Observability - a devtools discussion with Charity Majors (Honeycomb). Episode 3 (Season 2) of the Console Devtools Podcast.
In this episode we speak to Charity Majors, CTO at Honeycomb, an observability tool for distributed systems. We discuss why observability is based around events and not metrics, how developers should think about achieving appropriately observable systems, why Honeycomb implemented their own distributed columnar data store, and how you can delete most of your alerts by implementing service level objectives.
- High cardinality
- AWS Lambda
- Appropriate observability
- Akita Software
- Honeycomb blog
About Charity Majors
Charity Majors is an ops engineer and accidental startup founder at honeycomb.io. Prior to this she worked at Parse, Facebook, and Linden Labs. She is the co-author of O'Reilly's Database Reliability Engineering.
David: Welcome to the Console podcast. I'm David Mytton, co-founder of console.dev, a free weekly newsletter highlighting the best and most interesting tools for developers.
In this episode, I speak with Charity Majors, CTO at Honeycomb, an observability tool for distributed systems. We discuss why observability is based around events and not metrics, how developers should think about achieving appropriately observable systems, why Honeycomb implemented their own distributed column data store, and how you can delete most of your alerts by implementing service level objectives. We're keeping this to 30 minutes, so let's get started.
I'm here with Charity Majors. Charity, thanks for joining the Console podcast.
Charity: Yeah, thanks for having me. We go way back now, don't we David?
David: That's right. I go all the way back to the early days of MongoDB. A long time.
David: Yeah. Yeah.
Charity: Almost a decade? Holy crap.
David: I know. All those conferences, touring the world with Mongo.
Charity: Yeah. We were their favorite non hired [inaudible 00:01:06] folks there for a while I think.
David: The outsource marketing team.
David: Well, let's start with a brief background then. Tell us a little bit about what you are currently doing and how you got here.
Charity: Well, I'm the co-founder and CTO of honeycomb.io, which is, I would say the world first actual observability tool or platform. We got here because, as you were just saying, Parse early Mongo days and everything. Parse was mobile backend as a service. We were doing a lot of things before its time. We were doing microservices before there was really a term for it. We were doing a lot of platform things that the existing set of tools just really didn't work for, well, all the aggregates and everything. When you've got a million users and a different app hits the iTunes top 10 every week, you can't really predict and make dashboards, and just use that to explain what's going on in your system.
So Parse got acquired by Facebook and it was professionally embarrassing to me how often we were going down. It was just every day we'd go down and I could go on and on about that, but TLDR, we started using this one tool at Facebook called Scuba, which was this butt ugly, aggressively hostile to users tool, but it let you do one thing and one thing only very well, which was slice and dice on high cardinal dimensions and basically in real time, and not only that, but at high dimensionality as well, because you can do that as many times as you wanted, you can slice and dice by... You could see a spike of errors, then you could go "what is it?" Well slice and dice and figure out that, oh, all of these errors are coming from this version of iOS, right? This version of the build running, this language pack in this region, using these queries, it was infinite how many you could string together on the fly.
This was just world changing for us, because the amount of time it took us to identify and solve these really complex problems dropped like a rock, from hours, days to seconds, not even minutes. It wasn't even an engineering problem anymore, so much as a support problem, you could just click, click, click. Oh, there it is. Because it wasn't like with dashboards, you're very much jumping to the end of the story. You're like, oh, maybe it's this scenario, and then you're looking to validate, oh, maybe it's this scenario. Instead, with our workflow, with Scuba, was you were following the trail of breadcrumbs. You didn't have to know where you were going to end up in order to debug it. So I was leaving Facebook after a couple years and planning to go be an engineering manager at Slack or Stripe or something.
That's when I kind of went, "oh, I don't know how engineer anymore, without these tools that we've been using and developing around". So Christina and I started Honeycomb, and for the first six months, we realized pretty quickly that we were going to have to write a storage engine from scratch, which is something I was spent my entire career telling people, never write a database, never write a database, but we had to. We had to start writing it from scratch, because we needed a column restore and we needed all these things that nothing an open source would address. Honestly, the hardest part wasn't the column restore. The hardest part was trying to figure out how to talk about it to people. We knew that what we were doing wasn't anything like monitoring, it wasn't going to be post talk. It wasn't going to be around dashboards.
We knew it was supposed to be interactive, almost were like running GDP against a network piece of software with anything on the market. And I think it was July. Like we started in January and in July is when I first Googled like what does observability mean? And I found the mechanical engineering definition for it. It's the mathematical do of controllability, observability is how understand the inner working of system, just by asking question from the outside, without any prior knowledge of where it's supposed to go. And I went like, oh my God, light bulbs are just like, ah, this is what we're trying to build. This is exactly what we're trying to do. Then about three years, just trying to evangelize that and trying to explain to people, everybody had been told that high cardinality was impossible, that they just, it just couldn't be done.
