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The Service Mesh: What Engineers Need to Know

172 points by scott_s 7y ago

Animats 7y ago
How many transactions per second before you need all that stuff? If you're not in the top 100 sites, it seems unnecessary.
- SteveNuts 7y ago
  For us it's an easy way to get Microsegmentation for our services which is a huge boon to our security posture.
- tptacek 7y ago
  It's not as much about load as it is about complexity; it starts to make sense when you hit some threshold number of internal services, regardless of the amount of traffic you're doing. You use a service mesh to factor out network policy and observability from your services into a common layer.
  - thom 7y ago
    What is the threshold above which a service needs to exist at all, over a module in an existing codebase?
    - tptacek 7y ago
      This is more a religious question than a technical one. I tend to build monoliths. Some of our clients build microservices; some of them decompose into just a small number of services, and about half of them have monolithic API servers. But if you're going to do the fine-grained microservice thing, the service mesh concept makes sense. You might choose not to use it, the same way I choose not to use gRPC, but like, it's clear why people like it.
    - cpitman 7y ago
      The point at which you have multiple teams working on the same codebase, and their velocity is suffering from communication overhead and missteps.
      - koffiezet 7y ago
        A few remarks: * Codebase should be defined as 'the platform'. where one team will most likely never look at the code of other team's microservices. * this communication problems and overhead start the moment you go from 2 to 3 or more teams. * the term 'team' in this context should be interpreted very broadly. One dev working alone on a microservice should be considered "a team". Also, things mentioned in the article: you don't want to implement TLS, circuit breakers, retries, ... in every single microservice. Keep them as simple as possible. Adding stuff like that creates bloat very quickly.
tick_tock_tick 7y ago
My favorite use of this kind of system is to manage tls and acls. The service itself can be extremely dumb and just expose a unix socket. The 10:1 ratio of microservices to developer sounds like hell though that's just too much to reason about.
jayd16 7y ago
As someone who's familiar with the API gateway pattern, is it fair to say this is just another API gateway for internal services? Seems like it is but its also described in an extremely convoluted way with 'control planes' and such.
- tptacek 7y ago
  Not really. API gateways are typically single-point-deployment proxies, designed to create a coherent public interface out of a disparate group of services. An API gateway change is almost always going to be a PR for the application team. Service meshes are proxies deployed alongside all the services, and used as much by devops (and potentially security) as by the application developers.
  - jayd16 7y ago
    So a goal of the service mesh is to keep it an api agnostic appliance. I'm not sure that concept requires all this nomenclature. It seems like a very thin API Gateway that forwards calls directly to the microservice API without enforcing much would be much easier to manage and have all the same benefits. Whats the purpose of deploying the reverse proxy alongside the microservice?
    - tptacek 7y ago
      Yeah, you haven't grokked the concept yet. The idea behind a service mesh is that no matter how you design and implement a microservice architecture, you still have all these little services talking to each other somehow. By "default", they're communicating using native sockets and HTTP or gRPC. There's lots that can go wrong any time you have a bunch of things talking to each other on a network (see Tanenbaum's "Critique of RPCs" for a classic explanation). If everything was written in the same language, what you'd probably do is come up with a common networking/RPC library for all your services to use. That library would give you a common interface, so everything used the network the same way, and some measure of observability (maybe just by doing a standard log format), and maybe some security controls like a standard HTTPS connection and a standard token format. But if you've got multiple languages, that option isn't very attractive anymore, because even if it's feasible to build that library once for each platform, now you're keeping an additional component (the library) in sync between the platforms, and that's a drag. The insight behind a service mesh is that containers make it cheap and easy to just stack a tiny out-of-process proxy alongside your services. So you can just move all the logic you would have had in that common service library into the proxy. The proxy will give you the same features no matter whether your service is a Rust binary, Clojure running on the JVM, or a shell script. And, because it's an out-of-process standalone component, it can be built and maintained by a third party, which means the features it provides can be a lot more ambitious than you'd build in your own library. So now instead of just hoping to get some TLS and maybe a standard token, everything can be mTLS with client certificates, a standard dashboard for managing certificates, rule systems for what client certs will allow you to talk to which systems, graphical maps of who's communicating with who and trace collection for specific pairs of services, etc. This is all very un- like what an API gateway does, and the whole concept sort of revolves around having little reverse proxies running alongside the services.
