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張 旭

Pods - Kubernetes - 0 views

kubernetes.io/...pod

kubernetes pod system

shared by 張 旭 on 05 Jul 19 - No Cached
  • Pods are the smallest deployable units of computing
  • A Pod (as in a pod of whales or pea pod) is a group of one or more containersA lightweight and portable executable image that contains software and all of its dependencies. (such as Docker containers), with shared storage/network, and a specification for how to run the containers.
  • A Pod’s contents are always co-located and co-scheduled, and run in a shared context.
  • ...32 more annotations...
  • A Pod models an application-specific “logical host”
  • application containers which are relatively tightly coupled
  • being executed on the same physical or virtual machine would mean being executed on the same logical host.
  • The shared context of a Pod is a set of Linux namespaces, cgroups, and potentially other facets of isolation
  • Containers within a Pod share an IP address and port space, and can find each other via localhost
  • Containers in different Pods have distinct IP addresses and can not communicate by IPC without special configuration. These containers usually communicate with each other via Pod IP addresses.
  • Applications within a Pod also have access to shared volumesA directory containing data, accessible to the containers in a pod. , which are defined as part of a Pod and are made available to be mounted into each application’s filesystem.
  • a Pod is modelled as a group of Docker containers with shared namespaces and shared filesystem volumes
    • 張 旭
      張 旭 on 05 Jul 19
       
      類似 docker-compose 裡面宣告的同一坨？
  • Pods are considered to be relatively ephemeral (rather than durable) entities.
  • Pods are created, assigned a unique ID (UID), and scheduled to nodes where they remain until termination (according to restart policy) or deletion.
  • it can be replaced by an identical Pod
  • When something is said to have the same lifetime as a Pod, such as a volume, that means that it exists as long as that Pod (with that UID) exists.
  • uses a persistent volume for shared storage between the containers
  • Pods serve as unit of deployment, horizontal scaling, and replication
  • The applications in a Pod all use the same network namespace (same IP and port space), and can thus “find” each other and communicate using localhost
  • flat shared networking space
  • Containers within the Pod see the system hostname as being the same as the configured name for the Pod.
  • Volumes enable data to survive container restarts and to be shared among the applications within the Pod.
  • Individual Pods are not intended to run multiple instances of the same application
  • The individual containers may be versioned, rebuilt and redeployed independently.
  • Pods aren’t intended to be treated as durable entities.
  • Controllers like StatefulSet can also provide support to stateful Pods.
  • When a user requests deletion of a Pod, the system records the intended grace period before the Pod is allowed to be forcefully killed, and a TERM signal is sent to the main process in each container.
  • Once the grace period has expired, the KILL signal is sent to those processes, and the Pod is then deleted from the API server.
  • grace period
  • Pod is removed from endpoints list for service, and are no longer considered part of the set of running Pods for replication controllers.
  • When the grace period expires, any processes still running in the Pod are killed with SIGKILL.
  • By default, all deletes are graceful within 30 seconds.
  • You must specify an additional flag --force along with --grace-period=0 in order to perform force deletions.
  • Force deletion of a Pod is defined as deletion of a Pod from the cluster state and etcd immediately.
  • StatefulSet Pods
  • Processes within the container get almost the same privileges that are available to processes outside a container.
張 旭

Understanding Nginx HTTP Proxying, Load Balancing, Buffering, and Caching | DigitalOcean - 0 views

www.digitalocean.com/...alancing-buffering-and-caching

nginx proxy networking HA haproxy

shared by 張 旭 on 14 Mar 17 - No Cached
  • allow Nginx to pass requests off to backend http servers for further processing
  • Nginx is often set up as a reverse proxy solution to help scale out infrastructure or to pass requests to other servers that are not designed to handle large client loads
  • explore buffering and caching to improve the performance of proxying operations for clients
  • ...48 more annotations...
  • Nginx is built to handle many concurrent connections at the same time.
  • provides you with flexibility in easily adding backend servers or taking them down as needed for maintenance
  • Proxying in Nginx is accomplished by manipulating a request aimed at the Nginx server and passing it to other servers for the actual processing
  • The servers that Nginx proxies requests to are known as upstream servers.
  • Nginx can proxy requests to servers that communicate using the http(s), FastCGI, SCGI, and uwsgi, or memcached protocols through separate sets of directives for each type of proxy
  • When a request matches a location with a proxy_pass directive inside, the request is forwarded to the URL given by the directive
  • For example, when a request for /match/here/please is handled by this block, the request URI will be sent to the example.com server as http://example.com/match/here/please
  • The request coming from Nginx on behalf of a client will look different than a request coming directly from a client
  • Nginx gets rid of any empty headers
  • Nginx, by default, will consider any header that contains underscores as invalid. It will remove these from the proxied request
    • 張 旭
      張 旭 on 16 Mar 17
       
      這裡要注意一下，header 欄位名稱有設定底線的，要設定 Nginx 讓它可以通過。
  • The "Host" header is re-written to the value defined by the $proxy_host variable.
  • The upstream should not expect this connection to be persistent
  • Headers with empty values are completely removed from the passed request.
  • if your backend application will be processing non-standard headers, you must make sure that they do not have underscores
  • by default, this will be set to the value of $proxy_host, a variable that will contain the domain name or IP address and port taken directly from the proxy_pass definition
  • This is selected by default as it is the only address Nginx can be sure the upstream server responds to
  • (as it is pulled directly from the connection info)
  • $http_host: Sets the "Host" header to the "Host" header from the client request.
  • The headers sent by the client are always available in Nginx as variables. The variables will start with an $http_ prefix, followed by the header name in lowercase, with any dashes replaced by underscores.
  • preference to: the host name from the request line itself
  • set the "Host" header to the $host variable. It is the most flexible and will usually provide the proxied servers with a "Host" header filled in as accurately as possible
  • sets the "Host" header to the $host variable, which should contain information about the original host being requested
  • This variable takes the value of the original X-Forwarded-For header retrieved from the client and adds the Nginx server's IP address to the end.
  • The upstream directive must be set in the http context of your Nginx configuration.
  • http context
  • Once defined, this name will be available for use within proxy passes as if it were a regular domain name
  • By default, this is just a simple round-robin selection process (each request will be routed to a different host in turn)
  • Specifies that new connections should always be given to the backend that has the least number of active connections.
  • distributes requests to different servers based on the client's IP address.
  • mainly used with memcached proxying
  • As for the hash method, you must provide the key to hash against
  • Server Weight
  • Nginx's buffering and caching capabilities
  • Without buffers, data is sent from the proxied server and immediately begins to be transmitted to the client.
  • With buffers, the Nginx proxy will temporarily store the backend's response and then feed this data to the client
  • Nginx defaults to a buffering design
  • can be set in the http, server, or location contexts.
  • the sizing directives are configured per request, so increasing them beyond your need can affect your performance
  • When buffering is "off" only the buffer defined by the proxy_buffer_size directive will be used
  • A high availability (HA) setup is an infrastructure without a single point of failure, and your load balancers are a part of this configuration.
  • multiple load balancers (one active and one or more passive) behind a static IP address that can be remapped from one server to another.
  • Nginx also provides a way to cache content from backend servers
  • The proxy_cache_path directive must be set in the http context.
  • proxy_cache backcache;
    • 張 旭
      張 旭 on 16 Mar 17
       
