SRE Weekly Issue #230

Happy BTW: Wear a mask.

A message from our sponsor, StackHawk:

Add security testing to your CI pipelines with GitHub Actions. Check out this webinar recording (no email required) to learn how.


LaunchDarkly started off with a polling-based architecture and ultimately migrated to pushing deltas out to clients.

Dawn Parzych — LaunchDarkly

A brief overview of some problems with distributed tracing, along with a suggestion of another way involving AI.

Larry Lancaster — Zebrium

This is Google’s post-incident report for their Google Classroom incident on July 7.

Uber has long been a champion of microservices. Now, with several years of experience, they share the lessons they’ve learned and how they deal with some of the pitfalls.

Adam Gluck — Uber

This article opens with an interesting description of what the Cloudflare outage looked like from PagerDuty’s perspective.

Dave Bresci — PagerDuty

This post reflects on two distinct philosophies of safety:

the engineering design should ensure that the system is safe

design alone cannot ensure that the system is safe

Lorin Hochstein

You can’t use availability metrics to inform you about whether your system is reliable enough, because they can only tell you if you have a problem.

Lorin Hochstein


SRE Weekly Issue #229

A message from our sponsor, StackHawk:

Read about how to build test driven security with StackHawk + Travis CI + Docker Compose.


More details have emerged about the Twitter break-in last week, leading some to utter the quote above. Here’s a take on how to see it as not being about “stupidity”.

Lorin Hochstein

The data in your database should be consistent… but then again, incidents shouldn’t happen, right? Slack accepts that things routinely go wrong with data at their scale, and they have framework and a set of tools to deal with it.

Paul Hammond and Samantha Stoller — Slack

I learned a lot from this article. My favorite obstacle is “distancing through differencing”, e.g. “we would never have responded to an incident that way”.

Thai Wood — Learning from Incidents

[…] SRE, that is SRE as defined by Google, is not applicable for most organizations.

Sanjeev Sharma

Expert advice on what questions to ask as you try to figure out what your critical path is (and why you would want to know what it is).

Charity Majors

This podcast episode was kind of like a preview of J. Paul Reed and Tim Heckman’s joint talk at I love how they refer to the pandemic as a months-long incident, and point out that if you’re always in an incident then you’re never in an incident.

Julie Gunderson and Mandi Walls — Page it to the Limit

I love a good dual-write story. Here’s how LinkedIn transitioned to a new messaging storage mechanism.

Pradhan Cadabam and Jingxuan (Rex) Zhang — LinkedIn


SRE Weekly Issue #228

SRE From Home is back! It’s happening this Thursday, and I’ll be on the Ask an SRE panel answering your questions. And don’t miss the talks by lots of great folks, some of whom have had articles featured here previously!

A message from our sponsor, StackHawk:

StackHawk is built on the open source ZAP application security scanner, the most widely used AppSec tool out there. Now the founder of ZAP has joined our team to bring AppSec to developers. Read all about it.


They don’t. They just don’t.

[…] as deployments grow beyond a certain size it’s almost impossible to execute them successfully.

Alex Yates — Octopus Deploy

Whoops, forgot to include this one last week.

On June 30, Google’s email delivery service was targeted in what we believe was an attempt to bypass spam classification. The result was delayed message processing and increased message queuing.

My favorite part is the focus on blame awareness:

But it’s not enough to just be blameless—it’s also important to be blame-aware. Being blame-aware means that we are aware of our biases and how they may impact our ability to view an incident impartially.

Isabella Pontecorvo — PagerDuty

Netflix has a team dedicated to the overall reliability of their service.

Practically speaking, this includes activities such as systemic risk identification, handling the lifecycle of an incident, and reliability consulting.

Hank Jacobs– Netflix

Another good reference if you’re looking to bootstrap SRE at your organization.

Rich Burroughs — FireHydrant

Bill Duncan’s back with an easy and very close approximation for the “Tail at Scale” formula. The question it answers is: how many nines do you need on all of your backend microservices for X nines on the frontend?

Bill Duncan

Tons of great links in here with enticing descriptions to make you want to read them. Includes books, tools, hiring, certification, and general SRE goodness.

Emily Arnot — Blameless

SRE is all about keeping the user experience working, and working with product-focused folks can really help. For more on this, check out my former coworker Jen Wohlner’s awesome SRECon19 talk on SRE & product management.

Samantha Coffman — HelloFresh


  • Cloudflare
    • Cloudflare had a 50% drop in traffic served by their network subsequent to a BGP issue. Linked is their analysis including snippets of router configurations. Lots of services suffered contemporaneous outages possibly stemming from Cloudflare’s, including Discord, Postmates, Hosted Graphite, and DownDetector.John Graham-Cumming — Cloudflare
  • Twitter
    • Twitter had a major security breach, and as part of their response, they temporarily cut off large parts of their service. Click for their post about what happened.
  • GitHub
  • WhatsApp
  • Hulu
  • Snapchat
  • Microsoft Outlook
    • Notably, the outage involved the Outlook application that people run on their computer, not the cloud version.
  • Fastly

SRE Weekly Issue #227

A message from our sponsor, StackHawk:

When a team introduces security bugs, they don’t know because nothing tells them. We test for everything else… why not security bugs?


This is the first of a pair of articles this week on a major Slack outage in May. This one explores the technical side, with a lot of juicy details on what happened and how.

Laura Nolan — Slack

This is the companion article that describes Slack’s incident response process, using the same incident as a case study.

Ryan Katkov — Slack

The author saw room for improvement in the retrospective process at Indeed. The article explains the recommendations they made and why, including de-emphasizing generation remediation items in favor of learning.

Alex Elman

The datacenter was purposefully switched to generator power during planned power maintenance, but unfortunately the fuel delivery system failed.

This is a good primer on the ins and outs of running a post-incident analysis.

Anusuya Kannabiran — Squadcast

This article goes through an interesting technique for setting up SLO metrics and alerts in GCP using Terraform and OpenCensus.

Cindy Quach — Google

GitHub is committing to publishing a report on their availability each month with detail on incidents. This intro includes the reports for May and June with a description of 4 incidents.

Keith Ballinger — GitHub

This is neat: Blameless transitioned from “startup mode” toward an SRE methodology, becoming customer 0 of their own product in the process.



SRE Weekly Issue #226

A message from our sponsor, StackHawk:

When a team introduces security bugs, they don’t know because nothing tells them. We test for everything else… why not security bugs?


This is an article version of an interview with Dr. Danielle Ofri, author of a new book When We Do Harm, on NPR’s Fresh Air. I especially loved the part about near misses.

Bridget Bentz, Molly Seavy-Nesper, Deborah Franklin, Sam Briger, and Thea Chaloner — NPR

Maintenance of the logging system had unintended downstream effects including log loss and failure of the system that manages dynos.

In this incident, a TLS certificate was deployed without its intermediate, resulting in failures for some clients.

I wrote this after attending the Resilience Engienering Association’s webinar with panelists Dr. Richard Cook, John Allspaw, and Nora Jones, moderated by Laura Maguire. Once the recording is posted, I highly recommend watching!

Lex Neva

As SREs, we need to be laser focused on the user’s experience. Our SLIs should reflect that.

Emily Arnott — Blameless

This two-part series is an in-depth look at how Twitter adopted SRE, before SRE was even a thing.



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