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InfoQ Homepage Presentations Istio as a Platform for Running Microservices

Istio as a Platform for Running Microservices



Eitan Suez explores Istio's design and how it just might be a foundation for running microservices.


Eitan Suez is a content engineer and technical "explainer" at Tetrate, where he develops technical content and breaks down technical topics for audiences large and small. Prior to doing technical education, Eitan held the role of Principal Consultant at ThoughtWorks. Eitan's first open-source project dates back to 2002 when he developed a database-backed Java API documentation system.

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Suez: The title of my talk is Istio as a platform for running microservices. In the abstract for this talk, you might have noticed that I raise the following question that you see here on your screen, which is, for those organizations, for those of you who are working, either in the process of transitioning to microservices or have already transitioned to microservices, how do you deal with or address problems relating to service discovery and load balancing, and other concerns having to do with application resilience, keeping a secure system, making it observable, and dealing with issues relating to traffic management. Those are typically the types of issues that we come across in the context of transitioning to a microservice architecture.


Our agenda will be to begin by understanding the nature of the problem. It'll be a little bit of a journey, to try to understand the transition from monolith to microservice, understand the difficulties, and then explore how these difficulties are addressed, how they've been, perhaps, historically addressed. Then we transition to looking at Istio, an open source project, and understanding how it functions, its design and its architecture, in order to critically evaluate how suited it is as a foundation for running microservices or distributed applications in general.


My name is Eitan Suez. I work at a company called Tetrate. A relatively young company in the enterprise service mesh space. My role is with technical education and training. I've had the privilege in this role to spend time with this technology, with Istio and other related technologies, Envoy and so on, and really connect the dots. That's what inspired this talk.

From Monoliths to Microservice

I would like to begin by exploring the transition from monoliths to microservices. Specifically, what are the pressures or the forces that actually drive us in this direction? The assumption is that we're moving from an application that's running fine, that's been running fine for a long time where business has derived a great deal of value from. As our application becomes more important and more vital to the success of the business, things change, the application itself becomes more complex. We hire more developers, our team becomes larger, we might encounter contention with continuous integration.

Certain characteristics of our system become vital and more important than they were before, specifically high availability, uptime. The lack of availability could cost the business a lot of money. What we discover is a monolithic architecture perhaps doesn't lend itself as well, to those new criteria or more important criteria. We have issues with deployment coupling, the idea that there may be multiple features that are coupled together, you cannot release one independently of others. Teams have less control with respect to releasing and monitoring their systems. There's a central team that's in charge of releases. Releases happen less often than desired. Those lead to more risk, the risk of something going down, a risk of our system not being as available. We're pressured to move in a direction to solve these problems. That's essentially breaking our application up into a microservice architecture.


What I'd like to do is go through a very simple illustration to try to better understand the differences in these environments by going through a very simple or fictitious or maybe a common scenario that we typically interact with in the course of working with a system. Imagine an incoming request. The system is designed in such a way that the handler function inside our monolithic application is receiving this incoming request and perhaps a lot of the business logic is delegated to a particular service. We have a call to a service, and that service might have a number of delegates or it enlists the help of other services to get specific sub-tasks done. We may be calling some service that may be turning around and itself make maybe a call over the network to an external service and subsequently calling another service. That's a typical flow. What we can say about the environment in which this logic execute is that with a monolith, all this happens inside of a process. This is a very well-known very comfortable environment. This is the type of environment that you typically expect to be running your business logic in. The other thing that we can say is, these actors inside of this logic may be Spring Beans, if this were a Spring application. They may be just plain objects, or they could just be pure functions. Then the main point here that I want to make is the way in which these functions or actors communicate with one another is by making function calls. Function calls are a very simple, well understood, very fast type of thing that we don't really give much thought to, in the context of a monolith.

Distributed Application

Enter a distributed application. This is not necessarily so, of course, because we have different concerns. Let's just assume that the flow is more or less laid out in a similar fashion. An incoming request comes in and is handled by an ingress controller, which routes the request to a particular service, which handles that request, and again, enlists the help of a couple of other services, same exact business logic. Even though the picture is the same, I think I flipped some of the colors here, just to make it look a little bit different, but it's exactly the same picture, is an implied understanding that each of these boxes is now an independent deployable. Each may be running and deployed independently on different VMs, maybe in our data center on-prem, or they could be running in the cloud. They could be running in Kubernetes. If so, then maybe each one is deployed using a Kubernetes deployment, and so we've got pods, essentially, which represent our workloads. These, what used to be function calls are now network calls away.