      這裡的 backcache 是前文設定的 backcache 變數，看起來每個 location 都可以有自己的 cache 目錄。
  • The proxy_cache_bypass directive is set to the $http_cache_control variable. This will contain an indicator as to whether the client is explicitly requesting a fresh, non-cached version of the resource
  • any user-related data should not be cached
  • For private content, you should set the Cache-Control header to "no-cache", "no-store", or "private" depending on the nature of the data
張 旭

An Introduction to HAProxy and Load Balancing Concepts | DigitalOcean - 0 views

www.digitalocean.com/...xy-and-load-balancing-concepts

server haproxy loading HA architecture

shared by 張 旭 on 07 Dec 17 - No Cached
  • HAProxy, which stands for High Availability Proxy
  • improve the performance and reliability of a server environment by distributing the workload across multiple servers (e.g. web, application, database).
  • ACLs are used to test some condition and perform an action (e.g. select a server, or block a request) based on the test result.
  • ...28 more annotations...
  • Access Control List (ACL)
  • ACLs allows flexible network traffic forwarding based on a variety of factors like pattern-matching and the number of connections to a backend
  • A backend is a set of servers that receives forwarded requests
  • adding more servers to your backend will increase your potential load capacity by spreading the load over multiple servers
  • mode http specifies that layer 7 proxying will be used
  • specifies the load balancing algorithm
  • health checks
  • A frontend defines how requests should be forwarded to backends
  • use_backend rules, which define which backends to use depending on which ACL conditions are matched, and/or a default_backend rule that handles every other case
  • A frontend can be configured to various types of network traffic
  • Load balancing this way will forward user traffic based on IP range and port
  • Generally, all of the servers in the web-backend should be serving identical content--otherwise the user might receive inconsistent content.
  • Using layer 7 allows the load balancer to forward requests to different backend servers based on the content of the user's request.
  • allows you to run multiple web application servers under the same domain and port
  • acl url_blog path_beg /blog matches a request if the path of the user's request begins with /blog.
  • Round Robin selects servers in turns
  • Selects the server with the least number of connections--it is recommended for longer sessions
  • This selects which server to use based on a hash of the source IP
  • ensure that a user will connect to the same server
  • require that a user continues to connect to the same backend server. This persistence is achieved through sticky sessions, using the appsession parameter in the backend that requires it.
  • HAProxy uses health checks to determine if a backend server is available to process requests.
  • The default health check is to try to establish a TCP connection to the server
  • If a server fails a health check, and therefore is unable to serve requests, it is automatically disabled in the backend
  • For certain types of backends, like database servers in certain situations, the default health check is insufficient to determine whether a server is still healthy.
  • However, your load balancer is a single point of failure in these setups; if it goes down or gets overwhelmed with requests, it can cause high latency or downtime for your service.
  • A high availability (HA) setup is an infrastructure without a single point of failure
  • a static IP address that can be remapped from one server to another.
  • If that load balancer fails, your failover mechanism will detect it and automatically reassign the IP address to one of the passive servers.
張 旭

NAT Gateways - Amazon Virtual Private Cloud - 0 views

docs.aws.amazon.com/...vpc-nat-gateway.html

aws networking system amazon cloud

shared by 張 旭 on 10 Jul 18 - No Cached
  • a network address translation (NAT) gateway to enable instances in a private subnet to connect to the internet or other AWS services
  • but prevent the internet from initiating a connection with those instances
  • NAT gateways are not supported for IPv6 traffic
  • ...11 more annotations...
  • must specify the public subnet in which the NAT gateway should reside
  • update the route table associated with one or more of your private subnets to point Internet-bound traffic to the NAT gateway.
  • NAT gateway is created in a specific Availability Zone and implemented with redundancy in that zone.
  • ensure that resources use the NAT gateway in the same Availability Zone
  • The main route table sends internet traffic from the instances in the private subnet to the NAT gateway. The NAT gateway sends the traffic to the internet gateway using the NAT gateway’s Elastic IP address as the source IP address
  • A NAT gateway supports 5 Gbps of bandwidth and automatically scales up to 45 Gbps
  • You can associate exactly one Elastic IP address with a NAT gateway
  • A NAT gateway supports the following protocols: TCP, UDP, and ICMP
  • cannot associate a security group with a NAT gateway.
  • create a NAT gateway in the same subnet as your NAT instance, and then replace the existing route in your route table that points to the NAT instance with a route that points to the NAT gateway
  • A NAT gateway cannot send traffic over VPC endpoints, VPN connections, AWS Direct Connect, or VPC peering connections.
張 旭

What Is Amazon VPC? - Amazon Virtual Private Cloud - 0 views

docs.aws.amazon.com/...VPC_Introduction.html

aws networking

shared by 張 旭 on 31 Jul 18 - No Cached
  • to allow an instance in your VPC to initiate outbound connections to the internet but prevent unsolicited inbound connections from the internet, you can use a network address translation (NAT) device for IPv4 traffic
  • A NAT device has an Elastic IP address and is connected to the internet through an internet gateway.
  • By default, each instance that you launch into a nondefault subnet has a private IPv4 address, but no public IPv4 address, unless you specifically assign one at launch, or you modify the subnet's public IP address attribute.
  • ...11 more annotations...
  • Amazon VPC is the networking layer for Amazon EC2.
  • A virtual private cloud (VPC) is a virtual network dedicated to your AWS account. It is logically isolated from other virtual networks in the AWS Cloud.
  • Instances can connect to the internet over IPv6 through an internet gateway
  • IPv6 traffic is separate from IPv4 traffic; your route tables must include separate routes for IPv6 traffic.
  • You can optionally connect your VPC to your own corporate data center using an IPsec AWS managed VPN connection, making the AWS Cloud an extension of your data center.
  • A VPN connection consists of a virtual private gateway attached to your VPC and a customer gateway located in your data center.
  • A virtual private gateway is the VPN concentrator on the Amazon side of the VPN connection. A customer gateway is a physical device or software appliance on your side of the VPN connection.
  • AWS PrivateLink is a highly available, scalable technology that enables you to privately connect your VPC to supported AWS services, services hosted by other AWS accounts (VPC endpoint services)
  • Traffic between your VPC and the service does not leave the Amazon network
  • To use AWS PrivateLink, create an interface VPC endpoint for a service in your VPC. This creates an elastic network interface in your subnet with a private IP address that serves as an entry point for traffic destined to the service.
  • create your own AWS PrivateLink-powered service (endpoint service) and enable other AWS customers to access your service.
張 旭

How To Create a Kubernetes Cluster Using Kubeadm on Ubuntu 18.04 | DigitalOcean - 0 views

www.digitalocean.com/...-using-kubeadm-on-ubuntu-18-04

cluster ubuntu kubernetes system

shared by 張 旭 on 27 Mar 19 - No Cached
  • A pod is an atomic unit that runs one or more containers.
  • Pods are the basic unit of scheduling in Kubernetes: all containers in a pod are guaranteed to run on the same node that the pod is scheduled on.
  • Each pod has its own IP address, and a pod on one node should be able to access a pod on another node using the pod's IP.
  • ...12 more annotations...
  • Communication between pods is more complicated, however, and requires a separate networking component that can transparently route traffic from a pod on one node to a pod on another.
  • pod network plugins. For this cluster, you will use Flannel, a stable and performant option.
  • Passing the argument --pod-network-cidr=10.244.0.0/16 specifies the private subnet that the pod IPs will be assigned from.
  • kubectl apply -f descriptor.[yml|json] is the syntax for telling kubectl to create the objects described in the descriptor.[yml|json] file.
  • deploy Nginx using Deployments and Services
  • A deployment is a type of Kubernetes object that ensures there's always a specified number of pods running based on a defined template, even if the pod crashes during the cluster's lifetime.
  • NodePort, a scheme that will make the pod accessible through an arbitrary port opened on each node of the cluster
  • Services are another type of Kubernetes object that expose cluster internal services to clients, both internal and external.
  • load balancing requests to multiple pods
  • Pods are ubiquitous in Kubernetes, so understanding them will facilitate your work
  • how controllers such as deployments work since they are used frequently in stateless applications for scaling and the automated healing of unhealthy applications.
  • Understanding the types of services and the options they have is essential for running both stateless and stateful applications.
張 旭

