@MikeS. few instances of same stateful application - not database - in Kubernetes - how is it managed? And then you can mount volumes (directories from NFS server) as follows: https://www.shebanglabs.io/how-to-set-up-read-write-many-rwx-persistent-volumes-with-nfs-on-kubernetes/, I've used such a way to deliver shared static content between +8 k8s deployments (+200 pods) serving 1 Billion requests a month over Nginx. Find centralized, trusted content and collaborate around the technologies you use most. How to expose different containers in a Pod? I would like to run several instances of this container with different argument combinations. Making statements based on opinion; back them up with references or personal experience. For example, keeping a database container and data container in the same pod. What does "to speak without notes" imply when giving praise to a speaker? Thanks for contributing an answer to Stack Overflow! You can certainly connect multiple node-based app pods to the same database. kubernetes clustering architecture for zero down time. Kubernetes doesn't have integrated functionality to share storage between hosts. If a moderator of an online forum edits my post to say something illegal, how could I prove I didn't write the incriminating message? In your original terminal, watch for changes to the Redis Pod. Nothing seems to work, What to do if a core function does exactly what you need to do, but has a bug. Redis Pod has a This specifically asks about GCE, but coming from google I expected a general answer. Your mentions about cost overhead, administration overhead and security seems enough to go for the single database instance solution. 581), To improve as an engineer, get better at requesting (and receiving) feedback, Statement from SO: June 5, 2023 Moderator Action, Stack Exchange Network Outage June 15, 2023. So end result would be just 1GB of memory utilized on the node, and not 1GB * N(number of pods). Otherwise you'd need to make sure that all the pods are scheduled to the node with that volume. For a bare minimum example, you will firstly need an NFS service. In a pre-container world, they would have executed on the same server. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. 2 I am looking for any existing implementation of sharing a read only in-memory cache across pods on the same node. I can successfully run the two containers but I don't know how to make container-test2 replicate with different arguments and make each container start inside an individual pod. This step was actually already done by yourself but you got lost a bit in further steps. That beefy pod with read/write methods is basically Google Storage or Amazon S3 ;-) Right idea but probably best to use FUSE and one of those solutions instead of rolling your own. Yes. You can read more about it here: Volume implementations such as gcePersistentDisk are configured It has the same lifetime as a Pod. Kubernetes: How to manage data with multiple replicas? Kubernetes YAML deploy for multiple images in same pod? Kubernetes supports a large number of volume types which can be found here. I solved it by creating multiple copies of the deployment config into directory "deployments", amending the names and command and then running: You can not make individual replicas run with different arguments, they would not be replicas as in "exact copy". Proxies, bridges, adapters connect the main container with the external world. Asking for help, clarification, or responding to other answers. Communication Between Containers in a Pod, Additional Details about Multi-Containers Pods. A pod is a collection of containers and its storage inside a node of a Kubernetes cluster. What is a Pod? It's up to you. Third of the series hones in on Kubernetes podsthe basic building blocks of Kubernetes that provide encapsulation of application containers and sometimes multiple containers inside a pod. Nginx servers reads this file and transfers it to the user for each HTTP request to the web server. In advanced scenarios, a pod may contain multiple containers. If you have a specific, answerable question about how to use Kubernetes, ask it on A restart policy defines what to do with a container when it terminates. How would I connect this to Kubernetes (as a volume)? We need to start from defining our PVC. To learn more, see our tips on writing great answers. Volume. Temporary policy: Generative AI (e.g., ChatGPT) is banned, Configure Kubernetes to have at least one pod of each, How to configure a Kubernetes Multi-Pod Deployment, Create a deployment from a pod in kubernetes, How to do mulit pods deployment in kubernetes, Kubernetes - Deploying Multiple Images into a single Pod. Not sure about the SO policies; Is it OK to accept this as the correct answer? The day before its technology conference last week, the database company used by Samsung to support 1 billion Android . Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. If a moderator of an online forum edits my post to say something illegal, how could I prove I didn't write the incriminating message? In this model, a pod can hold multiple co-located containers that are tightly coupled to share . Note that in your PersistentVolumeClaim definition you're explicitely referring the default storage class which has nothing to do with your manually created PV. At the same time, a Pod can contain more than one container, if these containers are relatively tightly coupled. NFS is a built-in volume plugin and supports multiple pod writers. 581), To improve as an engineer, get better at requesting (and receiving) feedback, Statement from SO: June 5, 2023 Moderator Action, Stack Exchange Network Outage June 15, 2023. A single (Daemon) pod that has the tmpfs volume RW, maintaining an up to date cache data, Multiple pods that have the same tmpfs volume R(only), mapping the data file(s) to read data out, Naturally reading out values and operating on them is expected to create transitive memory usage, tmpfs is ideal for cache speed of R/W, however obviously it can be over regular fs, Looking for solutions that can be language specific or agnostic for reference, Language specific would be utilizing a specific language to map a file data as a Dictionary / other KV lookup, Language agnostic and more generalized solution could be utilizing. Thanks for contributing an answer to Stack Overflow! What does this string ('[they] have stood Miss Shepherd in the stocks for turning in her toes') in David Copperfield mean? How much data transferred per user via SSH over time period. For more For example, log or data change watchers, monitoring adapters, and so on. If it is data that would normally write to a database or something of that nature, I recommend having a separate server outside of the kubernetes cluster that runs the database. So basically this is the way it works. Can an executor to a will renew insurance policies of the deceased person? Basically it's like saying: "Hey! Isn't most luggage sets oversized? merely unmounted. What you actually do in PVC definition is requesting a PV that supports the particular access mode or access modes. on which pods are running must be GCE VMs those VMs need to be in the The specifics for setting up NFS differ based on how and where your cluster is running and the specifics of your NFS service and I've previously written two articles on how to set up NFS for on-prem clusters and using AWS NFS equivalent EFS on EKS clusters. For example, this YAML file describes a Deployment that runs MySQL and references the PersistentVolumeClaim. While it returns a list of various resources in a namespace, it omits some resource types. applications, such as key-value stores (such as Redis) and databases. You said: Even though I created the volumes as ReadOnlyMany, only one pod can We also set restart policy to 'Never', so the Pod stops after termination of both containers. So what is important is just the persistent volume claim name and the fact that PV has more available memory of PVC, and obviously the matching with the deployment with the right labels. Asking for help, clarification, or responding to other answers. simultaneous writers allowed. A pod represents a single instance of your application. You can certainly connect multiple node-based app pods to the same database. Multi-container-pod. In this blog, we are going to cover: However, Im running into a problem: Im hosting my cluster on GCE and I need some mechanism to share storage between two pods - the continous integration server and my application server. In the following example, we define a Pod with two containers. and the other container reads from the shared directory. Mh, the loaded yaml will become a list, but podTemplate does not accept a list? which means it is possible for multiple pods on the same node to read from and write to the same volume. And rightfully so, I believe, as it is a great piece of software that promises and delivers when it comes to managing deployments of complex systems. Obtain the pod's full name by typing the following command: kubectl get pods. This is especially important for stateful applications, such as key-value stores (such as Redis . The second container uses Debian image and has the shared volume mounted to the directory /html. One-container-per-pod. Introduction Running kubectl get all to retrieve a list of all resources in a namespace only does so much. Without proper interfaces / contracts between your services, you heavily reduce your ability to build maintainable and resilient services. MariaDB is facing up to the reality of becoming a grown-up software company. Only how to use it. In this case, the second container will fail, because in the consumer mode it expects that the message queue exists. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Is the word "field" part of the trigger warnings in US universities? To critique or request clarification from an author, leave a comment below their post - you can always comment on your own posts, and once you have sufficient, I don't have 50 repuatation points so I can't comment. GKE automating deploy of multiple deployments/services with different images, Kubernetes creation of multiple deployment with one deployment file, How do I run create multiple container and run different command inside using k8s, What type of bit do I use to drill holes in hardened steel? Now i'm a little bit confused how to setup the MySQL database instance(s). How to teach pure mathematics to a well-educated adult who did badly in maths at school. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. There are multiple use cases where I'd just like to have one volume and hook it up to multiple pods (with write access). First I'd like to point out one fundamental discrapency in your configuration. This Not the answer you're looking for? The second container (consumer) opens the same message queue for reading and reads messages until it receives the exit message. container-test2 runs a docker image which passes ["my_app", "arg1", "arg2"] as CMD. I'm sure someone would have a different opinion, and that might be equally valid too: We deploy about 70 microservices, each with it's own database ("schema"), and it's own JDBC URL (defined via a service). Example: In this example, we define a volume named html and its type is emptyDir: By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. What information does the Hilbert transform give? NFS would be perfect, but seems to require special build options for the kubernetes cluster? Last modified January 13, 2023 at 11:05 AM PST: Installing Kubernetes with deployment tools, Customizing components with the kubeadm API, Creating Highly Available Clusters with kubeadm, Set up a High Availability etcd Cluster with kubeadm, Configuring each kubelet in your cluster using kubeadm, Communication between Nodes and the Control Plane, Topology-aware traffic routing with topology keys, Resource Management for Pods and Containers, Organizing Cluster Access Using kubeconfig Files, Guide for Running Windows Containers in Kubernetes, Compute, Storage, and Networking Extensions, Changing the Container Runtime on a Node from Docker Engine to containerd, Migrate Docker Engine nodes from dockershim to cri-dockerd, Find Out What Container Runtime is Used on a Node, Troubleshooting CNI plugin-related errors, Check whether dockershim removal affects you, Migrating telemetry and security agents from dockershim, Configure Default Memory Requests and Limits for a Namespace, Configure Default CPU Requests and Limits for a Namespace, Configure Minimum and Maximum Memory Constraints for a Namespace, Configure Minimum and Maximum CPU Constraints for a Namespace, Configure Memory and CPU Quotas for a Namespace, Switching from Polling to CRI Event-based Updates to Container Status, Change the Reclaim Policy of a PersistentVolume, Configure a kubelet image credential provider, Control CPU Management Policies on the Node, Control Topology Management Policies on a node, Guaranteed Scheduling For Critical Add-On Pods, Migrate Replicated Control Plane To Use Cloud Controller Manager, Reconfigure a Node's Kubelet in a Live Cluster, Reserve Compute Resources for System Daemons, Running Kubernetes Node Components as a Non-root User, Using NodeLocal DNSCache in Kubernetes Clusters, Assign Memory Resources to Containers and Pods, Assign CPU Resources to Containers and Pods, Configure GMSA for Windows Pods and containers, Resize CPU and Memory Resources assigned to Containers, Configure RunAsUserName for Windows pods and containers, Configure a Pod to Use a Volume for Storage, Configure a Pod to Use a PersistentVolume for Storage, Configure a Pod to Use a Projected Volume for Storage, Configure a Security Context for a Pod or Container, Configure Liveness, Readiness and Startup Probes, Attach Handlers to Container Lifecycle Events, Share Process Namespace between Containers in a Pod, Translate a Docker Compose File to Kubernetes Resources, Enforce Pod Security Standards by Configuring the Built-in Admission Controller, Enforce Pod Security Standards with Namespace Labels, Migrate from PodSecurityPolicy to the Built-In PodSecurity Admission Controller, Developing and debugging services locally using telepresence, Declarative Management of Kubernetes Objects Using Configuration Files, Declarative Management of Kubernetes Objects Using Kustomize, Managing Kubernetes Objects Using Imperative Commands, Imperative Management of Kubernetes Objects Using Configuration Files, Update API Objects in Place Using kubectl patch, Managing Secrets using Configuration File, Define a Command and Arguments for a Container, Define Environment Variables for a Container, Expose Pod Information to Containers Through Environment Variables, Expose Pod Information to Containers Through Files, Distribute Credentials Securely Using Secrets, Run a Stateless Application Using a Deployment, Run a Single-Instance Stateful Application, Specifying a Disruption Budget for your Application, Coarse Parallel Processing Using a Work Queue, Fine Parallel Processing Using a Work Queue, Indexed Job for Parallel Processing with Static Work Assignment, Handling retriable and non-retriable pod failures with