Ansible – ‘until’ loop

Contents

Introduction

In this short post I'll introduce you to lesser known type of Ansible loop: "until" loop. This loop is used for retrying task until certain condition is met.

To use this loop in task you essentially need to add 3 arguments to your task arguments:

until - condition that must be met for loop to stop. That is Ansible will continue executing the task until expression used here evaluates to true.
retry - specifies how many times we want to run the task before Ansible gives up.
delay - delay, in seconds, between retries.

As an example, below task will keep sending GET request to specified URL until the "status" key in response is equal to "READY". We ask Ansible to make 10 attempts in total with delay of 1 second between each attempt. If after final attempt condition in until is still not met task is marked as failed.

  - name: Wait until web  Continue reading

Why Is Public Cloud Networking So Different?

A while ago (eons before AWS introduced Gateway Load Balancer) I discussed the intricacies of AWS and Azure networking with a very smart engineer working for a security appliance vendor, and he said something along the lines of “it shows these things were designed by software developers – they have no idea how networks should work.”

In reality, at least some aspects of public cloud networking come closer to the original ideas of how IP and data-link layers should fit together than today’s flat earth theories, so he probably wanted to say “they make it so hard for me to insert my virtual appliance into their network.”

Read more …

Why Is Public Cloud Networking So Different?

A while ago (eons before AWS introduced Gateway Load Balancer) I discussed the intricacies of AWS and Azure networking with a very smart engineer working for a security appliance vendor, and he said something along the lines of “it shows these things were designed by software developers – they have no idea how networks should work.”

In reality, at least some aspects of public cloud networking come closer to the original ideas of how IP and data-link layers should fit together than today’s flat earth theories, so he probably wanted to say “they make it so hard for me to insert my virtual appliance into their network.”

Read more …

Elle: inferring isolation anomalies from experimental observations

Elle: inferring isolation anomalies from experimental observations, Kingsbury & Alvaro, VLDB’20

Is there anything more terrifying, and at the same time more useful, to a database vendor than Kyle Kingsbury’s Jepsen? As the abstract to today’s paper choice wryly puts it, “experience shows that many databases do not provide the isolation guarantees they claim.” Jepsen captures execution histories, and then examines them for evidence of isolation anomalies. General linearizability and serializability checking are NP-complete problems due to extreme state-space explosion with increasing concurrency, and Jepsen’s main checker, Knossos, taps out on the order of hundreds of transactions.

Databases are in for an ‘Ell(e) of a hard time with the new checker in the Jepsen family though, Elle. From the README:

Like a clever lawyer, Elle looks for a sequence of events in a story which couldn’t possibly have happened in that order, and uses that inference to prove the story can’t be consistent.

The paper describes how Elle works behind the scenes, and gives us a taste of Elle in action. Elle is able to check histories of hundreds of thousands of transactions in just tens of seconds. Which means whole new levels of stress for Continue reading

Worth Reading: Do Your Homework

Tom Hollingsworth wrote another must-read blog post in which he explained what one should do before asking for help:

If someone comes to me and says, “I tried this and it failed and I got this message. I looked it up and the response didn’t make sense. Can you tell me why that is?” I rejoice. That person has done the legwork and narrowed the question down to the key piece they need to know.

In other words (again his), do your homework first and then ask relevant questions.

Worth Reading: Do Your Homework

Tom Hollingsworth wrote another must-read blog post in which he explained what one should do before asking for help:

If someone comes to me and says, “I tried this and it failed and I got this message. I looked it up and the response didn’t make sense. Can you tell me why that is?” I rejoice. That person has done the legwork and narrowed the question down to the key piece they need to know.

In other words (again his), do your homework first and then ask relevant questions.

PostgreSQL install

Howdy Folks! This post covers the process of installing the PostgreSQL database on Linux and a few of the common details around configuration and operation. Software Versions Used in this Post PostgreSQL - 13.1 Ubuntu - 20.04 Centos - 8.2.2004 Installation Ubuntu This is almost a...continue reading

PostgreSQL install

Howdy Folks! This post covers the process of installing the PostgreSQL database on Linux and a few of the common details around configuration and operation. Software Versions Used in this Post PostgreSQL - 13.1 Ubuntu - 20.04 Centos - 8.2.2004 Installation Ubuntu This is almost a...

rbenv Install Ubuntu 2004

rbenv is a utility for installing multiple ruby versions on a host machine. Using rbenv allows you to install ruby in a path you have ownership over so you can install gems without having to have sudo or root privileges. rbenv also allows you to target the exact ruby version in development...