Understanding the Nginx Configuration File Structure and Configuration Contexts | Digit... - 0 views

www.digitalocean.com/...ure-and-configuration-contexts

nginx web server

shared by 張 旭 on 05 Dec 17 - No Cached
  • discussing the basic structure of an Nginx configuration file along with some guidelines on how to design your files
  • /etc/nginx/nginx.conf
  • In Nginx parlance, the areas that these brackets define are called "contexts" because they contain configuration details that are separated according to their area of concern
  • ...50 more annotations...
  • contexts can be layered within one another
  • if a directive is valid in multiple nested scopes, a declaration in a broader context will be passed on to any child contexts as default values.
  • The children contexts can override these values at will
  • Nginx will error out on reading a configuration file with directives that are declared in the wrong context.
  • The most general context is the "main" or "global" context
  • Any directive that exist entirely outside of these blocks is said to inhabit the "main" context
  • The main context represents the broadest environment for Nginx configuration.
  • The "events" context is contained within the "main" context. It is used to set global options that affect how Nginx handles connections at a general level.
  • Nginx uses an event-based connection processing model, so the directives defined within this context determine how worker processes should handle connections.
  • the connection processing method is automatically selected based on the most efficient choice that the platform has available
  • a worker will only take a single connection at a time
  • When configuring Nginx as a web server or reverse proxy, the "http" context will hold the majority of the configuration.
  • The http context is a sibling of the events context, so they should be listed side-by-side, rather than nested
  • fine-tune the TCP keep alive settings (keepalive_disable, keepalive_requests, and keepalive_timeout)
  • The "server" context is declared within the "http" context.
  • multiple declarations
  • each instance defines a specific virtual server to handle client requests
  • Each client request will be handled according to the configuration defined in a single server context, so Nginx must decide which server context is most appropriate based on details of the request.
  • listen: The ip address / port combination that this server block is designed to respond to.
  • server_name: This directive is the other component used to select a server block for processing.
  • "Host" header
  • configure files to try to respond to requests (try_files)
  • issue redirects and rewrites (return and rewrite)
  • set arbitrary variables (set)
  • Location contexts share many relational qualities with server contexts
  • multiple location contexts can be defined, each location is used to handle a certain type of client request, and each location is selected by virtue of matching the location definition against the client request through a selection algorithm
  • Location blocks live within server contexts and, unlike server blocks, can be nested inside one another.
  • While server contexts are selected based on the requested IP address/port combination and the host name in the "Host" header, location blocks further divide up the request handling within a server block by looking at the request URI
  • The request URI is the portion of the request that comes after the domain name or IP address/port combination.
  • New directives at this level allow you to reach locations outside of the document root (alias), mark the location as only internally accessible (internal), and proxy to other servers or locations (using http, fastcgi, scgi, and uwsgi proxying).
  • These can then be used to do A/B testing by providing different content to different hosts.
  • configures Perl handlers for the location they appear in
  • set the value of a variable depending on the value of another variable
  • used to map MIME types to the file extensions that should be associated with them.
  • this context defines a named pool of servers that Nginx can then proxy requests to
  • The upstream context should be placed within the http context, outside of any specific server contexts.
  • The upstream context can then be referenced by name within server or location blocks to pass requests of a certain type to the pool of servers that have been defined.
  • function as a high performance mail proxy server
  • The mail context is defined within the "main" or "global" context (outside of the http context).
  • Nginx has the ability to redirect authentication requests to an external authentication server
  • the if directive in Nginx will execute the instructions contained if a given test returns "true".
  • Since Nginx will test conditions of a request with many other purpose-made directives, if should not be used for most forms of conditional execution.
  • The limit_except context is used to restrict the use of certain HTTP methods within a location context.
  • The result of the above example is that any client can use the GET and HEAD verbs, but only clients coming from the 192.168.1.1/24 subnet are allowed to use other methods.
  • Many directives are valid in more than one context
  • it is usually best to declare directives in the highest context to which they are applicable, and overriding them in lower contexts as necessary.
  • Declaring at higher levels provides you with a sane default
  • Nginx already engages in a well-documented selection algorithm for things like selecting server blocks and location blocks.
  • instead of relying on rewrites to get a user supplied request into the format that you would like to work with, you should try to set up two blocks for the request, one of which represents the desired method, and the other that catches messy requests and redirects (and possibly rewrites) them to your correct block.
  • incorrect requests can get by with a redirect rather than a rewrite, which should execute with lower overhead.
張 旭

作業系統 - 維基百科，自由的百科全書 - 0 views

zh.wikipedia.org/...%8D%E4%BD%9C%E7%B3%BB%E7%BB%9F

system linux

shared by 張 旭 on 22 Jun 21 - No Cached
  • 作業系統位於底層硬體與使用者之間，是兩者溝通的橋樑。
  • 行程管理（Processing management）
  • 安全機制（Security）
  • ...20 more annotations...
  • 記憶體管理（Memory management）
  • 核心 - 作業系統之最核心部分，通常執行在最高特權級，負責提供基礎性、結構性的功能。
  • 驅動程式 - 最底層的、直接控制和監視各類硬體的部分，它們的職責是隱藏硬體的具體細節，並向其他部分提供一個抽象的、通用的介面。
  • 作業系統的分類沒有一個單一的標準，可以根據工作方式分為批次處理作業系統、分時作業系統、即時作業系統、網路作業系統和分散式作業系統等
  • 根據帕金森定律：「你給程式再多記憶體，程式也會想盡辦法耗光」
  • 大部分的現代電腦記憶體架構都是階層式的，最快且數量最少的暫存器為首，然後是快取、記憶體以及最慢的磁碟儲存裝置。
  • 虛擬記憶體管理的功能大幅增加每個行程可獲得的記憶空間
  • 當年運用馮·諾伊曼結構建造電腦時，每個中央處理器最多只能同時執行一個行程。
  • 現代的作業系統，即使只擁有一個CPU，也可以利用多行程（multitask）功能同時執行多個行程。行程管理指的是作業系統調整多個行程的功能。
  • 作業系統尚有擔負起行程間通訊（IPC）、行程異常終止處理以及死結（Dead Lock）偵測及處理等較為艱深的問題。
  • 檔案系統，通常指稱管理磁碟資料的系統，可將資料以目錄或檔案的型式儲存。每個檔案系統都有自己的特殊格式與功能，例如日誌管理或不需磁碟重整。
  • 現代的作業系統都具備操作主流網路通訊協定TCP/IP的能力。也就是說這樣的作業系統可以進入網路世界，並且與其他系統分享諸如檔案、印表機與掃描器等資源。
  • 作業系統提供外界直接或間接存取數種資源的管道
  • 作業系統有能力認證資源存取的請求
  • 通常是一個正在執行的程式發出的資源請求。在某些系統上，一個程式一旦可執行就可做任何事情（例如DOS時代的病毒），但通常作業系統會給程式一個識別代號，並且在此程式發出請求時，檢查其代號與所需資源的存取權限關係。
  • 一個高安全等級的系統也會提供記錄選項，允許記錄各種請求對資源存取的行為（例如「誰曾經讀了這個檔案？」）
  • 大部分的作業系統都包含圖形化使用者介面（GUI）。有幾類較舊的作業系統將圖形化使用者介面與核心緊密結合，例如最早的Windows與Mac OS實作產品。
  • 驅動程式（Device driver）是指某類設計來與硬體互動的電腦軟體。通常是一設計完善的裝置互動介面，利用與此硬體連接的電腦匯排流或通訊子系統，提供對此裝置下令與接收資訊的功能；以及最終目的，將訊息提供給作業系統或應用程式。
  • 驅動程式是針對特定硬體與特定作業系統設計的軟體，通常以作業系統核心模組、應用軟體包或普通電腦程式的形式在作業系統核心底下執行，以達到通透順暢地與硬體互動的效果
  • 適合的驅動程式一旦安裝，相對應的新裝置就可以無誤地執行。此新驅動程式可以讓此裝置完美地切合在作業系統中，讓使用者察覺不到這是作業系統原本沒有的功能。
  • 張 旭 on 22 Jun 21
     