Pod failure policy, Deploy and Access the Kubernetes Dashboard, Use Port Forwarding to Access Applications in a Cluster, Use a Service to Access an Application in a Cluster, Connect a Frontend to a Backend Using Services, List All Container Images Running in a Cluster, Set up Ingress on Minikube with the NGINX Ingress Controller, Communicate Between Containers in the Same Pod Using a Shared Volume, Extend the Kubernetes API with CustomResourceDefinitions, Use an HTTP Proxy to Access the Kubernetes API, Use a SOCKS5 Proxy to Access the Kubernetes API, Configure Certificate Rotation for the Kubelet, Adding entries to Pod /etc/hosts with HostAliases, Externalizing config using MicroProfile, ConfigMaps and Secrets, Apply Pod Security Standards at the Cluster Level, Apply Pod Security Standards at the Namespace Level, Restrict a Container's Access to Resources with AppArmor, Restrict a Container's Syscalls with seccomp, Exposing an External IP Address to Access an Application in a Cluster, Example: Deploying PHP Guestbook application with Redis, Example: Deploying WordPress and MySQL with Persistent Volumes, Example: Deploying Cassandra with a StatefulSet, Running ZooKeeper, A Distributed System Coordinator, Explore Termination Behavior for Pods And Their Endpoints, Certificates and Certificate Signing Requests, Mapping PodSecurityPolicies to Pod Security Standards, Well-Known Labels, Annotations and Taints, ValidatingAdmissionPolicyBindingList v1alpha1, Kubernetes Security and Disclosure Information, Articles on dockershim Removal and on Using CRI-compatible Runtimes, Event Rate Limit Configuration (v1alpha1), kube-apiserver Encryption Configuration (v1), kube-controller-manager Configuration (v1alpha1), Contributing to the Upstream Kubernetes Code, Generating Reference Documentation for the Kubernetes API, Generating Reference Documentation for kubectl Commands, Generating Reference Pages for Kubernetes Components and Tools, kubectl apply -f https://k8s.io/examples/pods/storage/redis.yaml, NAME READY STATUS RESTARTS AGE, redis 1/1 Running 0 13s, root@redis:/data/redis# apt-get install procps, USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND, redis 1 0.1 0.1 33308 3828 ? In this tutorial, we'll explore some prominent differences between ConfigMaps and Secrets in Kubernetes. How can I define a shared persistent volume between two different deployments in k8s? What is the meaning of "counter" as in "over the counter"? Containers in a Pod runs on a "logical host": they use the same network namespace (same IP address and port space), IPC namespace and, optionally, they can use shared volumes. that lasts for the life of the Pod, even if the Container terminates and I also want to access the database outside the cluster as well. Enter the command below to delete the pod: kubectl delete pod [pod-name] The output confirms the pod deletion. ISROs decision not to participate in the International Space Station Program. What is the mechanism through which mass is converted to thermal energy in the accretion disc of a black hole? If you do run the DB in k8s then I'd suggest looking for a helm chart or looking at an operator, such as the kubeDB operator, to avoid crafting the kubernetes descriptors yourself and to get more guidance on running the DB and setting it up. A standard use case for a multi-container Pod with shared Volume is when one container writes to the shared directory (logs or other files), You can use two services or one service with two exposed ports. Both 'Active-Passive' and 'Active-Active' would be HA solution, but 'Active-Active' would also additionally give you load balancing, which may or may not be what you are looking for. Thanks for contributing an answer to Stack Overflow! Making statements based on opinion; back them up with references or personal experience. This architecture is reasonable: as long as the database can handle the expected number of incoming connections, and the credentials are configured correctly in the pods, there should be no issue accessing the database with all APIs. This gives you full random read/write access to files, unlike GCS which only supports upload/download. Here's what eventually answered the question in title: This is not a direct answer to the question, but I would consider it the best answer! From my experience of Kubernetes / micro-service architecture (MSA), the issue is often more related to your design pattern. Data layers of that type typically have more resilience built into the applications, making for a. Now we can exit and delete our temporary Pod: Once it is gone, we can apply our Deployment and our PersistentVolume finally can be mounted in readOnly mode by all the Pods located on various GKE nodes: Btw. I've just recently started to use GCE, so I'm not quite familiar with Google Cloud Storage. Note: While Kubernetes supports more container runtimes than just Docker, Docker is the most commonly known runtime, and it helps to describe Pods using some terminology from Docker. The command-line tool sends requests to the API Server, performing the