The CPU‑based health check says "HealthCheck":"CPU Busy" The configuration and programs are examples of possible ways to use active health checks on applications in Docker … They return "HealthCheck":"OK" if they’re successful. For example, if your servers need some warm‑up time when they come back to health, they may respond to the health check even though they’re still warming up caches and other things. rbusyhealthchecksunit_unitmem_1 is up-to-date We will set the Command while running the Docker Container. The downloaded nginx-proxy folder contains a docker-compose.yml file. Please write to us at [email protected] to report any issue with the above content. Stopping and removing rbusyhealthchecksunit_unitcpu_2... done error_page 502 =503 /apibusy.html NGINX Plus brings active health checks. It seems to happen for random URLs. 2:27 Base Topology for Demo I’m going to show what happens when I make them [the servers in the unitcnt upstream group] both busy. And I can also run this and see that I get "Busy". How to Get the IP Address of a Docker Container? And we can go ahead and run another test that consume less CPU – 10% to 15% – and it’s going to run just fine. For the memory-based health check, I’m actually limiting each container to 128 MB. Then I tell the health check that if the container is using more than 70% of that, it is unhealthy. I’m actually limiting it – because Docker makes this easy – to 128 MB. [email protected]:~# curl https://localhost:8001/testcnt.py/healthcheck 12:36 Demo: Failing the Count-Based Health Check Using this directive it is possible to verify whether the status is in a specified range, whether a response includes a header, or whether the header or body … I’m using Docker Compose for everything, so I’ll spin up some containers: [The resulting set of containers is] basically the picture I showed you a moment ago, and we should have a bunch of containers now, and we do. The CPU‑based health check is a little more complicated. Health Check Another Container So I have a docker-compose file for MariaDB and Adminer which I use for my local sql projects. This case is "OK", so I can actually hit it either way. In the case of Docker, a health check is a command used to determine the health of a running container. Contribute to eyal-lupu/docker-nginx-healthcheck-webserver development by creating an account on GitHub. $ docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 6337c95a1542 nginx:latest "nginx -g 'daemon of 5 minutes ago Up 18 seconds 443/tcp, 0.0.0.0:8080->80/tcp my-nginx コ … If you want to use something like them, you’ll need to do a lot more testing than I have. [While the one server in the unitcpu group is marked unhealthy], we can also see a failed health check by running the health check against it [it’s on port 32808]. 準備 Another place explains that Docker will stop sending traffic to tasks that are unhealthy. But, you see, it says "OK", and you’ll see my CPU utilization is minimal here because nothing’s happening. I wanted to be able to show you an unsuccessful health check, but it turns out that with regular server blocks I can never do that, because as soon as the server fails and goes unhealthy, NGINX Plus won’t send a request to it anymore because it’s down. F5, Inc. is the company behind NGINX, the popular open source project. The Nginx container uses both ports 80 and 443, I've set up the Target group for the servers, which include Nginx docker container, based on these ports but still the servers health check is Unhealthy. But anything that’s not "OK" is a failure. 14:22 Demo: Failing the CPU-Based Health Check This is the basic config. [email protected]:~# docker ps location /health { health_check; proxy_pass http://backend; proxy_http_version 1.1; proxy_set_header Host $host; } These parameters are separated by a colon and indicate : respectively. I listen to port 8082, and requests to the API will get me the raw JSON, which is what my program is using. The health check is still going to succeed. Talking TypeScript with the engineer who leads the team. I don’t know if you’ve ever run the top command in a Docker container, but you’ll find out that you’re seeing results from the Docker host. Next I want to show you the CPU‑based health check. Scaling down with Docker‑Compose takes a few seconds longer, but we should get it down there in a second. Instead of installing NGINX as a package on the operating system, you can rather run it as a Docker container. But now the health check is going to fail. Writing code in comment? But I’ve intentionally kept it to as few lines as possible. Next I want to show you the CPU‑based health check. Health Details: The Docker Compose’s Way A simple way to solve the problem is to use the built-in health checks functionality available in docker-compose 2.1.We can basically tell a service