    "作業系統位於底層硬體與使用者之間，是兩者溝通的橋樑。"
張 旭

Kubernetes 基本概念 · Kubernetes指南 - 0 views

feisky.gitbooks.io/...concepts.html

kubernetes volume namespace system devops

shared by 張 旭 on 30 May 19 - No Cached
  • Container（容器）是一种便携式、轻量级的操作系统级虚拟化技术。它使用 namespace 隔离不同的软件运行环境，并通过镜像自包含软件的运行环境，从而使得容器可以很方便的在任何地方运行。
  • 每个应用程序用容器封装，管理容器部署就等同于管理应用程序部署。+
  • Pod 是一组紧密关联的容器集合，它们共享 PID、IPC、Network 和 UTS namespace，是 Kubernetes 调度的基本单位。
  • ...9 more annotations...
  • 进程间通信和文件共享
  • 在 Kubernetes 中，所有对象都使用 manifest（yaml 或 json）来定义
  • Node 是 Pod 真正运行的主机，可以是物理机，也可以是虚拟机。
  • 每个 Node 节点上至少要运行 container runtime（比如 docker 或者 rkt）、kubelet 和 kube-proxy 服务。
  • 常见的 pods, services, replication controllers 和 deployments 等都是属于某一个 namespace 的（默认是 default）
  • node, persistentVolumes 等则不属于任何 namespace
  • Service 是应用服务的抽象，通过 labels 为应用提供负载均衡和服务发现。
  • 匹配 labels 的 Pod IP 和端口列表组成 endpoints，由 kube-proxy 负责将服务 IP 负载均衡到这些 endpoints 上。
  • 每个 Service 都会自动分配一个 cluster IP（仅在集群内部可访问的虚拟地址）和 DNS 名
  • 張 旭 on 30 May 19
     
    "常见的 pods, services, replication controllers 和 deployments 等都是属于某一个 namespace 的（默认是 default），而 node, persistentVolumes 等则不属于任何 namespace。"
crazylion lee

Nmap: the Network Mapper - Free Security Scanner - 1 views

nmap.org

security network

shared by crazylion lee on 22 Nov 15 - No Cached
  • crazylion lee on 22 Nov 15
     
    "Nmap ("Network Mapper") is a free and open source (license) utility for network discovery and security auditing. Many systems and network administrators also find it useful for tasks such as network inventory, managing service upgrade schedules, and monitoring host or service uptime. Nmap uses raw IP packets in novel ways to determine what hosts are available on the network, what services (application name and version) those hosts are offering, what operating systems (and OS versions) they are running, what type of packet filters/firewalls are in use, and dozens of other characteristics. It was designed to rapidly scan large networks, but works fine against single hosts. Nmap runs on all major computer operating systems, and official binary packages are available for Linux, Windows, and Mac OS X. In addition to the classic command-line Nmap executable, the Nmap suite includes an advanced GUI and results viewer (Zenmap), a flexible data transfer, redirection, and debugging tool (Ncat), a utility for comparing scan results (Ndiff), and a packet generation and response analysis tool (Nping)."
張 旭

Virtual Private Cloud (VPC)  |  Virtual Private Cloud  |  Google Cloud - 0 views

cloud.google.com/vpc

google gcp cloud system

shared by 張 旭 on 09 Nov 18 - No Cached
  • A single Google Cloud VPC can span multiple regions without communicating across the public Internet.
  • Google Cloud VPCs let you increase the IP space of any subnets without any workload shutdown or downtime.
  • Get private access to Google services, such as storage, big data, analytics, or machine learning, without having to give your service a public IP address.
  • ...3 more annotations...
  • Enable dynamic Border Gateway Protocol (BGP) route updates between your VPC network and your non-Google network with our virtual router.
  • Configure a VPC Network to be shared across several projects in your organization.
  • Hosting globally distributed multi-tier applications, by creating a VPC with subnets.
張 旭

elabs/pundit: Minimal authorization through OO design and pure Ruby classes - 0 views

github.com/pundit

authorization rails ruby gem library

shared by 張 旭 on 20 Mar 16 - No Cached
  • The class implements some kind of query method
  • Pundit will call the current_user method to retrieve what to send into this argumen
  • put these classes in app/policies
  • ...49 more annotations...
  • in leveraging regular Ruby classes and object oriented design patterns to build a simple, robust and scaleable authorization system
  • map to the name of a particular controller action
  • In the generated ApplicationPolicy, the model object is called record.
  • record
  • authorize
  • authorize would have done something like this: raise "not authorized" unless PostPolicy.new(current_user, @post).update?
  • pass a second argument to authorize if the name of the permission you want to check doesn't match the action name.
  • you can chain it
  • authorize returns the object passed to it
  • the policy method in both the view and controller.
  • have some kind of view listing records which a particular user has access to
  • ActiveRecord::Relation
  • Instances of this class respond to the method resolve, which should return some kind of result which can be iterated over.
  • scope.where(published: true)
    • 張 旭
      張 旭 on 29 Aug 16
       
      我想大概的意思就是：如果是 admin 可以看到全部 post，如果不是只能看到 published = true 的 post
  • use this class from your controller via the policy_scope method:
  • PostPolicy::Scope.new(current_user, Post).resolve
  • policy_scope(@user.posts).each
  • This method will raise an exception if authorize has not yet been called.
  • verify_policy_scoped to your controller. This will raise an exception in the vein of verify_authorized. However, it tracks if policy_scope is used instead of authorize
  • need to conditionally bypass verification, you can use skip_authorization
  • skip_policy_scope
  • Having a mechanism that ensures authorization happens allows developers to thoroughly test authorization scenarios as units on the policy objects themselves.
  • Pundit doesn't do anything you couldn't have easily done yourself. It's a very small library, it just provides a few neat helpers.
  • all of the policy and scope classes are just plain Ruby classes
  • rails g pundit:policy post
  • define a filter that redirects unauthenticated users to the login page
  • fail more gracefully
  • raise Pundit::NotAuthorizedError, "must be logged in" unless user
  • having rails handle them as a 403 error and serving a 403 error page.
  • config.action_dispatch.rescue_responses["Pundit::NotAuthorizedError"] = :forbidden
  • with I18n to generate error messages
  • retrieve a policy for a record outside the controller or view
  • define a method in your controller called pundit_user
  • Pundit strongly encourages you to model your application in such a way that the only context you need for authorization is a user object and a domain model that you want to check authorization for.
  • Pundit does not allow you to pass additional arguments to policies
  • authorization is dependent on IP address in addition to the authenticated user
  • create a special class which wraps up both user and IP and passes it to the policy.
  • set up a permitted_attributes method in your policy
  • policy(@post).permitted_attributes
  • permitted_attributes(@post)
  • Pundit provides a convenient helper method
  • permit different attributes based on the current action,
  • If you have defined an action-specific method on your policy for the current action, the permitted_attributes helper will call it instead of calling permitted_attributes on your controller
  • If you don't have an instance for the first argument to authorize, then you can pass the class
  • restart the Rails server
  • Given there is a policy without a corresponding model / ruby class, you can retrieve it by passing a symbol
  • after_action :verify_authorized
  • It is not some kind of failsafe mechanism or authorization mechanism.
  • Pundit will work just fine without using verify_authorized and verify_policy_scoped
  • crazylion lee on 20 Mar 16
     
