Cloudflare Deploys Really Slow Code, Takes Down Entire Company

Cloudflare is back at it again with more regex and state machines.
Previously on Cloudflare: • How One Line of Code A...
Sources:
blog.cloudflare.com/details-o...
blog.cloudflare.com/introduci...
swtch.com/~rsc/regexp/regexp1...
www.regular-expressions.info/...
cyberzhg.github.io/toolbox/nf...
www.businessinsider.com/cloud...
Chapters:
0:00 Part 1: Intro
0:51 Part 2: Regex
2:29 Part 3: Deployment Process
4:20 Part 4: Disaster Strikes
6:25 Part 5: Root Cause
12:22 Part 6: Aftermath
Corrections:
- Missed opening bracket [ in the domain name part of the expression 6:36
- This particular regex is worst case quadratic, not exponential 8:30. The example right after w/ 1 million steps is exponential.
- The DFAs at 10:40 and 11:50 should have the starting states marked as end states as well to properly match empty strings
Music:
- Nocturnal by LEMMiNO ( • LEMMiNO - Nocturnal (BGM) )
- Smooth by Silent Partner
- Encounters by LEMMiNO ( • LEMMiNO - Encounters (... )
- Cipher by LEMMiNO ( • LEMMiNO - Cipher (BGM) )
- Fine Dining by TrackTribe

[@rockyvillano777]

If I had a nickel for every time quadratic complexity passed testing but blew up in prod I'd be rich

[@allyourpie4323]

What if every time it quadratic complexity passed testing, you got a nickel for every time quadratic complexity passed testing?

[@renakunisaki]

If I had a nickel for every time I got a nickel...

[@Bollibompa]

If I got a nickel for every time someone says "If I got a nickel" I would be a gabbagillionaire!

[@Aaron.Thomas]

This is why we have and should have computer science and not just computer engineering - math is important.

[@yaksher]

This is exponential, not quadratic. If it were quadric, there wouldn't be any problems.

[@CYXXYC]

2:37 laughed my ass off at "delete master after the pull request is merged"

[@ABaumstumpf]

and there are people that would click that checkbox.

[@Ultrajuiced]

Chill, "master" is the dev branch here while "main" is the master branch of course.

[@zerto111]

@@Ultrajuiced Let's just agree that it's a funny easter egg in the video and laughing i justified.

[@nicholasfinch4087]

Glad to see others had seen that too 😂❤

[@MrWarlock616]

Yeah that was such a nice touch!😂

[@nwrocketman6438]

2:51 I like how the 1000x engineer just foreshadows all the events that about to happen, and then approves the change.

[@tehroflcopters]

par for the course tbh

[@1008OH]

Yeah average senior software engineer moment tbh

[@EgonFreeman]

Yeah, because if you go "Hey guise, this might actually break in a very non-obvious way, let me run some sims..." you're usually ignored and the go-ahead is given _anyway._ Nobody wants to sit around waiting for That One Guy Who Keeps Envisioning Black Day Scenarios to finish their petty "I must be included as a vital part this conversation" so-called-tests (because believe me, there are people who see it as such). Besides, production-level testing usually ends up being faster... :D

[@jfbeam]

@@EgonFreeman From experience... had they spoken up, they would almost certainly have been met with one of "who asked you?", "shut up, we're doing this!", or just ignored. Dozens of others didn't notice any issues, so who's going to listen to "that guy"?

[@xhivo97]

a true 1000x enginerd would not use regex lol

[@xorinzor]

Despite all this, I still very much love Cloudflare especially because of their transparency. They always go into great depth explaining what happened, what they did, and how they resolved it. Many companies can learn a thing or 2 from them in that regard. Customers tend to have more faith in a company that just owns up to it's mistakes rather then trying to have a PR department cover it up in nice words.

[@StkyDkNMeBlz]

​@@KabodankiCaptcha? Google the "Privacy Pass" extension. It lets you skip the tests by doing tests beforehand.

[@jacksoncremean1664]

@@StkyDkNMeBlz they don't have captcha anymore, they use turnstile

[@maskettaman1488]

I love my state sponsored man in the middle

[@returndislikes6906]

I hate cloudflare because its trying to become monopoly on internet ethics. Its not your job to pass judgement what is allowed on the internet. Banning something that is illegal is fair. But banning because its immoral according to them... yea I hate cloudflare.