reilly3000 7y ago
I'm evaluating using AWS App Mesh at the moment. We're a really small team so we're choosing Fargate vs Kubernetes- mainly because we don't have need of nodes nor want to deal with them. The appeal of App Mesh for us was initially around using it to facilitate canary deployments. AWS Code Deploy does a nice job with Blue / Green deployments and that may suffice for us, but it doesn't support canary for Fargate. Is that enough reason to add the additional complexity in our stack? Not sure, looking for input. Also, much of the documentation is focused on K8s. I'm murky on how to implement an internal namespace for routing. Most of what I've seen is like myenv.myservice.svc.cluster.local but its not clear to me that using that pattern is needed in the context of Fargate. Consistent observability is valuable, but again Fargate can do that pretty well- it just doesn't mandate access logging so that would be left to the app itself. We want to implement OIDC on the edge for some services, but App Mesh doesn't support that yet as other meshes like Ambassador, Gloo, and Istio seem to. Since App Mesh doesn't really act as a front-proxy on AWS, we'll still be using ALB to handle auth which is fine, I think. I get mixed messages about the need for JWT validation, but if so, that would need to be implemented in the app level with ALB fronting it. Can anybody help me find resources to sort this out? I've been through the `color-teller` example time and time again, but it still leaves lots of open questions about how to structure a larger project and handle deployments effectively.
- hardwaresofton 7y ago
  > The appeal of App Mesh for us was initially around using it to facilitate canary deployments. AWS Code Deploy does a nice job with Blue / Green deployments and that may suffice for us, but it doesn't support canary for Fargate. Is that enough reason to add the additional complexity in our stack? Not sure, looking for input. Maybe you should write a script for this? It sounds like you're about to take on a lot of complexity for just the ability to do canary deployments when you could probably hack up a script in a day or two. > We want to implement OIDC on the edge for some services, but App Mesh doesn't support that yet as other meshes like Ambassador, Gloo, and Istio seem to. Since App Mesh doesn't really act as a front-proxy on AWS, we'll still be using ALB to handle auth which is fine, I think. I get mixed messages about the need for JWT validation, but if so, that would need to be implemented in the app level with ALB fronting it. JWTs are only required for client-side identity tokens (you can use opaque ids and other kinds of stuff for backends) -- it seems like you're also at the same time looking for something to take authentication off your hands? App Mesh doesn't do that AFAIK, it's only the service<->service communication that it's trying to solve. I think it might be a good idea to make a concise need of what you're trying to accomplish here, it seems kind of over the place. From what I can tell it's: - Ability to do Canary deployments - The ability to shape traffic to services (?) - Observability, with access logging - AuthN via OIDC at the edge A lot of meshes do the above list of things, but the question of whether it's worth adopting one just to get the pieces you don't have already (which is only #2 really, assuming you scripted up #1), is a harder question.
tracer4201 7y ago
Good article - I must admit I’m vaguely familiar with the concept and this read certainly gave me some new insights. One meta call out on the writing - I read and scrolled at least 30% through the page on my iPhone until the author explained why I should care about a service mesh I.e. what problems it tries to simplify or solve. It seems to me there are some strong use cases here, but it’s only worth your while if you’re operating at sufficient scale. For instance, if my team at some FAANG scale company is responsible for vending the library that provides TLS or log rotation or <insert cross cutting/common use case here>, and it requires some non trivial on boarding and operational cost, migrating to this kind of architecture longer term where these concerns are handled out of the box may be beneficial. Still - it doesn’t mean the service owners are off the hook. They still need to tune their retry logic, or confirm the proxy is configured to call the correct endpoints (let say my service is a client of another service B and for us, B has a dedicated fleet because of our traffic patterns). This is an abstraction. Abstractions have cost. Trust but verify. The trap people fall into is, “Here’s a new technology or concept. Let’s all flock to it without considering the costs.”
cbsmith 7y ago
I'm going to sound like an old man but... What amuses me about this is back in the day everyone thought the Mach guys were crazy for thinking things like network routing and IPC services be implemented in user space... and others mocked the OSI model's 7 layers as overly complex (e.g. RFC3439's "layering considered harmful"). Now we've moved all our network services onto a layer 7 protocol (HTTP), and we've discovered we need to reinvent layers we skipped over on top of it. We're doing it all in user space with comparatively new and untested application logic, somehow forgetting that this can be done far more efficiently and scalably with established and far more sophisticated networking tools... if only we'd give up on this silly notion that everything must go over HTTP.