    "Minimal authorization through OO design and pure Ruby classes"
張 旭

Automated Nginx Reverse Proxy for Docker - 0 views

jasonwilder.com/...nginx-reverse-proxy-for-docker

docker nginx proxy haproxy system web server

shared by 張 旭 on 04 Dec 15 - No Cached
  • Docker containers are assigned random IPs and ports which makes addressing them much more complicated from a client perspsective
  • Binding the container to the hosts port can prevent multiple containers from running on the same host. For example, only one container can bind to port 80 at a time.
  • Docker provides a remote API to inspect containers and access their IP, Ports and other configuration meta-data.
  • ...1 more annotation...
  • nginx template can be used to generate a reverse proxy configuration for docker containers using virtual hosts for routing.
張 旭

从字节跳动到火山引擎（二）：私有云 PaaS 场景下的 Kubernetes 集群部署实践 - InfoQ 写作平台 - 0 views

xie.infoq.cn/...fbcb4e15472a517b858a76819

kubernetes system

shared by 張 旭 on 16 Jul 21 - No Cached
  • 在集群部署时，etcd、Kubelet、Containerd 等服务以二进制的方式运行，其他 Kubernetes 组件都以容器的方式运行。
  • 張 旭 on 16 Jul 21
     
    "Static Pod 的形式运行一个 Nginx 服务，用于监听本地 localhost:6443 端口。Nginx 服务使用反向代理的方式，在 upstream 中填写所有 Master 节点 IP 和 6443 端口。这时 node 上的 Kubelet 服务在请求 API Server 时，其实请求的是本地的 6443 端口。再通过 Nginx 把流量/请求转发到 Master 节点上，即实现了 Node 节点的请求。这样就可以避免上述 load balancer 单点的问题。"
張 旭

Kubernetes 架构浅析 - 0 views

jolestar.com/kubernetes-architecture

docker kubernetes google system development

shared by 張 旭 on 08 Aug 16 - No Cached
  • 将Loadbalancer改造成Smart Loadbalancer，通过服务发现机制，应用实例启动或者销毁时自动注册到一个配置中心（etcd/zookeeper），Loadbalancer监听应用配置的变化自动修改自己的配置。
  • Mysql计划该成域名访问方式，而不是ip。为了避免dns变更时的延迟问题，需要在内网架设私有dns。
  • 配合服务发现机制自动修改dns
  • ...23 more annotations...
  • 通过增加一层代理的机制实现
  • 操作系统和基础库的依赖允许应用自定义
  • 对磁盘路径以及端口的依赖通过Docker运行参数动态注入
  • Docker的自定义变量以及参数，需要提供标准化的配置文件
  • 每个服务器节点上要有个agent来执行具体的操作，监控该节点上的应用
  • 还要提供接口以及工具去操作。
  • 应用进程和资源（包括 cpu，内存，磁盘，网络）的解耦
  • 服务依赖关系的解耦
  • scheduler在Kubernetes中是一个plugin，可以用其他的实现替换（比如mesos）
  • 大多数接口都是直接读写etcd中的数据。
  • etcd 作为配置中心和存储服务
  • kubelet 主要包含容器管理，镜像管理，Volume管理等。同时kubelet也是一个rest服务，和pod相关的命令操作都是通过调用接口实现的。
  • kube-proxy 主要用于实现Kubernetes的service机制。提供一部分SDN功能以及集群内部的智能LoadBalancer。
  • Pods Kubernetes将应用的具体实例抽象为pod。每个pod首先会启动一个google_containers/pause docker容器，然后再启动应用真正的docker容器。这样做的目的是为了可以将多个docker容器封装到一个pod中，共享网络地址。
  • Replication Controller 控制pod的副本数量
  • Services service是对一组pods的抽象，通过kube-proxy的智能LoadBalancer机制，pods的销毁迁移不会影响services的功能以及上层的调用方。
  • Namespace Kubernetes中的namespace主要用来避免pod，service的名称冲突。同一个namespace内的pod，service的名称必须是唯一的。
  • Kubernetes的理念里，pod之间是可以直接通讯的
  • 需要用户自己选择解决方案: Flannel,OpenVSwitch,Weave 等。
  • Hypernetes就是一个实现了多租户的Kubernetes版本。
  • 如果运维系统跟不上，服务拆太细，很容易出现某个服务器的角落里部署着一个很古老的不常更新的服务，后来大家竟然忘记了，最后服务器迁移的时候给丢了，用户投诉才发现。
  • 在Kubernetes上的微服务治理框架可以一揽子解决微服务的rpc，监控，容灾问题
  • 同一个pod的多个容器定义中没有优先级，启动顺序不能保证
張 旭

Use swarm mode routing mesh | Docker Documentation - 0 views

docs.docker.com/...ingress

docker swarm cluster system server HA networking

shared by 張 旭 on 16 Jun 17 - No Cached
  • Docker Engine swarm mode makes it easy to publish ports for services to make them available to resources outside the swarm.
  • All nodes participate in an ingress routing mesh.
  • routing mesh enables each node in the swarm to accept connections on published ports for any service running in the swarm, even if there’s no task running on the node.
  • ...6 more annotations...
  • Port 7946 TCP/UDP for container network discovery
  • Port 4789 UDP for the container ingress network.
  • When you access port 8080 on any node, the swarm load balancer routes your request to an active container.
  • The routing mesh listens on the published port for any IP address assigned to the node.
  • publish a port for an existing service
  • To use an external load balancer without the routing mesh, set --endpoint-mode to dnsrr instead of the default value of vip
張 旭