to wait until another service (or multiple services) have completed a health check. The upstream 172.17.0.3 is on the very same machine on which runs Nginx. You’ll see that this one takes a while because I’m making an API request, I wait a second, I make another API request, and I do a calculation. I’ve got NGINX Plus at the frontend, load balancing three sets of upstreams. If it sees it, it marks the application as unhealthy. The health check will look for the existence of that file. But, you see, it says "OK", and you’ll see my CPU utilization is minimal here because nothing’s happening. They let you tell the platform how to test that your application is healthy, and the instructions for doing that are captured as part of your application package. Most popular in Advanced Computer Subject, More related articles in Advanced Computer Subject, We use cookies to ensure you have the best browsing experience on our website. That’s where I wanted to be. 8:14 NGINX Plus Configuration for Virtual Servers My name is Rick Nelson, and I head up the pre-sales engineering team here at NGINX. This can reflect … This post is adapted from a presentation at nginx.conf 2017 by Rick Nelson, Head of the Sales Engineering Team at NGINX, Inc. You can view the complete presentation on YouTube. When Docker starts a container, it monitors the process that the container runs. The HEALTHCHECK instruction declares the health check command that can be used to determine whether or not the service status of the container master process is normal. Again, I get the data from the Docker status API, to tell me how much memory it’s using. "OK" is a success. We should be able to see them in the NGINX Plus status dashboard [he opens the dashboard in the left half of the window]. I’m going to scale the number of instances of each upstream application to two: We can see how service discovery works with Consul. For the memory‑based health check, I’m actually limiting each container to 128 MB. This configuration and the CPU health check program utilize the the dashboard.html page and Version 2 of the NGINX Plus API, both included in the NGINX Plus R14 release. For the CPU‑based health check, I’ve set a threshold of 70% utilization by the application of the Docker host’s capacity. This one comes back a bit faster, and it tells me that I’m "OK" for the memory check as well. Check if nginx is healthy; Make Docker container Unhealthy and check; Create the nginx.conf file and Making the container go healthy; Writing a Dockerfile with HEALTHCHECK instruction. 1.17.6-alpine-perl, mainline-alpine-perl, 1-alpine-perl, 1.17-alpine-perl, alpine-perl [email protected]:~# curl https://localhost:8001/testcnt.py/healthcheck And we can go ahead and run another test that consume less CPU – 10% to 15% – and it’s going to run just fine. We’ll see, in 10 seconds, that it’s going to come back to life. The health check intervals for the other two health checks might be set to higher values in production. The Docker engine, starting back in version 1.12, provides a way to define custom commands as health checks. This was a new directive introduced during Docker 1.12. Docker images are configured using parameters passed at runtime (such as those above). shopify/nginx-ingress-controller-amd64 I’m going to briefly go through the configuration here; this will all be in [GitHub] after the conference. Health Details: As Docker health check is a shell command, it can test virtually anything.When the test fails few times in a row, problematic container will get into “unhealthy” state, which makes no difference in standalone mode (except for triggered health_status event), but causes container to restart in Swarm mode. These are the three use cases I’m going to talk about today. The statistics are about that container’s usage of the Docker host. We’ll see that it’s all automatic. I’m also using NGINX Plus status API because, when I’m looking at the CPU utilization, I actually need to know how many containers there are. NGINX Plus health checks have a slow‑start feature where you can tell NGINX Plus to ramp the load up slowly so servers doesn’t get hammered when they first come back to life. I’m going to briefly go through the configuration here; this will all be in [GitHub] after the conference. If all the upstreams are busy and failing health checks, NGINX Plus returns a special page to the client, /apibusy.html. It’s going run again every three seconds, but usage by one server will never hit 70%. nginx proxies any other request to the Grafana instance running inside the container. I’ve programmed the application so that if it gets another request while it’s processing one, it returns 503. Container. The moment we add a healthcheck to the docker compose file like this, not only does the healthcheck not pass but the /health endpoint can't be