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張 旭

Kubernetes Volumes Guide - Examples for NFS and Persistent Volume - 0 views

matthewpalmer.net/...ple-nfs-persistent-volume.html

kubernetes volume storage

shared by 張 旭 on 07 Jul 19 - No Cached
  • Persistent volumes exist beyond containers, pods, and nodes.
  • Volumes also let you share data between containers in the same pod.
  • data in that volume will be destroyed when the pod is restarted.
  • ...9 more annotations...
  • Persistent volumes are long-term storage in your Kubernetes cluster.
  • A pod uses a persistent volume claim to to get read and write access to the persistent volume.
  • NFS stands for Network File System – it's a shared filesystem that can be accessed over the network.
  • The NFS must already exist – Kubernetes doesn't run the NFS, pods in just access it.
  • what's already stored in the NFS is not deleted when a pod is destroyed. Data is persistent.
  • an NFS can be accessed from multiple pods at the same time. An NFS can be used to share data between pods!
  • volumes: - name: nfs-volume nfs: # URL for the NFS server server: 10.108.211.244 # Change this! path: /
  • volumeMounts: - name: nfs-volume mountPath: /var/nfs
  • Just add the volume to each pod, and add a volume mount to use the NFS volume from each container.
  • 張 旭 on 07 Jul 19
     
    "Persistent volumes exist beyond containers, pods, and nodes. "
張 旭

DNS Records: An Introduction - 0 views

www.linode.com/...dns-records-an-introduction

dns networking system

shared by 張 旭 on 28 Aug 19 - No Cached
  • Domain names are best understood by reading from right to left.
  • the top-level domain, or TLD
  • Every term to the left of the TLD is separated by a period and considered a more specific subdomain
  • ...40 more annotations...
  • Name servers host a domain’s DNS information in a text file called a zone file.
  • Start of Authority (SOA) records
  • specifying DNS records, which match domain names to IP addresses.
  • Every domain’s zone file contains the domain administrator’s email address, the name servers, and the DNS records.
  • Your ISP’s DNS resolver queries a root nameserver for the proper TLD nameserver. In other words, it asks the root nameserver, *Where can I find the nameserver for .com domains?*
  • In actuality, ISPs cache a lot of DNS information after they’ve looked it up the first time.
  • caching is a good thing, but it can be a problem if you’ve recently made a change to your DNS information
  • An A record points your domain or subdomain to your Linode’s IP address,
  • use an asterisk (*) as your subdomain
  • An AAAA record is just like an A record, but for IPv6 IP addresses.
  • An AXFR record is a type of DNS record used for DNS replication
  • DNS Certification Authority Authorization uses DNS to allow the holder of a domain to specify which certificate authorities are allowed to issue certificates for that domain.
  • A CNAME record or Canonical Name record matches a domain or subdomain to a different domain.
  • Some mail servers handle mail oddly for domains with CNAME records, so you should not use a CNAME record for a domain that gets email.
  • MX records cannot reference CNAME-defined hostnames.
  • Chaining or looping CNAME records is not recommended.
  • a CNAME record does not function the same way as a URL redirect.
  • A DKIM record or DomainKeys Identified Mail record displays the public key for authenticating messages that have been signed with the DKIM protocol
  • DKIM records are implemented as text records.
  • An MX record or mail exchanger record sets the mail delivery destination for a domain or subdomain.
  • An MX record should ideally point to a domain that is also the hostname for its server.
  • Priority allows you to designate a fallback server (or servers) for mail for a particular domain. Lower numbers have a higher priority.
  • NS records or name server records set the nameservers for a domain or subdomain.
  • You can also set up different nameservers for any of your subdomains
  • Primary nameservers get configured at your registrar and secondary subdomain nameservers get configured in the primary domain’s zone file.
  • The order of NS records does not matter. DNS requests are sent randomly to the different servers
  • A PTR record or pointer record matches up an IP address to a domain or subdomain, allowing reverse DNS queries to function.
  • opposite service an A record does
  • PTR records are usually set with your hosting provider. They are not part of your domain’s zone file.
  • An SOA record or Start of Authority record labels a zone file with the name of the host where it was originally created.
  • Minimum TTL: The minimum amount of time other servers should keep data cached from this zone file.
  • An SPF record or Sender Policy Framework record lists the designated mail servers for a domain or subdomain.
  • An SPF record for your domain tells other receiving mail servers which outgoing server(s) are valid sources of email so they can reject spoofed mail from your domain that has originated from unauthorized servers.
  • Make sure your SPF records are not too strict.
  • An SRV record or service record matches up a specific service that runs on your domain or subdomain to a target domain.
  • Service: The name of the service must be preceded by an underscore (_) and followed by a period (.)
  • Protocol: The name of the protocol must be proceeded by an underscore (_) and followed by a period (.)
  • Port: The TCP or UDP port on which the service runs.
  • Target: The target domain or subdomain. This domain must have an A or AAAA record that resolves to an IP address.
  • A TXT record or text record provides information about the domain in question to other resources on the internet.
  • 張 旭 on 28 Aug 19
     
