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張 旭

MySQL :: MySQL 5.7 Reference Manual :: 19.1 Group Replication Background - 0 views

dev.mysql.com/...up-replication-background.html

mysql cluster HA system database replication

shared by 張 旭 on 19 Mar 17 - No Cached
  • the component can be removed and the system should continue to operate as expected
  • network partitioning
  • split brain scenarios
  • ...8 more annotations...
  • the ultimate challenge is to fuse the logic of the database and data replication with the logic of having several servers coordinated in a consistent and simple way
  • MySQL Group Replication provides distributed state machine replication with strong coordination between servers.
  • Servers coordinate themselves automatically when they are part of the same group
  • The group can operate in a single-primary mode with automatic primary election, where only one server accepts updates at a time.
  • For a transaction to commit, the majority of the group have to agree on the order of a given transaction in the global sequence of transactions
  • Deciding to commit or abort a transaction is done by each server individually, but all servers make the same decision
  • group communication protocols
  • the Paxos algorithm. It acts as the group communication systems engine.
張 旭

MySQL :: MySQL 5.7 Reference Manual :: 19.1.1.2 Group Replication - 0 views

dev.mysql.com/...group-replication-summary.html

mysql HA system database replication

shared by 張 旭 on 19 Mar 17 - No Cached
  • The replication group is a set of servers that interact with each other through message passing.
  • The communication layer provides a set of guarantees such as atomic message and total order message delivery.
  • a multi-master update everywhere replication protocol
  • ...8 more annotations...
  • a replication group is formed by multiple servers and each server in the group may execute transactions independently
  • Read-only (RO) transactions need no coordination within the group and thus commit immediately
  • any RW transaction the group needs to decide whether it commits or not, thus the commit operation is not a unilateral decision from the originating server
  • when a transaction is ready to commit at the originating server, the server atomically broadcasts the write values (rows changed) and the correspondent write set (unique identifiers of the rows that were updated). Then a global total order is established for that transaction.
  • all servers receive the same set of transactions in the same order
  • The resolution procedure states that the transaction that was ordered first commits on all servers, whereas the transaction ordered second aborts, and thus is rolled back on the originating server and dropped by the other servers in the group. This is in fact a distributed first commit wins rule
  • Group Replication is a shared-nothing replication scheme where each server has its own entire copy of the data
  • MySQL Group Replication protocol
張 旭

MySQL :: MySQL 5.7 Reference Manual :: 19.2.1.2 Configuring an Instance for Group Repli... - 0 views

dev.mysql.com/...ion-configuring-instances.html

mysql database replication system

shared by 張 旭 on 19 Mar 17 - No Cached
  • store replication metadata in system tables instead of files
  • collect the write set and encode it as a hash using the XXHASH64 hashing algorithm
  • not start operations automatically when the server starts
  • ...10 more annotations...
  • for incoming connections from other members in the group
  • The server listens on this port for member-to-member connections. This port must not be used for user applications at all
  • The loose- prefix used for the group_replication variables above instructs the server to continue to start if the Group Replication plugin has not been loaded at the time the server is started.
  • For example, if each server instance is on a different machine use the IP and port of the machine, such as 10.0.0.1:33061. The recommended port for group_replication_local_address is 33061
  • does not need to list all members in the group
  • The server that starts the group does not make use of this option, since it is the initial server and as such, it is in charge of bootstrapping the group
  • start the bootstrap member first, and let it create the group
  • Creating a group and joining multiple members at the same time is not supported.
  • must only be used on one server instance at any time
  • Disable this option after the first server instance comes online
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

- Kinto 5.1.0 documentation - 0 views

kinto.readthedocs.io/...index.html

javascript db storage json

shared by crazylion lee on 21 Dec 16 - No Cached
  • crazylion lee on 21 Dec 16
     
    "Kinto is a minimalist JSON storage service with synchronisation and sharing abilities. "
張 旭

Transactions - RSpec Rails - RSpec - Relish - 0 views

relishapp.com/...transactions

rspec test rails programming

shared by 張 旭 on 03 Apr 17 - No Cached
  • before(:all) hooks are invoked before the transaction is opened. You can use this to speed things up by creating data once before any example in a group is run
張 旭