curled either inside or outside the container also the container doesn't accept any requests. If it sees it, it marks the application as unhealthy. In the case of Docker, a health check is a command used to determine the health of a running container. I have to come up with a solution so that, basically, when the service is processing a request, it’s considered unhealthy. For example, if I have one container, it can use 70% of the host, but if I have two containers, then each one can has 35%, and so on. nginx health check via docker. I do want to make a disclaimer here: these [health check types] have not been tested in production, they haven’t been tested at scale; they’re just some ideas I’ve been playing around with. These parameters are separated by a colon and indicate : respectively. I’ll be showing you a demo in a few minutes. That’s because that container is over the 35% that’s available for each one. Copyright © F5, Inc. All rights reserved.Trademarks | Policies | Privacy | California Privacy | Do Not Sell My Personal Information, NGINX Microservices Reference Architecture, Fun with Health Checks using NGINX Plus and Docker, Topology for the Three Types of Health Check, NGINX Plus Configuration for Upstream Servers, Health Checks, and Status, NGINX Plus Configuration for Virtual Servers. {"Error":"System busy"} Kubeaudit audits Kubernetes clusters for common security controls. You can configure what URI to hit, how often you run them, and what a proper response status code is. Stopping and removing rbusyhealthchecksunit_unitcpu_2... That again ties us into Consul and gives us SRV record support. He then corrects the URL with the following result.] For the memory‑based health check, it’s a little bit different. On the NGINX Plus dashboard, we should see one of the servers in the unitcnt group go red pretty quickly [the top one does]. The Overflow Blog The Overflow #25: New tools for new times. Returning to the count‑based health check, if we want to make one application instance busy, I have this program that I run. Starting rbusyhealthchecksunit_unitcpu_1... done They’re also very configurable. For the CPU-based health check, I’ve set a threshold of 70 percent of the Docker host utilization for the application. Docker nginx health check. Contribute to eyal-lupu/docker-nginx-healthcheck-webserver development by creating an account on GitHub. It just tells the client there’s nothing available at the requested URI. I’m going to show what happens when I make them [the servers in the unitcnt upstream group] both busy. Health checks can be configured to test a wide range of failure types. Now, for my server blocks, I’m going to go into detail here. For the count‑based health check, the service is so heavyweight that it can only handle one request at a time. If the usage goes above 70%, it marks it unhealthy; when it goes below 70%, it becomes healthy again. Then I tell the health check: if the container is using more than 70 percent of that, it marks it as unhealthy. In case you are using a proxy like ‘nginx’ & ‘haproxy’, you must configure these Docker APIs in that proxy service to enable health checks to be performed externally. I am trying to setup a production environment for multiple WordPress sites using Docker, Nginx reverse proxy, and Let’s Encrypt. FROM nginx:1.17.7 RUN apt-get update && apt-get install -y wget HEALTHCHECK CMD wget -q --method=HEAD localhost/system-status.txt Writing a Custom Health Check in Nodejs docker build -t docker-health . That again ties us into Consul and gives us SRV record support. I have no Docker containers here. This configuration and the CPU health‑check program uses the built‑in live activity monitoring dashboard that uses version 2 of the NGINX Plus API, introduced in NGINX Plus R14. I didn’t have to do anything but basically point NGINX Plus at it. And again, I chose 70% as my threshold. I do have the intervals [Editor – Rick says “durations” but is referring to the interval parameter] on the health_check directives to be a bit different: For this case, notice the second one from the top [in the output from docker stats] – it’s the one limited to 128 MB, which is how I can identify it. We can see how service discovery works with Consul. If we run this command, it should take up 50 to 60% of the CPU. On the right side of the slide, I’ve configured the NGINX Plus API – which, again, I’m using to get the count of the number of containers. We can build the Docker Image using the build command. comments [email protected]:~# curl https://localhost:8001/testcng.py?sleep=15& Docker introduced native health check implementation after version 1.12. There it goes [on the dashboard, one of the servers in the unitcpu group goes red]. When the test finishes, if we send the health check again see that it’s says "OK". I had that special URL so I can see these things directly [he’s referring to the first server block he talked about, for seeing a failed healthcheck]. They’re also very configurable. Again, I use the Docker API to get the CPU utilization for the container, making two calls, one second apart, to gather the data. This document introduces the health check of Docker containers. That tells us that the health check went to a different server. This will launch three services: nginx: the nginx-reverse proxy, uses the default nginx image. Healthchecks for nginx in docker - Esteban, Healthcheck Dockerfile. 