Jaromir Hamala
@jerrinot
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I play with distributed systems by day and poke various runtimes by night. Engineer @QuestDB , @Hazelcast alumnus.
EU
Joined December 2009
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My new blogpost was just released. If you have ever wondered how are System.currentTimeMillis() or System.nanoTime() implemented and what's the price of single timestamp then read the post!
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It turns out my
#1BRC
solution is the fastest of all when running on many cores! That's totally unexpected, I was not optimizing for this scenario at all.
I'm coining a new term: 'Accidental Scalability' :-D
#1BRC
Update: While handful of remaining entries awaits evaluation, I did an update of the 32 core / 64 threads leaderboard for the 25 top contenders.
@jerrinot
and
@thomaswue
at the top for this eval, processing the 13G file in ~0.32 sec!
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Modern B-tree🎄 Techniques:
I thought it was impossible to have 200 pages about a single data-structure. I was wrong.
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When
@quananh1999
created his magical branch-free parser for
#1BRC
I borrowed it even though I did not understand it. I only knew it was fast and looked like magic!🪄
Today
@mtopolnik
published a
#questdb
blog explaining each line of the code to mere mortals like myself and it
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The Inner Workings of Distributed Databases:
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Developers: We are so smart, we wouldn't fall for marketing tricks!
Also developers: We have to rewrite this application into a bunch microservices, deploy on managed Kubernetes and use all serverless services in existence!
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PostgreSQL ✅
Debezium ✅
Apache Kafka ✅
QuestDB ✅
Grafana ✅
What's not to love about the article? 🤩
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Learning about debuggers:
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Does "vpmovzxbd" Scare You? Here's Why it Doesn't Have To!
Another wonderful blog by
@mtopolnik
🤓
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I found this YouTube channel where a guy casually builds a video card from a bunch of counters and NAND gates.
He starts sending sync signals:
Then a static pic from EEPROM,then a pic from RAM of a homegrown computer. Bus mastering included. Mad respect.
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The Hazelcast engineering team loves me so much they created a special GitHub label just for me!
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Why Apache Kafka doesn't need fsync to be safe:
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Someone reported a
#QuestDB
bug in a binary search algo.
The report links to an article by
@joshbloch
:
It's almost 20 years old and I still find the story fascinating.
tl;dr: `auto mid = (low + high) / 2;` may overflow. it's rare -> it goes unnoticed⏱️💣
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I love learning about things. Some people are natural educators. Today, I discovered
@BCiechanowski
's brilliant website.
His explanation of the Internal Combustion Engine is the best I've ever seen:
The whole archive is a gem, simply brilliant!
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My
#1BRC
swag has arrived! Morning coffee has never tasted better :) Thank you,
@gunnarmorling
and
@Decodableco
!
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10 days ago I published a new
#questdb
blog and went on vacation🚲🇳🇱
I am back and learning the blog has been pretty successful!
ICYMI: Concurrent Data Structure Design Walkthrough
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The One Billion Row Challenge in CUDA: from 17m to 17s
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Today is my last day at Hazelcast. I started contributing in 2013, joining full-time in 2014.
It's been an incredible ride. I'll be forever grateful to the people who made this possible!
I'm leaving the company, but the project&people will always have a special place in my ❤️!
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The disconnect between western and Chinese open source ecosystems keeps surprising me.
Apache Dubbo has 33k GitHub stars, predominately from Asia. Yet I have never heard of the project.
Alibaba Canal - CDC with 15k stars:
There are others examples.
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Quarkus is a great framework, but it has one fatal flaw: There is no Hazelcast extension!
This is about to change, awesome
@pivovarit
sent a PR integrating Hazelcast:
This extension will make the Supersonic Subatomic Java truly feature complete! ;-)
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My new blogpost: LockSupport.parkNanos() Under the Hood and The Curious Case of Parking -
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Announcing rust-maven-plugin: Compile and bundle Rust JNI libraries in Java Maven projects.
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1/9: My take on the ongoing debate between Redpanda & Confluent folks:
* Yes, safety can be guaranteed without fsync().
* No, Byzantine Fault Tolerance isn't a must.
Curious? Let's unpack this: 🧵
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@PanBloumal
@Fbeyeee
"Šok! Roskosmos má přístup k téměř stejně kvalitní technologii, jako Jan Boháč!"
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Something is telling me I have yet to master git configuration syntax.
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Developers: Let's use microservices to decrease team coupling and cognitive load.
Also developers: Let's use monorepo so I get to see all the code we have!
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There is tension between fast startup times (AOT) and peak performance (JIT).