[@returndislikes6906]

@@StkyDkNMeBlz I really want to be tracked by Google across the internet with their corpo issued cryptographic IDs. You do understand what you are shilling?

[@eldrago19]

"Some programmers run into a problem and think, 'I will use regex to solve this!' Now they have two problems." - Zawinski

[@ejcx_]

I was actually at Cloudflare in the room for Cloudbleed and this issue, in SF for Cloudbleed and happened to be in London for this one. The real story is much better than this. We were at lunch doing a tech talk in the lunchroom when someone grabbed the mic and announced we were having a P0. We stampeded back to our desks and got to work fixing it. The issue was obviously related to the WAF from the start and it was just a matter of cleaning up. Keep up the videos they are great

[@Nayayom]

So how's working with cloudflare like ? :)

[@0xggbrnr]

@@NayayomIt’s actually really awesome. Tons of really smart, kind, curious people. Everything internally is about transparency, execution, and learning. Definitely engineering-centric, but also super product-focused in that the customer is always considered during meetings/talks/decisions.

[@Nayayom]

@@0xggbrnr sounds like a good place to work! Glad to hear that

[@CarlosISoares]

Ok, but is not BETTER than the video story lol

[@magno5157]

What happened to the employee who made the regex?

[@Thect]

"like re2, which work by converting regex to a state machine, or fancy computer science flowcharts" Damn, I wish I can say this line to the professor who teaches compiler course in my university lol

[@mr_confuse]

I had straight vietnam flashbacks when the statemachine came up lmao

[@skyhappy]

State machines were the most useless thing I learned 2nd year in "computational theory" class. Whole class was academic fluff.

[@tissuepaper9962]

​@@skyhappy FSMs are used everywhere, they're the basic building block of most digital protocols and embedded systems. Definitely not "useless".

[@DNX3M]

I call them spaghetti meatballs. Feel free to use that one.

[@arthurpenndragon6434]

@@skyhappy average framework enthusiast with no understanding of computer science.

[@mwissel]

Love the little details, like the upside down cloudflare icon in Australia. Good job editing!

[@tunahanyilmazdev]

0:36 if anyone missed it

[@somerandomdudefromtheinter5333]

2:37 'Delete master after the pull request is merged' xD

[@greg_289]

Worth mentioning that Cloudflare isn’t just a CDN. It’s predominantly used by most websites as a web proxy responsible for the majority if not all requests to the origin.

[@emeraldbonsai]

the webproxy is a cdn last i checked

[@VeggieRice]

users can elect their own dns service

[@hoo2042]

@@emeraldbonsai Typically a CDN serves static or at least mostly static data. A CDN may be implemented as a caching web proxy, but a web proxy can do a lot more than what usually falls under the definition of "CDN". In CloudFlare's case, they basically offer both and blur the line about which is which, which is fine since it's a blurry line, but the person you are replying to isn't wrong.

[@hoo2042]

@@VeggieRice ⁠DNS has nothing to do with what's being discussed here (aside from being an earlier step in the chain that would take you to the page's configured web proxy or CDN, of course, but equivalently so to saying "the user can elect their own browser").

[@benhook1013]

The distinction is useful here as the outage is much more impactful if your web pages wont even load themselves (because the web proxy is down) rather than just CDN assets not loading (which could be only large assets).

[@evilsqirrel]

I work in a cybersecurity administration space where regex is used all the time as a necessity. This is a story we tell people all the time to make sure they understand how important it is to make efficient regex.

[@Wyvernnnn]

The regex is fine there was no reason for the engine to backtrack on it

[@Zei33]

@@WyvernnnnI disagree. The pattern didn’t make much sense. It was clearly missing something between the initial wildcard and non-capturing group. There’s never any reason to put two wildcards next to each other like that.

[@Wyvernnnn]

@@Zei33 Yeah that was weird, but it should still get O(n) in the end, that's the whole point of regular expressions (as long as you don't have capturing groups that can be re-used within the regex aka backtracking)

[@Croz89]

I can understand how it happened, even an experienced programmer can struggle to parse a regex by eye and it's easy to make something that's a resource hog without realising. It's certainly a lesson to test your regex thoroughly before release.