    "Domain names are best understood by reading from right to left."
張 旭

DNS - FreeIPA - 0 views

www.freeipa.org/DNS

dns networking system bind freeipa

shared by 張 旭 on 30 Aug 19 - No Cached
  • FreeIPA DNS integration allows administrator to manage and serve DNS records in a domain using the same CLI or Web UI as when managing identities and policies.
  • Single-master DNS is error prone, especially for inexperienced admins.
  • a decent Kerberos experience.
  • ...14 more annotations...
  • Goal is NOT to provide general-purpose DNS server.
  • DNS component in FreeIPA is optional and user may choose to manage all DNS records manually in other third party DNS server.
  • Clients can be configured to automatically run DNS updates (nsupdate) when their IP address changes and thus keeping its DNS record up-to-date. DNS zones can be configured to synchronize client's reverse (PTR) record along with the forward (A, AAAA) DNS record.
  • It is extremely hard to change DNS domain in existing installations so it is better to think ahead.
  • You should only use names which are delegated to you by the parent domain.
  • Not respecting this rule will cause problems sooner or later!
  • DNSSEC validation.
  • For internal names you can use arbitrary sub-domain in a DNS sub-tree you own, e.g. int.example.com.. Always respect rules from the previous section.
  • General advice about DNS views is do not use them because views make DNS deployment harder to maintain and security benefits are questionable (when compared with ACL).
  • The DNS integration is based on the bind-dyndb-ldap project, which enhances BIND name server to be able to use FreeIPA server LDAP instance as a data backend (data are stored in cn=dns entry, using schema defined by bind-dyndb-ldap
  • FreeIPA LDAP directory information tree is by default accessible to any user in the network
  • As DNS data are often considered as sensitive and as having access to cn=dns tree would be basically equal to being able to run zone transfer to all FreeIPA managed DNS zones, contents of this tree in LDAP are hidden by default.
  • standard system log (/var/log/messages or system journal)
  • BIND configuration (/etc/named.conf) can be updated to produce a more detailed log.
  • 張 旭 on 30 Aug 19
     
    "FreeIPA DNS integration allows administrator to manage and serve DNS records in a domain using the same CLI or Web UI as when managing identities and policies."
張 旭

Forwarding (DNS and BIND, 4th Edition) - 0 views

docstore.mik.ua/...ch10_05.htm

dns networking network

shared by 張 旭 on 16 Apr 20 - Cached
  • Forwarders are also useful if you need to shunt name resolution to a particular name server
  • If you designate one or more servers at your site as forwarders, your name servers will send all their off-site queries to the forwarders first.
  • A primary master or slave name server's mode of operation changes slightly when it is configured to use a forwarder.
  • ...2 more annotations...
  • If a resolver requests records that are already in the name server's authoritative data or cached data, the name server answers with that information
  • if the records aren't in its database, the name server sends the query to a forwarder and waits a short period for an answer before resuming normal operation and contacting the remote name servers itself. What the name server is doing differently here is sending a recursive query to the forwarder, expecting it to find the answer.
張 旭

