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張 旭

Outbound connections in Azure | Microsoft Docs - 0 views

  • When an instance initiates an outbound flow to a destination in the public IP address space, Azure dynamically maps the private IP address to a public IP address.
  • After this mapping is created, return traffic for this outbound originated flow can also reach the private IP address where the flow originated.
  • Azure uses source network address translation (SNAT) to perform this function
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  • When multiple private IP addresses are masquerading behind a single public IP address, Azure uses port address translation (PAT) to masquerade private IP addresses.
  • If you want outbound connectivity when working with Standard SKUs, you must explicitly define it either with Standard Public IP addresses or Standard public Load Balancer.
  • the VM is part of a public Load Balancer backend pool. The VM does not have a public IP address assigned to it.
  • The Load Balancer resource must be configured with a load balancer rule to create a link between the public IP frontend with the backend pool.
  • VM has an Instance Level Public IP (ILPIP) assigned to it. As far as outbound connections are concerned, it doesn't matter whether the VM is load balanced or not.
  • When an ILPIP is used, the VM uses the ILPIP for all outbound flows.
  • A public IP assigned to a VM is a 1:1 relationship (rather than 1: many) and implemented as a stateless 1:1 NAT.
  • Port masquerading (PAT) is not used, and the VM has all ephemeral ports available for use.
  • When the load-balanced VM creates an outbound flow, Azure translates the private source IP address of the outbound flow to the public IP address of the public Load Balancer frontend.
  • Azure uses SNAT to perform this function. Azure also uses PAT to masquerade multiple private IP addresses behind a public IP address.
  • Ephemeral ports of the load balancer's public IP address frontend are used to distinguish individual flows originated by the VM.
  • When multiple public IP addresses are associated with Load Balancer Basic, any of these public IP addresses are a candidate for outbound flows, and one is selected at random.
  • the VM is not part of a public Load Balancer pool (and not part of an internal Standard Load Balancer pool) and does not have an ILPIP address assigned to it.
  • The public IP address used for this outbound flow is not configurable and does not count against the subscription's public IP resource limit.
  • Do not use this scenario for whitelisting IP addresses.
  • This public IP address does not belong to you and cannot be reserved.
  • Standard Load Balancer uses all candidates for outbound flows at the same time when multiple (public) IP frontends is present.
  • Load Balancer Basic chooses a single frontend to be used for outbound flows when multiple (public) IP frontends are candidates for outbound flows.
  • the disableOutboundSnat option defaults to false and signifies that this rule programs outbound SNAT for the associated VMs in the backend pool of the load balancing rule.
  • Port masquerading SNAT (PAT)
  • Ephemeral port preallocation for port masquerading SNAT (PAT)
  • determine the public source IP address of an outbound connection.
張 旭

git - What is the difference between GitHub Flow and GitLab Flow? - Stack Overflow - 0 views

  • in order to keep master a true record of known working production code the actual deployment to production should happen from the feature branch before merging it into master.
  • This approach works well if we seldom publish results of our work. (Maybe once every 2 weeks).
  • Aside from promoting ready to deploy master branch and feature branches (same as GitHub Flow) it introduces three other kinds of branches
張 旭