And they just accepted that. It is impossible when you start with metrics because the cost of them rises linearly with your cardinality. It's not impossible if you use these arbitrarily wide structured data blocks, which is, you know what, we were basing our [ bleeped 00:05:14] on. So it took about three years, I think for us to find product market fit, it was grueling. And honestly it was just as much the world changing to meet us as it was us changing our product to meet the world. But finally, it all clicked when we introduced these sort of auto instrumentation and the landing page where you would be met, not with an empty query browser, but with the traditional errors, latency, requests per second, people could orient themselves. So at this point, we're almost six years in. We really hit our stride around year four and a half, which is forever in VC years.
We went through a few different investors who are just like, "If you haven't succeeded yet, you're never going to succeed." And I'm like, "But we had to write a storage engine. You don't understand how long this takes." There are so many barriers to actually innovating in the infrastructure space that we finally got there. We finally have investors who believe in us and we finally are hitting all of our numbers and doing that growth curve, like a hockey stick. And what I will say is that as people have tried us, we have almost no churn. Almost nobody goes back because once it's clicked in your mind, you just write software so much faster and so much better. And it's so much clearer and it's so much more attractable. And one of our best sources of new customers is when an engineer leaves a company that was using Honeycomb and they to go to a new company and they have the exact same experience that I did, which is just like, "Holy, I don't know how to engineer without this anymore." And they bring us in.
David: Can you explain what you mean by high cardinality and what that means for focusing on events rather than metrics?
Charity: Yeah. High cardinality is, well, imagine you have a collection of a hundred million users and you've got all of these variables about them, like gender height, wait, first name, last name. Well anything like first name, last name is going to be very high cardinality. Anything that is a unique ID is going to be the highest possible cardinality, social security number. Anything that is a single value, like species equals human will be the lowest possible cardinality. And the thing about metrics is a metric is a single number with a few tags appended and metrics are really designed for efficiency and not for describe ability or correlation or anything like that. They're designed to be very efficient, but they only really handle low cardinality dimensions. They can be aggregated really easily on things like gender or species, but they cannot be aggregated on things like social security number or weight or height because there are just too many possible values.
And when you're using events instead, you have these arbitrarily wide structured data blocks. And when I say arbitrarily wide, like a well instrumented system using Honeycomb tends to have like 400 or 500 dimensions. So that's 400, 500 key value pairs per request that come in. And the beauty of that is that any one of those can be high cardinality. All of them can be high cardinality. None of them can be, you can have a tag equals everything from operating system to tag equals the build ID, tag equals height, weight, whatever. It really doesn't matter. And using the column store like Honeycomb has, you can then just slice and dice and perform these queries really fast. This is the other thing people get hooked on is that it's like make the change and it's there. There's none of this lag.
When you're using metrics and aggregates, there's always a window which the window has to close so it can aggregate the values. And just traditionally, when I was using Datadog, I'd be like four or five minutes until I get my change back. What the hell is this? That's an eternity in SRE years. But with Honeycomb, we actually have an end to end check that will go off and page someone, if it's been more than 10 seconds from when the record was written when you can read it back because it needs to be that fast. And your ability to ask these questions needs to be that fast because you need to be in a state of flow. You can't have to compose a query and then go to the bathroom or get your coffee before it, that's not debugging. That's like doing BI stuff. The whole point of observability is that you should be able to iterate swiftly, like is it this? Is it this? That is it that? And just like follow the path.
David: So take us through the decision to build your own data store then because if we go back to, when we first met, there were a few options for data stores. MongoDB was the brand new shiny one and there were SQL databases, relational databases. And there are a few new ideas coming around with Cassandra. But today, if you just look at like AWS's database tab on their website, they've got a lot of products there. So how have things evolved?
Charity: We would still need to write our own, sadly. We did a lot of investigation at the time and, and we tried out a bunch of things. And honestly the one data storage type that we came closest to using was called Druid. I don't know if you're familiar with Druid IO, but Druid, it's a high performance database that was basically developed for some marketing stuff it's associated with. I don't remember what the name of the company is, but it had a lot of the things that we wanted, like the capacity to ingest any type of data, whether it's strings or numbers or whatever. The one thing that it didn't do, we estimated we would've had to rewrite about a third of the database just to get what we wanted, any ingest layer, which was arbitrarily wide.
