Sentry is an application monitoring tool that surfaces errors and performance problems. It minimizes the need to manually look at logs or dashboards by identifying common problems across applications and frameworks.

David Cramer is the co-founder and CTO of Sentry.

This episode originally aired on Software Engineering Radio.

Topics covered:

• What's Sentry?


• Treating performance problems as errors


• Why you might no need logs


• Identifying common problems in applications and frameworks


• Issues with Open Telemetry data


• Why front-end applications are difficult to instrument


• The evolution of Sentry's architecture


• Switching from a permissive license to the Business Source License

Related Links

• Sentry


• David's Blog


• Sentry 9.1 and Upcoming Changes


• Re-Licensing Sentry

Transcript

You can help edit this transcript on GitHub.

[00:00:00 ] Jeremy: Today I'm talking to David Kramer. He's the founder and CTO of Sentry. David, welcome to Software Engineering Radio.

[00:00:08 ] David: Thanks for having me. Excited for today's conversation.

What's Sentry?

[00:00:11 ] Jeremy: I think the first thing we could start with is defining what Sentry is. I know some people refer to it as an error tracker. Some people have referred to it as, an application performance monitoring tool. I wonder if you could kind of describe in, in your words what it is.

[00:00:30 ] David: You know, as somebody who doesn't work in marketing, I just tell it how it is. So Sentry started out doing error monitoring, which. You know, dependent on who you talk to, you might just think of as logging, right? Like that's the honest truth. It is just logging just a different shape or form. these days it's hard to not classify us as just an APM tool that's like the industry that exists.

It's like the tools people understand. So I would just say it's an APM tool, right? We do a bunch of things within that space, and maybe it's not, you know, item for item the same as say a product like New Relic. but a lot of the overlap's there, so it's like errors performance, which is like latency and sort of throughput.

And then we have some stuff that just goes a little bit deeper within that. The, the one thing i would say that is different for us versus a lot of these tools is we actually only do application monitoring. So we don't do any since like systems or infrastructure monitoring. Meaning Sentry is not gonna tell you when you need to replace a hard drive or even that you need new hard, like more disk space or something like that because it's just, it's a domain that we don't think is relevant for sort of our customers and product.

Application Performance Monitoring is about finding crashes and performance problems that users would associate with bugs

[00:01:31 ] Jeremy: For people who aren't familiar with the term application performance monitoring, what is that compared to just error tracking?

[00:01:41 ] David: The way I always reason about it, this is what I tell new hires and what I would tell, like my mother, if I had to explain what I do, is like, you load Uber and it crashes. We all know that's bad, right? That's error monitoring. We capture the crash report, we send it to developers. You load Uber and it's a 30 second spinner, like a loading indicator as a customer.

Same outcome for me. I assume the app is broken, right? So we also know that's bad. Um, but that's different than a crash. Okay. Sentry captures that same thing and send it to developers. lastly the third example we use, which is a little bit more. I think, untraditional, but a non-traditional rather, uh, you load the Uber app and it's like a blank screen or there's no button to submit, like log in or something like this.

So it's kind of like a, it's broken, but it maybe isn't erroring and it's not like a slow thing. Right. Same outcome. It's probably a bug of some sorts. Like it's what an end user would describe it as a bug. So for me, APM just translates to there are bugs, user perceived bugs in your application and we're able to monitor and, and help the software teams sort of prioritize and resolve those, those concerns.

[00:02:42 ] Jeremy: Earlier you were talking about actual crashes, and then your second case is, may be more of if the app is running slowly, then that's not necessarily a crash, but it's still something that an APM would monitor.

[00:02:57 ] David: Yeah. Yeah. And I, I think to be fair, APM, historically, it's not a very meaningful term. Like I as a, when I was more of just an individual contributor, I would associate APM to, like, there's a dashboard that will tell me what's slow in my application, which it does. And that is kind of core to APM, but it would also, none of the traditional tools, pre sentry would actually tell you why it's broken, like when there's an error, a crash.

It was like most of those tools were kind of useless. And I don't know, I do actually know, but I'm gonna pretend I don't know about most people and just say for myself. But most of the time my problems are errors. They are not like it's fast or slow, you know? and so we just think of it as like it's a holistic thing to say, when I've changed the application and something's broken, or it's a bug, you know, what is that bug?

How do we help people fix it? And that comes from a lot of different, like data signals and things like that. the end result is still the same. You either are gonna fix it or it's not important and you ignore it. I don't know. So it's a pretty straightforward, premise for us. But again, most companies in the space, like the traditional company is when you grow a big company, what happens is like you build one thing and then you build lots of check boxes to sell more things.

And so I think a lot of the APM vendors, like they've created a lot of different products. Like RUM is a good example of another acronym that lives with an APM. And I would tell you RUM is completely meaningless. It, it stands for real user monitoring. And so I'm like, well, what's not real about monitoring the application?

Well, nothing's not real, but like they created a new category because that's how marketing engines work. And that new category is more like analytics than it is like application telemetry. And it's only because they couldn't collect the app, the application telemetry at the time. And so there's just a lot of fluff, i would say.

But at the end of the day too, like developers or engineering teams, it's like new version of the application. You broke something, let's tell you about it so you can fix it.

You might not need logging or performance monitoring

[00:04:40 ] Jeremy: And, and so earlier you were saying how this is a kind of logging, but there's also other companies, other products that are considered like logging infrastructure. Like I, I would think of companies like Paper Trail or Log Tail. So what space does Sentry fill that's that's different than that kind of logging?

[00:05:03 ] David: Um, so the way I always think about it, and this is both personally true, and what I advise other folks is when you're building something new, when you start from zero, right, you can often take Sentry put it in, and that's good enough. You don't even need performance monitoring. You just need like errors, right?

Like you're just causing bugs all the time. And you could do that with logging, but like the delta between air monitoring and logging is night and day. From a user experience, like error monitoring for us, or what we built at the very least, aggregates the errors. It, it helps you understand the frequency. It helps you when they're new versus old.

it really gives you a lot of detail where logs don't, and so you don't need logging often. And I will tell you today at Sentry. Engineers do not use logs for the most part. Uh, I had a debate with one of our, our team members about it, like, why does he use logs recently? But you should not need them because logs serve a different purpose.

Like if you have traces which tell you like, like fast and slow in a bunch of other network data and you have this sort of crash report collection or error monitoring thing, logs become like a compliance or an audit trail or like a security forensics, tool, and there's just not a lot of value that you would get out of them otherwise, like once in a while, maybe there's like some weird obscure use case, but generally speaking, you can just pretend that you don't need logs most days.

Um, and to me that's like an evolution of the industry. And so when, when Sentry is getting started, most people were still logs. And if you go talk to SRE teams, they're like, oh, login is what we know. Some of that's changed a little bit, but. But at the end of the day, they should only be needed for more complicated audit trails because they're just not a good solution to the problem.

It's just free form data. Structured or not, doesn't really matter. It's not aggregated. It's not something that you can really use. And it's why whenever you see logging tools, um, not even the papertrails of the world, but the bigger ones like Splunk or Caban