787 Downloads. [email protected]:~# curl https://localhost:8001/testcnt.py/ {"HealthCheck":"CPU Busy","CPUUsage":51.5,"TotalThreshold":70,"ThresholdPerNode":35... I’ve told it I want status code 200 and I want to see the body starting with "HealthCheck":"OK" because, as I showed you a couple of slides ago, that’s the response for a successful health check. The Python server block is a little bit different [from the PHP ones] because with Python and Unit, I have one Python program on each listener. Home› GitHub Gist: instantly share code, notes, and snippets. Once a health check fails, the server gets marked as down. All requests received on the port defined by the healthz-port parameter are forwarded internally to this path. I’m actually limiting it – because Docker makes this easy – to 128 MB. {"HealthCheck":"OK","MemUsedPercent":32.1,"MemUsed":41.1,"MemLimit":128,"Threshold"... The Docker Registry HTTP API is the protocol to facilitate distribution of images to the docker engine. They’re all running NGINX Unit. {"HealthCheck":"OK","Host":"cdb601bf181a"} If you know NGINX and NGINX Plus, this one is fairly straightforward and quite minimal. Let’s get on with the demo. If you know NGINX and NGINX Plus, this one is fairly straightforward and quite minimal. All the code … 16:36 Demo: Failing the Memory-Based Health Check I only have one container, so that container can use up to 70% of the CPU without causing a problem. In the above Dockerfile, we pull the nginx base image and perform a HEALTHCHECK with the specified interval and timeout. Official kubeaudit image. [Editor – The slide above and the following text has been updated to refer to the NGINX Plus API, which replaces and deprecates the separate status module originally discussed here. Right now, I have the threshold set at 70%. Please note — in our example, the name of the container is also the name of the application. [While the one server in the unitcpu group is marked unhealthy], we can also see a failed health check by running the health check against it [it’s on port 32808]. But again, for the demo, I want things to be very quick. The other two, for my CPU and memory utilization checks, are written in PHP. You have a service where you’re very concerned about CPU utilization, or maybe it’s memory utilization, or maybe you have some really heavy requests and your backend can only handle so many requests at a time. For the count‑based health check – the one limited by how many requests can be processed at a time – the app is written in Python. In a distributed system, the service availability is frequently checked by using the health check to avoid exceptions when being called by other services. I’ve got my Python application [for the count‑based health check] in the lower left, and my PHP applications [for the CPU‑based and memory‑based health checks] on the right. Accept cookies for analytics, social media, and advertising, or learn more and adjust your preferences. This deactivation will work even if you later click Accept or submit a form. I could make it 1 second as well, but I thought 2 was good enough for this. It performs health checks at regular intervals. I forgot to mention that all of the server blocks have this line here: If all the upstreams are busy and failing health checks, NGINX Plus returns a special page to the client, /apibusy.html. 10:18 Demo: Spinning Up Containers Once a health check fails, the server gets marked as down. Here’s where I define my upstreams. If they then get slammed with load [because they responded successfully to a health check], they’ll fall over again. We’ll see that it’s all automatic. If not, then have a great day. [email protected]:~# curl https://localhost/healthcheckpy?server=172.17.0.1:32804 Here is the sample dockerfile command where health check is enabled. When it comes to getting system stats in a Docker container, you’ll find that you can’t really get them very easily from the container itself, so you use the Docker API. I have 3 containers for the proxy group using the jwilder/docker-gen, I assume, since you’re here at an NGINX conference, that most of you know about NGINX Open Source 0:47 NGINX Plus Active Health Checks I’ll talk about that in a little more detail in a minute. For