你到底知不知道什麼是 Kubernetes? | Hwchiu Learning Note - 0 views

www.hwchiu.com/kubernetes-concept.html

kubernetes storage networking programming system

shared by 張 旭 on 03 Feb 19 - No Cached
  • Storage(儲存) 實際上一直都不是一個簡單處理的問題，從軟體面來看實際上牽扯到非常多的層級，譬如 Linux Kernel, FileSystem, Block/File-Level, Cache, Snapshot, Object Storage 等各式各樣的議題可以討論。
  • DRBD
  • 異地備援，容錯機制，快照，重複資料刪除等超多相關的議題基本上從來沒有一個完美的解法能夠滿足所有使用情境。
  • ...20 more annotations...
  • 管理者可能會直接在 NFS Server 上進行 MDADM 來設定相關的 Block Device 並且基於上面提供 Export 供 NFS 使用，甚至底層套用不同的檔案系統 (EXT4/BTF4) 來獲取不同的功能與效能。
  • Kubernetes 就只是 NFS Client 的角色
  • CSI(Container Storage Interface)。CSI 本身作為 Kubernetes 與 Storage Solution 的中介層。
  • 基本上 Pod 裡面每個 Container 會使用 Volume 這個物件來代表容器內的掛載點，而在外部實際上會透過 PVC 以及 PV 的方式來描述這個 Volume 背後的儲存方案伺服器的資訊。
  • 整體會透過 CSI 的元件們與最外面實際上的儲存設備連接，所有儲存相關的功能是否有實現，有支援全部都要仰賴最後面的實際提供者， kubernetes 只透過 CSI 的標準去執行。
  • 在網路部分也有與之對應的 CNI(Container Network Interface). kubernetes 透過 CNI 這個介面來與後方的 網路解決方案 溝通
  • CNI 最基本的要求就是在在對應的階段為對應的容器提供網路能力
  • 目前最常見也是 IPv4 + TCP/UDP 的傳輸方式，因此才會看到大部分的 CNI 都在講這些。
  • 希望所有容器彼此之間可以透過 IPv4 來互相存取彼此，不論是同節點或是跨節點的容器們都要可以滿足這個需求。
  • 容器間到底怎麼傳輸的，需不需要封裝，透過什麼網卡，要不要透過 NAT 處理? 這一切都是 CNI 介面背後的實現
  • 外部網路存取容器服務 (Service/Ingress)
  • kubernetes 在 Service/Ingress 中間自行實現了一個模組，大抵上稱為 kube-proxy, 其底層可以使用 iptables, IPVS, user-space software 等不同的實現方法，這部分是跟 CNI 完全無關。
  • CNI 跟 Service/Ingress 是會衝突的，也有可能彼此沒有配合，這中間沒有絕對的穩定整合。
  • CNI 一般會處理的部份，包含了容器內的 網卡數量,網卡名稱,網卡IP, 以及容器與外部節點的連接能力等
  • CRI (Container Runtime Interface) 或是 Device Plugin
  • 對於 kubernetes 來說，其實本身並不在意到底底下的容器化技術實際上是怎麼實現的，你要用 Docker, rkt, CRI-O 都無所謂，甚至背後是一個偽裝成 Container 的 Virtaul Machine virtlet 都可以。
  • 去思考到底為什麼自己本身的服務需要容器化，容器化可以帶來什麼優點
  • 太多太多的人都認為只要寫一個 Dockerfile 將原先的應用程式們全部包裝起來放在一起就是一個很好的容器 來使用了。
  • 最後就會發現根本把 Container 當作 Virtual Machine 來使用，然後再補一句 Contaienr 根本不好用啊
  • 容器化 不是把直接 Virtual Machine 的使用習慣換個環境使用就叫做 容器化，而是要從概念上去暸解與使用
chiehting

Top 5 Kubernetes Best Practices From Sandeep Dinesh (Google) - DZone Cloud - 0 views

dzone.com/...t-practices-from-sandeep-dines

docker

shared by chiehting on 06 Mar 19 - No Cached
  • Best Practices for Kubernetes
  • #1: Building Containers
  • Don’t Trust Arbitrary Base Images!
  • ...29 more annotations...
  • There’s a lot wrong with this: you could be using the wrong version of code that has exploits, has a bug in it, or worse it could have malware bundled in on purpose—you just don’t know.
  • Keep Base Images Small
  • Node.js for example, it includes an extra 600MB of libraries you don’t need.
  • Use the Builder Pattern
  • #2: Container Internals
  • Use a Non-Root User Inside the Container
  • Make the File System Read-Only
  • One Process per Container
  • Don’t Restart on Failure. Crash Cleanly Instead.
  • Log Everything to stdout and stderr
  • #3: Deployments
  • Use the “Record” Option for Easier Rollbacks
  • Use Weave Cloud
  • Use Sidecars for Proxies, Watchers, Etc.
  • Don’t Use Sidecars for Bootstrapping!
  • Don’t Use :Latest or No Tag
  • Readiness and Liveness Probes are Your Friend
  • #4: Services
  • Don’t Use type: LoadBalancer
  • Type: Nodeport Can Be “Good Enough”
  • Use Static IPs They Are Free!
  • Map External Services to Internal Ones
  • #5: Application Architecture
  • Use Helm Charts
  • All Downstream Dependencies Are Unreliable
  • Use Plenty of Descriptive Labels
  • Make Sure Your Microservices Aren’t Too Micro
  • Use Namespaces to Split Up Your Cluster
  • Role-Based Access Control
張 旭

