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crazylion lee

How to record your terminal session on Linux - 0 views

www.howtoforge.com/...your-terminal-session-on-linux

session linux record terminal cwb

shared by crazylion lee on 15 Jun 16 - No Cached
  • crazylion lee on 15 Jun 16
     
    "Recording a terminal session may be important in helping someone learn a process, sharing information in an understandable way, and also presenting a series of commands in a proper manner. Whatever the purpose, there are many times when copy-pasting text from the terminal won't be very helpful while capturing a video of the process is quite far-fetched and may not be always possible. In this quick guide, we will take a look at the easiest way to record and share a terminal session in .gif format."
張 旭

How To Use Bash's Job Control to Manage Foreground and Background Processes | DigitalOcean - 0 views

www.digitalocean.com/...round-and-background-processes

linux system server command

shared by 張 旭 on 06 Feb 18 - No Cached
  • Most processes that you start on a Linux machine will run in the foreground. The command will begin execution, blocking use of the shell for the duration of the process.
  • By default, processes are started in the foreground. Until the program exits or changes state, you will not be able to interact with the shell.
  • stop the process by sending it a signal
  • ...17 more annotations...
  • Linux terminals are usually configured to send the "SIGINT" signal (typically signal number 2) to current foreground process when the CTRL-C key combination is pressed.
  • Another signal that we can send is the "SIGTSTP" signal (typically signal number 20).
  • A background process is associated with the specific terminal that started it, but does not block access to the shell
  • start a background process by appending an ampersand character ("&") to the end of your commands.
  • type commands at the same time.
  • The [1] represents the command's "job spec" or job number. We can reference this with other job and process control commands, like kill, fg, and bg by preceding the job number with a percentage sign. In this case, we'd reference this job as %1.
  • Once the process is stopped, we can use the bg command to start it again in the background
  • By default, the bg command operates on the most recently stopped process.
  • Whether a process is in the background or in the foreground, it is rather tightly tied with the terminal instance that started it
  • When a terminal closes, it typically sends a SIGHUP signal to all of the processes (foreground, background, or stopped) that are tied to the terminal.
  • a terminal multiplexer
  • start it using the nohup command
  • appending output to ‘nohup.out’
  • pgrep -a
  • The disown command, in its default configuration, removes a job from the jobs queue of a terminal.
  • You can pass the -h flag to the disown process instead in order to mark the process to ignore SIGHUP signals, but to otherwise continue on as a regular job
  • The huponexit shell option controls whether bash will send its child processes the SIGHUP signal when it exits.
張 旭