Before we begin to investigate how this new environment affects and creates a new set of problems, let's pause for a minute, and think of the benefits of what we've gained in the process of transitioning maybe by using the Strangler pattern, and other mechanisms to transition from our monolith to extract logic out into separate deployables that can be run as a distributed application. If we think of all of the pressures that we've had, we may get to a point where we now have smaller teams that each work on smaller code bases and separate code bases. That means it allows us to parallelize workstreams better. Our velocity comes back up. We eliminate the contention we used to have with continuous integration. We have more flexibility, we can become a polyglot. We have the freedom to choose different tools and languages for different tasks. We can eliminate the deployment coupling, eliminate risks, increase high availability. We can deploy each of these services independently of one another. In general, we've moved to perhaps a better place. That's the good part of the story.

Fallacies of Distributed Computing

Of course, this is a warning that is almost 30 years old in a publication from Sun Microsystems by Peter Deutsch and others, James Gosling, the fallacies of distributed computing. You move to a distributed computing environment, and we typically make the mistake of overlooking the fact that a network call is not a function call. The network is not always reliable, those calls may sometimes fail. Latency is not zero, it's orders of magnitude more than a typical function call. We have to be very mindful of that, otherwise, we're going to run into a variety of problems. I'd like to call out a couple more here. One is topology is very dynamic these days, when we autoscale services in environments and maybe deploy things or have failover, multiple data centers or what have you. The network is secure is another fallacy. Things to be mindful, and these lessons typically if we heed them, will serve us well.

The Problems

Let us then move on and speak about the very specific problems that you typically encounter in the course of running a distributed system. As I go through each concern one by one, what I want you to do is to vet the concern, not only with respect to distributed applications, but ask yourself, why is this not a problem with a monolith? Or, how is this problem solved in the context of a monolith as well? The first and perhaps most evident, most fundamental problem is the problem of service discovery. You've got multiple services deployed in some environment, service A may need to collaborate with service B and C, it needs to know where instances of service B and C are located. There's a need for a service registry. It's interesting to think about in the monolith scenario, typically objects have references to other objects. Maybe we have a dependency injection framework that does all this for us, so we take that for granted. That's built in. We have to rebuild similar capabilities in our new environment. That's essentially what we've been busy doing over the last decade or so, or maybe longer. We're now running at cloud scale. We may have 100 instances of service B, or 100 replicas. We scale out horizontally, and that gives us a great deal of flexibility, but with that flexibility, also the added burden of clients needing to load balance requests to those target workloads. What typically starts to happen is we add logic or library dependency, I like to call this maybe a barnacle of code that becomes encrusted in service A, that is necessary. It's not related at all to the business logic, but it is necessary in order to function in this environment in which we basically know that we need to load balance requests to services that we rely on.

What happens when we have failures? What if one of these endpoints is not healthy? That's basically the fallacy that we were talking about, about the network not always being reliable, so some requests will fail and so now we need to build in perhaps, retry mechanisms, a little bit more code inside our clients to deal with that possibility. Again, in the monolith, we did not have that problem, because we were not using the network as a mechanism for messaging because everything was, of course, in process. The matter of resilience. There are multiple concerns here. Here I depict the prototypical situation or scenario that was made popular by the Hystrix project, the idea of a cascading failure that when you have latency in the network, that latency could tie up resources, it could tie up connections in the connection pool. What happens when a service is slow? It may actually have downstream impacts, and may bring the caller down in a cascading failure scenario, especially in the face of lots of downstream requests coming into the service. There are other situations. The lesson that we've learned is this idea of failing fast, of having timeouts can really go a long way to resolving some of these issues that manifest themselves in the context of distributed systems.