Introduction to GitLab Flow | GitLab - 0 views

  • GitLab flow as a clearly defined set of best practices. It combines feature-driven development and feature branches with issue tracking.
  • In Git, you add files from the working copy to the staging area. After that, you commit them to your local repo. The third step is pushing to a shared remote repository.
  • branching model
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  • The biggest problem is that many long-running branches emerge that all contain part of the changes.
  • It is a convention to call your default branch master and to mostly branch from and merge to this.
  • Nowadays, most organizations practice continuous delivery, which means that your default branch can be deployed.
  • Continuous delivery removes the need for hotfix and release branches, including all the ceremony they introduce.
  • Merging everything into the master branch and frequently deploying means you minimize the amount of unreleased code, which is in line with lean and continuous delivery best practices.
  • GitHub flow assumes you can deploy to production every time you merge a feature branch.
  • You can deploy a new version by merging master into the production branch. If you need to know what code is in production, you can just checkout the production branch to see.
  • Production branch
  • Environment branches
  • have an environment that is automatically updated to the master branch.
  • deploy the master branch to staging.
  • To deploy to pre-production, create a merge request from the master branch to the pre-production branch.
  • Go live by merging the pre-production branch into the production branch.
  • Release branches
  • work with release branches if you need to release software to the outside world.
  • each branch contains a minor version
  • After announcing a release branch, only add serious bug fixes to the branch.
  • merge these bug fixes into master, and then cherry-pick them into the release branch.
  • Merging into master and then cherry-picking into release is called an “upstream first” policy
  • Tools such as GitHub and Bitbucket choose the name “pull request” since the first manual action is to pull the feature branch.
  • Tools such as GitLab and others choose the name “merge request” since the final action is to merge the feature branch.
  • If you work on a feature branch for more than a few hours, it is good to share the intermediate result with the rest of the team.
  • the merge request automatically updates when new commits are pushed to the branch.
  • If the assigned person does not feel comfortable, they can request more changes or close the merge request without merging.
  • In GitLab, it is common to protect the long-lived branches, e.g., the master branch, so that most developers can’t modify them.
  • if you want to merge into a protected branch, assign your merge request to someone with maintainer permissions.
  • After you merge a feature branch, you should remove it from the source control software.
  • Having a reason for every code change helps to inform the rest of the team and to keep the scope of a feature branch small.
  • If there is no issue yet, create the issue
  • The issue title should describe the desired state of the system.
  • For example, the issue title “As an administrator, I want to remove users without receiving an error” is better than “Admin can’t remove users.”
  • create a branch for the issue from the master branch
  • If you open the merge request but do not assign it to anyone, it is a “Work In Progress” merge request.
  • Start the title of the merge request with [WIP] or WIP: to prevent it from being merged before it’s ready.
  • When they press the merge button, GitLab merges the code and creates a merge commit that makes this event easily visible later on.
  • Merge requests always create a merge commit, even when the branch could be merged without one. This merge strategy is called “no fast-forward” in Git.
  • Suppose that a branch is merged but a problem occurs and the issue is reopened. In this case, it is no problem to reuse the same branch name since the first branch was deleted when it was merged.
  • At any time, there is at most one branch for every issue.
  • It is possible that one feature branch solves more than one issue.
  • GitLab closes these issues when the code is merged into the default branch.
  • If you have an issue that spans across multiple repositories, create an issue for each repository and link all issues to a parent issue.
  • use an interactive rebase (rebase -i) to squash multiple commits into one or reorder them.
  • you should never rebase commits you have pushed to a remote server.
  • Rebasing creates new commits for all your changes, which can cause confusion because the same change would have multiple identifiers.
  • if someone has already reviewed your code, rebasing makes it hard to tell what changed since the last review.
  • never rebase commits authored by other people.
  • it is a bad idea to rebase commits that you have already pushed.
  • If you revert a merge commit and then change your mind, revert the revert commit to redo the merge.
  • Often, people avoid merge commits by just using rebase to reorder their commits after the commits on the master branch.
  • Using rebase prevents a merge commit when merging master into your feature branch, and it creates a neat linear history.
  • every time you rebase, you have to resolve similar conflicts.
  • Sometimes you can reuse recorded resolutions (rerere), but merging is better since you only have to resolve conflicts once.
  • A good way to prevent creating many merge commits is to not frequently merge master into the feature branch.
  • keep your feature branches short-lived.
  • Most feature branches should take less than one day of work.
  • If your feature branches often take more than a day of work, try to split your features into smaller units of work.
  • You could also use feature toggles to hide incomplete features so you can still merge back into master every day.
  • you should try to prevent merge commits, but not eliminate them.
  • Your codebase should be clean, but your history should represent what actually happened.
  • If you rebase code, the history is incorrect, and there is no way for tools to remedy this because they can’t deal with changing commit identifiers
  • Commit often and push frequently
  • You should push your feature branch frequently, even when it is not yet ready for review.
  • A commit message should reflect your intention, not just the contents of the commit.
  • each merge request must be tested before it is accepted.
  • test the master branch after each change.
  • If new commits in master cause merge conflicts with the feature branch, merge master back into the branch to make the CI server re-run the tests.
  • When creating a feature branch, always branch from an up-to-date master.
  • Do not merge from upstream again if your code can work and merge cleanly without doing so.
張 旭