Ingress - Kubernetes - 0 views

kubernetes.io/...ingress

kubernetes networking network ingress

shared by 張 旭 on 04 Jul 19 - No Cached
  • An API object that manages external access to the services in a cluster, typically HTTP.
  • load balancing
  • SSL termination
  • ...62 more annotations...
  • name-based virtual hosting
  • Edge routerA router that enforces the firewall policy for your cluster.
  • Cluster networkA set of links, logical or physical, that facilitate communication within a cluster according to the Kubernetes networking model.
  • A Kubernetes ServiceA way to expose an application running on a set of Pods as a network service. that identifies a set of Pods using labelTags objects with identifying attributes that are meaningful and relevant to users. selectors.
  • Services are assumed to have virtual IPs only routable within the cluster network.
  • Ingress exposes HTTP and HTTPS routes from outside the cluster to services within the cluster.
  • Traffic routing is controlled by rules defined on the Ingress resource.
  • An Ingress can be configured to give Services externally-reachable URLs, load balance traffic, terminate SSL / TLS, and offer name based virtual hosting.
  • Exposing services other than HTTP and HTTPS to the internet typically uses a service of type Service.Type=NodePort or Service.Type=LoadBalancer.
  • You must have an ingress controller to satisfy an Ingress. Only creating an Ingress resource has no effect.
  • As with all other Kubernetes resources, an Ingress needs apiVersion, kind, and metadata fields
  • Ingress frequently uses annotations to configure some options depending on the Ingress controller,
  • Ingress resource only supports rules for directing HTTP traffic.
  • An optional host.
  • A list of paths
  • A backend is a combination of Service and port names
  • has an associated backend
  • Both the host and path must match the content of an incoming request before the load balancer directs traffic to the referenced Service.
  • HTTP (and HTTPS) requests to the Ingress that matches the host and path of the rule are sent to the listed backend.
  • A default backend is often configured in an Ingress controller to service any requests that do not match a path in the spec.
  • An Ingress with no rules sends all traffic to a single default backend.
  • Ingress controllers and load balancers may take a minute or two to allocate an IP address.
  • A fanout configuration routes traffic from a single IP address to more than one Service, based on the HTTP URI being requested.
  • nginx.ingress.kubernetes.io/rewrite-target: /
  • describe ingress
  • get ingress
  • Name-based virtual hosts support routing HTTP traffic to multiple host names at the same IP address.
  • route requests based on the Host header.
  • an Ingress resource without any hosts defined in the rules, then any web traffic to the IP address of your Ingress controller can be matched without a name based virtual host being required.
  • secure an Ingress by specifying a SecretStores sensitive information, such as passwords, OAuth tokens, and ssh keys. that contains a TLS private key and certificate.
  • Currently the Ingress only supports a single TLS port, 443, and assumes TLS termination.
  • An Ingress controller is bootstrapped with some load balancing policy settings that it applies to all Ingress, such as the load balancing algorithm, backend weight scheme, and others.
  • persistent sessions, dynamic weights) are not yet exposed through the Ingress. You can instead get these features through the load balancer used for a Service.
  • review the controller specific documentation to see how they handle health checks
  • edit ingress
  • After you save your changes, kubectl updates the resource in the API server, which tells the Ingress controller to reconfigure the load balancer.
  • kubectl replace -f on a modified Ingress YAML file.
  • Node: A worker machine in Kubernetes, part of a cluster.
  • in most common Kubernetes deployments, nodes in the cluster are not part of the public internet.
  • Edge router: A router that enforces the firewall policy for your cluster.
  • a gateway managed by a cloud provider or a physical piece of hardware.
  • Cluster network: A set of links, logical or physical, that facilitate communication within a cluster according to the Kubernetes networking model.
  • Service: A Kubernetes Service that identifies a set of Pods using label selectors.
  • An Ingress may be configured to give Services externally-reachable URLs, load balance traffic, terminate SSL / TLS, and offer name-based virtual hosting.
  • An Ingress does not expose arbitrary ports or protocols.
  • You must have an Ingress controller to satisfy an Ingress. Only creating an Ingress resource has no effect.
  • The name of an Ingress object must be a valid DNS subdomain name
  • The Ingress spec has all the information needed to configure a load balancer or proxy server.
  • Ingress resource only supports rules for directing HTTP(S) traffic.
  • An Ingress with no rules sends all traffic to a single default backend and .spec.defaultBackend is the backend that should handle requests in that case.
  • If defaultBackend is not set, the handling of requests that do not match any of the rules will be up to the ingress controller
  • A common usage for a Resource backend is to ingress data to an object storage backend with static assets.
  • Exact: Matches the URL path exactly and with case sensitivity.
  • Prefix: Matches based on a URL path prefix split by /. Matching is case sensitive and done on a path element by element basis.
  • multiple paths within an Ingress will match a request. In those cases precedence will be given first to the longest matching path.
  • Hosts can be precise matches (for example “foo.bar.com”) or a wildcard (for example “*.foo.com”).
  • No match, wildcard only covers a single DNS label
  • Each Ingress should specify a class, a reference to an IngressClass resource that contains additional configuration including the name of the controller that should implement the class.
  • secure an Ingress by specifying a Secret that contains a TLS private key and certificate.
  • The Ingress resource only supports a single TLS port, 443, and assumes TLS termination at the ingress point (traffic to the Service and its Pods is in plaintext).
  • TLS will not work on the default rule because the certificates would have to be issued for all the possible sub-domains.
  • hosts in the tls section need to explicitly match the host in the rules section.
crazylion lee