[@Zei33]

@@Croz89 oh yeah I’m constantly making mistakes. No one is perfect, that’s why debugging and beta testing exists. After over a decade of programming, I don’t make a lot of mistakes, but when I do they’re usually obscure cases or subtle logic errors. When you’re working with tens of thousands of lines of code and looking at them for 8 to 20 hours a day, mistakes are gonna happen.

[@violabrockman5284]

It's important to note that re2 actually has other downsides compared to other regex engines, such as being unable to handle lookaheads and lookbehinds. This isn't just an implementation issue either: adding these operations actually makes regex strictly stronger than a finite state machine (instead it becomes a pushdown automaton). There's also a lot of fun math with finite state machines, where it turns out they're strictly equivalent to generating functions, which are basically power series where you don't care about convergence!

[@Ceelvain]

I think "look-around" assertions could still be implemented to run in linear time. As far as I know, back references is the only feature that can make the run time go exponential. In fact, matching regexes with backrefs is proven NP-hard.

[@hoo2042]

Lacking some of the more advanced PCRE features in order to make guarantees about the maximum runtime seems like the right compromise to make for a high-volume security frontend that sits between the global population and a large swath of the internet.

[@Ceelvain]

@@hoo2042 That's actually why Russ Cox developed RE2 in the first place. He made it for google code search (now defunct). You can't really be Google and expect tech people to only input well-behaved regexes. He has a very interesting series of articles named "Implementing Regular Expressions". I really recommend every developer to read them.

[@tommihommi1]

shouldn't regex expanded like this be called cfex instead, since it's, well, no longer a regular expression

[@mustard96]

@@hoo2042The problem now is that they use it on every Google product. re2 is the regex engine of BigQuery and I’m stuck with this limitations. It doesn’t make sense in a data warehouse.

[@royalepros669]

my brain automatically shut down when you start explaining the regex...

[@TMRick1]

Same here dude. I can't understand how people are still relying on regex for such important aspects of the code. It's just mind-blowing that a firewall rule is managed with that in 2023.

[@arielcg_]

@@TMRick1 what alternative is there that is universally supported and has the same level of flexibility for how "compact" it is?

[@tissuepaper9962]

​@@TMRick1 you just don't know the pain of using anything else to do what regex can do. What do you suggest? awk?

[@user-eh7hy2xn3w]

lol just write your own parser. You are acting as if that's a hard problem to solve and as if customers are not important. You just want to make your lives as "programmers" easier. Have some responsibility for the unnecessary amount of code that runs on users machines.

[@jtfoog5220]

@@user-eh7hy2xn3wI use arch btw lol

[@Aldrasio]

This is why as a general rule I NEVER use .* in my regexes. If I want to match everything before an equals sign, I'd use [^=]*= rather than .*= because it's always better to be as explicit as possible.

[@framegrace1]

But that would match just the first '=' , not all of them. If you have a lot of parameters on a URL , you will have a lot of '=' and you will want to search all of them for certain things.

[@HenryLoenwind]

​@@framegrace1 That's why you don't anchor the expression to the end of the string in this case. We don't care what else is at the end of the URL if we find a "bad thing" near the start. Also, most regex engines have a shortcut implementation for regexes ending in ".*"/".*$", so the one at the end is of no concern. And BTW, the issue was mostly the ".*.*", not so much the ".*=". Backtracking the latter isn't so expensive---it doesn't really matter if the engine has to search for the = from the start of the end of the remaining string. It most likely has a shortcut for "fixed character after match all" anyway. There's a good chance that ".*?=" is faster than "[^=]*?="/"[^=]*=" as it can scan the string using a simple "equals" comparison and be done. This, however, all goes out the window once there are multiple ways to match, like the infamous ".*.*". So when using this optimisation on purpose, it makes sense to manually commit after the "=" (e.g. with "(*COMMIT)").