我必须得告诉大家的MySQL优化原理 - 简书 - 0 views

www.jianshu.com/d7665192aaaf

mysql performance system

shared by 張 旭 on 19 Aug 17 - No Cached
  • 很多的查询优化工作实际上就是遵循一些原则让MySQL的优化器能够按照预想的合理方式运行而已
  • MySQL客户端/服务端通信协议是“半双工”的：在任一时刻，要么是服务器向客户端发送数据，要么是客户端向服务器发送数据，这两个动作不能同时发生。
  • 当查询语句很长的时候，需要设置max_allowed_packet参数。
  • ...70 more annotations...
  • 如果查询实在是太大，服务端会拒绝接收更多数据并抛出异常
  • 服务器响应给用户的数据通常会很多，由多个数据包组成
  • 减小通信间数据包的大小和数量是一个非常好的习惯
  • 查询中尽量避免使用SELECT *以及加上LIMIT限制
  • 在解析一个查询语句前，如果查询缓存是打开的，那么MySQL会检查这个查询语句是否命中查询缓存中的数据。
  • 两个查询在任何字符上的不同（例如：空格、注释），都会导致缓存不会命中。
  • MySQL将缓存存放在一个引用表
  • 如果查询中包含任何用户自定义函数、存储函数、用户变量、临时表、mysql库中的系统表，其查询结果 都不会被缓存。
  • MySQL的查询缓存系统会跟踪查询中涉及的每个表，如果这些表（数据或结构）发生变化，那么和这张表相关的所有缓存数据都将失效。
  • 在任何的写操作时，MySQL必须将对应表的所有缓存都设置为失效。
  • 查询缓存对系统的额外消耗也不仅仅在写操作，读操作也不例外
  • 任何的查询语句在开始之前都必须经过检查，即使这条SQL语句永远不会命中缓存
  • 如果查询结果可以被缓存，那么执行完成后，会将结果存入缓存，也会带来额外的系统消耗
  • 并不是什么情况下查询缓存都会提高系统性能，缓存和失效都会带来额外消耗
  • 用多个小表代替一个大表
  • 批量插入代替循环单条插入
  • 合理控制缓存空间大小
  • 可以通过SQL_CACHE和SQL_NO_CACHE来控制某个查询语句是否需要进行缓存
  • 不要轻易打开查询缓存，特别是写密集型应用
  • 将query_cache_type设置为DEMAND，这时只有加入SQL_CACHE的查询才会走缓存，其他查询则不会，这样可以非常自由地控制哪些查询需要被缓存。
  • 预处理则会根据MySQL规则进一步检查解析树是否合法。比如检查要查询的数据表和数据列是否存在等等。
  • 一条查询可以有很多种执行方式，最后都返回相应的结果。优化器的作用就是找到这其中最好的执行计划。
  • 查询当前会话的last_query_cost的值来得到其计算当前查询的成本。
  • 尝试预测一个查询使用某种执行计划时的成本
  • 有非常多的原因会导致MySQL选择错误的执行计划
  • MySQL值选择它认为成本小的，但成本小并不意味着执行时间短
  • 提前终止查询（比如：使用Limit时，查找到满足数量的结果集后会立即终止查询）
  • 找某列的最小值，如果该列有索引，只需要查找B+Tree索引最左端，反之则可以找到最大值
  • 在完成解析和优化阶段以后，MySQL会生成对应的执行计划，查询执行引擎根据执行计划给出的指令逐步执行得出结果。
  • 查询过程中的每一张表由一个handler实例表示。
  • MySQL在查询优化阶段就为每一张表创建了一个handler实例，优化器可以根据这些实例的接口来获取表的相关信息
  • 即使查询不到数据，MySQL仍然会返回这个查询的相关信息，比如改查询影响到的行数以及执行时间等等。
  • 结果集返回客户端是一个增量且逐步返回的过程
  • 整型就比字符操作代价低，因而会使用整型来存储ip地址，使用DATETIME来存储时间，而不是使用字符串。
  • 如果计划在列上创建索引，就应该将该列设置为NOT NULL
  • UNSIGNED表示不允许负值，大致可以使正数的上限提高一倍。
  • 没有太大的必要使用DECIMAL数据类型。即使是在需要存储财务数据时，仍然可以使用BIGINT
  • 大表ALTER TABLE非常耗时
  • MySQL执行大部分修改表结果操作的方法是用新的结构创建一个张空表，从旧表中查出所有的数据插入新表，然后再删除旧表
  • 索引是提高MySQL查询性能的一个重要途径，但过多的索引可能会导致过高的磁盘使用率以及过高的内存占用，从而影响应用程序的整体性能。
  • 索引是指B-Tree索引，它是目前关系型数据库中查找数据最为常用和有效的索引，大多数存储引擎都支持这种索引
  • B+Tree中的B是指balance，意为平衡。
  • 平衡二叉树首先需要符合二叉查找树的定义，其次必须满足任何节点的两个子树的高度差不能大于1。
  • 索引往往以索引文件的形式存储的磁盘上
  • 如何减少查找过程中的I/O存取次数？
  • 减少树的深度，将二叉树变为m叉树（多路搜索树），而B+Tree就是一种多路搜索树。
  • 页是计算机管理存储器的逻辑块，硬件及OS往往将主存和磁盘存储区分割为连续的大小相等的块
  • B+Tree为了保持平衡，对于新插入的值需要做大量的拆分页操作，而页的拆分需要I/O操作，为了尽可能的减少页的拆分操作，B+Tree也提供了类似于平衡二叉树的旋转功能。
  • 在多数情况下，在多个列上建立独立的索引并不能提高查询性能。理由非常简单，MySQL不知道选择哪个索引的查询效率更好
  • 当出现多个索引做联合操作时（多个OR条件），对结果集的合并、排序等操作需要耗费大量的CPU和内存资源，特别是当其中的某些索引的选择性不高，需要返回合并大量数据时，查询成本更高。
  • explain时如果发现有索引合并（Extra字段出现Using union），应该好好检查一下查询和表结构是不是已经是最优的
  • 索引选择性是指不重复的索引值和数据表的总记录数的比值
  • 唯一索引的选择性是1，这时最好的索引选择性，性能也是最好的。
  • 如果一个索引包含或者说覆盖所有需要查询的字段的值，那么就没有必要再回表查询，这就称为覆盖索引。
  • 对结果集进行排序的操作
  • 按照索引顺序扫描得出的结果自然是有序的
  • 如果explain的结果中type列的值为index表示使用了索引扫描来做排序。
  • 在设计索引时，如果一个索引既能够满足排序，有满足查询，是最好的。
  • 比如有一个索引(A,B)，再创建索引(A)就是冗余索引。
  • 对于非常小的表，简单的全表扫描更高效。对于中到大型的表，索引就非常有效。对于超大型的表，建立和维护索引的代价随之增长，这时候其他技术也许更有效，比如分区表。
  • explain后再提测是一种美德。
  • 如果要统计行数，直接使用COUNT(*)，意义清晰，且性能更好。
  • 执行EXPLAIN并不需要真正地去执行查询，所以成本非常低。
  • 确保ON和USING字句中的列上有索引。在创建索引的时候就要考虑到关联的顺序
  • 确保任何的GROUP BY和ORDER BY中的表达式只涉及到一个表中的列，这样MySQL才有可能使用索引来优化
  • MySQL关联执行的策略非常简单，它对任何的关联都执行嵌套循环关联操作，即先在一个表中循环取出单条数据，然后在嵌套循环到下一个表中寻找匹配的行，依次下去，直到找到所有表中匹配的行为为止。然后根据各个表匹配的行，返回查询中需要的各个列。
  • 最外层的查询是根据A.xx列来查询的，A.c上如果有索引的话，整个关联查询也不会使用。再看内层的查询，很明显B.c上如果有索引的话，能够加速查询，因此只需要在关联顺序中的第二张表的相应列上创建索引即可。
  • MySQL处理UNION的策略是先创建临时表，然后再把各个查询结果插入到临时表中，最后再来做查询。
  • 要使用UNION ALL，如果没有ALL关键字，MySQL会给临时表加上DISTINCT选项，这会导致整个临时表的数据做唯一性检查，这样做的代价非常高。
  • 尽可能不要使用存储过程
張 旭

Volumes - Kubernetes - 0 views

kubernetes.io/...volumes

kubernetes volume disk nfs

shared by 張 旭 on 28 May 19 - No Cached
  • On-disk files in a Container are ephemeral,
  • when a Container crashes, kubelet will restart it, but the files will be lost - the Container starts with a clean state
  • In Docker, a volume is simply a directory on disk or in another Container.
  • ...105 more annotations...
  • A Kubernetes volume, on the other hand, has an explicit lifetime - the same as the Pod that encloses it.
  • a volume outlives any Containers that run within the Pod, and data is preserved across Container restarts.
    • 張 旭
      張 旭 on 06 Jul 19
       
      Kubernetes Volume 是跟著 Pod 的生命週期在走
  • Kubernetes supports many types of volumes, and a Pod can use any number of them simultaneously.
  • To use a volume, a Pod specifies what volumes to provide for the Pod (the .spec.volumes field) and where to mount those into Containers (the .spec.containers.volumeMounts field).
  • A process in a container sees a filesystem view composed from their Docker image and volumes.
  • Volumes can not mount onto other volumes or have hard links to other volumes.
  • Each Container in the Pod must independently specify where to mount each volume
  • localnfs
  • cephfs
  • awsElasticBlockStore
  • glusterfs
  • vsphereVolume
  • An awsElasticBlockStore volume mounts an Amazon Web Services (AWS) EBS Volume into your Pod.
  • the contents of an EBS volume are preserved and the volume is merely unmounted.
  • an EBS volume can be pre-populated with data, and that data can be “handed off” between Pods.
  • create an EBS volume using aws ec2 create-volume
  • the nodes on which Pods are running must be AWS EC2 instances
  • EBS only supports a single EC2 instance mounting a volume
  • check that the size and EBS volume type are suitable for your use!
  • A cephfs volume allows an existing CephFS volume to be mounted into your Pod.
  • the contents of a cephfs volume are preserved and the volume is merely unmounted.
    • 張 旭
      張 旭 on 06 Jul 19
       
