I would like to ask you if you have an microservice architecture (based on Spring Boot) involving Amazon Elastic Container Service (ECS) with Application Load Balancer(ALB), service discovery is performed automatically by the platform, or do you need a special mechanism (such as Eureka or Consul)?
From the documentation (ECS and ALB) is not clear you have this feature provided.
I have talked this with the Amazon support team and they respond the following:
"...using Service Discovery on AWS ECS[..] just with ALBs.
So, there could be three options here:
1) Using ALB/ELB as service endpoints (Target groups for ALBs, separate ELBs if using ELBs)
2) Using Route53 and DNS for Service Discovery
3) Using a 3rd Party product like Consul.io in combination with Nginx.
Let me speak about each of these options.
Using ALBs/ELBs
For this option the idea is to use the ELBs or ALB Target groups in front of each service.
We define an Amazon CloudWatch Events filter which listens to all ECS service creation messages from AWS CloudTrail and triggers an Amazon Lambda function.
This function identifies which Elastic Load Balancing load balancer (or an ALB Target group) is used by the new service and inserts a DNS resource record (CNAME) pointing to it, using Amazon Route 53.
The Lambda function also handles service deletion to make sure that the DNS records reflect the current state of applications running in your cluster.
The down side here is that it can incur higher costs if you are using ELBs - as you need an ELB for each service. And it might not be the simplest solution out there.
If you wish to read more on this you can do so here[1]
Using Route53
This approach involves the use of Route53 and running a simple agent[2] on your ECS container instances.
As your containers stop/start the agent will update the Route53 DNS records. It creates a SRV record. Likewise it will delete said records once the container is stopped.
Another part of this method is a Lambda function that performs health checks on ECS container instances - and removes them from R53 in case of a failure.
You can read up more on this method, on our blog post here[3].
Using a 3rd Party tool like Consul.io Using tools like Consul.io on ECS, will work - but is not supported by AWS. So you are free to use it, but we - unfortunately - do not offer support for it.
So, in conclusion - there are a few ways of implementing service discovery on AWS ECS - the two ways I showed here that use AWS resources, and of course the way of using 3rd party applications.
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you dont have an out-of-the-box solution in AWS, although it is possible with some effort as described in https://aws.amazon.com/es/blogs/compute/service-discovery-an-amazon-ecs-reference-architecture/
You may also install Zuul + Ribbon + Eureka or Nginx + Consul and use ALB to distribute traffic among Zuul or Nginx
Related
I have read other questions about this that all mention enabling service discovery, but my issue is a little different as to how to go about setting this up for my current Fargate deployments.
I have four spring boot api containers built via Gradle, pushed to ECR, and deployed in ECS Fargate with Terraform IaC setting up the appropriate resources. Three of these containerized apis have environment variables set within them to reference the fourth container, thus making an external api call outside of the container to that one service. DNS and 443 load balancer is setup for these deployments.
I have created a new service in the cluster containing the api that needs to be discovered. I have enabled service discover and created a local CloudMap A record for the api and then set each environment variable in the other containzers to use that local A record url, e.g., ecsservicename.local. Additionally I have tried to dig the service that I am connecting to in the other apis and that returns an IP so I am sure that that is working.
My questions are as follows:
(1) Since really only one services should be picked up by the others, was it correct to set service discovery on that one api and not the others or should I set up service discovery on all the other apis?
(2) Even if route53 is setup should this be an A record or SRV? I was confused by the documentation as to when to use which on aws.
(3) Is there a better or easier approach to use for inter-container communication that I am missing?
That's correct. Discovery should be set only for the one service. Other discoveries are not needed, as you are not inter-connection to those other services.
SRV also gives port, so from docs:
if the task definition that your service task specifies uses the bridge or host network mode, an SRV record is the only supported DNS record type.
I think your architecture is well thought and can't think of anything "easier" or better.
I have a Node-Express website running on a microservices based architecture. I deployed the microservices on Amazon ECS cluster with one EC2 instance. The microservices sit behind an Application Load Balancer that routes external traffic correctly to the services. This system is working as expected except for one problem: I need to make a POST request from one service to the other. I am trying to use axios for this but I don't know what url to post to in axios. When testing locally, I just used axios.post('http://localhost:3000/service2',...) inside service 1 but how should I do it here?
So There are various ways.
1. Use Application Load Balancer behind the service
In this method, you put your micro services behind the load balancer(s) and to send request, you give load balancer URL. You can have path based routing for same load balancer or you can use multiple load balancers.
2. Use Service Discovery
In this method, you let your requester discover it. Now Service discovery can be done in various way like using ALB or Route 53 or ECS or Key Value Store or Configuration Management or Third Party Software such as Consul
I have been working with spring and now would like to learn spring boot and microservices. I understand what microservice is all about and how it works. While going through docs i came across many things used to develop microservices along with spring boot which i am very much confused.
I have listed the systems below.and the questions:
Netflix Eureka - I understand this is service discovery platform.