The next problem is one that, again, is absent in the monolith, the idea that when we break two pieces of logic, and they're now separated, and one calls the other over the network. There's the matter of identity. What I talk about here is not the identity of the end user, but rather the identity of the workload. How does service B know that service A is calling it? How can it trust that it's really service A? There's a new concern here that pertains to security, which is a very important one, and increasingly being mandated by regulation as well. On top of authentication is authorization. If we have the identity of the caller, the calling service, are they allowed to call us? Do we embed those rules? Do we inject those configuration rules into every single service and add yet another layer, another dependency in our application to deal with this particular scenario? That's the matter here. Observability. Again, back in the monolith, we begin to appreciate a lot of the tooling and a lot of the design of things, the way that they allow us to diagnose issues. For example, the very simple call stack, a stack trace goes a long way to helping us understand and reason about what's actually happening inside the thread, the chain of calls, from object to object or function to function. Whereas, do we have something similar in the distributed world to see the chain of calls from service to service. That's essentially what distributed traces help us do in the microservices world.

Traffic management becomes a very important thing to support high availability, to support failover. Think about the ability to govern how traffic is routed, again in a manner that's orthogonal to the applications themselves. This supports zero downtime deployments, canary deployments, maybe rolling back after we've deployed a new version. There are other scenarios besides. The ability to really control and having the flexibility to control how we route a request from service A to service B, which particular subsets of a service we want to target, can help us a great deal. Here's the situation. The idea here is maybe we want to favor service A making calls to local instances of service B in the same availability zone, but be able to fail over to another AZ or another region in a situation where the local instance is not available. That's a potpourri of so many different concerns that are new problems that we need to tackle. Some of them already, to some extent, have solutions. That's what we turn our attention to next.

Netflix OSS and Spring Cloud

The problems that I just described are not new, they're typically encountered by every organization in the context of their transition to distributed services. A case in point is the story of Netflix, and the codification of a lot of their solutions, their open source solutions by the Spring engineering team. You can almost see almost a one-to-one mapping between the problems I just described and these particular solutions. Netflix in the course of moving to the public cloud and going to a microservice architecture had to develop, or they maybe didn't have to, but chose to develop their own service registry in the form of Eureka. Ribbon is an implementation of the client-side load balancer. Hystrix was designed to really help them with dealing with resiliency matters. Zuul was their dynamic frontend edge gateway that allowed them to really be able to dynamically control routing. Then, the other solutions in their respective spaces. They deal with observability, or exposing metrics and making your applications more observable and more visible.

If you go and visit the Spring Cloud project landing page, you come across this illustration, which I like very much, because it gives you a sense, not at a detailed level, but of how these things are arranged. We see in this picture, a variety of microservices that are running that supposedly can find each other because of that box up at the top the service registry, they register with the service registry, become discoverable. The API gateway in front is able to control routing to particular services. Maybe these microservices also are designed to emit distributed tracing and other information to a collector, a telemetry collector, so that we have more visibility into the functioning of our system. What's implied in this picture is the fact that the way in which we enable our microservices is by adopting dependencies. Through third party dependencies, we essentially have a microservice that has extra capabilities that we didn't have to write ourselves to be able to, for example, serve as a client to the service registry API. We don't have to code those ourselves, which is terrific. It's implied that these things happen in process.

Desired Traits and Design Objectives

Let's try to imagine or envision, and in the process, create a list of desired traits, and maybe even design objectives for a system that can solve many of the problems that we've just described. The first one, it sounds like maybe a tall order, this idea of maybe turning the tables and rather than make an application adapt to an environment by adding dependencies in process, could we create a platform whereby the application as-is, without any changes, can just begin to function as a member of a larger distributed application? Wouldn't it be nice if we could also bake in to that infrastructure all of these ancillary concerns I was mentioning earlier, retries, timeouts could be configured outside of the context of applications. The basic theme here is, let's not disturb our applications. Can we actually, somehow deal with these matters in an external fashion? The realization that the workload identity problem which is intertwined with a secure environment for running distributed applications, is one that must be addressed and recognized and solved. Finally, a very general statement here with respect to separation of concerns. That is to say that if we are going to have a chance at having systems that are responsive, that we can very quickly be able to modify how they behave with respect to security policy, network policy, routing policy or other orthogonal cross-cutting concerns, that we should be able to apply them without having to rebuild, redeploy, or restart, or even reconfigure an application. That is that they're truly orthogonal concerns that somehow can be applied without disturbing all of these running applications.