Docker ARG, ENV and .env - a Complete Guide · vsupalov.com - 1 views

vsupalov.com/docker-arg-env-variable-guide

docker development system server environment

shared by 張 旭 on 10 Dec 18 - No Cached
  • understand and use Docker build-time variables, environment variables and docker-compose templating the right way.
  • ARG is only available during the build of a Docker image (RUN etc), not after the image is created and containers are started from it (ENTRYPOINT, CMD).
  • ENV values are available to containers, but also RUN-style commands during the Docker build starting with the line where they are introduced.
  • ...20 more annotations...
  • set an environment variable in an intermediate container using bash (RUN export VARI=5 && …) it will not persist in the next command.
  • An env_file, is a convenient way to pass many environment variables to a single command in one batch.
  • not be confused with a .env file
  • the dot in front of env - .env, not an “env_file”.
  • If you have a file named .env in your project, it’s only used to put values into the docker-compose.yml file which is in the same folder. Those are used with Docker Compose and Docker Stack.
  • Just type docker-compose config. This way you’ll see how the docker-compose.yml file content looks after the substitution step has been performed without running anything else.
  • ARG are also known as build-time variables. They are only available from the moment they are ‘announced’ in the Dockerfile with an ARG instruction up to the moment when the image is built.
  • Running containers can’t access values of ARG variables.
  • ENV variables are also available during the build, as soon as you introduce them with an ENV instruction. However, unlike ARG, they are also accessible by containers started from the final image.
  • ENV values can be overridden when starting a container,
  • If you don’t provide a value to expected ARG variables which don’t have a default, you’ll get an error message.
  • args block
  • You can use ARG to set the default values of ENV vars.
  • dynamic on-build env values
  • 2. Pass environment variable values from your host
  • 1. Provide values one by one
  • 3. Take values from a file (env_file)
  • for each RUN statement, a new container is launched from an intermediate image.
  • An image is saved by the end of the command, but environment variables do not persist that way.
  • The precedence is, from stronger to less-strong: stuff the containerized application sets, values from single environment entries, values from the env_file(s) and finally Dockerfile defaults.
張 旭

Variables - Ansible Documentation - 0 views

docs.ansible.com/...playbooks_variables.html

ansible devops system

shared by 張 旭 on 05 Sep 18 - No Cached
  • with the last listed variables winning prioritization
  • anything that goes into “role defaults” (the defaults folder inside the role) is the most malleable and easily overridden.
  • Anything in the vars directory of the role overrides previous versions of that variable in namespace.
  • ...1 more annotation...
  • with command line -e extra vars always winning
張 旭

Basics - Træfik - 0 views

docs.traefik.io/basics

docker proxy networking

shared by 張 旭 on 28 Aug 18 - No Cached
  • Modifier rules only modify the request. They do not have any impact on routing decisions being made.
  • A frontend consists of a set of rules that determine how incoming requests are forwarded from an entrypoint to a backend.
  • Entrypoints are the network entry points into Træfik
  • ...27 more annotations...
  • Modifiers and matchers
  • Matcher rules determine if a particular request should be forwarded to a backend
  • if any rule matches
  • if all rules match
  • In order to use regular expressions with Host and Path matchers, you must declare an arbitrarily named variable followed by the colon-separated regular expression, all enclosed in curly braces.
  • Use a *Prefix* matcher if your backend listens on a particular base path but also serves requests on sub-paths. For instance, PathPrefix: /products would match /products but also /products/shoes and /products/shirts. Since the path is forwarded as-is, your backend is expected to listen on /products
  • Use Path if your backend listens on the exact path only. For instance, Path: /products would match /products but not /products/shoes.
  • Modifier rules ALWAYS apply after the Matcher rules.
  • A backend is responsible to load-balance the traffic coming from one or more frontends to a set of http servers
  • wrr: Weighted Round Robin
  • drr: Dynamic Round Robin: increases weights on servers that perform better than others.
  • A circuit breaker can also be applied to a backend, preventing high loads on failing servers.
  • To proactively prevent backends from being overwhelmed with high load, a maximum connection limit can also be applied to each backend.
  • Sticky sessions are supported with both load balancers.
  • When sticky sessions are enabled, a cookie is set on the initial request.
  • The check is defined by a path appended to the backend URL and an interval (given in a format understood by time.ParseDuration) specifying how often the health check should be executed (the default being 30 seconds). Each backend must respond to the health check within 5 seconds.
  • The static configuration is the global configuration which is setting up connections to configuration backends and entrypoints.
  • We only need to enable watch option to make Træfik watch configuration backend changes and generate its configuration automatically.
  • Separate the regular expression and the replacement by a space.
  • a comma-separated key/value pair where both key and value must be literals.
  • namespacing of your backends happens on the basis of hosts in addition to paths
  • Modifiers will be applied in a pre-determined order regardless of their order in the rule configuration section.
  • customize priority
  • Custom headers can be configured through the frontends, to add headers to either requests or responses that match the frontend's rules.
  • Security related headers (HSTS headers, SSL redirection, Browser XSS filter, etc) can be added and configured per frontend in a similar manner to the custom headers above.
  • Servers are simply defined using a url. You can also apply a custom weight to each server (this will be used by load-balancing).
  • Maximum connections can be configured by specifying an integer value for maxconn.amount and maxconn.extractorfunc which is a strategy used to determine how to categorize requests in order to evaluate the maximum connections.
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