Charity: You can't have to deal schema if you're dealing with observability, anything that is schema based is verboten, because you need to be able to toss in a new key value pair whenever it comes up and you need to be able to stop writing that. It has to have that flexibility and that fluidity in order for you to have the value of observability and most databases don't like that. Most databases for good reasons, for efficiency and for all this stuff, they want you to define schema. MongoDB famously is one that doesn't make you, you can do some fancy tricks with Postgres. Postgres has now JSON block store and everything. But in the end, having the ability to do completely flexible schema was huge for us. And we also knew that having a column or database was key.
Charity: For those who don't know having column or database is basically like the opposite of an RDBMS. Everything is an index. Everything that you put in there is an index. And then the way we developed it, based on this [Scuba White Paper 00:11:27] was in a widely distributed fashion where, well we use [Kafka 00:11:31] , the events come in through the API, they get dropped into Kafka. And then we have a pair of retriever data stores reading each topic from Kafka. Each topic translates into a column. You can distribute any user's traffic widely over many columns, over many nodes. It's very flexible. We've got, I don't know, a couple hundred data store notes at this point. Each have a pair for fail. But it's just really flexible and elastic the changes that we needed to make. And we actually age out the data to S3 after just a couple hours too.
Charity: And our query planner, this is funny. Our query planner runs mostly in serverless queries, Lambda, AWS queries. We move the query planner to AWS. We thought that it would slow the whole thing down, turns out it didn't, the performance footprint is different, but not slower on the whole. At the end of the day, having that ability of control over also how many databases will take the trade off of fast and close to right is better than done and perfect?
Charity: For databases, that's not a good story to tell, but for ours it is because it matters way more for people to be able to get their results very quickly. And if it's off, by 0.5%, once in a while, doesn't matter so much as it getting to them very swiftly. We're actually working on a blog post right now. The title is like, "10 reasons why you really don't want us to open store our data store." And it basically just comes down to all these reasons. It's narrowly optimized for observability use cases and for our use cases. And it would be pathologically difficult for most people to run because it's not just like spin up a node. It's at the level of complexity of you remember anything that had to use Zookeeper back in the day, it's like, okay, now I've got five problems.
David: Right. So it's optimized for those really high performance queries in a very short time window where you're debugging something happening. And then the S3 latency is acceptable for the longer queries?
Charity: Actually our 99th percentile latency is still under a second. S3 is faster than you'd expect when you're fanning it out widely enough. Not if you're running a query over 60 days worth, then it might take a few seconds, but it's pretty fast. I mean, aging out is key too, but also just the ability to distribute it horizontally. Because you're basically going to be doing a full table scan across all of the indexes that you're trying to pull from having the ability to write out columns that are very wide strings and index on those and do groupings with all the other SQL operators and stuff. There's just a lot of stuff that nobody in their right mind would write a database to handle.
David: And how does cost come into the equation? Because that was always the big issue with trying to get really good before from queries is just the cost of memory or some specialized database that you might buy as a service. How have you thought about that?
Yeah, that's a great question because I think that observability, the reason it came around when it did apart from us being there, it is like any scientific invention when the time comes, someone able to figure it out. The converging reasons that this was the time for observability I think is because the cheapness of hardware like SSDs are now, at Facebook, they were in all the [Bleeped 00:14:44] Ram, they had these giant Ram discs that they would... And nobody's going to pay for that, but now we can put it on SSDs and then age it out to S3 pretty quickly, given that like over 90% of all queries are for within the last day or two. So we run that on SSDs that are local run the rest in S3, you can handle some stuff visually to be like, okay, here's the fast results waiting a couple seconds to you load the S3 results. People are really happy with that.
So I think that the emergence of really fast commodity hardware and coupled with the rise of microservices, because when what you had was the web tier, the application, the database, all the complexity was basically bound. 90% of it was bound up in the app and the rest of it was bound up in the database. And there wasn't really, if alls failed, you could attach DBD and step through it or you could do a bunch of fancy, MySQL stuff, whatever.
But the hardest problem with modern systems is not so much debugging your code. It's where the [bleeped 00:15:41] in the system is the code that I need to debug when you bought hundreds of services? Everything is a high cardinality field now. The number of servers, the containers that you have, the number of queries you run, the number of just everything. And so much of modern stacks may not even run on your own hardware. It might be a third party thing. It might be Lambda jobs. Anything that you could instrument for yourself though, should be able to be collected and in one place that you can tell just that at a glance where the problem is coming from.
David: Where do you see the role of some of the more specialist time series databases becoming quite popular now, particularly open source databases? Are those still relevant? Could developers just run their own?