All services will be registered to eureka server and all
microservices are eureka clients. Now my doubt is , without having
an API gateway is there any use with this service registry ? This is
to understand the actual use of service registry.
ZUULApi gateway- I understand ZUUL can be used as API gateway which is basically a load balancer , that calls appropriate
microservice corresponding to request URL. iS that assumption
correct? will the api gateway interact with Eureka for getting the
appropriate microservice?
NGINX - I have read NGINX can also be used as API gateway? Is that possible? Also i read some where else like NGINX can be used as a service registry , that is as an alternate for Eureka ! Thus which is right? Api gateway or service registry or both? I know nginx is a webserver and reverse proxies can be powerfully configured.
AWS api gateway - Is this can also be used as an alternate for ZUUL?
RIBBON - for what ribbon is used? I didn't understand !
AWS ALB- This can also be used for load balancing. Thus do we need ZUUL if we have AWS ALB?
Please help
without having an API gateway is there any use with this service registry ?
Yes. For example you can use it to locate (IP and port) of all your microservices. This comes in handy for devops type work. For example, at one project I worked on, we used Eureka to find all instances of our microservices and ping them for their status (/health, /info).
I understand ZUUL can be used as API gateway which is basically a load balancer , that calls appropriate microservice corresponding to request URL. iS that assumption correct?
Yes but it can do a lot more. Essentially because Zuul is more of a framework/library that you turn into a microservice, you can code it to implement any kind of routing logic you can come up with. It is very powerful in that sense. For example, lets say you want to change how you route based on time of day or any other external factors, with Zuul you can do it.
will the api gateway interact with Eureka for getting the appropriate microservice?
Yes. You configure Zuul to point to Eureka. It becomes a client to Eureka and even subscribes to Eureka for realtime updates (which instances have joined or left).
I have read NGINX can also be used as API gateway? Also i read some where else like NGINX can be used as a service registry , that is as an alternate for Eureka ! Thus which is right? Api gateway or service registry or both?
Nginx is pretty powerful and can do API gateway type work. But there are some major differences. AFAIK, microservices cannot dynamically register with Nginx, please correct me if I am wrong... as they can with Eureka. Second, while I know Nginx is highly (very highly) configurable, I suspect its configuration abilities do not come close to Zuul's routing capabilities (due to having the whole Java language at your disposal within Zuul to code your routing logic). It could be the case that there are service discovery solutions that work with Nginx. So Nginx will take care of the routing and such, but service discovery will still require a solution.
Is this can also be used as an alternate for ZUUL?
Yes AWS API Gateway can be used as a Zuul replacement of sorts. The issue here, just like Nginx, is service discovery. AWS API Gateway lets you apply logic to your routing... though not as open ended as Zuul.
for what ribbon is used?
While you can use the Ribbon library directly, for the most part consider it as an internal dependency of Zuul. It helps Zuul do the simple load balancing that it does. Please note that this project is in maintenance mode and not recommended any more.
This can also be used for load balancing. Thus do we need ZUUL if we have AWS ALB?
You can use ALB with ECS (elastic container service) to replace Eureka/Zuul. ECS will take care of the service discover for you and will map all instances of a particular service to a Target Group. Your ALB routing table can then route to Target Groups based on simple routing rules. The routing rules in ALB are very simple though, but improving over time.
Different systems which can be used for the working of microservices, that comes along with spring boot:
Eureka:
Probably the first microservice to be UP. Eureka is a service registry, means , it knows which ever microservices are running and in which port. Eureka is deploying as a sperate application and we can use #EnableEurekaServer annotation along with #SpringBootAPplication to make that app a eureka server. So our eureka service registery is UP and running. From now on all microservices will be registered in this eureka server by using #EnableDiscoveryClient annotation along with #SpringBootAPplication in all deployed microservices.
Zuul: ZUUL is a load balancer , routing application and reverse proxy server as well. That is before we were using apache for reverse proxy things , now , for microservices we can use ZUUL. Advantage is, in ZUUL we can programatically set configurations, like if /customer/* comes go to this microservice like that. Also ZUUL can act as a load balancer as well , which will pick the appropriate microservice in a round robin fashion. SO how does the ZUUL knows the details of microservices, the answer is eureka. It will work along with eureka to get microservice details. And in fact this ZUUL is also a Eureka client where we should mark using #EnableDiscoveryClient, thats how these 2 apps(Eureka and zuul) linked.
Ribbbon:
Ribbon use for load balancing. This is already available inside ZUUL, in which zuul is using Ribbon for load balancing stuff. Microservices are identified by service-name in properties file. IF we run 2 instances of one microservices in different port, this will be identified by Eureka and along with Ribbon(Inside zuul), requests will be redirected in a balanced way.
Aws ALB , NGINX , AWS Api gateway etc: There are alternatives for all the above mentioned things. Aws is having own load balancer, service discovery , api gateway etc . Not only AWS all cloud platofrms ,like Azure, have these. Its depends which one to use.
Adding a general question as well , How these microservices communicate each other: Using Resttemplate or Feignclient actual rest API can be called or Message queues like Rabbit MQ etc can be used .