[@AbiGail-ok7fc]

@@framegrace1 You can still get the last '=' by being more explicit: /([^=]*=)*=/ or /=[^=]*$/

[@MindLaboratory]

It's amazing how casually things are actually handled behind the scenes in the IT world. I once wrote some software for a bank, did a 3 hour audit of the code with 5 of their top developers, after which they installed a pre-compiled earlier test version on their prod system. smh

[@jnz007]

😂

[@DanielSmedegaardBuus]

I once fixed a globally crashing iOS app by hacking the backend to send out technically incorrect data. The app passed all tests because the test suites didn't include any data to reveal division-by-zero bugs. This was especially bad since the time to get Apple to review and deploy an updated version could take a week or more, IIRC. After conversing with the dev responsible, I asked him how he habdled fractional numbers, and he was sure that fractional numbers were always displayed as integers, so I changed the API to send instances of 0 as 0.001, effectively circumventing the bug while displaying calculated numbers (and 0s) correctly in the app. I think it's the most hacky fix I've ever deployed. It felt terrible and exhilarating and awesome all at the same time 😂 I'm actually a little proud 😇

[@Kabodanki]

upside down cloudflare logo for australia was gold

[@thewhitefalcon8539]

Someone wrote a paper ages ago about backtracking vs non-backtracking regex engines and the state of software slowness... The title is "Regular Expression Matching Can Be Simple And Fast (but is slow in Java, Perl, PHP, Python, Ruby, ...)" written by a Russ Cox in 2007. I bet he's feeling vindicated

[@lhpl]

That article, and several others, should be mandatory reading for anyone using regular expressions.

[@UnrealOG137]

3:50 Putting cloudlfare upside down above Australia was a hilarious touch!

[@chewcodes]

this is my new favorite channel. explaining everything clearly, and being humorous with small jokes here and there

[@gblargg]

And explosions, lots of explosions.

[@princesssshortie]

Same. And the upside-down cloudflare logo on Australia killed me. 😂

[@andrewallbright658]

These stories are so cathartic. Thanks for applying your storytelling to these niche topics!

[@pav431]

I work as a sysadmin, yet I wish I had this much insight into how all the technologies I use daily work this deeply. I never finished my college, so I only ever heard of DFA, but despite that, your video explained it very well, and showed how much of an issue a simple regex can be, when executed thousands a times a second. Please make more videos, I cannot wait for more

[@Atlantis357]

It is interesting to note that any regex can be represented as a nondeterministic finite automata (NFA) and any NFA can be converted into a DFA using a simple algorithm. The only downside is that the DFA may end up with exponentially more states than the NFA which can take up a lot of memory.

[@Nayayom]

Good thing you enjoyed it, i have not so fun memories doing DFAs and NFAs by hand on college. :(

[@habama1077]

​@@Nayayombro same. I hated it. But understanding them is pretty good. We can see how google's devs used automata and formal grammar theory to develop a useful practical application with regex.

[@lhpl]

@pav431 even without some formal education, I'd say anyone working as sysadmin should know something about algorithms and complexity theory. Especially when writing code that systems used by others depend on. And shell scripts _are_ code. Knowing that there are regular expressions, and highly irregular expressions that are just _called_ something like "Perl compatible regular expressions" or "extended regexp" or whatever, is important. So is not writing script that unnecessarily nest three or more loops, and work fine on small testdata, but take "forever" with realistic sizes of data. Know and understand the various o-notations. Just because quicksort is usually quick, doesn't prevent it from having O(n²) worst case complexity. You may be fine with that, but you will want to know why you can live with it. There has to be a metric ton of good books on this, so it's possible to learn. Enjoy!

[@Aaron.Thomas]

​@@lhpl As someone who's inherited, and then had to completely rewrite from scratch, core automation scripts for clusters that were written by novice sysadmins, I concur that learning these things is important. Some aysadmins learn that awk and grep exist and that's the end of their training. Rewriting from scratch saved me hours upon hours it would have cost me to try to maintain the poorly made code inherited from novice sysadmins.

[@glitchy_weasel]

Absolutely crazy videos you're pumping up. Love your comedic editing style too! Every video of yours makes me feel like to the entire internet could break at any moment lol

[@LordMegatherium]

Regex is great like shell scripts: works everywhere and does it jobs... up until a certain script size when the chance of bugs starts increasing and you should think of using another tool instead or in conjunction. Also this sounds like GitOps to the extreme: when you can only change your state via your repo and all the triggers that come with it you might as well replace your CD with a single bash script (see above).

[@MrMCMaxLP]

Ken Thompson is crying really hard. His work has been around for decades. As a CS guy who has specialized in algorithms, this hurts in the middle of the heart.