Hyper.app - 0 views

hyper.is

terminal javascript html

shared by crazylion lee on 16 Nov 16 - No Cached
  • crazylion lee on 16 Nov 16
     
    "JS/HTML/CSS Terminal"
張 旭

Controllers | Kubernetes - 0 views

kubernetes.io/...controller

kubernetes system auto

shared by 張 旭 on 14 May 21 - No Cached
  • In robotics and automation, a control loop is a non-terminating loop that regulates the state of a system.
  • controllers are control loops that watch the state of your cluster, then make or request changes where needed
  • Each controller tries to move the current cluster state closer to the desired state.
  • ...12 more annotations...
  • A controller tracks at least one Kubernetes resource type.
  • The controller(s) for that resource are responsible for making the current state come closer to that desired state.
  • in Kubernetes, a controller will send messages to the API server that have useful side effects.
  • Built-in controllers manage state by interacting with the cluster API server.
  • By contrast with Job, some controllers need to make changes to things outside of your cluster.
  • the controller makes some change to bring about your desired state, and then reports current state back to your cluster's API server. Other control loops can observe that reported data and take their own actions.
  • As long as the controllers for your cluster are running and able to make useful changes, it doesn't matter if the overall state is stable or not.
  • Kubernetes uses lots of controllers that each manage a particular aspect of cluster state.
  • a particular control loop (controller) uses one kind of resource as its desired state, and has a different kind of resource that it manages to make that desired state happen.
  • There can be several controllers that create or update the same kind of object.
  • you can have Deployments and Jobs; these both create Pods. The Job controller does not delete the Pods that your Deployment created, because there is information (labels) the controllers can use to tell those Pods apart.
  • Kubernetes comes with a set of built-in controllers that run inside the kube-controller-manager.
  • 張 旭 on 14 May 21
     
    "In robotics and automation, a control loop is a non-terminating loop that regulates the state of a system. "
crazylion lee

Fluent interface - Wikipedia, the free encyclopedia - 1 views

en.wikipedia.org/...Fluent_interface

code interface programming

shared by crazylion lee on 10 Jul 16 - No Cached
  • crazylion lee on 10 Jul 16
     
    "In software engineering, a fluent interface (as first coined by Eric Evans and Martin Fowler) is an implementation of an object oriented API that aims to provide more readable code. A fluent interface is normally implemented by using method cascading (concretely method chaining) to relay the instruction context of a subsequent call (but a fluent interface entails more than just method chaining [1]). Generally, the context is defined through the return value of a called method self-referential, where the new context is equivalent to the last context terminated through the return of a void context."
張 旭

Introduction to CI/CD with GitLab | GitLab - 0 views

docs.gitlab.com/...index.html

devops CI

shared by 張 旭 on 16 Apr 19 - No Cached
  • deploying code changes at every small iteration, reducing the chance of developing new code based on bugged or failed previous versions
  • based on automating the execution of scripts to minimize the chance of introducing errors while developing applications.
  • For every push to the repository, you can create a set of scripts to build and test your application automatically, decreasing the chance of introducing errors to your app.
  • ...5 more annotations...
  • checked automatically but requires human intervention to manually and strategically trigger the deployment of the changes.
  • instead of deploying your application manually, you set it to be deployed automatically.
  • .gitlab-ci.yml, located in the root path of your repository
  • all the scripts you add to the configuration file are the same as the commands you run on a terminal in your computer.
  • GitLab will detect it and run your scripts with the tool called GitLab Runner, which works similarly to your terminal.
  • 張 旭 on 16 Apr 19
     
    "deploying code changes at every small iteration, reducing the chance of developing new code based on bugged or failed previous versions"
張 旭

Gracefully Shutdown Docker Container - Kakashi's Blog - 1 views

kkc.github.io/...ully-shutdown-docker-container

docker process nodejs

shared by 張 旭 on 17 Nov 20 - No Cached
  • The initial idea is to make application invokes deconstructor of each component as soon as the application receives specific signals such as SIGTERM and SIGINT
  • When you run a docker container, by default it has a PID namespace, which means the docker process is isolated from other processes on your host.
  • The PID namespace has an important task to reap zombie processes.
  • ...11 more annotations...
  • This uses /bin/bash as PID1 and runs your program as the subprocess.
  • When a signal is sent to a shell, the signal actually won’t be forwarded to subprocesses.
  • By using the exec form, we can run our program as PID1
  • if you use exec form to run a shell script to spawn your application, remember to use exec syscall to overwrite /usr/bin/bash otherwise it will act as senario1
  • /bin/bash can handle repeating zombie process
  • with Tini, SIGTERM properly terminates your process even if you didn’t explicitly install a signal handler for it.
  • run tini as PID1 and it will forward the signal for subprocesses.
  • tini is a signal proxy and it also can deal with zombie process issue automatically.
  • run your program with tini by passing --init flag to docker run
  • use docker stop, docker will wait for 10s for stopping container before killing a process (by default). The main process inside the container will receive SIGTERM, then docker daemon will wait for 10s and send SIGKILL to terminate process.
  • kill running containers immediately. it’s more like kill -9 and kill --SIGKILL
crazylion lee