- skywhopper 7y ago
  You aren't wrong about the trend of solving the same problems over and over at higher points in the stack. But you missed the mark on responding to this article and the Service Mesh pattern, which usually operates at a lower network layer. In fact, if anything, the trend in microservices architecture is away from HTTP and back towards binary protocols over TCP (but, in this case, proxied via authenticated mTLS connections managed by an external service, but which also operate over TCP).
- taneq 7y ago
  Network-over-network is just another Inner Platform Effect.
  - jonahx 7y ago
    Wonderful term. I've been aware of the phenomenon for a while but not its name. Link for others: https://en.wikipedia.org/wiki/Inner-platform_effect https://en.wikipedia.org/wiki/Inner-platform_effect
    - Bombthecat 7y ago
      Oh wow! I had a customer who was really bad at it. All! there Software was effected by it in one way or another. Now I have a name for that at least :)
theamk 7y ago
It’s a pity “fat clients” are dismissed so quickly. I think that when your tech stack is uniform enough to use them, they can provide much more that service meshes, and do it faster as well. After all, why does “service is down” and “service is sending nonsense” have to be handled via completely different paths?
- omeze 7y ago
  The main problem with fat clients is that for polyglot architectures (which most large companies that end up building a service mesh evolve into over time) you have to maintain a fat client library for every language. You can get very far leveraging existing tools like gRPC that codegens fatty clients for you but the quality of tooling is very uneven depending on the language of choice. By pushing all of this into the network layer you skip all of that.
  - theamk 7y ago
    Right, polyglot architectures have no choice, but this text talks about “5 person startups” as well. Surely they can keep the set of languages limited? Plus, it’s not either/or situation. A fat clients for Go + Node.js; and a proxy for all others. This way your core logic can enjoy increased introspection / more speed / higher reliability; while special purpose services get a proxy which allow interoperability.
ajessup 7y ago
One reason for the explosive interest in service mesh over the last 24 months that this article glosses over is that it's deeply threatening to a range of existing industries, that are now responding. Most immediately to API gateways (eg. Apigee, Kong, Mulesoft), which provide similar value to SM (in providing centralized control and auditing of an organization's East-West service traffic) but implemented differently. This is why Kong, Apigee, nginx etc. are all shipping service mesh implementations now before their market gets snatched away from them. Secondly to cloud providers, who hate seeing their customers deploy vendor-agnostic middleware rather than use their proprietary APIs. None of them want to get "Kubernetted" again. Hence Amazon's investment in the very Istio-like "AppMesh" and Microsoft (who already had "Service Fabric") attempt to do an end run around Istio with the "Service Mesh Interface" spec. Both are part of a strategy to ensure if you are running a service mesh the cloud provider doesn't cede control. Then there's a slew of monitoring vendors who aren't sure if SM is a threat (by providing a bunch of metrics "for free" out of the box) or an opportunity to expand the footprint of their own tools by hooking into SM rather than require folks to deploy their agents everywhere. Finally there's the multi-billion dollar Software Defined Networking market - who are seeing a lot of their long term growth and value being threatened by these open source projects that are solving at Layer 7 (and with much more application context) what they had been solving for at Layer 3-4. VMWare NSX already have a SM implementation (NSX-SM) that is built on Istio and while I have no idea what Nutanix et al are doing I wouldn't be surprised if they launched something soon. It will be interesting to see where it all nets out. If Google pulls off the same trick that they did with Kubernetes and creates a genuinely independent project with clean integration points for a wide range of vendors then it could become the open-source Switzerland we need. On the other hand it could just as easily become a vendor-driven tire fire. In a year or so we'll know.
- streetcat1 7y ago
  This is a good overview. However, I think that the reason that we see a lot of service variations is because the core tech - namely - Envoy, contains all the "hard" tech (the data plane) while creating a "service mesh", basically comes down to creating a management layer on top of it. Another intresting note is that Google did NOT recede control over Istio to CNCF.
djohnston 7y ago
This is quite interesting. I used to work in more devopsy kind of roles but at the current gig it has been almost entirely removed from my purview. It's impressive to step away for a few years and return to see so many changes, but the article laid out the concepts in an easy to understand manner.
lycidas 7y ago