What is a CAA record? - DNSimple Help - 0 views

support.dnsimple.com/...caa-record

networking network dns

shared by 張 旭 on 10 Mar 20 - No Cached
  • The purpose of the CAA record is to allow domain owners to declare which certificate authorities are allowed to issue a certificate for a domain.
  • If a CAA record is present, only the CAs listed in the record(s) are allowed to issue certificates for that hostname.
  • CAA records can set policy for the entire domain, or for specific hostnames.
  • ...4 more annotations...
  • The CAA record consists of a flags byte and a tag-value pair referred to as a ‘property’.
  • example.com. CAA 0 issue "letsencrypt.org"
  • each CAA record contains only one tag-value pair
  • dig google.com type257
張 旭

Warnings, Notes, & Tips - 0 views

clouddocs.f5.com/...tips-warnings.html

terraform networking network firewall bigip

shared by 張 旭 on 04 May 20 - No Cached
  • AS3 manages topology records globally in /Common, it is required that records only be managed through AS3, as it will treat the records declaratively.
  • If a record is added outside of AS3, it will be removed if it is not included in the next AS3 declaration for topology records (AS3 completely overwrites non-AS3 topologies when a declaration is submitted).
  • using AS3 to delete a tenant (for example, sending DELETE to the /declare/<TENANT> endpoint) that contains GSLB topologies will completely remove ALL GSLB topologies from the BIG-IP.
  • ...12 more annotations...
  • When posting a large declaration (hundreds of application services in a single declaration), you may experience a 500 error stating that the save sys config operation failed.
  • Even if you have asynchronous mode set to false, after 45 seconds AS3 sets asynchronous mode to true (API swap), and returns an async response.
  • When creating a new tenant using AS3, it must not use the same name as a partition you separately create on the target BIG-IP system.
  • If you use the same name and then post the declaration, AS3 overwrites (or removes) the existing partition completely, including all configuration objects in that partition.
  • use AS3 to create a tenant (which creates a BIG-IP partition), manually adding configuration objects to the partition created by AS3 can have unexpected results
  • When you delete the Tenant using AS3, the system deletes both virtual servers.
  • if a Firewall_Address_List contains zero addresses, a dummy IPv6 address of ::1:5ee:bad:c0de is added in order to maintain a valid Firewall_Address_List. If an address is added to the list, the dummy address is removed.
  • use /mgmt/shared/appsvcs/declare?async=true if you have a particularly large declaration which will take a long time to process.
  • reviewing the Sizing BIG-IP Virtual Editions section (page 7) of Deploying BIG-IP VEs in a Hyper-Converged Infrastructure
  • To test whether your system has AS3 installed or not, use GET with the /mgmt/shared/appsvcs/info URI.
  • You may find it more convenient to put multi-line texts such as iRules into AS3 declarations by first encoding them in Base64.
  • no matter your BIG-IP user account name, audit logs show all messages from admin and not the specific user name.
張 旭

Ruby and AOP: Decouple your code even more - Arkency Blog - 0 views

blog.arkency.com/...p-decouple-your-code-even-more

ruby aop programming algorithm pattern code

shared by 張 旭 on 03 Jun 17 - No Cached
  • Dark Parts in our apps - persistence, networking, logging, notifications… these parts are scattered in our code
  • aspect-oriented programming!
  • components are parts we can easily encapsulate into some kind of code abstraction - a methods, objects or procedures.
  • ...16 more annotations...
  • application’s logic is a great example of a component
  • Aspects cross-cut our application - when we use some kind of persistence (e.g. a database) or network communication (such as ZMQ sockets) our components need to know about it.
  • Aspect-oriented programming aims to get rid of cross-cuts by separating aspect code from component code using injections of our aspects in certain join points in our component code.
  • It’s responsible for pushing snippets scenario
  • SRP-conformant object
  • the join points in Ruby
  • advice
    • 張 旭
      張 旭 on 03 Jun 17
       
      AOP 裡面的術語
  • In most cases after and before advice are sufficient.
  • what does it mean to “evaluate code around” something? In our case it means: Don’t run this method. Take it and push to my advice as an argument and evaluate this advice
  • to provide a join point
  • You’ll often see empty methods in code written in AOP paradigm
  • provide aspect code to link with our use case
  • use case is a pure domain object, without even knowing it’s connected with some kind of persistence and logging layer.
  • Aspect-oriented programming is fixing the problem with polluting pure logic objects with technical context of our applications.
  • we treat our glues as a configuration part, not the logic part of our apps.
  • Glues should not contain any logic at all
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