It's high time that we discuss Istio. I want to give you an overview of the architecture of Istio. After which we can discuss how Istio solves the problems that we just described. The first thing that we should say about Istio is that it is a project that was created after the advent of Kubernetes. It leverages Kubernetes and extends it, in fact. Let's go together through this exercise of understanding the architecture of Istio. Imagine the smallest possible building block of a distributed application, which is two services trying to call one another. We mentioned that this is going to happen in the context of a Kubernetes cluster. That's not exactly true in that Istio supports workloads running both on and off clusters. They can be running on VMs. If these services are going to run in Kubernetes, they're going to be deployed as Kubernetes deployments, so we're going to end up with pods. Perhaps the first problem we tackle is the problem of service discovery. We've got to have somewhere to collect a registry. Istio's main deployment is called istiod. We draw a box, maybe another pod that's running in our Kubernetes cluster called istiod. The way this works is as a service is deployed, or as a pod is deployed to your Kubernetes cluster, the idea is that Istio can be notified of the event and update its registry, and thus build up a list of all of the services and their endpoints. That list obviously needs to be communicated to the pods. Here we have a conundrum because the desire is for the applications to not be aware of the platform, but the other way around.

The way Istio solves this problem is by introducing the Envoy sidecar. The idea is the sidecar is the landing spot where we're going to send our copy of our registry. Those Envoys are going to do our bidding, unbeknownst to our applications. What is Envoy? Envoy has a very interesting story in that it came out of Lyft. It's an open source project. The lead developer of this project is Matt Klein, who still today is at Lyft. The website is It's, you could say, a modern proxy in that it's remotely programmable. You can configure it to essentially dictate its behavior. The way that it works is through an API known as discovery services. It can be controlled remotely via REST, or via more commonly gRPC. That's exactly what istiod does, it has connections to all of these Envoys and it can push configuration to those Envoy's at any time. It's perfectly suited for this particular task. Another advantage, again, is that you do not have to restart those Envoys as you reconfigure them. They're dynamically configurable, you can say. These sidecars are injected automatically, as a developer deploys their workloads, their manifests do not need to be modified. There's one more important point that must be made here in terms of how this actually works. These Envoys cannot serve a useful purpose unless those pods are reconfigured in such a way that they can intercept traffic going in and out of each of our applications. That's why I personally like to depict Envoy as a ring around each of these containers to make that more explicit, the fact that when service A calls service B, it's going to have to go through that Envoy, and vice versa.

Where do we go next? Let's talk about two particular flows. The first one I like to call the control plane flow. The second one we'll see afterwards is a data plane flow. The idea that, ok, we've set the stage. We have a proxy, it's intercepting requests to and from services. It doesn't yet know what to do. It doesn't know the state of the world. Who does? It's istiod. Istiod as services are deployed to your Kubernetes cluster or to the mesh in general, which can be expanded to encompass multiple clusters or additional VMs, or whatever you may have. The event notifications allow Istio to essentially keep up to date, its state of the world, in what I depict here as a registry. Then Istio does the obvious next thing, which is to translate that information to an Envoy configuration, a configuration Envoy understands, and it distributes them in real time to all of these Envoys. Now we finally have all the pieces of the puzzle in place. These Envoys are armed with the information they need to know how to route requests according to that configuration. It's important to mention that this works out of the box. You have a cluster, you deploy your workloads, assuming Istio is deployed as well, of course. Where service A is deployed, and calls service B, unbeknownst to it, that request is intercepted by the proxy. The proxy then has configuration, it's already been armed with that configuration by Istio, but Istio is not in the path of this request. It's strictly concerned with the control plane flow that we just went through. That proxy is able to load balance requests just like Ribbon used to. It's able to retry requests that fail. Dealing with issues with a network is a concern that is no longer one that our application proper has to be concerned about. It's been pushed down to the platform. On the receiving side, the other proxy receives the request and forwards it to service B. The response follows the reverse path.

We can go even further. What I just described functions out of the box, you don't need to configure your services in any special way. That's the beauty of Istio. If you so wish to influence the behavior of these proxies, you can. This is what exactly this picture is depicting, the idea that Istio provides a list of a handful of custom resource definitions. This one is called the destination rule, which allows us to custom configure, in this case, the exact load balancing algorithm we wish Envoy to use as it makes calls to a particular service, or this could have been configured globally for the entire mesh. The idea is you apply this custom resource to your Kubernetes cluster. Istio takes that information and updates the Envoy configuration which it distributes then to all of the proxies so that they now behave according to the specification, a cross-cutting concern.