At my company, we were migrating all our apps to a kubernetes + istio platform over the past couple of months and my advice is this - don't use a service mesh unless you really, really need to. We initially choose istio because it seemed to satisfy all our requirements and more - mTLS, sidecar authz, etc - but configuring it turned out to be a huge pain. Things like crafting a non-superadmin pod security policy for it, trying to upgrade versions via helm, and trying to debug authz policies took up a non-trivial amount of time. In the end, we got everything working but I probably wouldn't recommend it again. It's funny that I was at kubecon last week and there was a start up whose value prop was hassle-free istio and the linkerd people stressed that they were less complex than istio.
- snupples 7y ago
  I would go as far as to say I think the vast majority of people don't need a specialized service mesh. We unfortunately started with Linkerd and it actually is the cause of most reliability/troubleshooting issues. I don't think lack of complexity is actually a good selling point for it, because it's inherently more complex that not using a service mesh. Istio may appear more complex but that's because it has a superior abstraction model and supports greater flexibility. We're beginning to migrate from Linkerd to Istio at this point. I had the same initial frustrations with podsecuritypolicy (and linkerd suffers from the same), but istio-cni solves the superuser problem, and I believe even the istio control plane is now much more locked down in the latest release. However if I had my way I would be telling every team they don't need service mesh. We don't have any particular service large and complex enough to really take advantage of its sold features.
  - Bombthecat 7y ago
    Yeah, most people / projects can live with just kong for example.
  - bogomipz 7y ago
    >"We unfortunately started with Linkerd and it actually is the cause of most reliability/troubleshooting issues" Would you mind elaborating on what those Linkerd issue are/were that were effecting reliability and troubleshooting?
peterwwillis 7y ago
Every part of a service mesh could be baked into operating systems so that all this extra technology was just there by default. This would put a fair amount of start-ups out of business, but it would also mean a lot less people having to be hired to set up and maintain all this stuff. Devs could just... develop software, with a clear view into how their apps run at scale. And Ops wouldn't have to custom-integrate 100 different services. This is really the future of distributed parallel computing, but we're still just bolting it on rather than baking it in.
adolph 7y ago
If one were to implement a service mesh of microservices wouldn’t the services need to be versioned similar to how the packages used by a microservice are version-pinned?
- deleted 7y ago
  [deleted]
- dodobirdlord 7y ago
  Sort of, but only for major versions, and it's preferable to bake that sort of thing into the API itself. The API exposed by a microservice should only ever be updated in backwards compatible ways unless you can verify that you have no callers, which is hard. New functionality should be introduced using backwards compatible constructs like adding fields to JSON or protobuf. Breaking changes go in a new API. This is easily managed conceptually by having the microservice expose version information as part of the API. A FooService might define "v1/DestroyFoo" and "v2/DestroyFoo" with different calling contracts. Perhaps v1 was eventually consistent and returns a completion token that can be used with a separate "v1/CheckFooDeletionStatus", but now with v2 the behavior has been made strongly consistent and there is no "v2/CheckFooDeletionStatus". The v2 of the API can thus be thought of really as a separate API that happens to be exposed by the same microservice, and pre-existing callers can continue to call the (perhaps now inefficient) v1 API.
solatic 7y ago
Re. "fat client" libraries: > Sure, it only worked for JVM languages, and it had a programming model that you had to build your whole app around, but the operational features it provided were almost exactly those of the service mesh. The thing is, all of our microservices communicate with each other using Kafka. Envoy has an issue open for Kafka protocol support [1], but it's a fundamentally difficult issue because adopting Kafka forces you to build out "fat client" code and building a network intercept that can work with pre-existing Kafka client code is non-trivial. On observability, Kafka produces its own metrics. Granted, Kafka doesn't offer the same level of control. But Kafka does offer incredible request durability guarantees. We don't have "outages" - we have increased processing latency, and Istio/Envoy and other service meshes can't offer that because they do not replicate and persist network requests to disk. [1] https://github.com/envoyproxy/envoy/issues/2852 https://github.com/envoyproxy/envoy/issues/2852
golover721 7y ago
While nobody ever seems to want to hear it, the vast majority of companies utilizing service meshes and k8s are wasting huge amounts of time and money on things they don’t need. Unfortunately these technologies are at peak hype so everyone seems to be implementing them for their small to medium crud apps. But get very sensitive if you try and point it out.
reissbaker 7y ago
Opinionated read, but interesting. That being said, Linkerd wasn't the first service mesh — SmartStack predates it by three years. [1] Although they didn't use the (then-nonexistent) "service mesh" term at the time, it pioneered the concept of userspace TCP proxies configured by a control plane management daemon. I doubt the Linkerd folks are unaware of it, so it was a surprising omission. [1]: https://medium.com/airbnb-engineering/smartstack-service-discovery-in-the-cloud-4b8a080de619 https://medium.com/airbnb-engineering/smartstack-service-dis...