MetalLB, bare metal load-balancer for Kubernetes - 0 views

metallb.universe.tf

kubernetes network

shared by 張 旭 on 14 Apr 21 - No Cached
  • Kubernetes does not offer an implementation of network load-balancers (Services of type LoadBalancer) for bare metal clusters
  • If you’re not running on a supported IaaS platform (GCP, AWS, Azure…), LoadBalancers will remain in the “pending” state indefinitely when created.
  • Bare metal cluster operators are left with two lesser tools to bring user traffic into their clusters, “NodePort” and “externalIPs” services.
張 旭

ALB vs ELB | Differences Between an ELB and an ALB on AWS | Sumo Logic - 0 views

www.sumologic.com/...aws-elb-alb

aws HA proxy

shared by 張 旭 on 06 Apr 21 - No Cached
  • If you use AWS, you have two load-balancing options: ELB and ALB.
  • An ELB is a software-based load balancer which can be set up and configured in front of a collection of AWS Elastic Compute (EC2) instances.
  • The load balancer serves as a single entry point for consumers of the EC2 instances and distributes incoming traffic across all machines available to receive requests.
  • ...14 more annotations...
  • the ELB also performs a vital role in improving the fault tolerance of the services which it fronts.
  • he Open Systems Interconnection Model, or OSI Model, is a conceptual model which is used to facilitate communications between different computing systems.
  • Layer 1 is the physical layer, and represents the physical medium across which the request is sent.
  • Layer 2 describes the data link layer
  • Layer 3 (the network layer)
  • Layer 7, which serves the application layer.
  • The Classic ELB operates at Layer 4. Layer 4 represents the transport layer, and is controlled by the protocol being used to transmit the request.
  • A network device, of which the Classic ELB is an example, reads the protocol and port of the incoming request, and then routes it to one or more backend servers.
  • the ALB operates at Layer 7. Layer 7 represents the application layer, and as such allows for the redirection of traffic based on the content of the request.
  • Whereas a request to a specific URL backed by a Classic ELB would only enable routing to a particular pool of homogeneous servers, the ALB can route based on the content of the URL, and direct to a specific subgroup of backing servers existing in a heterogeneous collection registered with the load balancer.
  • The Classic ELB is a simple load balancer, is easy to configure
  • As organizations move towards microservice architecture or adopt a container-based infrastructure, the ability to merely map a single address to a specific service becomes more complicated and harder to maintain.
  • the ALB manages routing based on user-defined rules.
  • oute traffic to different services based on either the host or the content of the path contained within that URL.
張 旭