Eureka can be used in conjunction with NGINX, which leads to very powerful combination.
I am using it on AWS EC2 environment. Previously instead of NGINX I was using Spring Cloud Gateway and before that Zuul. Depending of the load Spring Cloud Gateway was running on AWS t3.medium or t3.large instances. After moving to NGINX I am using t3.micro (8 times less memory) instance. I am almost sure that I can do the trick and with t3.nano (16 times less memory) instance, but I wanted to be sure that there will be no surprises.
Below are the high level steps what you have to do in order to plug NGINX in the Eureka ecosystem. More details you can find in NGINX With Eureka Instead of Spring Cloud Gateway or Zuul article.
Create a service which can read the configuration of all applications from Eureka and to 'translate' it to NGINX configuration.
Create a cronjob entry which at certain period will read the configuration from the above service and will call the NGINX hot reload
NGINX which will consume the configuration produced from the service and the cronjob and will work as API Gateway
I am developing a set of frontend webapps (for instance vaadin or angular) and backend RESTful services. Each frontend webapp will consume one or more of these backend services. I want both webapps and services to be secured over https.
Now, I want to register a single domain, say mydomain.com, and deploy the backend services such that they are available at
service1.api.mydomain.com, service2.api.mydomain.com etc. The frontend apps should be available at webapp1.mydomain.com, webapp2.mydomain.com etc.
I need to be able to setup two or more EC2 instances for the services, and the same for the webapps. For instance, service1 may be running instance A, service2 on instance B, and webapp1 on instance C, and webapp2 on instance D.
How do I configure this setup in AWS Route 53?
Since there is a limit to the max number of Elastic IPs (max 5) that can be allocated for one AWS account, I suppose separate public IPs for all the EC2 instances is not a solution, since I will be having more than 5 such subdomains.
I hope you can provide a practical example configuration with two services and two webapps.
You can submit a request to get the Elastic IP (EIP) limit increased for your account. Small increases (e.g. from 5 to 10) should be fairly quick and easy to obtain. Larger increases should be obtainable if you can justify it to AWS support.
https://console.aws.amazon.com/support/home#/case/create?issueType=service-limit-increase&limitType=service-code-vpc
If you're open to using path-based routing instead of subdomain based (e.g. mydomain.com/app1 and mydomain.com/app1/api) or a mix of the two (e.g. app1.mydomain.com and app1.mydomain.com/api), you could look at using an Application Load Balancer (ALB). You would need one ALB per subdomain used.
http://docs.aws.amazon.com/elasticloadbalancing/latest/application/tutorial-load-balancer-routing.html
Note: I expect subdomain-based routing to be available with the ALB in the future, but it hasn't been released yet.
ALBs could be cheaper than using Classic Elastic Load Balancers (ELBs), but if you're not using the load balancing functionality at all, EIPs may be your best bet since they're free when attached to a running instance.
I'm trying to setup a basic web application, which has an associated database, in AWS ECS. Locally I have these setup in different containers, and on ECS, I'd like to have separate task definitions so that I may scale the two separately.
I registered my first task definition as david_mongodb successfully in ECS. It has a container named david_mongodb in it.
Then I attempted to register my second task definition as david_web, which has a container named david_web that links the database via david_mongodb:db.
When I click 'Create', it returns an error:
Unable to create Task Definition
Linked container 'david_mongodb:db' doesn't exist.
It seems like task definitions can't see container names in other task definitions? I'm thinking putting both david_web and david_mongodb containers in the same task definition would work, but I don't want to do that: it would prevent me from scaling either web app or database separately. This overview seems to confirm that my architecture is recommended...
So how do I link containers that live in different task definitions? Or is there another clever way of handling this?
Links in an ECS task definition are analogous to Docker links and only work when the containers are part of the same task definition (containers that are part of a single task definition are placed together on the same host). In order to communicate between containers in different task definitions, you'll need a mechanism for discovering where the containers are located (what host) as well as the port for communication.
ECS has integration with Elastic Load Balancing (Application Load Balancers, Network Load Balancers, and Classic Load Balancers) through the service feature, where tasks will be automatically registered in the ELB and deregistered in the ELB appropriately.
ECS also has integration with Route 53 Auto Naming for DNS-based service discovery using A and SRV records. Your service's tasks can be automatically entered into and removed from DNS records.
Service Discovery for Amazon ECS Using DNS describes a different approach where a Lambda function listens to the ECS event stream through CloudWatch Events and updates Route 53 DNS records. This method has been superceded by the Route 53 Auto Naming feature described above.
If you want to avoid load balancers and DNS, another pattern might be an ambassador container (there's a sample called the ecs-task-kite that uses the ECS API) or you might be interested in an overlay network (Weave has a fairly detailed getting started guide for their solution).
Nathan Peck is keeping track of a number of different subjects related to ECS, including service discovery, here.
you could now refer to this official best practices guide on networking between Amazon ECS services in a VPC, discussing on the considerations when adopting service discovery, ELB or service mesh for service-to-service communication with ECS.