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--- GitHub 24-hour outage post mortem ---
As many of you will remember; Github fell over earlier this month and cracked its head on the counter top on the way down. For more or less a full 24 hours the repo-wrangling behemoth had inconsistent data being presented to users, slow response times and failing requests during common user actions such as reporting issues and questioning your career choice in code reviews.
It's been revealed in a post-mortem of the incident (link at the end of the article) that DB replication was the root cause of the chaos after a failing 100G network link was being replaced during routine maintenance. I don't pretend to be a rockstar-ninja-wizard DBA but after speaking with colleagues who went a shade whiter when the term "replication" was used - It's hard to predict where a design decision will bite back and leave you untanging the web of lies and misinformation reported by the databases for weeks if not months after everything's gone a tad sideways.
When the link was yanked out of the east coast DC undergoing maintenance - Github's "Orchestrator" software did exactly what it was meant to do; It hit the "ohshi" button and failed over to another DC that wasn't reporting any issues. The hitch in the master plan was that when connectivity came back up at the east coast DC, Orchestrator was unable to (un)fail-over back to the east coast DC due to each cluster containing data the other didn't have.
At this point it's reasonable to assume that pants were turning funny colours - Monitoring systems across the board started squealing, firing off messages to engineers demanding they rouse from the land of nod and snap back to reality, that was a bit more "on-fire" than usual. A quick call to Orchestrator's API returned a result set that only contained database servers from the west coast - none of the east coast servers had responded.
Come 11pm UTC (about 10 minutes after the initial pant re-colouring) engineers realised they were well and truly backed into a corner, the site was flipped into "Yellow" status and internal mechanisms for deployments were locked out. 5 minutes later an Incident Co-ordinator was dragged from their lair by the status change and almost immediately flipped the site into "Red" status, a move i can only hope was accompanied by all the lights going red and klaxons sounding.
Even more engineers were roused from their slumber to help with the recovery effort, By this point hair was turning grey in real time - The fail-over DB cluster had been processing user data for nearly 40 minutes, every second that passed made the inevitable untangling process exponentially more difficult. Not long after this Github made the call to pause webhooks and Github Pages builds in an attempt to prevent further data loss, causing disruption to those of us using Github as a way of kicking off our deployment processes (myself included, I had to SSH in and run a git pull myself like some kind of savage).
Glossing over several more "And then things were still broken" sections of the post mortem; Clever engineers with their heads screwed on the right way successfully executed what i can only imagine was a large, complex and risky plan to untangle the mess and restore functionality. Github was picked up off the kitchen floor and promptly placed in a comfy chair with a sweet tea to recover. The enormous backlog of webhooks and Pages builds was caught up with and everything was more or less back to normal.
It goes to show that even the best laid plan rarely survives first contact with the enemy, In this case a failing 100G network link somewhere inside an east coast data center.
Link to the post mortem: https://blog.github.com/2018-10-30-...7 -
EoS1: This is the continuation of my previous rant, "The Ballad of The Six Witchers and The Undocumented Java Tool". Catch the first part here: https://devrant.com/rants/5009817/...
The Undocumented Java Tool, created by Those Who Came Before to fight the great battles of the past, is a swift beast. It reaches systems unknown and impacts many processes, unbeknownst even to said processes' masters. All from within it's lair, a foggy Windows Server swamp of moldy data streams and boggy flows.
One of The Six Witchers, the Wild One, scouted ahead to map the input and output data streams of the Unmapped Data Swamp. Accompanied only by his animal familiars, NetCat and WireShark.
Two others, bold and adventurous, raised their decompiling blades against the Undocumented Java Tool beast itself, to uncover it's data processing secrets.
Another of the witchers, of dark complexion and smooth speak, followed the data upstream to find where the fuck the limited excel sheets that feeds The Beast comes from, since it's handlers only know that "every other day a new one appears on this shared active directory location". WTF do people often have NPC-levels of unawareness about their own fucking jobs?!?!
The other witchers left to tend to the Burn-Rate Bonfire, for The Sprint is dark and full of terrors, and some bigwigs always manage to shoehorn their whims/unrelated stories into a otherwise lean sprint.
At the dawn of the new year, the witchers reconvened. "The Beast breathes a currency conversion API" - said The Wild One - "And it's claws and fangs strike mostly at two independent JIRA clusters, sometimes upserting issues. It uses a company-deprecated API to send emails. We're in deep shit."