Logstash Alternatives: Pros & Cons of 5 Log Shippers [2019] - Sematext - 0 views

sematext.com/...logstash-alternatives

log monitor system logstash fluentd

shared by 張 旭 on 05 Nov 19 - No Cached
  • In this case, Elasticsearch. And because Elasticsearch can be down or struggling, or the network can be down, the shipper would ideally be able to buffer and retry
  • Logstash is typically used for collecting, parsing, and storing logs for future use as part of log management.
  • Logstash’s biggest con or “Achille’s heel” has always been performance and resource consumption (the default heap size is 1GB).
  • ...37 more annotations...
  • This can be a problem for high traffic deployments, when Logstash servers would need to be comparable with the Elasticsearch ones.
  • Filebeat was made to be that lightweight log shipper that pushes to Logstash or Elasticsearch.
  • differences between Logstash and Filebeat are that Logstash has more functionality, while Filebeat takes less resources.
  • Filebeat is just a tiny binary with no dependencies.
  • For example, how aggressive it should be in searching for new files to tail and when to close file handles when a file didn’t get changes for a while.
  • For example, the apache module will point Filebeat to default access.log and error.log paths
  • Filebeat’s scope is very limited,
  • Initially it could only send logs to Logstash and Elasticsearch, but now it can send to Kafka and Redis, and in 5.x it also gains filtering capabilities.
  • Filebeat can parse JSON
  • you can push directly from Filebeat to Elasticsearch, and have Elasticsearch do both parsing and storing.
  • You shouldn’t need a buffer when tailing files because, just as Logstash, Filebeat remembers where it left off
  • For larger deployments, you’d typically use Kafka as a queue instead, because Filebeat can talk to Kafka as well
  • The default syslog daemon on most Linux distros, rsyslog can do so much more than just picking logs from the syslog socket and writing to /var/log/messages.
  • It can tail files, parse them, buffer (on disk and in memory) and ship to a number of destinations, including Elasticsearch.
  • rsyslog is the fastest shipper
  • Its grammar-based parsing module (mmnormalize) works at constant speed no matter the number of rules (we tested this claim).
  • use it as a simple router/shipper, any decent machine will be limited by network bandwidth
  • It’s also one of the lightest parsers you can find, depending on the configured memory buffers.
  • rsyslog requires more work to get the configuration right
  • the main difference between Logstash and rsyslog is that Logstash is easier to use while rsyslog lighter.
  • rsyslog fits well in scenarios where you either need something very light yet capable (an appliance, a small VM, collecting syslog from within a Docker container).
  • rsyslog also works well when you need that ultimate performance.
  • syslog-ng as an alternative to rsyslog (though historically it was actually the other way around).
  • a modular syslog daemon, that can do much more than just syslog
  • Unlike rsyslog, it features a clear, consistent configuration format and has nice documentation.
  • Similarly to rsyslog, you’d probably want to deploy syslog-ng on boxes where resources are tight, yet you do want to perform potentially complex processing.
  • syslog-ng has an easier, more polished feel than rsyslog, but likely not that ultimate performance
  • Fluentd was built on the idea of logging in JSON wherever possible (which is a practice we totally agree with) so that log shippers down the line don’t have to guess which substring is which field of which type.
  • Fluentd plugins are in Ruby and very easy to write.
  • structured data through Fluentd, it’s not made to have the flexibility of other shippers on this list (Filebeat excluded).
  • Fluent Bit, which is to Fluentd similar to how Filebeat is for Logstash.
  • Fluentd is a good fit when you have diverse or exotic sources and destinations for your logs, because of the number of plugins.
  • Splunk isn’t a log shipper, it’s a commercial logging solution
  • Graylog is another complete logging solution, an open-source alternative to Splunk.
  • everything goes through graylog-server, from authentication to queries.
  • Graylog is nice because you have a complete logging solution, but it’s going to be harder to customize than an ELK stack.
  • it depends
crazylion lee

GitHub - fonoster/fonos: - 0 views

github.com/fonos

voip

shared by crazylion lee on 29 Oct 20 - No Cached
  • crazylion lee on 29 Oct 20
     
    "Project Fonos is open-source telecommunications for the cloud. It helps VoIP integrators quickly deploy new networks and benefit from value-added services such as Programmable Voice, Messaging, and Video. This repository assembles the various components needed to deploy a telephony system at scale."
crazylion lee

Riemann - A network monitoring system - 0 views

riemann.io/index.html

monitoring dashboard sysadmin

shared by crazylion lee on 17 Apr 16 - No Cached
  • crazylion lee on 17 Apr 16
     
    "Riemann aggregates events from your servers and applications with a powerful stream processing language. Send an email for every exception in your app. Track the latency distribution of your web app. See the top processes on any host, by memory and CPU. Combine statistics from every Riak node in your cluster and forward to Graphite. Track user activity from second to second."
張 旭

Docker Explained: Using Dockerfiles to Automate Building of Images | DigitalOcean - 0 views

www.digitalocean.com/...to-automate-building-of-images

docker tutorial

shared by 張 旭 on 01 Jun 15 - No Cached
  • CMD would be running an application upon creation of a container which is already installed using RUN (e.g. RUN apt-get install …) inside the image
  • ENTRYPOINT argument sets the concrete default application that is used every time a container is created using the image.
  • ENV command is used to set the environment variables (one or more).
  • ...6 more annotations...
  • EXPOSE command is used to associate a specified port to enable networking between the running process inside the container and the outside world
  • defines the base image to use to start the build process
  • Unlike CMD, it actually is used to build the image (forming another layer on top of the previous one which is committed).
  • VOLUME command is used to enable access from your container to a directory on the host machine
  • set where the command defined with CMD is to be executed
  • To detach yourself from the container, use the escape sequence CTRL+P followed by CTRL+Q
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