172 points by scott_s 7y ago

How many transactions per second before you need all that stuff? If you're not in the top 100 sites, it seems unnecessary.

SteveNuts 7y ago
For us it's an easy way to get Microsegmentation for our services which is a huge boon to our security posture.
tptacek 7y ago
It's not as much about load as it is about complexity; it starts to make sense when you hit some threshold number of internal services, regardless of the amount of traffic you're doing. You use a service mesh to factor out network policy and observability from your services into a common layer.
- thom 7y ago
  What is the threshold above which a service needs to exist at all, over a module in an existing codebase?
  - tptacek 7y ago
    This is more a religious question than a technical one. I tend to build monoliths. Some of our clients build microservices; some of them decompose into just a small number of services, and about half of them have monolithic API servers. But if you're going to do the fine-grained microservice thing, the service mesh concept makes sense. You might choose not to use it, the same way I choose not to use gRPC, but like, it's clear why people like it.
  - cpitman 7y ago
    The point at which you have multiple teams working on the same codebase, and their velocity is suffering from communication overhead and missteps.
    - koffiezet 7y ago
      A few remarks: * Codebase should be defined as 'the platform'. where one team will most likely never look at the code of other team's microservices. * this communication problems and overhead start the moment you go from 2 to 3 or more teams. * the term 'team' in this context should be interpreted very broadly. One dev working alone on a microservice should be considered "a team". Also, things mentioned in the article: you don't want to implement TLS, circuit breakers, retries, ... in every single microservice. Keep them as simple as possible. Adding stuff like that creates bloat very quickly.

tick_tock_tick 7y ago

My favorite use of this kind of system is to manage tls and acls. The service itself can be extremely dumb and just expose a unix socket. The 10:1 ratio of microservices to developer sounds like hell though that's just too much to reason about.

jayd16 7y ago

As someone who's familiar with the API gateway pattern, is it fair to say this is just another API gateway for internal services? Seems like it is but its also described in an extremely convoluted way with 'control planes' and such.

tptacek 7y ago
Not really. API gateways are typically single-point-deployment proxies, designed to create a coherent public interface out of a disparate group of services. An API gateway change is almost always going to be a PR for the application team. Service meshes are proxies deployed alongside all the services, and used as much by devops (and potentially security) as by the application developers.
- jayd16 7y ago
  So a goal of the service mesh is to keep it an api agnostic appliance. I'm not sure that concept requires all this nomenclature. It seems like a very thin API Gateway that forwards calls directly to the microservice API without enforcing much would be much easier to manage and have all the same benefits. Whats the purpose of deploying the reverse proxy alongside the microservice?
  - tptacek 7y ago
    Yeah, you haven't grokked the concept yet. The idea behind a service mesh is that no matter how you design and implement a microservice architecture, you still have all these little services talking to each other somehow. By "default", they're communicating using native sockets and HTTP or gRPC. There's lots that can go wrong any time you have a bunch of things talking to each other on a network (see Tanenbaum's "Critique of RPCs" for a classic explanation). If everything was written in the same language, what you'd probably do is come up with a common networking/RPC library for all your services to use. That library would give you a common interface, so everything used the network the same way, and some measure of observability (maybe just by doing a standard log format), and maybe some security controls like a standard HTTPS connection and a standard token format. But if you've got multiple languages, that option isn't very attractive anymore, because even if it's feasible to build that library once for each platform, now you're keeping an additional component (the library) in sync between the platforms, and that's a drag. The insight behind a service mesh is that containers make it cheap and easy to just stack a tiny out-of-process proxy alongside your services. So you can just move all the logic you would have had in that common service library into the proxy. The proxy will give you the same features no matter whether your service is a Rust binary, Clojure running on the JVM, or a shell script. And, because it's an out-of-process standalone component, it can be built and maintained by a third party, which means the features it provides can be a lot more ambitious than you'd build in your own library. So now instead of just hoping to get some TLS and maybe a standard token, everything can be mTLS with client certificates, a standard dashboard for managing certificates, rule systems for what client certs will allow you to talk to which systems, graphical maps of who's communicating with who and trace collection for specific pairs of services, etc. This is all very un- like what an API gateway does, and the whole concept sort of revolves around having little reverse proxies running alongside the services.