example, -p 8080:80 would expose port 80 from inside the container to be accessible from the host's IP on port 8080 outside the container. This one in the upper left is a special one I put in just for the demo. 6.2k members in the nginx community. This can detect cases such as a web server that is stuck in an infinite loop and unable to handle new connections, even though the server process is still running. Now let’s take a look at the different health checks. All downstream connections come from CloudFront. It says it’s "OK". For this, I want to run docker stats so we can see the CPU utilization on these guys. {"Status":"Count test complete in 10 seconds","Host":"cdb601bf181a"} For the count‑based health check, I have a 1‑second [interval], because I really want to get that one quickly. The health check will look for the existence of that file. This case is "OK", so I can actually hit it either way. ... Cantaloupe can run behind a reverse-proxy web server like Apache or nginx. GitHub Gist: instantly share code, notes, and snippets. Now let’s take a look at the different health checks. There we go. When the application finishes processing the request, it removes the file. [email protected]:~# docker-compose up --scale unitcnt=2 --scale unitcpu=2 --scale unitmem=2... NGINX Plus will stop sending any actual traffic to it, but it’ll keep checking, and it won’t send traffic to it again until it has actually verified that the server is up. If we run that same program again (I’m going to run it for a little longer this time): We’re going to see CPU utilization for one container going to go up again to 60% or so: But now the health check is going to fail. The match directive enables NGINX Plus to check the status code, header fields, and the body of a response. The memory‑based health check says "HealthCheck":"Memory low" The mandatory parameter ensures that the health check must pass before traffic is sent on an instance, for example, when it is introduced or reloaded. It’s very quick, and it’s all automatic. When a request is received, the application will create the file /tmp/busy. The proxy_next_upstream directive tells NGINX Plus to try another server in that case. And if we look at our upstreams, we should see three upstreams, each with one server: [the one for] count‑based [health checks], the CPU‑based, and the memory‑based. The initial state is starting and after a successful checkup, the state becomes healthy. ... Let’s now check if it’s working for real: ... (official images use the library repository so nginx should be referred as library/nginx). docker run --rm --name docker-health -p 8080:80 docker-health An NGINX container is now running and listening on local port 8080. Nginx Plus can continually check upstream servers for responsiveness and avoid servers that have failed. To conclude, in this article we discussed what is HEALTHCHECK instructions, what are its uses, the various options you can use along with it. By default, this does it, and it waits for 10 seconds. I have another docker-compose for nginx proxy manager with a few bundled services that are proxied through this service. Configured inside the NGINX status server. If I try again, we’re going to get that special page I talked about which basically shows that they’re all busy. Requests for dashboard.html get us the NGINX Plus live activity monitoring dashboard page, which some of you may have seen, and which I’ll show you in a minute. CONTAINER ID IMAGE COMMAND CREATED STA... On the right side of the slide, I’ve configured the NGINX Plus API – which, again, I’m using to get the count of the number of containers. I divide the threshold by the number of containers, which tells me how much each container can have. Tips to Manage Docker Containers using CLI, Sign in Geeksforgeeks using Python Selenium, Classifying data using Support Vector Machines(SVMs) in Python, Basic Concept of Classification (Data Mining), Extendible Hashing (Dynamic approach to DBMS), How to create a REST API using Java Spring Boot, Write Interview For that, I can actually scale [the number of application servers] back down to one to show you the difference, and what happens as we scale up and down. Featured on Meta We're switching to CommonMark. The container builds and runs fine.Curling the /health endpoint works both inside the container and outside. The statistics are about that container’s usage of the Docker host. They’re on by default for everybody else. If you look at the two outputs, you’ll see the Host has changed. (default "/healthz")--health-check-timeout: Time limit, in seconds, for a probe to health-check-path to succeed. That’s where I wanted to be. We can pass in the server name for any one of the application servers, so I’ll do the first one listed on the dashboard. I hope that was interesting. I forgot to mention that