[@tehlaser]

I had a regex blow up on me like that once. Not **quite** as silly as .*(?:.*=.*), but pretty close. The regex library we were using implemented backtracking with recursion, so instead of eating CPUs like a bag of chips it would instead masticate for a while before eventually running out of stack, whereupon it would puke Pringles. This was an especially fun one to fix because if you google “regex stack overflow” you’ll find that there are zillions of questions on stackoverflow about regexes that have nothing to do with stack overflows. And yes, in shame I must admit the regex in question did not fit on my screen all at once. In my defense, however, that was because a year or so earlier I had torn the line noise apart and put 3 to 5 characters of actual regex on each line, followed by a comment. Only two lines had // I have no idea, this shouldn’t do anything, but it doesn’t work without it.

[@hentai824]

lmaoo man i feel you

[@tehlaser]

Come to the dark side. We indent our regexes.

[@aethese]

Love these videos Kevin! Your amazing storytelling, editing, animations, and everything else comes together in an amazing way! Love watching every video you put out, keep it up :)

[@mariadragonbreath7130]

I stumbled across your videos yesterday, and i find them really entertaining and interesting to watch! Thank you explaining these topics in a clear way that even if I know nothing about regex or cloudfare, i can still follow along and understand the video :)

[@EndMaster0]

I guarantee all the engineers who reviewed it didn't even look at the regex. you don't go poking someone elses regex

[@BrandonCallender]

I dont blame you for doing Cloudflare again, their RCAs are always excellent. This is such an excellent channel, you deserve far more subs! These are exceedingly entertaining and interesting for software engineers (and probably most other folks too!)

[@RandomFish-gx7pj]

It's kinda funny that the Internet was designed to be a `web` that hopefully would prevent failures of a single node taking down the whole system, but nowadays we heavily rely on a handful of service providers just to run the Internet.

[@patterntrader690]

Your videos are amazing, keep going you are bound to blow up

[@RMDragon3]

I kept wondering why they didn't just do a rollback to fix the issue, thanks for addressing that at the end.

[@romannasuti25]

Yeah, as much as I love Cloudflare for smaller stuff there's a reason a lot of large enterprises use Akamai. A little overpriced for a simple growth phase startup and not as transparent as Cloudflare when something breaks on their end, but that massive bucket list of features available with Ion Premier, Cloudlets, and many more, especially Datastreams and their web security analytics portal, is an absolute lifesaver. Hell, it helps us debug all sorts of broken stuff upstream of it too, although I wouldn't be surprised if Cloudflare offered something like Akamai Reference IDs for easy, enterprise-friendly tracing. Specifically, Akamai is really particular about having identical Staging and Production sections with really fast rollback when production error rates increase even a little.

[@framegrace1]

All those rules are stored locally to each node, and you cannot rollback to a machine that is dead or so high on CPU that can't even handle a connection. I presume they globally disabled WAF and restarted the nodes, so when up, they didn't try to apply the WAF rules and were free to be rolled back/forward. Then they re-enabled WAF (very slowly, I presume :) ) and all was back to normal.

[@ballinlikebill8334]

love the style keep it up man

[@minimalist_zero]

This is an incredible video. You took very complex and difficult to understand concepts and simplified it well. Well done.

[@CALEB94]

Awesome and informative video! A small correction: NFA matching is still linear in the input string. You just have to store the configuration as a set of NFA states, rather than a single state. You don't get exponentially many paths in the way you describe in the video because paths ending at the same state are merged in this set representation.

[@creamyhorror]

I can't believe I've only just run across your content - it's really well done and humorous, you're going places!

[@D0Samp]

The reason we predominantly use NFA regular expression engines is not just because they're usually faster if we don't throw non-degenerative expressions at them, but also because they support expressions that exceed the capabilities of a regular grammar, such as back references to a specific capture group that has been seen previously.

[@MH_VOID]

I was under the impression that they're generally slower

[@georgehelyar]

​@@MH_VOIDfor a normal case the performance is generally similar, but the difference is that these linear engines like RE2 are more predictable and less likely to blow up in your face. If you don't have control of the pattern and the input, they are *much* safer, and losing features that depend on backtracking is generally not a big deal. If it's really performance critical just don't use regex at all if you can avoid it.

[@teunmathijssen7459]

NFAs and DFAs are computationally equivalent and recognise only exactly the regular languages. So a NFA-backed RE engine would have to implement additional functionality as languages with backreferences are not regular.