reilly3000 7y ago

I'm evaluating using AWS App Mesh at the moment. We're a really small team so we're choosing Fargate vs Kubernetes- mainly because we don't have need of nodes nor want to deal with them. The appeal of App Mesh for us was initially around using it to facilitate canary deployments. AWS Code Deploy does a nice job with Blue / Green deployments and that may suffice for us, but it doesn't support canary for Fargate. Is that enough reason to add the additional complexity in our stack? Not sure, looking for input. Also, much of the documentation is focused on K8s. I'm murky on how to implement an internal namespace for routing. Most of what I've seen is like myenv.myservice.svc.cluster.local but its not clear to me that using that pattern is needed in the context of Fargate. Consistent observability is valuable, but again Fargate can do that pretty well- it just doesn't mandate access logging so that would be left to the app itself. We want to implement OIDC on the edge for some services, but App Mesh doesn't support that yet as other meshes like Ambassador, Gloo, and Istio seem to. Since App Mesh doesn't really act as a front-proxy on AWS, we'll still be using ALB to handle auth which is fine, I think. I get mixed messages about the need for JWT validation, but if so, that would need to be implemented in the app level with ALB fronting it. Can anybody help me find resources to sort this out? I've been through the `color-teller` example time and time again, but it still leaves lots of open questions about how to structure a larger project and handle deployments effectively.

hardwaresofton 7y ago
> The appeal of App Mesh for us was initially around using it to facilitate canary deployments. AWS Code Deploy does a nice job with Blue / Green deployments and that may suffice for us, but it doesn't support canary for Fargate. Is that enough reason to add the additional complexity in our stack? Not sure, looking for input. Maybe you should write a script for this? It sounds like you're about to take on a lot of complexity for just the ability to do canary deployments when you could probably hack up a script in a day or two. > We want to implement OIDC on the edge for some services, but App Mesh doesn't support that yet as other meshes like Ambassador, Gloo, and Istio seem to. Since App Mesh doesn't really act as a front-proxy on AWS, we'll still be using ALB to handle auth which is fine, I think. I get mixed messages about the need for JWT validation, but if so, that would need to be implemented in the app level with ALB fronting it. JWTs are only required for client-side identity tokens (you can use opaque ids and other kinds of stuff for backends) -- it seems like you're also at the same time looking for something to take authentication off your hands? App Mesh doesn't do that AFAIK, it's only the service<->service communication that it's trying to solve. I think it might be a good idea to make a concise need of what you're trying to accomplish here, it seems kind of over the place. From what I can tell it's: - Ability to do Canary deployments - The ability to shape traffic to services (?) - Observability, with access logging - AuthN via OIDC at the edge A lot of meshes do the above list of things, but the question of whether it's worth adopting one just to get the pieces you don't have already (which is only #2 really, assuming you scripted up #1), is a harder question.

tracer4201 7y ago

Good article - I must admit I’m vaguely familiar with the concept and this read certainly gave me some new insights. One meta call out on the writing - I read and scrolled at least 30% through the page on my iPhone until the author explained why I should care about a service mesh I.e. what problems it tries to simplify or solve. It seems to me there are some strong use cases here, but it’s only worth your while if you’re operating at sufficient scale. For instance, if my team at some FAANG scale company is responsible for vending the library that provides TLS or log rotation or <insert cross cutting/common use case here>, and it requires some non trivial on boarding and operational cost, migrating to this kind of architecture longer term where these concerns are handled out of the box may be beneficial. Still - it doesn’t mean the service owners are off the hook. They still need to tune their retry logic, or confirm the proxy is configured to call the correct endpoints (let say my service is a client of another service B and for us, B has a dedicated fleet because of our traffic patterns). This is an abstraction. Abstractions have cost. Trust but verify. The trap people fall into is, “Here’s a new technology or concept. Let’s all flock to it without considering the costs.”

cbsmith 7y ago

I'm going to sound like an old man but... What amuses me about this is back in the day everyone thought the Mach guys were crazy for thinking things like network routing and IPC services be implemented in user space... and others mocked the OSI model's 7 layers as overly complex (e.g. RFC3439's "layering considered harmful"). Now we've moved all our network services onto a layer 7 protocol (HTTP), and we've discovered we need to reinvent layers we skipped over on top of it. We're doing it all in user space with comparatively new and untested application logic, somehow forgetting that this can be done far more efficiently and scalably with established and far more sophisticated networking tools... if only we'd give up on this silly notion that everything must go over HTTP.