Final Term - 0 views

finalterm.org

terminal linux

shared by crazylion lee on 17 Jan 14 - No Cached
crazylion lee

GitHub - skavanagh/KeyBox: KeyBox is a web-based SSH console that centrally manages adm... - 2 views

github.com/KeyBox

ssh web terminal

shared by crazylion lee on 12 Oct 18 - No Cached
  • crazylion lee on 12 Oct 18
     
    "KeyBox is a web-based SSH console that centrally manages administrative access to systems. Web-based administration is combined with management and distribution of user's public SSH keys. https://www.sshkeybox.com"
張 旭

Let's Encrypt & Docker - Træfik - 0 views

docs.traefik.io/...docker-and-lets-encrypt

traefik docker networking proxy

shared by 張 旭 on 19 Sep 18 - No Cached
  • automatically discover any services on the Docker host and let Træfik reconfigure itself automatically when containers get created (or shut down) so HTTP traffic can be routed accordingly.
  • use Træfik as a layer-7 load balancer with SSL termination for a set of micro-services used to run a web application.
  • Docker containers can only communicate with each other over TCP when they share at least one network.
  • ...15 more annotations...
  • Docker under the hood creates IPTable rules so containers can't reach other containers unless you'd want to
  • Træfik can listen to Docker events and reconfigure its own internal configuration when containers are created (or shut down).
  • Enable the Docker provider and listen for container events on the Docker unix socket we've mounted earlier.
  • Enable automatic request and configuration of SSL certificates using Let's Encrypt. These certificates will be stored in the acme.json file, which you can back-up yourself and store off-premises.
  • there isn't a single container that has any published ports to the host -- everything is routed through Docker networks.
  • Thanks to Docker labels, we can tell Træfik how to create its internal routing configuration.
  • container labels and service labels
  • With the traefik.enable label, we tell Træfik to include this container in its internal configuration.
  • tell Træfik to use the web network to route HTTP traffic to this container.
  • Service labels allow managing many routes for the same container.
  • When both container labels and service labels are defined, container labels are just used as default values for missing service labels but no frontend/backend are going to be defined only with these labels.
  • In the example, two service names are defined : basic and admin. They allow creating two frontends and two backends.
  • Always specify the correct port where the container expects HTTP traffic using traefik.port label.
  • all containers that are placed in the same network as Træfik will automatically be reachable from the outside world
  • With the traefik.frontend.auth.basic label, it's possible for Træfik to provide a HTTP basic-auth challenge for the endpoints you provide the label for.
張 旭

The Twelve-Factor App - 0 views

12factor.net/disposability

development application programming

shared by 張 旭 on 20 Feb 19 - No Cached
  • they can be started or stopped at a moment’s notice.
  • Processes should strive to minimize startup time
  • Processes shut down gracefully when they receive a SIGTERM signal from the process manager.
  • ...4 more annotations...
  • returning the current job to the work queue
  • all jobs are reentrant, which typically is achieved by wrapping the results in a transaction, or making the operation idempotent
  • Processes should also be robust against sudden death, in the case of a failure in the underlying hardware.
  • a twelve-factor app is architected to handle unexpected, non-graceful terminations
張 旭