Let's look at another scenario. This one is called a VirtualService, which allows us to manipulate traffic. Here we define supposedly somewhere, subsets, the fact that there's a service by the name of reviews. There are two subsets, one which happens to be version two, the second one, which is version three, in this case. What we specify is that we want 50% of traffic to be sent to one subset and the rest to the other. Again, you apply this Kubernetes resource to your Kubernetes cluster. Istio will take that information, generate an updated Envoy configuration, and distribute it to all of the Envoys that need to know about it. The reason that I repeat this pattern is to impress upon you this particular pattern that Istio implements, knowingly or unknowingly is beside the point. The idea that it injects or pushes configuration, not to the service, but to its delegate, so you could think about the service, so that it can then resolve requests to other services and do other tasks besides. That pattern is a very familiar one in the monolith world, it's called dependency injection. Just like Spring does dependency injection within the monolith to give one service references to other services so it doesn't have to look them up. The same thing happens in a distributed application with respect to the different actors in our distributed system that need to communicate with one another.


Let us then proceed and talk about other facets of Istio that address other problems. Resilience. Let's talk about resilience. This is just a simple example of another way of adding a bit of configuration to govern how many times we want to retry a particular call to a particular service. In this case, we're saying we want three retry attempts, and we can even specify a per try timeout, and also, the type of error that should trigger a retry. We could be selective there. Retries can be incorporated again, or communicated to the platform without disturbing our applications. Here's an example of specifying a timeout. The idea is that when I call out to a particular service, if it doesn't respond within, typically, a good value should be in the order of tens or hundreds of milliseconds, then we can fail fast, and just terminate that call. Because, obviously, this particular service we're calling or the instance of this service is having some issues, and we're going to fail fast.

This is an example of a circuit breaker implementation in Istio. There are two things going on here, one is a configuration of a connection pool. The basic idea here is to limit the amount of pressure on a particular service by specifying a maximum number of requests, in aggregate, that service and all of its backing endpoints are supporting. If we exceed that maximum, we can have those Envoys just return 503s. Outlier detection is a little more sophisticated, it's the idea that we can identify an offending pod, for example. If it throws in this case, more than seven 500 type errors or in an interval of 5 minutes, that we're going to eject it and no longer give it any traffic for a duration that we specify, which in this case, is that base ejection time. That's resilience.


We have a bunch of knobs that allow us to configure, and get our timeouts and retries and circuit breaker configuration to tune in such a way that our system is working perfectly well. The next step is, let's talk about addressing the problem of security. With respect to security, Istio leverages a framework known as spiffe, which stands for secure production identity framework for everyone. The basic idea is to give every service its own unique identity, a cryptographic identity based on an x.509 certificate. The basic idea is to embed in a particular field, the SAN field, a subject alternative name, a URI that follows a particular pattern that can help identify every single service in the mesh. I've got this illustration that I've taken straight out of the Istio documentation that illustrates the process by which that identity is imprinted on every workload. The theme here, again, is to not put that burden on the shoulders of developers. It's automated. As every new pod is deployed, there is an Istio agent, that essentially creates a Certificate Signing Request, sends it to Istio which delegates it to a certificate authority. Signs the certificate, issues it. The Istio agent keeps it in memory for the Envoy proxy to fetch and be able to use as it upgrades connections to other services to use mutual TLS. That's the security story. It happens transparently. You get it out of the box without any configuration whatsoever.

If we then revisit the same flow that we saw earlier, we can add on the fact that this is actually taking place. It can be configured, of course, but the basic idea is that that Istio proxy has a certificate, and it establishes a mutual TLS connection with the service that it's calling. That certificate is communicated in both directions. Here, I depict only one but it's happening mutually, of course. The certificate is verified and the identity of the caller extracted from that spiffe URI. The next step is that now that identity is known that we solve workload authentication in the service mesh, we can then overlay on top of it a higher-level concept, which is authorization policy. The receiving Istio proxy can look up its authorization policy from its local configuration, determine that this call is either allowed or denied, and then choose to whether pass on the request to the service or deny it. In this case, you see Envoy acting as a policy enforcement point.