skywhopper 7y ago
You aren't wrong about the trend of solving the same problems over and over at higher points in the stack. But you missed the mark on responding to this article and the Service Mesh pattern, which usually operates at a lower network layer. In fact, if anything, the trend in microservices architecture is away from HTTP and back towards binary protocols over TCP (but, in this case, proxied via authenticated mTLS connections managed by an external service, but which also operate over TCP).
taneq 7y ago
Network-over-network is just another Inner Platform Effect.
- jonahx 7y ago
  Wonderful term. I've been aware of the phenomenon for a while but not its name. Link for others: https://en.wikipedia.org/wiki/Inner-platform_effect https://en.wikipedia.org/wiki/Inner-platform_effect
  - Bombthecat 7y ago
    Oh wow! I had a customer who was really bad at it. All! there Software was effected by it in one way or another. Now I have a name for that at least :)

theamk 7y ago

It’s a pity “fat clients” are dismissed so quickly. I think that when your tech stack is uniform enough to use them, they can provide much more that service meshes, and do it faster as well. After all, why does “service is down” and “service is sending nonsense” have to be handled via completely different paths?

omeze 7y ago
The main problem with fat clients is that for polyglot architectures (which most large companies that end up building a service mesh evolve into over time) you have to maintain a fat client library for every language. You can get very far leveraging existing tools like gRPC that codegens fatty clients for you but the quality of tooling is very uneven depending on the language of choice. By pushing all of this into the network layer you skip all of that.
- theamk 7y ago
  Right, polyglot architectures have no choice, but this text talks about “5 person startups” as well. Surely they can keep the set of languages limited? Plus, it’s not either/or situation. A fat clients for Go + Node.js; and a proxy for all others. This way your core logic can enjoy increased introspection / more speed / higher reliability; while special purpose services get a proxy which allow interoperability.

ajessup 7y ago

One reason for the explosive interest in service mesh over the last 24 months that this article glosses over is that it's deeply threatening to a range of existing industries, that are now responding. Most immediately to API gateways (eg. Apigee, Kong, Mulesoft), which provide similar value to SM (in providing centralized control and auditing of an organization's East-West service traffic) but implemented differently. This is why Kong, Apigee, nginx etc. are all shipping service mesh implementations now before their market gets snatched away from them. Secondly to cloud providers, who hate seeing their customers deploy vendor-agnostic middleware rather than use their proprietary APIs. None of them want to get "Kubernetted" again. Hence Amazon's investment in the very Istio-like "AppMesh" and Microsoft (who already had "Service Fabric") attempt to do an end run around Istio with the "Service Mesh Interface" spec. Both are part of a strategy to ensure if you are running a service mesh the cloud provider doesn't cede control. Then there's a slew of monitoring vendors who aren't sure if SM is a threat (by providing a bunch of metrics "for free" out of the box) or an opportunity to expand the footprint of their own tools by hooking into SM rather than require folks to deploy their agents everywhere. Finally there's the multi-billion dollar Software Defined Networking market - who are seeing a lot of their long term growth and value being threatened by these open source projects that are solving at Layer 7 (and with much more application context) what they had been solving for at Layer 3-4. VMWare NSX already have a SM implementation (NSX-SM) that is built on Istio and while I have no idea what Nutanix et al are doing I wouldn't be surprised if they launched something soon. It will be interesting to see where it all nets out. If Google pulls off the same trick that they did with Kubernetes and creates a genuinely independent project with clean integration points for a wide range of vendors then it could become the open-source Switzerland we need. On the other hand it could just as easily become a vendor-driven tire fire. In a year or so we'll know.

streetcat1 7y ago
This is a good overview. However, I think that the reason that we see a lot of service variations is because the core tech - namely - Envoy, contains all the "hard" tech (the data plane) while creating a "service mesh", basically comes down to creating a management layer on top of it. Another intresting note is that Google did NOT recede control over Istio to CNCF.

djohnston 7y ago

This is quite interesting. I used to work in more devopsy kind of roles but at the current gig it has been almost entirely removed from my purview. It's impressive to step away for a few years and return to see so many changes, but the article laid out the concepts in an easy to understand manner.

lycidas 7y ago

At my company, we were migrating all our apps to a kubernetes + istio platform over the past couple of months and my advice is this - don't use a service mesh unless you really, really need to. We initially choose istio because it seemed to satisfy all our requirements and more - mTLS, sidecar authz, etc - but configuring it turned out to be a huge pain. Things like crafting a non-superadmin pod security policy for it, trying to upgrade versions via helm, and trying to debug authz policies took up a non-trivial amount of time. In the end, we got everything working but I probably wouldn't recommend it again. It's funny that I was at kubecon last week and there was a start up whose value prop was hassle-free istio and the linkerd people stressed that they were less complex than istio.