      相當於自己的 AWS EBS
  • CephFS can be mounted by multiple writers simultaneously.
  • have your own Ceph server running with the share exported
  • configMap
  • The configMap resource provides a way to inject configuration data into Pods
  • When referencing a configMap object, you can simply provide its name in the volume to reference it
  • volumeMounts: - name: config-vol mountPath: /etc/config volumes: - name: config-vol configMap: name: log-config items: - key: log_level path: log_level
  • create a ConfigMap before you can use it.
  • A Container using a ConfigMap as a subPath volume mount will not receive ConfigMap updates.
  • An emptyDir volume is first created when a Pod is assigned to a Node, and exists as long as that Pod is running on that node.
  • When a Pod is removed from a node for any reason, the data in the emptyDir is deleted forever.
  • By default, emptyDir volumes are stored on whatever medium is backing the node - that might be disk or SSD or network storage, depending on your environment.
  • you can set the emptyDir.medium field to "Memory" to tell Kubernetes to mount a tmpfs (RAM-backed filesystem)
  • volumeMounts: - mountPath: /cache name: cache-volume volumes: - name: cache-volume emptyDir: {}
  • An fc volume allows an existing fibre channel volume to be mounted in a Pod.
  • configure FC SAN Zoning to allocate and mask those LUNs (volumes) to the target WWNs beforehand so that Kubernetes hosts can access them.
  • Flocker is an open-source clustered Container data volume manager. It provides management and orchestration of data volumes backed by a variety of storage backends.
  • emptyDir
  • flocker
  • A flocker volume allows a Flocker dataset to be mounted into a Pod
  • have your own Flocker installation running
  • A gcePersistentDisk volume mounts a Google Compute Engine (GCE) Persistent Disk into your Pod.
  • Using a PD on a Pod controlled by a ReplicationController will fail unless the PD is read-only or the replica count is 0 or 1
  • A glusterfs volume allows a Glusterfs (an open source networked filesystem) volume to be mounted into your Pod.
  • have your own GlusterFS installation running
  • A hostPath volume mounts a file or directory from the host node’s filesystem into your Pod.
  • a powerful escape hatch for some applications
  • access to Docker internals; use a hostPath of /var/lib/docker
  • allowing a Pod to specify whether a given hostPath should exist prior to the Pod running, whether it should be created, and what it should exist as
  • specify a type for a hostPath volume
  • the files or directories created on the underlying hosts are only writable by root.
  • hostPath: # directory location on host path: /data # this field is optional type: Directory
  • An iscsi volume allows an existing iSCSI (SCSI over IP) volume to be mounted into your Pod.
  • have your own iSCSI server running
  • A feature of iSCSI is that it can be mounted as read-only by multiple consumers simultaneously.
  • A local volume represents a mounted local storage device such as a disk, partition or directory.
  • Local volumes can only be used as a statically created PersistentVolume.
  • Compared to hostPath volumes, local volumes can be used in a durable and portable manner without manually scheduling Pods to nodes, as the system is aware of the volume’s node constraints by looking at the node affinity on the PersistentVolume.
  • If a node becomes unhealthy, then the local volume will also become inaccessible, and a Pod using it will not be able to run.
  • PersistentVolume spec using a local volume and nodeAffinity
  • PersistentVolume nodeAffinity is required when using local volumes. It enables the Kubernetes scheduler to correctly schedule Pods using local volumes to the correct node.
  • PersistentVolume volumeMode can now be set to “Block” (instead of the default value “Filesystem”) to expose the local volume as a raw block device.
  • When using local volumes, it is recommended to create a StorageClass with volumeBindingMode set to WaitForFirstConsumer
  • An nfs volume allows an existing NFS (Network File System) share to be mounted into your Pod.
  • NFS can be mounted by multiple writers simultaneously.
  • have your own NFS server running with the share exported
  • A persistentVolumeClaim volume is used to mount a PersistentVolume into a Pod.
  • PersistentVolumes are a way for users to “claim” durable storage (such as a GCE PersistentDisk or an iSCSI volume) without knowing the details of the particular cloud environment.
  • A projected volume maps several existing volume sources into the same directory.
  • All sources are required to be in the same namespace as the Pod. For more details, see the all-in-one volume design document.
  • Each projected volume source is listed in the spec under sources
  • A Container using a projected volume source as a subPath volume mount will not receive updates for those volume sources.
  • RBD volumes can only be mounted by a single consumer in read-write mode - no simultaneous writers allowed
  • A secret volume is used to pass sensitive information, such as passwords, to Pods
  • store secrets in the Kubernetes API and mount them as files for use by Pods
  • secret volumes are backed by tmpfs (a RAM-backed filesystem) so they are never written to non-volatile storage.
  • create a secret in the Kubernetes API before you can use it
  • A Container using a Secret as a subPath volume mount will not receive Secret updates.
  • StorageOS runs as a Container within your Kubernetes environment, making local or attached storage accessible from any node within the Kubernetes cluster.
  • Data can be replicated to protect against node failure. Thin provisioning and compression can improve utilization and reduce cost.
  • StorageOS provides block storage to Containers, accessible via a file system.
  • A vsphereVolume is used to mount a vSphere VMDK Volume into your Pod.
  • supports both VMFS and VSAN datastore.
  • create VMDK using one of the following methods before using with Pod.
  • share one volume for multiple uses in a single Pod.
  • The volumeMounts.subPath property can be used to specify a sub-path inside the referenced volume instead of its root.
  • volumeMounts: - name: workdir1 mountPath: /logs subPathExpr: $(POD_NAME)
  • env: - name: POD_NAME valueFrom: fieldRef: apiVersion: v1 fieldPath: metadata.name
  • Use the subPathExpr field to construct subPath directory names from Downward API environment variables
  • enable the VolumeSubpathEnvExpansion feature gate
  • The subPath and subPathExpr properties are mutually exclusive.
  • There is no limit on how much space an emptyDir or hostPath volume can consume, and no isolation between Containers or between Pods.
  • emptyDir and hostPath volumes will be able to request a certain amount of space using a resource specification, and to select the type of media to use, for clusters that have several media types.
  • the Container Storage Interface (CSI) and Flexvolume. They enable storage vendors to create custom storage plugins without adding them to the Kubernetes repository.
  • all volume plugins (like volume types listed above) were “in-tree” meaning they were built, linked, compiled, and shipped with the core Kubernetes binaries and extend the core Kubernetes API.
  • Container Storage Interface (CSI) defines a standard interface for container orchestration systems (like Kubernetes) to expose arbitrary storage systems to their container workloads.
  • Once a CSI compatible volume driver is deployed on a Kubernetes cluster, users may use the csi volume type to attach, mount, etc. the volumes exposed by the CSI driver.
  • The csi volume type does not support direct reference from Pod and may only be referenced in a Pod via a PersistentVolumeClaim object.
  • This feature requires CSIInlineVolume feature gate to be enabled:--feature-gates=CSIInlineVolume=true
  • In-tree plugins that support CSI Migration and have a corresponding CSI driver implemented are listed in the “Types of Volumes” section above.
  • Mount propagation allows for sharing volumes mounted by a Container to other Containers in the same Pod, or even to other Pods on the same node.
  • Mount propagation of a volume is controlled by mountPropagation field in Container.volumeMounts.
  • HostToContainer - This volume mount will receive all subsequent mounts that are mounted to this volume or any of its subdirectories.
  • Bidirectional - This volume mount behaves the same the HostToContainer mount. In addition, all volume mounts created by the Container will be propagated back to the host and to all Containers of all Pods that use the same volume.
  • Edit your Docker’s systemd service file. Set MountFlags as follows:MountFlags=shared
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