Helm | Flow Control - 0 views

  • Control structures (called "actions" in template parlance) provide you, the template author, with the ability to control the flow of a template's generation
  •  
    "Control structures (called "actions" in template parlance) provide you, the template author, with the ability to control the flow of a template's generation"
crazylion lee

flowchart.js - 0 views

  •  
    "Draws simple SVG flow chart diagrams from textual representation of the diagram"
張 旭

Introduction to GitLab Flow | GitLab - 0 views

  • Git allows a wide variety of branching strategies and workflows.
  • not integrated with issue tracking systems
  • The biggest problem is that many long-running branches emerge that all contain part of the changes.
  • ...47 more annotations...
  • most organizations practice continuous delivery, which means that your default branch can be deployed.
  • Merging everything into the master branch and frequently deploying means you minimize the amount of unreleased code, which is in line with lean and continuous delivery best practices.
  • you can deploy to production every time you merge a feature branch.
  • deploy a new version by merging master into the production branch.
  • you can have your deployment script create a tag on each deployment.
  • to have an environment that is automatically updated to the master branch
  • commits only flow downstream, ensures that everything is tested in all environments.
  • first merge these bug fixes into master, and then cherry-pick them into the release branch.
  • Merging into master and then cherry-picking into release is called an “upstream first” policy
  • “merge request” since the final action is to merge the feature branch.
  • “pull request” since the first manual action is to pull the feature branch
  • it is common to protect the long-lived branches
  • After you merge a feature branch, you should remove it from the source control software
  • When you are ready to code, create a branch for the issue from the master branch. This branch is the place for any work related to this change.
  • A merge request is an online place to discuss the change and review the code.
  • If you open the merge request but do not assign it to anyone, it is a “Work In Progress” merge request.
  • Start the title of the merge request with “[WIP]” or “WIP:” to prevent it from being merged before it’s ready.
  • To automatically close linked issues, mention them with the words “fixes” or “closes,” for example, “fixes #14” or “closes #67.” GitLab closes these issues when the code is merged into the default branch.
  • If you have an issue that spans across multiple repositories, create an issue for each repository and link all issues to a parent issue.
  • With Git, you can use an interactive rebase (rebase -i) to squash multiple commits into one or reorder them.
  • you should never rebase commits you have pushed to a remote server.
  • Rebasing creates new commits for all your changes, which can cause confusion because the same change would have multiple identifiers.
  • if someone has already reviewed your code, rebasing makes it hard to tell what changed since the last review.
  • never rebase commits authored by other people.
  • it is a bad idea to rebase commits that you have already pushed.
  • always use the “no fast-forward” (--no-ff) strategy when you merge manually.
  • you should try to avoid merge commits in feature branches
  • people avoid merge commits by just using rebase to reorder their commits after the commits on the master branch. Using rebase prevents a merge commit when merging master into your feature branch, and it creates a neat linear history.
  • you should never rebase commits you have pushed to a remote server
  • Sometimes you can reuse recorded resolutions (rerere), but merging is better since you only have to resolve conflicts once.
  • not frequently merge master into the feature branch.
  • utilizing new code,
  • resolving merge conflicts
  • updating long-running branches.
  • just cherry-picking a commit.
  • If your feature branch has a merge conflict, creating a merge commit is a standard way of solving this.
  • keep your feature branches short-lived.
  • split your features into smaller units of work
  • you should try to prevent merge commits, but not eliminate them.
  • Your codebase should be clean, but your history should represent what actually happened.
  • Splitting up work into individual commits provides context for developers looking at your code later.
  • push your feature branch frequently, even when it is not yet ready for review.
  • Commit often and push frequently
  • A commit message should reflect your intention, not just the contents of the commit.
  • Testing before merging
  • When using GitLab flow, developers create their branches from this master branch, so it is essential that it never breaks. Therefore, each merge request must be tested before it is accepted.
  • When creating a feature branch, always branch from an up-to-date master
  •  
    "Git allows a wide variety of branching strategies and workflows."
張 旭