snupples 7y ago
I would go as far as to say I think the vast majority of people don't need a specialized service mesh. We unfortunately started with Linkerd and it actually is the cause of most reliability/troubleshooting issues. I don't think lack of complexity is actually a good selling point for it, because it's inherently more complex that not using a service mesh. Istio may appear more complex but that's because it has a superior abstraction model and supports greater flexibility. We're beginning to migrate from Linkerd to Istio at this point. I had the same initial frustrations with podsecuritypolicy (and linkerd suffers from the same), but istio-cni solves the superuser problem, and I believe even the istio control plane is now much more locked down in the latest release. However if I had my way I would be telling every team they don't need service mesh. We don't have any particular service large and complex enough to really take advantage of its sold features.
- Bombthecat 7y ago
  Yeah, most people / projects can live with just kong for example.
- bogomipz 7y ago
  >"We unfortunately started with Linkerd and it actually is the cause of most reliability/troubleshooting issues" Would you mind elaborating on what those Linkerd issue are/were that were effecting reliability and troubleshooting?

peterwwillis 7y ago

Every part of a service mesh could be baked into operating systems so that all this extra technology was just there by default. This would put a fair amount of start-ups out of business, but it would also mean a lot less people having to be hired to set up and maintain all this stuff. Devs could just... develop software, with a clear view into how their apps run at scale. And Ops wouldn't have to custom-integrate 100 different services. This is really the future of distributed parallel computing, but we're still just bolting it on rather than baking it in.

adolph 7y ago

If one were to implement a service mesh of microservices wouldn’t the services need to be versioned similar to how the packages used by a microservice are version-pinned?

deleted 7y ago
[deleted]
dodobirdlord 7y ago
Sort of, but only for major versions, and it's preferable to bake that sort of thing into the API itself. The API exposed by a microservice should only ever be updated in backwards compatible ways unless you can verify that you have no callers, which is hard. New functionality should be introduced using backwards compatible constructs like adding fields to JSON or protobuf. Breaking changes go in a new API. This is easily managed conceptually by having the microservice expose version information as part of the API. A FooService might define "v1/DestroyFoo" and "v2/DestroyFoo" with different calling contracts. Perhaps v1 was eventually consistent and returns a completion token that can be used with a separate "v1/CheckFooDeletionStatus", but now with v2 the behavior has been made strongly consistent and there is no "v2/CheckFooDeletionStatus". The v2 of the API can thus be thought of really as a separate API that happens to be exposed by the same microservice, and pre-existing callers can continue to call the (perhaps now inefficient) v1 API.

solatic 7y ago

Re. "fat client" libraries: > Sure, it only worked for JVM languages, and it had a programming model that you had to build your whole app around, but the operational features it provided were almost exactly those of the service mesh. The thing is, all of our microservices communicate with each other using Kafka. Envoy has an issue open for Kafka protocol support [1], but it's a fundamentally difficult issue because adopting Kafka forces you to build out "fat client" code and building a network intercept that can work with pre-existing Kafka client code is non-trivial. On observability, Kafka produces its own metrics. Granted, Kafka doesn't offer the same level of control. But Kafka does offer incredible request durability guarantees. We don't have "outages" - we have increased processing latency, and Istio/Envoy and other service meshes can't offer that because they do not replicate and persist network requests to disk. [1] https://github.com/envoyproxy/envoy/issues/2852 https://github.com/envoyproxy/envoy/issues/2852

golover721 7y ago

While nobody ever seems to want to hear it, the vast majority of companies utilizing service meshes and k8s are wasting huge amounts of time and money on things they don’t need. Unfortunately these technologies are at peak hype so everyone seems to be implementing them for their small to medium crud apps. But get very sensitive if you try and point it out.

reissbaker 7y ago

Opinionated read, but interesting. That being said, Linkerd wasn't the first service mesh — SmartStack predates it by three years. [1] Although they didn't use the (then-nonexistent) "service mesh" term at the time, it pioneered the concept of userspace TCP proxies configured by a control plane management daemon. I doubt the Linkerd folks are unaware of it, so it was a surprising omission. [1]: https://medium.com/airbnb-engineering/smartstack-service-discovery-in-the-cloud-4b8a080de619 https://medium.com/airbnb-engineering/smartstack-service-dis...