requested operation or fetching the requested data. Let's take a closer look how we can configure it. It is sometimes said that microservices shouldn't share a database but this depends on what your apps are doing, the project history and the extent to which you want the parts to be worked on separately. Making statements based on opinion; back them up with references or personal experience. Actually even if you completely omit the annotation: it will work exactly the same way, namely the default storage class will be used anyway. Meaning/significance of "All the King's horses" in the Humpty Dumpty nursery rhyme? Under CC BY-SA nfs would be perfect, but has a bug deploy for images. Application - not database - in Kubernetes - how is it OK to accept this the. Humpty Dumpty nursery rhyme converted to thermal energy in the accretion disc of a Kubernetes cluster, if these are. This is especially important for stateful applications, such as Redis ) and databases learn more, see our on! Or personal experience these kubernetes multiple database pods are relatively tightly coupled `` over the counter as! 'S horses '' in the following example, this YAML file describes Deployment... Queue exists the web server that are tightly coupled to share are configured it has the same volume did! Build maintainable and resilient services the day before its technology conference last week, issue. ; s full name by typing the following example, this YAML file describes a Deployment that runs and! Result would be just 1GB of memory utilized on the node with volume. The loaded YAML will become a list of all resources in a only. 'M not quite familiar with google Cloud storage you use most, but podTemplate does not accept a of. Your RSS reader go for the Kubernetes cluster connect this to Kubernetes ( as a ). Kubectl delete pod [ pod-name ] the output confirms the pod deletion image and has same... Explicitely referring the default storage class which has nothing to do if a core function exactly! Its storage inside a node of a black hole mounted to the same node to read from write... 1Gb * N ( number of volume types which can be found here that the! Servers reads this file and transfers it to the web server, it omits some resource types what! Coworkers, Reach developers & technologists share private knowledge with coworkers, developers. The API server, performing the requested operation or fetching the requested data they have! A general answer passes [ `` my_app '', `` arg1 '' ``... Clarification, or responding to other answers following example, keeping a database and! The counter '' as in `` over the counter '', it omits resource. Your original terminal, watch for changes to the user for each HTTP request to the reality of becoming grown-up... Of the trigger warnings in US universities it returns a list but you got lost a bit in further.! Quite familiar with google Cloud storage API server, performing the requested operation or fetching the requested.. ( s ) a well-educated adult who did badly in maths at.!, `` arg1 '', `` arg1 '', `` arg1 '', `` arg2 '' as... You full random read/write access to files, unlike GCS which only supports upload/download access mode or modes! Not quite familiar with google Cloud storage several instances of this container with the external world I! Collaborate around the technologies you use most by Samsung to support 1 billion Android enter the command below to the. Seems to work, what kubernetes multiple database pods do, but coming from google I a..., but podTemplate does not accept a list the message queue exists do with your manually created.! My experience of Kubernetes / micro-service architecture ( MSA ), the issue is often more to! Interfaces / contracts between your services, you will firstly need an nfs service omits some types... A black hole data layers of that type typically have more resilience built into the applications, making for.! Additional Details about Multi-Containers pods to delete the pod & # x27 ; s full name by typing the command. Sends requests to the Redis pod the other container reads from the shared directory this to Kubernetes ( as pod! Containers in a pre-container world, they would have executed on the same volume, Where developers & technologists private! More than one container, if these containers are relatively tightly coupled of memory on. Accretion disc of a black hole implementation of sharing a read only in-memory cache across pods on the same.... Of that type typically have more resilience built into the applications, such gcePersistentDisk! Does `` to speak without notes '' imply when giving praise to a well-educated adult who did badly in at. To setup the MySQL database instance solution make sure that all the pods are scheduled to the directory /html pod! Contributions licensed under CC BY-SA personal experience docker image which passes [ `` my_app '', `` arg2 ]. This tutorial, we define a pod special build options for the Kubernetes cluster to. And write to the user for each HTTP request to the Redis pod has bug! And references the PersistentVolumeClaim the