Queues - Laravel - The PHP Framework For Web Artisans - 0 views

laravel.com/queues

php programming laravel queue worker framework

shared by 張 旭 on 02 Mar 19 - No Cached
  • Laravel queues provide a unified API across a variety of different queue backends, such as Beanstalk, Amazon SQS, Redis, or even a relational database.
  • The queue configuration file is stored in config/queue.php
  • a synchronous driver that will execute jobs immediately (for local use)
  • ...56 more annotations...
  • A null queue driver is also included which discards queued jobs.
  • In your config/queue.php configuration file, there is a connections configuration option.
  • any given queue connection may have multiple "queues" which may be thought of as different stacks or piles of queued jobs.
  • each connection configuration example in the queue configuration file contains a queue attribute.
  • if you dispatch a job without explicitly defining which queue it should be dispatched to, the job will be placed on the queue that is defined in the queue attribute of the connection configuration
  • pushing jobs to multiple queues can be especially useful for applications that wish to prioritize or segment how jobs are processed
  • specify which queues it should process by priority.
  • If your Redis queue connection uses a Redis Cluster, your queue names must contain a key hash tag.
  • ensure all of the Redis keys for a given queue are placed into the same hash slot
  • all of the queueable jobs for your application are stored in the app/Jobs directory.
  • Job classes are very simple, normally containing only a handle method which is called when the job is processed by the queue.
  • we were able to pass an Eloquent model directly into the queued job's constructor. Because of the SerializesModels trait that the job is using, Eloquent models will be gracefully serialized and unserialized when the job is processing.
  • When the job is actually handled, the queue system will automatically re-retrieve the full model instance from the database.
  • The handle method is called when the job is processed by the queue
  • The arguments passed to the dispatch method will be given to the job's constructor
  • delay the execution of a queued job, you may use the delay method when dispatching a job.
  • dispatch a job immediately (synchronously), you may use the dispatchNow method.
  • When using this method, the job will not be queued and will be run immediately within the current process
  • specify a list of queued jobs that should be run in sequence.
  • Deleting jobs using the $this->delete() method will not prevent chained jobs from being processed. The chain will only stop executing if a job in the chain fails.
  • this does not push jobs to different queue "connections" as defined by your queue configuration file, but only to specific queues within a single connection.
  • To specify the queue, use the onQueue method when dispatching the job
  • To specify the connection, use the onConnection method when dispatching the job
  • defining the maximum number of attempts on the job class itself.
  • to defining how many times a job may be attempted before it fails, you may define a time at which the job should timeout.
  • using the funnel method, you may limit jobs of a given type to only be processed by one worker at a time
  • using the throttle method, you may throttle a given type of job to only run 10 times every 60 seconds.
  • If an exception is thrown while the job is being processed, the job will automatically be released back onto the queue so it may be attempted again.
  • dispatch a Closure. This is great for quick, simple tasks that need to be executed outside of the current request cycle
  • When dispatching Closures to the queue, the Closure's code contents is cryptographically signed so it can not be modified in transit.
  • Laravel includes a queue worker that will process new jobs as they are pushed onto the queue.
  • once the queue:work command has started, it will continue to run until it is manually stopped or you close your terminal
  • queue workers are long-lived processes and store the booted application state in memory.
  • they will not notice changes in your code base after they have been started.
  • during your deployment process, be sure to restart your queue workers.
  • customize your queue worker even further by only processing particular queues for a given connection
  • The --once option may be used to instruct the worker to only process a single job from the queue
  • The --stop-when-empty option may be used to instruct the worker to process all jobs and then exit gracefully.
  • Daemon queue workers do not "reboot" the framework before processing each job.
  • you should free any heavy resources after each job completes.
  • Since queue workers are long-lived processes, they will not pick up changes to your code without being restarted.
  • restart the workers during your deployment process.
  • php artisan queue:restart
  • The queue uses the cache to store restart signals
  • the queue workers will die when the queue:restart command is executed, you should be running a process manager such as Supervisor to automatically restart the queue workers.
  • each queue connection defines a retry_after option. This option specifies how many seconds the queue connection should wait before retrying a job that is being processed.
  • The --timeout option specifies how long the Laravel queue master process will wait before killing off a child queue worker that is processing a job.
  • When jobs are available on the queue, the worker will keep processing jobs with no delay in between them.
  • While sleeping, the worker will not process any new jobs - the jobs will be processed after the worker wakes up again
  • the numprocs directive will instruct Supervisor to run 8 queue:work processes and monitor all of them, automatically restarting them if they fail.
  • Laravel includes a convenient way to specify the maximum number of times a job should be attempted.
  • define a failed method directly on your job class, allowing you to perform job specific clean-up when a failure occurs.
  • a great opportunity to notify your team via email or Slack.
  • php artisan queue:retry all
  • php artisan queue:flush
  • When injecting an Eloquent model into a job, it is automatically serialized before being placed on the queue and restored when the job is processed
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