Understanding the GitHub flow · GitHub Guides - 0 views

  • anything in the master branch is always deployable.
  • Your branch name should be descriptive
  • Commits also create a transparent history of your work that others can follow to understand what you've done and why.
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  • each commit is considered a separate unit of change.
  • By writing clear commit messages, you can make it easier for other people to follow along and provide feedback.
  • Pull Requests initiate discussion about your commits.
  • If you're using a Fork & Pull Model, Pull Requests provide a way to notify project maintainers about the changes you'd like them to consider.
  • Pull Requests are designed to encourage and capture this type of conversation.
  • You can also continue to push to your branch in light of discussion and feedback about your commits.
  • If your branch causes issues, you can roll it back by deploying the existing master into production.
  • With GitHub, you can deploy from a branch for final testing in production before merging to master.
  • your changes have been verified in production, it is time to merge your code into the master branch.
  •  
    "anything in the master branch is always deployable."
張 旭

VPCs and Subnets - Amazon Virtual Private Cloud - 0 views

  • you must specify a range of IPv4 addresses for the VPC in the form of a Classless Inter-Domain Routing (CIDR) block
  • A VPC spans all the Availability Zones in the region
  • add one or more subnets in each Availability Zone.
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  • Each subnet must reside entirely within one Availability Zone and cannot span zones.
  • Availability Zones are distinct locations that are engineered to be isolated from failures in other Availability Zones
  • If a subnet's traffic is routed to an internet gateway, the subnet is known as a public subnet.
  • If a subnet doesn't have a route to the internet gateway, the subnet is known as a private subnet.
  • If a subnet doesn't have a route to the internet gateway, but has its traffic routed to a virtual private gateway for a VPN connection, the subnet is known as a VPN-only subnet.
  • By default, all VPCs and subnets must have IPv4 CIDR blocks—you can't change this behavior.
  • The allowed block size is between a /16 netmask (65,536 IP addresses) and /28 netmask (16 IP addresses).
  • The first four IP addresses and the last IP address in each subnet CIDR block are not available for you to use
  • The allowed block size is between a /28 netmask and /16 netmask
  • The CIDR block must not overlap with any existing CIDR block that's associated with the VPC.
  • Each subnet must be associated with a route table
  • Every subnet that you create is automatically associated with the main route table for the VPC
  • Security groups control inbound and outbound traffic for your instances
  • network ACLs control inbound and outbound traffic for your subnets
  • each subnet must be associated with a network ACL
  • You can create a flow log on your VPC or subnet to capture the traffic that flows to and from the network interfaces in your VPC or subnet.
  • A VPC peering connection enables you to route traffic between the VPCs using private IP addresses
  • you cannot create a VPC peering connection between VPCs that have overlapping CIDR blocks
  • recommend that you create a VPC with a CIDR range large enough for expected future growth, but not one that overlaps with current or expected future subnets anywhere in your corporate or home network, or that overlaps with current or future VPCs
crazylion lee