Networking with overlay networks | Docker Documentation - 0 views

docs.docker.com/...network-tutorial-overlay

docker networking

shared by 張 旭 on 14 Sep 18 - No Cached
  • The manager host will function as both a manager and a worker, which means it can both run service tasks and manage the swarm.
  • connected together using an overlay network called ingress
  • each of them now has an overlay network called ingress and a bridge network called docker_gwbridge
  • ...7 more annotations...
  • The docker_gwbridge connects the ingress network to the Docker host’s network interface so that traffic can flow to and from swarm managers and workers
  • recommended that you use separate overlay networks for each application or group of applications which will work together
  • You don’t need to create the overlay network on the other nodes, beacause it will be automatically created when one of those nodes starts running a service task which requires it.
  • The default publish mode of ingress, which is used when you do not specify a mode for the --publish flag, means that if you browse to port 80 on manager, worker-1, or worker-2, you will be connected to port 80 on one of the 5 service tasks, even if no tasks are currently running on the node you browse to.
  • Even though overlay networks are automatically created on swarm worker nodes as needed, they are not automatically removed.
  • The -dit flags mean to start the container detached (in the background), interactive (with the ability to type into it), and with a TTY (so you can see the input and output).
  • alpine containers running ash, which is Alpine’s default shell rather than bash
張 旭

VMware ISO - Builders - Packer by HashiCorp - 0 views

www.packer.io/...vmware-iso.html

packer virtualization image devops vmware

shared by 張 旭 on 12 Apr 19 - No Cached
  • Packer can use a remote VMware Hypervisor to build the virtual machine.
  • enable GuestIPHack
  • When using a remote VMware Hypervisor, the builder still downloads the ISO and various files locally, and uploads these to the remote machine.
  • ...3 more annotations...
  • Packer needs to decide on a port to use for VNC when building remotely.
  • vnc_disable_password - This must be set to "true" when using VNC with ESXi 6.5 or 6.7
  • remote_type (string) - The type of remote machine that will be used to build this VM rather than a local desktop product. The only value accepted for this currently is esx5. If this is not set, a desktop product will be used. By default, this is not set.
  • 張 旭 on 12 Apr 19
     
    "Packer can use a remote VMware Hypervisor to build the virtual machine."
張 旭

Configuration - docker-sync 0.5.10 documentation - 0 views

docker-sync.readthedocs.io/...configuration.html

docker development rsync volume performance

shared by 張 旭 on 13 Feb 19 - No Cached
  • Be sure to use a sync-name which is unique, since it will be a container name.
    • 張 旭
      張 旭 on 13 Feb 19
       
      慣例是 docker-sync 的 container name 後綴都是 -sync
  • split your docker-compose configuration for production and development (as usual)
  • ...9 more annotations...
  • production stack (docker-compose.yml) does not need any changes and would look like this (and is portable, no docker-sync adjustments).
  • docker-compose-dev.yml ( it needs to be called that way, look like this ) will override
    • 張 旭
      張 旭 on 13 Feb 19
       
      開發版的 docker-compose-dev.yml 僅會覆寫 production docker-compose.yml 的 volumes 設定，也就接上 docker-sync.yml 的 volumes，其它都維持不變
  • nocopy # nocopy is important
  • nocopy # nocopy is important
  • docker-compose -f docker-compose.yml -f docker-compose-dev.yml up
  • add the external volume and the mount here
  • In case the folder we mount to has been declared as a VOLUME during image build, its content will be merged with the name volume we mount from the host
    • 張 旭
      張 旭 on 13 Feb 19
       
      如果在 Dockerfile 裡面有宣告一個 volume，那麼在 docker build 的時候這個 volume mount point 會被記錄起來，在 container 跑起來的時候，會將 host (server) 上的同名的 volume 內容合併進來 (取代)。也就是說 container 跑起來的時候，會去接上已經存在的既有的 host (server) 上的 volume。
  • enforce the content from our host on the initial wiring
  • set your environment variables by creating a .env file at the root of your project
  • 張 旭 on 13 Feb 19
     