all of the server blocks have this line here: The resolver directive at the top tells NGINX Plus to use Consul as the DNS server and dynamically re‑resolve all domain names every 2 seconds: I’m ignoring the time‑to‑live specified in the DNS response and saying to re‑resolve every 2 seconds. (In the PHP ones – you can’t see it here, but you’ll see it in a minute during the demo – I have one program for health checks and one program as the application.) I use the NGINX Plus status API to find how many containers there are. This is particularly important in dynamic and containerized environments. It just tells the client there’s nothing available at the requested URI. We can build the Docker Image using the build command. When the test finishes, if we send the health check again see that it’s says "OK". That will cause NGINX Plus to stop sending any requests to it. With the count‑based health check, there’s a use case where the request comes, and before a second expires until the health check gets called, NGINX Plus sends another request to it because it thinks it’s healthy. {"HealthCheck":"OK","Host":"d8dd08e46dc7"} It determines whether the Container is running in a normal state or not. It’s letting one go through because it’s using too much CPU, and the one that’s using less CPU – I mean, it’s blocking one and letting the other go through. For the count‑based health check, I have a 1‑second [interval], because I really want to get that one quickly. Here [with the Python server], I’m using one program, and based on the query parameter NGINX Plus knows whether to do the health check or whether to run the application. We offer a suite of technologies for developing and delivering modern applications. ... Docker. That’s it for the demo. Press question mark to learn the rest of the keyboard shortcuts Docker health checks - Dots and Brackets: Code Blog. They’re also very configurable. You’ll see that this one takes a while because I’m making an API request, I wait a second, I make another API request, and I do a calculation. I do have the intervals [Editor – Rick says “durations” but is referring to the interval parameter] on the health_check directives to be a bit different: Now, in production, you might increase these to be quite a bit longer. Get an NGINX Plus free trial and download the Unit beta and give it a try! 4:22 Implementation Details A little more detail: all three types of health check return JSON data. NGINX Plus will stop sending any actual traffic to it, but it’ll keep checking, and it won’t send traffic to it again until it has actually verified that the server is up. I could make it 1 second as well, but I thought 2 was good enough for this. For the CPU‑based health check, I’ve set a threshold of 70% utilization by the application of the Docker host’s capacity. The lower rectangle on the slide is a match block. But again, for the demo, I want things to be very quick. [email protected]:~# curl https://localhost:8001/testcng.py Suppose we have a simple Web service. You can set a Host header or HTTP/1.1 (or both) yourself to override these. For example, if I have one container, it can use 70% of the host, but if I have two containers, then each one can has 35%, and so on. When a health check command is specified, it tells Docker how to test the container to … I wanted to be able to show you an unsuccessful health check, but it turns out that with regular server blocks I can never do that, because as soon as the server fails and goes unhealthy, NGINX Plus won’t send a request to it anymore because it’s down. NGINX Plus active health checks are an easy way to deal with capacity limitations of services running in Docker, helping to make sure that service instances aren’t overloaded. nginx health check via docker. My answer: Like every other use of proxy_pass nginx defaults to making an HTTP/1.0 connection to the upstream with the Host header set to the defined name of the upstream or its IP address. Uncheck it to withdraw consent. The HEALTHCHECK instruction tells Docker how to test a container to check that it is still working. NGINX Plus R23 supports the gRPC health checking protocol so that upstream gRPC services can be tested for their ability to handle new requests. [email protected]:~# curl https://localhost:8002/testcpu.php?level=2 I don’t know if you’ve ever run the top command in a Docker container, but you’ll find out that you’re seeing results from the Docker host. A HEATHCHECK instruction determines the state of a Docker Container. I said, “Oh, that’s not good.” But the Docker API does allow you to get [per‑container statistics]. [Editor – The NGINX Plus API does not provide the raw JSON for the entire set of metrics at a single endpoint as the deprecated status module did; for information about the available endpoints, see the reference documentation.]