Vim anti-patterns | Arabesque - 0 views

  •  
    "The benefits of getting to grips with Vim are immense in terms of editing speed and maintaining your "flow" when you're on a roll, whether writing code, poetry, or prose, but because the learning curve is so steep for a text editor, it's very easy to retain habits from your time learning the editor that stick with you well into mastery. Because Vim makes you so fast and fluent, it's especially hard to root these out because you might not even notice them, but it's worth it. Here I'll list some of the more common ones."
張 旭

Networking with overlay networks | Docker Documentation - 0 views

  • 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
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  • 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

The Twelve-Factor App - 0 views

  • Logs are the stream of aggregated, time-ordered events collected from the output streams of all running processes and backing services.
  • Logs have no fixed beginning or end, but flow continuously as long as the app is operating.
  • each running process writes its event stream, unbuffered, to stdout.
  • ...2 more annotations...
  • long-term archival. These archival destinations are not visible to or configurable by the app, and instead are completely managed by the execution environment.
  • Most significantly, the stream can be sent to a log indexing and analysis system such as Splunk, or a general-purpose data warehousing system such as Hadoop/Hive.
張 旭

Azure 101: Networking Part 1 - Cloud Solution Architect - 0 views

  • Virtual Private Gateways and it is these combined set of services that allow you to provide traffic flow to/from your Virtual Network and any external network, such as your On-Prem DataCenter.
  • No matter which version of the gateway you plan on implementing, there are three resources within Azure that you will need to implement and then connect to one of your Virtual Networks.
  • "Gateway Subnet". This is a specialized Subnet within your Virtual Network that can only be used for connecting Virtual Private Gateways to a VPN connection of some kind.
  • ...2 more annotations...
  • The Local Gateway is where you define the configuration of your external network's VPN access point with the most important piece being the external IP of that device so that Azure knows exactly how to establish the VPN connection.
  • The VPN Gateway is the Azure resource that you tie into your Gateway Subnet within your Virtual Network.
張 旭

Trunk-based Development | Atlassian - 0 views

  • Trunk-based development is a version control management practice where developers merge small, frequent updates to a core “trunk” or main branch.
  • Gitflow and trunk-based development. 
  • Gitflow, which was popularized first, is a stricter development model where only certain individuals can approve changes to the main code. This maintains code quality and minimizes the number of bugs.
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  • Trunk-based development is a more open model since all developers have access to the main code. This enables teams to iterate quickly and implement CI/CD.
  • Developers can create short-lived branches with a few small commits compared to other long-lived feature branching strategies.
  • Gitflow is an alternative Git branching model that uses long-lived feature branches and multiple primary branches.
  • Gitflow also has separate primary branch lines for development, hotfixes, features, and releases.
  • Trunk-based development is far more simplified since it focuses on the main branch as the source of fixes and releases.
  • Trunk-based development eases the friction of code integration.
  • trunk-based development model reduces these conflicts.
  • Adding an automated test suite and code coverage monitoring for this stream of commits enables continuous integration.
  • When new code is merged into the trunk, automated integration and code coverage tests run to validate the code quality.
  • Trunk-based development strives to keep the trunk branch “green”, meaning it's ready to deploy at any commit.
  • With continuous integration, developers perform trunk-based development in conjunction with automated tests that run after each committee to a trunk.
  • If trunk-based development was like music it would be a rapid staccato -- short, succinct notes in rapid succession, with the repository commits being the notes.
  • Instead of creating a feature branch and waiting to build out the complete specification, developers can instead create a trunk commit that introduces the feature flag and pushes new trunk commits that build out the feature specification within the flag.
  • Automated testing is necessary for any modern software project intending to achieve CI/CD.
  • Short running unit and integration tests are executed during development and upon code merge.
  • Automated tests provide a layer of preemptive code review.
  • Once a branch merges, it is best practice to delete it.
  • A repository with a large amount of active branches has some unfortunate side effects
  • Merge branches to the trunk at least once a day
  • The “continuous” in CI/CD implies that updates are constantly flowing.
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