigh the urgency of the fix against the potential risks of deploying it quickly. In cases where the issue is severe and the risks of not fixing it immediately outweigh the risks of a quick deployment, a hotfix is justified. However, if the issue is not critical, and there’s a significant risk that a rushed hotfix could introduce new problems, it might be safer to include the fix in the next scheduled release.
Hotfixes are one of many tools in your toolbox
The decision to deploy a hotfix should be made based on the criticality of the issue, the impact on users, and the potential risks involved — it should not be the first tool you reach for when something goes wrong.
For severe issues that could cause significant harm or disruption, a hotfix is often the best course of action. For less critical problems, it may be more appropriate to wait for the next release, ensuring that the fix is thoroughly tested and integrated into the broader development cycle.