[@D0Samp]

I've learned in the meantime that the biggest speed advantage is actually due to unrelated technologies such as a JIT compiler in PCRE2, which is in fact a top-down parser that happens to accept regex-like expressions. The only thing that is definitely faster about NFA is compiling regular expressions.

[@paulstelian97]

@@D0SampCertain types of things that regex engines/matchers support aren't true regex, and can't be covered by a DFA/NFA. That's a bit BS to me.

[@kanal7523]

I love your videos and goofy animations please never stop doing these

[@thedoble]

The animation and comedic aspect of this video is great. Plus its explained extremely well. Nice

[@RSZA011]

this is by far my most interesting youtube channel . please keep it up ! I really enjoy this content

[@BurzowySzczurek]

Another nice dev store, with interesting storytelling, really enjoyable to watch. Thanks, we are waiting for more : )

[@hanlonm]

Great video! Really like the style and explanations

[@NishthaSharma-nt9hk]

loving these vids. keep em coming!

[@dasherreal]

This channel concept is brilliant. Thank you so much.

[@kleinekip1234]

Love your content, motivating me to learn more about coding and software development (have always been interested in) and you are able to explain it in a way where you somehow use terms used by those actually working with databases yet I'm able to follow what you're talking about and how it all works, keep it up man :)

[@Cyber_Chriis]

Dude your illustrations are so good and funny! :D

[@quixadhal]

Well, from the thumbnail image, the regexp (.*=.*) says "find the LARGEST chunk of text possible before a literal = sign, then find the largest chunk after it, including other = signs if they exist", and it will walk the entire chunk of data many times to ensure it gets ALL of them. They probably meant to do (.*?=.*?), which would have found the SMALLEST chunks of text around literal = signs, and would stop as soon as it found even a single = sign.

[@EchoingRuby]

I mean they could have just done .*?=.* but I guess RE2 is safer long-term. Still this screams "I don't understand regex, it's just magic to me" on the part of that developer.

[@killingtimeitself]

which is fair honestly, regex is basically just magic and once you understand the syntax you dont question it's ways. though im surprised nowhere else along the development process was anybody concerned over it. Apparently nobody that looked over it had any idea what it was doing.

[@TheDarkWayne]

Your content is pure gold. Keep up the great work!

[@maddoggLP]

Didn't expect to hear about theoretical computer science (which is a subject I take this year) in this video but nice work. It's nice to see actual real-world usage of converting e-NFA to DFA's. I wish our prof would have included this video in his lecture...

[@violetwtf]

you are my favorite channel. so excited to watch this on my business trip

[@owenschwartz]

Loving these videos!

[@jacobclark288]

these videos are so well produced, the jokes in the imagery are so on point.

[@Dardasha_Studios]

You are a gem, thanks for the detailed information. You didn't only explain complex information, you also explained how WAF companies work. Thanks again. Salam!!

[@sairao4492]

This is a great video. You made it very easy to follow. Took me back to my computational models class.

[@DiegoGuerrero-zy5ne]

Great videos! Keep ‘em coming

[@mattym8]

Excellent vid. Couldn't have been shorter. Didn't need to be longer. Learned lots. You might've achieved perfection.

[@Timi7007]

I love the graphics, depicting real processes very well but hilariously funny at the same time!

[@LKRaider]

I like the part of explaining non-capturing groups and then throwing them out the window immediately after

[@yfakolh7154]

Except it's wrong. You do non-capturing for performance reasons, to consume characters in some group (this is simply parentheses syntax reuse). In this particular case this was so obviously wrong I can't imagine anyone familiar not to spot this, but in general you shouldn't capture what's not required after the match is done.

[@mangoodbad13]

Things exploding in your videos is the entire reason I wake up every morning, thank you friend, it's freakin hilarious

[@MrNobbless]

i love these videos, keep them coming please!

[@Kevin-wj1do]

I love these videos, they make me actually lol. Keep up the great work on these.

[@ighsight]

A beautiful explanation, wrapped in humor. I need to subscribe to this channel.

[@morgankuphal3417]

I’m a subscriber after this! Excellent content!

[@candle_eatist]

every time this dude uploads it's an absolute banger

[@ladyravendale1]

I love your videos on the internet blowing up. Perfect blend of programming, memes, and good graphics

[@Danielo515]

This is the best explanation of the incident that I saw. Good job

[@shroomer3867]

The regex that ChatGPT creates:

[@himanshutripathi7441]

Thanks for the dfa nfa part ,, loved it.