CertSimple | An nginx config for 2017 - 0 views

certsimple.com/...nx-http2-load-balancing-config

nginx web server performance

shared by 張 旭 on 19 Mar 17 - No Cached
  • HAProxy can't terminate a HTTP/2 connection itself.
  • a server OS which includes OpenSSL 1.02 to have ALPN.
  • a new nginx (anything newer than 1.9.5 supports HTTP/2)
  • ...6 more annotations...
  • we like HTTPS/non-www since HTTPS is needed for current browsers and non-www is short.
  • visit the Mozilla TLS Generator to get the latest cipher suites and TLS versions
  • add the necessary headers for GeoIP and proper logging.
  • HTML5 SSE simpler than websockets
  • nginx -t
  • Scan your site with SSL Labs scan
crazylion lee

Fig - 0 views

fig.io

terminal

shared by crazylion lee on 30 May 21 - No Cached
張 旭

Logging Architecture | Kubernetes - 0 views

kubernetes.io/...logging

kubernetes log

shared by 張 旭 on 27 May 21 - No Cached
  • Application logs can help you understand what is happening inside your application
  • container engines are designed to support logging.
  • The easiest and most adopted logging method for containerized applications is writing to standard output and standard error streams.
  • ...26 more annotations...
  • In a cluster, logs should have a separate storage and lifecycle independent of nodes, pods, or containers. This concept is called cluster-level logging.
  • Cluster-level logging architectures require a separate backend to store, analyze, and query logs
  • Kubernetes does not provide a native storage solution for log data.
  • use kubectl logs --previous to retrieve logs from a previous instantiation of a container.
  • A container engine handles and redirects any output generated to a containerized application's stdout and stderr streams
  • The Docker JSON logging driver treats each line as a separate message.
  • By default, if a container restarts, the kubelet keeps one terminated container with its logs.
  • An important consideration in node-level logging is implementing log rotation, so that logs don't consume all available storage on the node
  • You can also set up a container runtime to rotate an application's logs automatically.
  • The two kubelet flags container-log-max-size and container-log-max-files can be used to configure the maximum size for each log file and the maximum number of files allowed for each container respectively.
  • The kubelet and container runtime do not run in containers.
  • On machines with systemd, the kubelet and container runtime write to journald. If systemd is not present, the kubelet and container runtime write to .log files in the /var/log directory.
  • System components inside containers always write to the /var/log directory, bypassing the default logging mechanism.
  • Kubernetes does not provide a native solution for cluster-level logging
  • Use a node-level logging agent that runs on every node.
  • implement cluster-level logging by including a node-level logging agent on each node.
  • the logging agent is a container that has access to a directory with log files from all of the application containers on that node.
  • the logging agent must run on every node, it is recommended to run the agent as a DaemonSet
  • Node-level logging creates only one agent per node and doesn't require any changes to the applications running on the node.
  • Containers write stdout and stderr, but with no agreed format. A node-level agent collects these logs and forwards them for aggregation.
  • Each sidecar container prints a log to its own stdout or stderr stream.
  • It is not recommended to write log entries with different formats to the same log stream
  • writing logs to a file and then streaming them to stdout can double disk usage.
  • If you have an application that writes to a single file, it's recommended to set /dev/stdout as the destination
  • it's recommended to use stdout and stderr directly and leave rotation and retention policies to the kubelet.
  • Using a logging agent in a sidecar container can lead to significant resource consumption. Moreover, you won't be able to access those logs using kubectl logs because they are not controlled by the kubelet.
張 旭