Charity: People could get a lot out of metrics. It's a 30 year old technology. We have gotten used to contorting ourselves in all sorts of ways and it's the thing that people are familiar with. At the end of the day, I wouldn't actually call anything that's built on time series database observability that I've seen. It just doesn't measure up to the level of... Which is so unfortunate that people have co-opted the term observability for anything that you're doing, "Oh, we have metrics, logs and traces. Therefore we have..." In my mind, if you have to hop from tool to tool to tool to answer the question, that's definitely not observability, but I have no match for hundreds of millions of dollars in marketing spent. So we are where we are. But I will say that the engineers who experience the difference, understand it and won't go back.
Charity: There's always going to be use cases for time series databases, they're so good at aggregating stuff. They're so good at doing things cheaply and at Honeycomb, we just added a metrics capability, both so that people can get more easily onboarded and because there are a few metrics that are worth paying attention to. In my mind, most of the metrics stuff should be infrastructure because it's stuff that you're interested in asking the, for the perspective of your service or the perspective of your hardware. You're asking, am I good? Am I safe? Am I running as expected? Metrics work really great for that because that's how you aggregate. For observability, it's really centered around how is my user's experience? How is each and every one of my users experience today, being able to slice and dice by that high cardinal dimension, which is your user ID and just ask, how is the application behaving for them?
Charity: There's non overlapping or minimally overlapping [inaudible 00:18:05] where if you run a lot of infrastructure, absolutely need lots of time series databases. If you mostly run your own software, this is the stuff that's your bread and butter that you ship every day, you mostly need observability. But you still probably want to answer the question, if I just shipped some code, did my memory usage triple or did the CPU usage spike or did my data usage explode? Other than those three questions, it's not clear to me that you need much more of that from your infrastructure layer. I think honestly, that thinking about instrumentation, the way the serverless kids do is the right paradigm moving forward. You don't have access to a lot of the low level infrastructure stuff, but you ask the questions that you need to know in order to keep your users' experiences healthy. Maybe a container isn't performing well anymore. Just stop sending traffic to it, because that's someone else's problem. Your problem is keeping track of your user's experience.
David: And is this where the concept of appropriate observability comes in? What does that mean for granularity and developers having to instrument everything? Or is it just certain things?
Charity: I think the right way to instrument for observability is, like I said, by aggregating around the user's experience, which means like the way Honeycomb does it is the request enters a service. We open a new Honeycomb event. We pre-populate it with everything we know about it. The variables that we fed in via the request, anything about the AWS environment, anything about the language internals, all that stuff. While that request is executing, you as a developer could go, what might be useful to be in the future? Oh, user ID might be useful. Pop that one. Copy code ID might be useful, pop that one. Whatever you think might be useful to you in the future. And then as the request is ready to exit or error that gets shipped off in one arbitrarily wide structured data block. And what you basically end up with is one of these events per request per service, which is how you can tell at a glance where in your entire system the badness is coming from.
Charity: And because you have these wide events, you could correlate a [ 00:20:07] ton of information. You can go, "Oh, all of these errors have these 20 different variables in common," or stuff like that. Which is materially different from what you did with metrics, because if you wanted to be able to ask those questions, you had to predict them in advance. You had to go, "Ah, maybe someday we will get a bunch of errors that are coming from this iOS device, this version, this build ID." You have to predict and create a dashboard up front for it. And there's just an infinite number of things that can go wrong. That just doesn't work anymore.
**David:**Does that mean you are storing all of the raw data all of the time or does sampling come in?
Charity: Well, that's a client side decision. We don't make that decision for you. Our client side libraries support dynamic sampling, because I mean like at the end of the day, if you want your health check request to have the same level of importance as your errors to slash payments, that's up to you. Many people don't, but that's up to you, but we store it all. We give everybody, even our free tier, 60 days worth of storage because storage is cheap now it really me off the way. So many companies are still charging on storage like that's what's costly for them. That's not costly at all. What's costly is the engineering effort to make a great user experience.
David: That makes sense. So in terms of the next step, once all the data's in there, I suppose there's two route to using it. There's something's gone wrong and you need to access the data, you are running some kind of query, but then the step before that is knowing that something has gone wrong and that's alerting. And the typical problem is too many alerts, alert fatigue. How do you think about that?