"I've found The Source of Fucking Excel Sheets" - said the smooth witcher - "It is The Temple of Cash-Flow, where the priests weave the Tapestry of Transactions. Our Fucking Excel Sheets are but a snapshot of the latest updates on the balance of some billing accounts. I spoke with one of the priestesses, and she told me that The Oracle (DB) would be able to provide us with The Data directly, if we were to learn the way of the ODBC and the Query"
"We stroke at the beast" - said the bold and adventurous witchers, now deserving of the bragging rights to be called The Butchers of Jarfile - "It is actually fewer than twenty classes and modules. Most are API-drivers. And less than 40% of the code is ever even fucking used! We found fucking JIRA API tokens and URIs hard-coded. And it is all synchronous and monolithic - no wonder it takes almost 20 hours to run a single fucking excel sheet".
Together, the witchers figured out that each new billing account were morphed by The Beast into a new JIRA issue, if none was open yet for it. Transactions were used to update the outstanding balance on the issues regarding the billing accounts. The currency conversion API was used too often, and it's purpose was only to give a rough estimate of the total balance in each Jira issue in USD, since each issue could have transactions in several currencies. The Beast would consume the Excel sheet, do some cryptic transformations on it, and for each resulting line access the currency API and upsert a JIRA issue. The secrets of those transformations were still hidden from the witchers. When and why would The Beast send emails, was still a mistery.
As the Witchers Council approached an end and all were armed with knowledge and information, they decided on the next steps.
The Wild Witcher, known in every tavern in the land and by the sea, would create a connector to The Red Port of Redis, where every currency conversion is already updated by other processes and can be quickly retrieved inside the VPC. The Greenhorn Witcher is to follow him and build an offline process to update balances in JIRA issues.
The Butchers of Jarfile were to build The Juggler, an automation that should be able to receive a parquet file with an insertion plan and asynchronously update the JIRA API with scores of concurrent requests.
The Smooth Witcher, proud of his new lead, was to build The Oracle Watch, an order that would guard the Oracle (DB) at the Temple of Cash-Flow and report every qualifying transaction to parquet files in AWS S3. The Data would then be pushed to cross The Event Bridge into The Cluster of Sparks and Storms.
This Witcher Who Writes is to ride the Elephant of Hadoop into The Cluster of Sparks an Storms, to weave the signs of Map and Reduce and with speed and precision transform The Data into The Insertion Plan.
However, how exactly is The Data to be transformed is not yet known.
Will the Witchers be able to build The Data's New Path? Will they figure out the mysterious transformation? Will they discover the Undocumented Java Tool's secrets on notifying customers and aggregating data?
This story is still afoot. Only the future will tell, and I will keep you posted.6 -
Instead of accepting reality like a big man and acknowledging that making software with a cargo culted process that has no function in organizing the development work, the boss is insisting I'm to blame and wants me to "take responsibility". Taking responsibility my *****. I slay the dragon in its lair.
Since I'm leaving, I tried to give him some sincere advice, totally flipped him out.
#6 days left. -
English:
"I'm a liar."
Supposing I tell the truth, I'm not a liar. But that would mean that I am a liar, since I said that I am a liar.
Assuming I did not tell the truth, I would be a liar. But since I said the truth, I would not be a liar.
If one starts from the classical logic, one can make no logical statement. If one starts from the three-valued logic, I would say that "unknown" (u, ½
Is that true, what do you mean?
German:
"Ich bin ein Lügner."
Angenommen, ich würde die Wahrheit sagen, bin ich keine Lügner. Dies würde aber bedeuten dass ich ein Lügner bin, da ich ja gesagt habe dass ich ein Lügner bin.
Angenommen ich würde nicht die Wahrheit sagen, wäre ich ein Lügner. Aber da ich die Wahrheit gesagt habe wäre ich kein Lügner.
Wenn man von der klassischen logik ausgeht, kann man keine logische Aussage machen. Wenn man von der Dreiwertige Logik ausgeht, würde ich sagen, das "unbekannt"(u, ½) rauskommt.
Stimmt das, was meinst du?
https://en.wikipedia.org/wiki/...
https://code.sololearn.com/cFvKb3r8...14
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