Production Notes - MongoDB Manual - 0 views

docs.mongodb.com/...production-notes

mongodb database performance

shared by 張 旭 on 29 Apr 21 - No Cached
  • mongod will not start if dbPath contains data files created by a storage engine other than the one specified by --storageEngine.
  • mongod must possess read and write permissions for the specified dbPath.
  • WiredTiger supports concurrent access by readers and writers to the documents in a collection
  • ...9 more annotations...
  • Journaling guarantees that MongoDB can quickly recover write operations that were written to the journal but not written to data files in cases where mongod terminated due to a crash or other serious failure.
  • To use read concern level of "majority", replica sets must use WiredTiger storage engine.
  • Write concern describes the level of acknowledgement requested from MongoDB for write operations.
  • With stronger write concerns, clients must wait after sending a write operation until MongoDB confirms the write operation at the requested write concern level.
  • By default, authorization is not enabled, and mongod assumes a trusted environment
  • The HTTP interface is disabled by default. Do not enable the HTTP interface in production environments.
  • Avoid overloading the connection resources of a mongod or mongos instance by adjusting the connection pool size to suit your use case.
  • ensure that each mongod or mongos instance has access to two real cores or one multi-core physical CPU.
  • The WiredTiger storage engine is multithreaded and can take advantage of additional CPU cores
張 旭