Charity: Oh, I'm so glad you asked. What we see is that when people adopt SLOs, they get to delete like 90% of their paging alerts. You want to align your alerts with your customers actually being in pain and you want to align them with as this alert is being burned down, is it so bad that you need to wake someone up in the middle of the night or is it not? So you get to optimize for engineering happiness. Besides that though, I really think that observability demands a different of interacting with your data than monitoring does. Monitoring is all about, you should never have to look at your dashboards. It will alert you. It will tell you when it's time to look at it. Otherwise you don't have to look at them at all.
With observability, I think it's about being a constant kind of conversation with your code in production, as you're writing and shipping code. Hopefully you have very short feedback loop between the time when you write the code and when it's live in production, that's what makes this magical. If it's 15 minutes or less, you're writing it and instrumenting it with an eye to your future self. How will I know if this is good code or not? How will I understand if this is working or not, then you merge it to main in a few minutes, it's live. And then you go look at it and you ask, is it doing what I expected it to do? Does anything else look weird?
Most bugs that we write will never actually rise to the level of paging us. They shouldn't. In distributed systems, your system is comprised of so many bugs right now. The joy is not making it so there are no bugs it's making so that it's resilient from lots of bugs, but you should have a habit of just going and looking at it and seeing if it's doing what you expect it to do.
This is how you build your intuition, the intuition that any senior engineer should have, just the gut feeling of what is happening. Does it feel right? I think of instrumentation as being commenting, but for real, because you include the state of production in your actual commenting. So you're asking the system, is it doing what I expected it to do? And getting yourself into that feedback loop and learning to go to go look at the system and explore the system and follow the...
I feel like so often we put new engineers on call and they'll see red on the screen. They're like, "Ah, something's wrong." And we're like, "Oh grasshopper, so many things are wrong. Don't waste your time trying to figure out what it is." But with observability, I feel like you can often follow that trail and figure out pretty quickly what it is and if it matters and you can fix the thing. We became engineers because we love solving problems. And once you hook up that joy and that feedback loop, that dopamine hit of being able to answer the questions and figure out what's happening and fix the problems and make your system much more tractable and comprehensible, over time that leads to a much better systems. And it leads to a culture where people aren't afraid of production and at least to a culture where people want to see what's happening. They're not afraid to see what's happening. And that I think is the ultimate goal.
David: And this plays into the idea that developers should be responsible for the code that they write. Once it goes into production, it's not just throwing it over to another team, right?
It's inevitable. I mean, our systems are becoming so complex that you can't run them like black boxes. I come from ops. I think this is wonderful for ops people and SREs. I know that this is can sound a little scary and we can be a little resistant to change. And I know that our scars come from a good place. We've been scarred. We've seen engineers do terrible things, but it's not that we want to invite software engineers into our tendencies for masochism. That's not the goal here. The goal is to make it actually better for all of us. And honestly, systems are getting to the point where the only people who have any hope of debugging them quickly are the people who wrote them. So our jobs as ops people are much more to create guardrails, to make it safe for engineers to be in production, to bring observability to the team, to train them on how to have that virtuous feedback loop, where you're looking at it to take their hands and lead them to the water, so to speak because it doesn't work any other way.
David: Great. Well, before we wrap up, I have two lightning questions for you. So first is, are there any interesting dev tools that you're playing around with at the moment?
Charity: Yeah. I've been looking at [Akeda 00:25:50] and some other of the streaming software stuff. I'm not quite sure how it fits into the future yet, but there's something there. I'm afraid that it's going to be like the way tracing was for too long and still kind of is where it's off putting and complicated and only the top 5% of elite engineers ever interact with it. That's the bad view, but I'm trying to figure out how it could be better than that. And [Liz Fong-Jones 00:26:14] and I have been talking about, maybe this is actually the answer to auto instrumentation. If we can be generating source graphs and providing a glimpse into here's where your code is actually failing. I don't know. We'll see.
David: And then the second question is what your current tech setup, what hardware and software are using on a daily basis?
Charity: MacBook Pro, Chrome and Quip, sadly. I still use VIM for all of my to-do lists and stuff, but it's been a long time since I've actually gotten a log-in or do anything useful.
David: Excellent. Well, that's all we've got time for today. Unfortunately. Where can people find you online?
Charity: My personal site is charity.wtf. Honeycomb blog is honeycomb.io/blog, and I'm occasionally on Twitter at Nipseytipsy.
David: Excellent. Well, thanks joining the Console podcast.
Charity: Thanks for having me, super fun.
David: Thanks for listening to the Console Dev Tools podcast. Please let us know what you think on Twitter. I'm at David Mytton, and you can follow @consoledotdev. Don't forget to subscribe and rate us in your podcast player. And if you are playing around with or building any interesting dev tools, please get in touch. Our email's in this show notes. See you next time.
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