[@GottgleicherMaster]

excellent Video and great explanation and great visuals. subbed :)

[@RandomDeforge]

out of the 10,000 times that this topic has been covered on KZbin in this exact amount of detail, this is so far the most recent. kudos!

[@ThisIsAnAccount]

God I love watching these vids, I love the duality of high quality, digestible, information coupled with a nice sprinkling of "don't be a dipsh*t" commentary over issues and causation. Developer wise, nothing brings me more joy about my job than someone pointing out how much of an imbecile I *could* have been on that one day.

[@OlegDorbitt]

11:00 Wow, you've explained the usefulness of using DFA way better than my professor! Now it all makes sense!

[@riddixdan5572]

love the content. lots to learn from

[@fabricio5p]

Your channel is awesome learning material, keep it up

[@Not_Even_Wrong]

Wow great explanation of the matching process, I already did not like regex but this is next level... especially because one could easily write UNDERSTANDABLE code that does the job, but runs in O(n)...

[@n0tharv]

loving the videos bro keep it up 👍

[@beep6844]

The Lemmino music really rounds this video off

[@Shimasen.]

Never have I ever expected to hear LEMMiNO soundtracks anywhere, glad to hear it from this channel!

[@krozareq]

When in doubt, implement your expression in a delayed loop so it doesn't murder everything.

[@PinePizza]

Even without being into coding I understand how this could work and it puzzles me why they didn't do this lol.

[@soumyadeepbasak4565]

i found this channel by mistake but i am glad pls continuw posting:)

[@CFEF44AB1399978B0011]

The entire world runs on regular expressions that were written in rage.

[@BurnerWah]

This video has a pretty good explanation of regex engines TBH

[@qm3ster]

Non-capturing groups (unlike lookahead and lookbehind) do get included in the match result (think $0), they just don't create an additional sub-match. Eg at 6:35, that would match $0: $1: $2: while removing the ?: would make it $0: $1: $2: $3:

[@Giuwu_]

> Delete master after the pull request is merged LMAOO

[@alexanderjohnston2658]

Love your vids

[@MogDog66]

2:37 I love that he checks the "delete master branch after merging" box

[@nwordfword8073]

This shit is very informational and great funny editing! Glad I found you king

[@qu765]

just wanna say that this is a high quality video, very nice

[@TheDarkestPaladin]

Greatest youtube recommendation in a very long time.

[@catalystlover]

Great video, really informative!

[@seansull]

Dude your graphics are so funny 💀 I just about died when you edited the flow chart for WAF deployments

[@yaksher]

@11:50 You don't need a DFA to guarantee time linear in the input length because you don't actually need to follow every path, you just need to keep track of the set of states that the NFA is in. This does make it more expensive proportional to the size of the NFA, but it's still linear in the input length.

[@user-xo2iw6lz2n]

breuuugh, how has this channel not been suggested to me much sooner

[@rousseauramirez]

I'm starting to hope another outage somewhere on the internet occurs just to see a Kevin Fang video with hundreds of explosion effects in my recommendations yet again

[@QuickQuips]

I really like how you described the newer forms of regex. They look like Moore/Meely machines which use 1s and 0s and are handy with digital design.

[@abebuckingham8198]

Mealy/Moore Machines are a kind of deterministic finite automata for a special case. So it's no coincidence they look the same.

[@hemal7551]

12:17 I really loved how you used sarcasm throughout the video😂 You have perfect combination bro ngl

[@lowe7372]

Amazing videos man

[@christopheralbright9650]

...been trying to grok coding how i do geometry. After years of intermediate searching, you helped me see some of said "theory"...thank you!

[@dorboi]

love your videos!

[@Vulcapyro]

The line at the end could be revised; it isn't that "convoluted" regex should be avoided, in fact writing regex that appears more complicated often ends up being better in that it's more specific. Really bad regex happens when people want to write something quick and dirty that will consume all valid cases, but without considering constraints, which was part of the issue here. I know this is probably what you meant by saying convoluted, but one thing missing here is a bit talking about what you should consider writing instead, and people unfamiliar with good vs bad regex might not come away with the right idea.

[@hentai824]

another based regex enjoyer