鳥哥的 Linux 私房菜 -- 第一章、Linux是什麼與如何學習 - 0 views

linux.vbird.org/...0110whatislinux.php

system linux

shared by 張 旭 on 22 Jun 21 - Cached
  • Linux就是核心與系統呼叫介面那兩層
  • 核心與硬體的關係非常的強烈
  • Linux提供了一個完整的作業系統當中最底層的硬體控制與資源管理的完整架構， 這個架構是沿襲Unix良好的傳統來的，所以相當的穩定而功能強大
  • ...31 more annotations...
  • Linux的核心是由Linus Torvalds在1991年的時候給他開發出來的， 並且丟到網路上提供大家下載，後來大家覺得這個小東西(Linux Kernel)相當的小而精巧， 所以慢慢的就有相當多的朋友投入這個小東西的研究領域裡面去
  • 1960年代初期麻省理工學院(MIT)發展了所謂的： 『相容分時系統(Compatible Time-Sharing System, CTSS)』， 它可以讓大型主機透過提供數個終端機(terminal)以連線進入主機，來利用主機的資源進行運算工作
  • 為了更加強化大型主機的功能，以讓主機的資源可以提供更多使用者來利用，所以在1965年前後， 由貝爾實驗室(Bell)、麻省理工學院(MIT)及奇異公司(GE, 或稱為通用電器)共同發起了Multics的計畫
  • 以組合語言(Assembler)寫出了一組核心程式，同時包括一些核心工具程式， 以及一個小小的檔案系統。那個系統就是Unix的原型！ 當時Thompson將Multics龐大的複雜系統簡化了不少，於是同實驗室的朋友都戲稱這個系統為：Unics。(當時尚未有Unix的名稱)
  • 所有的程式或系統裝置都是檔案
  • 不管建構編輯器還是附屬檔案，所寫的程式只有一個目的，且要有效的完成目標。
  • Dennis Ritchie (註3) 將B語言重新改寫成C語言，再以C語言重新改寫與編譯Unics的核心， 最後正名與發行出Unix的正式版本！
  • 由於Unix是以較高階的C語言寫的，相對於組合語言需要與硬體有密切的配合， 高階的C語言與硬體的相關性就沒有這麼大了！所以，這個改變也使得Unix很容易被移植到不同的機器上面喔！
  • AT&T此時對於Unix是採取較開放的態度，此外，Unix是以高階的C語言寫成的， 理論上是具有可移植性的！亦即只要取得Unix的原始碼，並且針對大型主機的特性加以修訂原有的原始碼(Source Code)， 就可能將Unix移植到另一部不同的主機上頭了。
  • 柏克萊大學的Bill Joy (註4)在取得了Unix的核心原始碼後，著手修改成適合自己機器的版本， 並且同時增加了很多工具軟體與編譯程式，最終將它命名為Berkeley Software Distribution (BSD)。
  • 每一家公司自己出的Unix雖然在架構上面大同小異，但是卻真的僅能支援自身的硬體， 所以囉，早先的Unix只能與伺服器(Server)或者是大型工作站(Workstation)劃上等號！
  • AT&T在1979年發行的第七版Unix中，特別提到了 『不可對學生提供原始碼』的嚴格限制！
  • 純種的Unix指的就是System V以及BSD
  • AT&T自家的System V
  • 既然1979年的Unix第七版可以在Intel的x86架構上面進行移植， 那麼是否意味著可以將Unix改寫並移植到x86上面了呢？在這個想法上， 譚寧邦教授於是乎自己動手寫了Minix這個Unix Like的核心程式！
  • 『既然作業系統太複雜，我就先寫可以在Unix上面運行的小程式，這總可以了吧？』
  • 如果能夠寫出一個不錯的編譯器，那不就是大家都需要的軟體了嗎？ 因此他便開始撰寫C語言的編譯器，那就是現在相當有名的GNU C Compiler(gcc)！
  • 他還撰寫了更多可以被呼叫的C函式庫(GNU C library)，以及可以被使用來操作作業系統的基本介面BASH shell！ 這些都在1990年左右完成了！
  • 有鑑於圖形使用者介面(Graphical User Interface, GUI) 的需求日益加重，在1984年由MIT與其他協力廠商首次發表了X Window System ，並且更在1988年成立了非營利性質的XFree86這個組織。所謂的XFree86其實是 X Window System + Free + x86的整合名稱呢！
  • 譚寧邦教授為了教育需要而撰寫的Minix系統！ 他在購買了最新的Intel 386的個人電腦後，就立即安裝了Minix這個作業系統。 另外，上個小節當中也談到，Minix這個作業系統是有附上原始碼的， 所以托瓦茲也經由這個原始碼學習到了很多的核心程式設計的設計概念喔！
  • 托瓦茲自己也說：『我始終是個性能癖』^_^。 為了徹底發揮386的效能，於是托瓦茲花了不少時間在測試386機器上！ 他的重要測試就是在測試386的多功性能。首先，他寫了三個小程式，一個程式會持續輸出A、一個會持續輸出B， 最後一個會將兩個程式進行切換。他將三個程式同時執行，結果，他看到螢幕上很順利的一直出現ABABAB...... 他知道，他成功了！ ^_^
  • 為了讓所有的軟體都可以在Linux上執行，於是托瓦茲開始參考標準的POSIX規範。
  • POSIX是可攜式作業系統介面(Portable Operating System Interface)的縮寫，重點在規範核心與應用程式之間的介面， 這是由美國電器與電子工程師學會(IEEE)所發佈的一項標準喔
  • 因為托瓦茲放置核心的那個FTP網站的目錄為：Linux， 從此，大家便稱這個核心為Linux了。(請注意，此時的Linux就是那個kernel喔！ 另外，托瓦茲所丟到該目錄下的第一個核心版本為0.02呢！)
  • Linux其實就是一個作業系統最底層的核心及其提供的核心工具。 他是GNU GPL授權模式，所以，任何人均可取得原始碼與可執行這個核心程式，並且可以修改。
  • Linux參考POSIX設計規範，於是相容於Unix作業系統，故亦可稱之為Unix Like的一種
  • 為了讓使用者能夠接觸到Linux，於是很多的商業公司或非營利團體， 就將Linux Kernel(含tools)與可運行的軟體整合起來，加上自己具有創意的工具程式， 這個工具程式可以讓使用者以光碟/DVD或者透過網路直接安裝/管理Linux系統。 這個『Kernel + Softwares + Tools + 可完整安裝程序』的咚咚，我們稱之為Linux distribution， 一般中文翻譯成可完整安裝套件，或者Linux發佈商套件等。
  • 在1994年終於完成的Linux的核心正式版！version 1.0。 這一版同時還加入了X Window System的支援呢！且於1996年完成了2.0版、2011 年釋出 3.0 版，更於 2015 年 4 月釋出了 4.0 版哩！ 發展相當迅速喔！此外，托瓦茲指明了企鵝為Linux的吉祥物。
  • Linux本身就是個最陽春的作業系統，其開發網站設立在http://www.kernel.org，我們亦稱Linux作業系統最底層的資料為『核心(Kernel)』。
  • 常見的 Linux distributions 分類有『商業、社群』分類法，或『RPM、DPKG』分類法
  • 事實上鳥哥認為distributions主要分為兩大系統，一種是使用RPM方式安裝軟體的系統，包括Red Hat, Fedora, SuSE等都是這類； 一種則是使用Debian的dpkg方式安裝軟體的系統，包括Debian, Ubuntu, B2D等等。
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