Let's look at an example authorization policy. These are actually quite flexible and versatile. This one is called the name of the resource, the kind is AuthorizationPolicy. The basic idea here on line 10, is we target a database pod, which is receiving database connections from a variety of services, but it will only allow callers that match a particular identity. The source principal here is using a spiffe URI that identifies the book application. In this case, we're saying the book application is the only service that can talk to the book application database, which makes perfect sense. There we see Envoy serving the role of the Security Enforcer, so we apply this Kubernetes resource to our cluster. Again, the Envoy configuration has an extra filter in its filter chain, which tells it to actually check that that rule is satisfied.


Next up, observability. Observability is another very important facet of the equation that can help you reduce mean time to detection, improve mean time to recovery, and so on. Let's talk about it for a minute. Specifically, what value does Istio bring to the table here? If we go back to this picture of two services communicating with one another. With respect to observability, the main idea here is that we have three separate and complementary pieces of information, or subsystems that bring something to the table. The first one is logs. The fact that we stream and aggregate logs, and that really does not concern Istio to a very great degree. You can configure your Envoys to also send logs to the same location that your services receive logs. The other piece is distributed tracing. Collecting of distributed traces, configuring distributed tracing, the Envoys can actually add trace IDs and these B3 trace headers to initiating requests. The thing to be mindful of is that there's no way that they can ensure that every service will propagate those headers. That's something that you have to be mindful that your development teams must propagate those trace headers.

The third piece is metrics. This is where because Envoy is in the path of all of these requests, it can collect and it does collect metrics with respect to requests that are happening between services, the volume of requests, whether they succeed or failed, all kinds of requests, metadata, and latencies as well. It exposes them itself on a particular scrape endpoint that you see there on the screen, for Prometheus to collect, and for Grafana to report upon. Istio indeed provides standard dashboards, pre-built Grafana dashboards that you can use to monitor your entire mesh. In my mind, the biggest value there is uniformity. The fact that, first of all, your teams don't have to each fend for themselves and build their own monitoring solutions. The fact that it's uniform, the names of the metrics, the dashboards are all the same. It gives you the uniformity that makes it very easy for your entire IT staff to become familiar with and monitor the entire mesh in the same uniform way.

There's another tool worth talking about. Kiali is a bespoke, observability console for Istio that leverages all this information to give you these compelling visualizations and other ability to monitor and also control your mesh from a single visual dashboard. Here's a screenshot, perhaps not a very useful one, of a service running in a mesh running locally on my machine, where you see the basic rate metrics, request volumes, success rate, and latencies durations. Here's a screenshot from Kiali showing a visualization of an incoming request all the way from the ingress gateway on the left to database on the right, traversing a variety of microservices. That gives you a sense of the observability story with respect to Istio.

Observations and Summary

Going back to this picture, I had mentioned how vis-à-vis security, these sidecars play the role of policy enforcement points. At some point it dawned on me that it's more general than that. More generally, these sidecars are what we call a join point, in the parlance of Aspect Oriented Programming. That's when it dawned on me that really Istio is an AOP framework for distributed applications. One could make the case that AOP has had perhaps limited success in the realm of monoliths because it involved having to weave all of these concerns into your codebase, literally. What we see in the context of distributed application is Istio is able to weave all of these concerns through the Envoy sidecars, so when we explode the monolith into a distributed application where these services are really independent of one another, and we can put the sidecars in the path of requests between the services. It's the perfect join point at which to apply all of these concerns, whether they be security concerns, or traffic management concerns, or network policy concerns, and the list goes on.

Let's summarize by going back to my opening question, now you know how Istio essentially solves or addresses the problems relating to service discovery, resilience, security, observability, and traffic management. My advice is that you want a platform that is application aware and not the other way around, the dependency injection. You want all of these concerns to be baked into the infrastructure and not coupled to your applications. You want a platform that's inherently secure with the notion of workload identities built in. Finally, and most generally, you want a clear separation of concerns, where all of these different concerns can be tuned and modified, without having to disturb the applications running in your mesh. That creates for a very highly available environment in which to run your systems.

Questions and Answers

Reisz: I don't know that I've ever heard the phrase Istio is an AOP framework for distributed systems, but I think I like it. Whenever I record one of these talks, particularly ahead of time, there's always something I wish I had added, or something I wish I had put in there, is there anything that comes to mind as it was playing or did you get everything out?