    "Be sure to use a sync-name which is unique, since it will be a container name."
張 旭

The Twelve-Factor App - 0 views

12factor.net/concurrency

development application programming

shared by 張 旭 on 20 Feb 19 - No Cached
  • PHP processes run as child processes of Apache, started on demand as needed by request volume.
  • Java processes take the opposite approach, with the JVM providing one massive uberprocess that reserves a large block of system resources (CPU and memory) on startup, with concurrency managed internally via threads
  • Processes in the twelve-factor app take strong cues from the unix process model for running service daemons.
  • ...3 more annotations...
  • application must also be able to span multiple processes running on multiple physical machines.
  • The array of process types and number of processes of each type is known as the process formation.
  • Twelve-factor app processes should never daemonize or write PID files.
張 旭

Docker for AWS persistent data volumes | Docker Documentation - 0 views

docs.docker.com/...persistent-data-volumes

aws docker system

shared by 張 旭 on 08 Oct 18 - No Cached
  • Cloudstor is a modern volume plugin built by Docker
  • Docker swarm mode tasks and regular Docker containers can use a volume created with Cloudstor to mount a persistent data volume.
  • Global shared Cloudstor volumes mounted by all tasks in a swarm service.
  • ...14 more annotations...
  • Workloads running in a Docker service that require access to low latency/high IOPs persistent storage, such as a database engine, can use a relocatable Cloudstor volume backed by EBS.
  • Each relocatable Cloudstor volume is backed by a single EBS volume.
  • If a swarm task using a relocatable Cloudstor volume gets rescheduled to another node within the same availability zone as the original node where the task was running, Cloudstor detaches the backing EBS volume from the original node and attaches it to the new target node automatically.
  • in a different availability zone,
  • Cloudstor transfers the contents of the backing EBS volume to the destination availability zone using a snapshot, and cleans up the EBS volume in the original availability zone.
  • Typically the snapshot-based transfer process across availability zones takes between 2 and 5 minutes unless the work load is write-heavy.
  • A swarm task is not started until the volume it mounts becomes available
  • Sharing/mounting the same Cloudstor volume backed by EBS among multiple tasks is not a supported scenario and leads to data loss.
  • a Cloudstor volume to share data between tasks, choose the appropriate EFS backed shared volume option.
  • When multiple swarm service tasks need to share data in a persistent storage volume, you can use a shared Cloudstor volume backed by EFS.
  • a volume and its contents can be mounted by multiple swarm service tasks without the risk of data loss
  • over NFS
  • the persistent data backed by EFS volumes is always available.
  • shared Cloudstor volumes only work in those AWS regions where EFS is supported.
張 旭

A Tour of Rails' jQuery UJS - 0 views

robots.thoughtbot.com/a-tour-of-rails-jquery-ujs

rails jquery javascript frontend helper

shared by 張 旭 on 03 Oct 16 - No Cached
  • “I should really figure out what that does someday.”
  • today is that day
  • jquery-ujs wires event handlers to eligible DOM elements to provide enhanced functionality.
  • ...11 more annotations...
  • In most cases, the eligible DOM elements are identified by HTML5 data attributes.
  • using JavaScript to progressively enhance the user experience for capable browsers without negatively impacting clients that do not support or do not enable JavaScript.
    • 張 旭
      張 旭 on 03 Oct 16
       
      讓 user 有更好體驗，但是也不影響到那些沒有 JS 支援的 user
  • jquery-ujs attaches a handler to links with the data-method attribute
  • When the link is clicked, the handler constructs an HTML form along with a hidden input that sets the _method parameter to the requested HTTP verb
  • jquery-ujs attaches a handler to links or forms with the data-confirm attribute that displays a JavaScript confirmation dialog
  • Users double click links and buttons all the time.
  • Links and buttons that have a data-disable-with attribute get a click handler that disables the element and updates the text of the button to that which was provided in the data attribute and disables the button.
    • 張 旭
      張 旭 on 03 Oct 16
       
      優雅地處理了使用者重複點擊傳送按鈕的問題。
  • If the action is performed via AJAX, the handler will re-enable the button and reset the text when the request completes.
  • Thanks to jquery-ujs and Rails’ respond_with, setting remote: true is likely the quickest way to get your Rails application making AJAX requests.
  • support both AJAX and standard requests at the same time.
  • Cross-Site Request Forgery (CSRF) is an attack wherein the attacker tricks the user into submitting a request to an application the user is likely already authenticated to.
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