SRE Weekly Issue #198


Last week, I came across Lorin Hochstein and started to read through his blog.  Lorin has a lot of awesome stuff to say, as you can see in this issue.  Thanks, Lorin!

A message from our sponsor, VictorOps:

[You’re Invited] Learn how to modernize your approach to incident management and slash MTTA/MTTR in the latest webinar from VictorOps + Splunk, Thursday, December 19th:


“in aviation safety, it’s like we’ve been trying to learn about marriage by only studying divorce.”

Kristy Kiernan — Forbes

Use the right tool for the job, not the coolest one.

Mattias Geniar

In line with last week’s article on patience by Will Gallego, this one emphasizes the importance of continued learning about resilience engineering.

Lorin Hochstein

Here are some really thought-provoking tips on how (and why) to write an effective post-incident analysis.

Lorin Hochstein

To get better at avoiding or mitigating future incidents, you need to understand the conditions that enabled past incidents to occur. Counterfactual reasoning is actively harmful for this, because it circumvents inquiry into those conditions.

Lorin Hochstein

Some great observations and questions related to the Cloudflare outage in July.

Lorin Hochstein

Sometimes, things are off, and you just know an incident is brewing. What is this skill, and how can we learn it?

Silvia Botros — Learning From Incidents


SRE Weekly Issue #197

It’s been four years since I started SRE Weekly.  I’m having a ton of fun and learning a lot, and I can’t tell you all how happy it makes me that you read the newsletter.

A huge thank you to everyone who writes amazing SRE content every week.  Without you folks, SRE Weekly would be nothing.  Thanks also to everyone who sends links in — I definitely don’t catch every interesting article!

A message from our sponsor, VictorOps:

From everyone at VictorOps, we wanted to wish you a happy holiday season and give thanks for this SRE community. So, we put together this fun post to highlight the highs and lows of being on-call during the holidays.


Here’s an intro to the Learning From Incidents community. I can’t wait to see what these folks write. They’re coming out of the gate fast, with a post every day for the first week.

Nora Jones

In order to understand how things went wrong, we need to first understand how they went right

I love the move toward using the term “operational surprise” rather than “incident”.

Lorin Hochstein

Fascinating detail about the space shuttle Columbia’s accident, and the confusing jargon at NASA that may have contributed.

Dwayne A. Day — The Space Review

Google released free material (slides, handbooks, worksheets) to help you run a workshop on effective SLOs.

Lots of really interesting detail about how LinkedIn routes traffic to datacenters and what happens when a datacenter goes down.

Nishant Singh — LinkedIn

Our field is learning a ton, and it can be tempting to short-circuit that learning.  It takes time to really grok and integrate what we’re learning.

Now it may be easy to accept all of this and think “Yeah yeah, I got it. Let me at that ‘resilience’. I’m going to ‘add so much resilience’ to my system!”.

Will Gallego

I like the distinction between “unmanaged” and “untrained” incident response.Author: Jesus Climent — Google

This chronicle of learning about observability makes for an excellent reading list to those just diving in.

Mads Hartmann


SRE Weekly Issue #196

A message from our sponsor, VictorOps:

From everyone at VictorOps, we wanted to wish you a happy holiday season and give thanks for this SRE community. So, we put together this fun post to highlight the highs and lows of being on-call during the holidays.


My favorite:

Don’t wait until the post-mortem; consider doing a “pre-mortem” brainstorm to identify potential issues.

John Agger — Fastly

Full disclosure: Fastly is my employer.

Let’s Encrypt deals with pretty heavy traffic. This post goes into what it takes for them to run a successful Certificate Transparency log.

 Phil Porada — Let’s Encrypt

In this air traffic radio recording from Las Vegas (2018), the air traffic controller becomes impaired and starts issuing confusing and dangerously incorrect directives. The pilots work together to correct the situation and no accidents occur. This is a classic example of a resilient system.

I don’t normally link to posts that heavily cover product offerings, but this one has some real gems. I especially like the discussion toward the end of the importance of analyzing an incident shortly after it happens.

John Allspaw — Adaptive Capacity Labs

This is a striking analogue for an infrastructure with many unactionable alerts.

The commission has estimated that of the thousands of alarms going off throughout a hospital every day, an estimated 85 to 99 percent do not require clinical intervention.

Melissa Bailey — The Washington Post

A fascinating look at the early days of Etsy, in which a system is rewritten, the rewrite blows up, the rewrite is rewritten, and finally that is rewritten again. Ouch.

Dan McKinley (@mcfunley)

If your DR test involves carefully contrived circumstances that don’t match the real world, then it’s not a real test. Point your upper management at this article if you need to argue for true DR testing.

Ivan Pepelnjak


SRE Weekly Issue #195

A message from our sponsor, VictorOps:

Understanding the incident lifecycle can guide DevOps and IT engineers into a future where on-call sucks less. See how you can breakdown the stages of the incident lifecycle and use automation, transparency and collaboration to improve each stage:


An entertaining take on defining Observability.

Joshua Biggley

There are some really great tips in here, wrapped up in a handy mnemonic, the Five As:

  • actionable
  • accessible
  • accurate
  • authoritative
  • adaptable

Dan Moore — Transposit

“The Internet routes around damage”, right? Not always, and if it does, it’s often too slow. Fastly has a pretty interesting solution to that problem.

Lorenzo Saino and Raul Landa — Fastly

Full disclosure: Fastly is my employer.

The stalls were caused by a gnarly kernel performance issue. They had to use bcc and perf to dig into the kernel in order to figure out what was wrong.

Theo Julienne — GitHub

Heading to Las Vegas for re:Invent? Here’s a handy guide of talks you might want to check out.

Rui Su — Blameless

How can you tell when folks are learning effectively from incident reviews? Hint: not by measuring MTTR and the like.

John Allspaw — Adaptive Capacity Labs


SRE Weekly Issue #194

A message from our sponsor, VictorOps:

As DevOps and IT teams ingest more alerts and respond to more incidents, they collect more information and historical context. Today, teams are using this data to optimize incident response through constant automation and machine learning.


Last week, I mistakenly listed an outage as “Connectivity Issues”, when it should have been attributed to Squarespace. Sorry about that!

From the authors of the new Post-Incident Review Zine comes this summary of Niall Murphy’s SRECon talk. It’s way more than a talk recap, tying together related blog posts and talks from other authors.

Jaime Woo and Emil Stolarsky

They didn’t trust the datacenter’s backup power, so they added rack UPSes. Little did they realize that a single UPS failure could take down all of the rest.

Richard Speed — The Register

Taiji chooses which datacenter to route a Facebook user’s traffic to. It identifies clusters of users that have friended each other and routes them to the same place, on the theory that they’re likely to be interested in the same content.

Adrian Colyer (summary)

Xu et al., SOSP’19 (original paper)

<3 detailed debugging stories. TIL: Google Compute Engine’s network drops connections from its state table after 10 minutes with no packets.

Stan Hu — GitHub

Vortex is DropBox’s custom-built metrics system, designed for horizontal scalability. Find out why they rolled their own and learn how it works in this article that includes shiny diagrams.

Dave Zbarsky — DropBox

How do we come up with our SLOs, anyway? This one puts me in mind of Will Gallego’s post on error budgets.

Dean Wilson (@unixdaemon)

A network stack in userland as an alternative to TCP/IP? Yup, that seems like a pretty Google thing to do.

Adrian Colyer (summary)

Marty et al., SOSP’19 (original paper)


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