Suez: In my opinion, I got everything I wanted to say. I'm really fascinated by the questions and the comments about alternative architectures supporting event-based models. That's really triggering a lot of interesting conversations. That was my idea, is to essentially provoke and to put out statements out there that help us connect the dots sometimes. Sometimes we study a new technology, but the pattern sometimes is familiar. It's a lot of fun to be able to dive into technology deep enough to see those connections.

Reisz: There's a lot of overlap, particularly when we talk north-south between load balancers, API gateway, service mesh. Where do you draw the line?

Suez: In my opinion, I think it might have started at the ingress level, load balancers, and ingress, because everybody needed that. As we break our applications, we see the same needs crop up even internally within the mesh. I think that's where I see Istio satisfy a lot of that, and fill that gap. It's an interesting fact that there are plenty of ingress gateways that are based on Envoy. That speaks to the fact that Envoy is a pretty good building block for supporting these scenarios.

Reisz: Would you agree that it's at the setup where you choose to enforce it, whether it's at the front or between?

Suez: That's something that a lot of folks in the service mesh ecosystem try to impress is this idea, the term for it is zero trust architectures. The idea that, can we have a perimeter that we secure within which our services are safe and don't have to worry about issues of security. Increasingly, that's not the case, for many reasons. We're no longer in a data center exclusively. We have code running in the cloud. We have hybrid clouds, and so being able to draw this line around all of your workloads is increasingly difficult. Maybe it's a fallacy. The idea there is let's just assume that we can't trust anything, and just give me your certificate. Let's just make everything mutual TLS, and now, it solves problems. It goes beyond just even a single Kubernetes cluster. It doesn't matter how wide your footprint is, you're going to be able to make more intelligent decisions that pertain to security. I like to interject how this naturally then brings the conversation to a higher level, which is the authorization policy and the kinds of things you can do there.

Reisz: Istio is amazing. It can do, like you said, cross-cutting concerns for a distributed system, but it introduces a sidecar. In the most common implementation, it introduces a sidecar. How do you talk to people when they say, yes, but you're doubling the number of containers? What is your response to that? How do you have to think about it.

Suez: Indeed, you are. That's a very apropos topic of conversation today, specifically with Istio has been in the news with respect to trying to refine and optimize that implementation. They've got an early implementation of this sidecarless option. It's a refinement of the implementation. My personal beef is to really let one's experiences in production speak for themselves, that is, if you apply Istio to a problem, and it solves those problems, and really alters what you're able to do as a consequence, you've benefited more than it's cost you to adopt it. I look to practitioners to vet whether that implementation has problems. There's a company in the UK called Auto Trader, and one of its architects, his name is Karl Stoney, he is a very outspoken tech individual. I think he was at Thoughtworks, before he was at Auto Trader, and they went through a journey of adopting Istio with really amazing success. I'm not sure how many situations are really, in a sense, bitten by the presence of extra sidecars.

Now, obviously, it's clear that you're doubling number of containers within each pod, and so it's going to have some extra cost in terms of operationalizing your cloud costs and so on. I think it's myopic to really jump to the conclusion that it's not going to work. I think the segregation of the concerns to me trumps the extra cost. Specifically, when we talk about eliminating duplication of effort, you have teams that create their own separate implementations of some cross-cutting concern for their services, but they're only one piece of the puzzle, you got a dozen teams that are doing that, so that cost is probably orders of magnitude greater than the cost of the sidecar.

Reisz: Like I said, there's no free lunch. Things do definitely have a cost. You gain a lot of capability, but you got to pay at some point. In some cases, some of these things are being addressed. In some cases, you're paying with a small performance penalty to be able to do it. However, there's lots of interesting things out there that are happening that are better at paying down some of that cost.

Suez: One takeaway that I'm going to just throw out there is how interesting it is. Sometimes when you go a little out of your comfort zone if you're a developer type and you look at something that's more about platform type solution, the extent to which those things are really intertwined and connected, and it's not really something that you should consider outside your domain of expertise. Rather embrace it, and you'll be surprised to find out to what degree it may even solve some problems that you maybe originally did envision they would help you solve.

Reisz: The service mesh is an amazing space and we're lucky to be all involved with it.


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Recorded at:

Apr 19, 2023