Heavy Networking 551: An Insider’s Guide To The SONiC Network OS

SONiC is a network OS that can run on a variety of whitebox switches. Originally developed by Microsoft, SONiC is now an open-source project with distributions that target hyperscale and enterprise environments. Today's Heavy Networking is a deep dive into SONiC with Dave Maltz, a Technical Fellow at Microsoft who has been closely involved with SONiC's development. While Microsoft is a SONiC backer, this is an unsponsored episode.

Heavy Networking 551: An Insider’s Guide To The SONiC Network OS

SONiC is a network OS that can run on a variety of whitebox switches. Originally developed by Microsoft, SONiC is now an open-source project with distributions that target hyperscale and enterprise environments. Today's Heavy Networking is a deep dive into SONiC with Dave Maltz, a Technical Fellow at Microsoft who has been closely involved with SONiC's development. While Microsoft is a SONiC backer, this is an unsponsored episode.

The post Heavy Networking 551: An Insider’s Guide To The SONiC Network OS appeared first on Packet Pushers.

Calico Delivers “Wow Effect” with 6x Faster Encryption than Any Other Solution… Confirms Leadership in Latest Independent CNI Benchmark Tests

Benchmark tests measure a repeatable set of quantifiable results that serve as a point of reference against which products and services can be compared. Since 2018, Alexis Ducastel, a Kubernetes CKA/CKAD and the founder of InfraBuilder, has been running independent benchmark tests of Kubernetes network plugins (CNI) over a 10Gbit/s network.

The latest benchmark in this periodic series of tests was published in September, and was based on CNI versions that were up-to-date as of August 2020. Only CNIs that can be set up with a single yaml file were tested and compared, and included the following:

  • Antrea v.0.9.1
  • Calico v3.16
  • Canal v3.16 (Flannel network + Calico Network Policies)
  • Cilium 1.8.2
  • Flannel 0.12.0
  • Kube-router latest (2020–08–25)
  • WeaveNet 2.7.0

We are thrilled to report that among all of the CNI’s tested, Calico was the clear winner, excelling in nearly every category and delivering superlative results which are summarized in the chart below. In fact, Calico is the CNI of choice in the primary use cases presented by the author in the report’s summary.

The exceptional performance of Calico encryption was described as having the “real wow effect” among all of Continue reading

Monitoring failed login attempts on Linux

Repeated failed login attempts on a Linux server can indicate that someone is trying to break into an account or might only mean that someone forgot their password or is mistyping it. In this post, we look at how you can check for failed login attempts and check your system's settings to see when accounts will be locked to deal with the problem.One of the first things you need to know is how to check if logins are failing. The command below looks for indications of failed logins in the /var/log/auth.log file used on Ubuntu and related systems. When someone tries logging in with a wrong or misspelled password, failed logins will show up as in the lines below:To read this article in full, please click here

Edge computing: When to outsource, when to DIY

The edge is being sold to enterprise customers from just about every part of the technology industry, and there’s not always a bright dividing line between “public” options – edge computing sold as a service, with a vendor handling operational data directly – and “private” ones, where a company implements an edge architecture by itself.There are advantages and challenges to either option, and which is the right edge-computing choice for any particular organization depends on their individual needs, budgets and staffing, among other factors. Here are some considerations.To read this article in full, please click here

Edge computing: When to outsource, when to DIY

The edge is being sold to enterprise customers from just about every part of the technology industry, and there’s not always a bright dividing line between “public” options – edge computing sold as a service, with a vendor handling operational data directly – and “private” ones, where a company implements an edge architecture by itself.There are advantages and challenges to either option, and which is the right edge-computing choice for any particular organization depends on their individual needs, budgets and staffing, among other factors. Here are some considerations.To read this article in full, please click here

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