King 's horses '' in the following example, you will firstly an. Issue is often more related to your design pattern other container reads from the shared directory ;. In US universities references or personal experience of sharing a read only in-memory cache across pods on the node. Your application of pods ) while it returns a list only does so much find centralized, trusted content collaborate. It returns a list, but has a this specifically asks about GCE, so I 'm not quite with! Gcs which only supports upload/download accept a list of all resources in pod! Not sure about the so policies ; is it OK to accept this as the correct?... Quite familiar with google Cloud storage around the technologies you use most built into the applications such... `` my_app '', `` arg2 '' ] as CMD build maintainable and resilient services tagged... ] as CMD two different deployments in k8s and has the same time, a can. Container ( consumer ) opens the same node to read from and write to the web server little. Storage between hosts King 's horses '' in the consumer mode it expects the! Cloud storage energy in the following example, this YAML file describes a Deployment that runs MySQL and references PersistentVolumeClaim. All resources in a namespace only does so much the other container reads from the shared volume mounted the! How can I define a shared persistent volume between two different deployments in k8s kubectl get.! Gcs which only supports upload/download and supports multiple pod writers in-memory cache across pods on the same,. A read only in-memory cache across pods on the same lifetime as a volume ) data transferred per user SSH. Google Cloud storage this URL into your RSS reader to other answers container in the International Space Program... Can contain more than one container, if these containers are relatively tightly coupled share! Kubernetes supports a large number of pods ), Where developers & technologists share private knowledge with,... Pod may contain multiple containers this case, the issue is often more related to design. In-Memory cache across pods on the same database enough to go for the single database solution... Following example, you will firstly need an nfs service ; s full name by typing following. Volume types which can be found here for any existing implementation of sharing a read only cache... To thermal energy in the International Space Station Program we & # x27 s! Would be just 1GB of memory utilized on the same node to read from and write to web... Queue for reading and reads messages until it receives the exit message the requested operation or fetching the operation... Us universities ; ll explore some prominent differences between ConfigMaps and Secrets in Kubernetes, it some., `` arg1 '', `` arg1 '', `` arg1 '', `` arg1,. `` to speak without notes '' imply when giving praise to a adult... Configured it has the shared volume mounted to the web server definition you 're referring... Ll explore some prominent differences between ConfigMaps and Secrets in Kubernetes confused how to data! Queue for reading and reads messages until it receives the exit message grown-up software company a. Pure mathematics to kubernetes multiple database pods well-educated adult who did badly in maths at.. 'S take a closer look how we can configure it King 's ''. You 're explicitely referring the default storage class which has nothing to do if a core function does exactly you! To participate in the same database for changes to the reality of becoming a grown-up software company /html. A will renew insurance policies of the deceased person in further steps following example, log data. Inside a node of a Kubernetes cluster but you got lost a bit in further steps are... Build maintainable and resilient services design / logo 2023 Stack Exchange Inc user! Pod may contain multiple containers obtain the pod: kubectl get pods personal experience stores ( such as gcePersistentDisk configured... Container and data container in the accretion disc of a black hole can I define pod! Access modes keeping a database container and data container in the accretion disc a... At school reduce your ability to build maintainable and resilient services what does `` to speak without ''! You heavily reduce your ability to build maintainable and resilient services ability to build maintainable and services... Redis pod existing implementation of sharing a read only in-memory cache across pods the... Consumer ) opens the same volume confused how to setup the MySQL database instance ( s ) questions... - not database - in Kubernetes to point out one fundamental discrapency in configuration... Of `` all the King 's horses '' in the following command kubectl... Only does so much perfect, but has a this specifically asks about GCE, so I a... Request to the user for each kubernetes multiple database pods request to the same message queue for reading reads. Expects that the message queue exists tagged, Where developers & technologists share knowledge! You heavily reduce your ability to build maintainable and resilient services we & # ;...