Historically the peak performance was more important for server-side applications.
Cloud is changing it, at least partially, and people go a long way to improve startup times. Some examples:
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The Power of Open Source ♥️: Todd Greer from Google is working on Envoy Proxy HTTP cache filter. It's still WIP, but
@ozcannot
from Hazelcast is already validating the API by implementing Hazelcast-based filter.
It Feels Good to be an Early Adapter!
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According to Hazelcast is the most popular Raft implementation in Java and 2nd most popular implementation overall! 💖
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I love how Postgres JDBC documentation explains SSL modes.
Plain English yet concise description. Even people with limited exposure to security can understand it.
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I fixed a bug. By replacing `map.put()` with `map.putIfAbsent()`. This change took me over an hour.
That's like 1 character / 10 minutes. Should I feel good or bad? :)
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Did you know the Postgres type "timestamp with time zone" actually does not store the timezone at all?
Postgres has 2 basic types for storing timestamps: timestamp and timestamptz. Neither stores any timezone information, they both store just a single 64-bit integer.
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TIL: Sorting UTF-8 encoded strings by their bytes gives the same result as sorting them by actual codepoints.
It's all because of how UTF-8's leading bytes are set up.
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I've always been skeptical to this FaaS fashion.
AWS Lambda screams 📢📢CLOUD VENDOR LOCK-IN☢️
But I have to say: Google Cloud Run + Quarkus is a pretty neat combination.
My app has no GCP-specific code, Quarkus does not feel too possessive either. Serverless Done Right.
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How many CPUs a containerized Java see?
docker run <container image> java -Xlog:os+container=trace -version|grep active_processor_count
In Kubernetes:
kubectl exec <pod name> -- java -Xlog:os+container=trace -version|grep active_processor_count
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HotSpot Escape Analysis and Scalar Replacement Status:
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TIL: -XX:+StressLCM / -XX:+StressGCM are JVM flags to randomize instruction scheduling.
It allows finding concurrency bugs that would be otherwise hidden on a given architecture.
Apparently, JCStress makes use of it. Thanks to
@PeterVeentjer
for showing me this.
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Great paper on evolution of RocksDB. Read it to cure any kind of urges to implement a custom LSM storage. So many concerns to deal with!
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I've been playing with Upstash, Decodable and Cockroach Serverless.
It works nicely together: Upstash webhook produces a Kafka message, Decodable polls Upstash and pushes new rows into Cockroach. Working like a charm!
Next steps:
1. Connect QuestDB
2. Try window aggregations
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TIL: j.u.LinkedList.size() can return a negative value 😮
How? Just insert more than 2^31-1 values. This makes the internal size counter to overflow.
Warning: This will use high 10s of GB of memory.
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Friday evening project: Hazelcast Jet is running on my mobile phone! Feels good. Can your distributed stream processing engine do that? 🚀
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connect() - why are you so slow?
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Me: It's 2021 and I would hesitate to promise anything. I am not even 100% certain the sun will rise tomorrow again.
JDBC driver: This write will definitely succeed!
Me: I admire your confidence!
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🧵Thread: Classification of Concurrent Algorithms by Progress Conditions🔒🧪
Let's have a look at terms like blocking, non-blocking, lock-free, and wait-free.
Read on to see how these classifications impact the progress of threads in your programs. 👇
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JMM Pragmatics by
@shipilev
is such a gem!
It goes deep yet it builds-up slowly and does not make you feel you an idiot:
Also I like the references to other areas. Example:
Hackers culture:
Philosophy:
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@DanPriban
To je uplna fascinace :)
Ja vubec netusil, ze kdykoliv nejakej hmyz resi, nez jsem ti precetl u vas. Jsem ignorant (nebo) zavrenej v bubline? Je to mozny.
Vubec nechapu, proc by takova pitomost mela byl tema.
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The community around
#1BRC
is so amazing. Cross-pollination is actively encouraged and it's making everyone's programs faster.
So let me show you something else:
Not only does it make your own program faster, chances are it makes someone else's solution slower! 👿
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Static Compilation of Java Applications at Alibaba at Scale:
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In related news: I'm joining QuestDB!
Life runs in time series and I'll be helping to build the fastest🔥 time series database out there:
Stop by and say Hi👋at
Today is my last day at Hazelcast. I started contributing in 2013, joining full-time in 2014.
It's been an incredible ride. I'll be forever grateful to the people who made this possible!
I'm leaving the company, but the project&people will always have a special place in my ❤️!
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Woot! My friend
@mtopolnik
is joining
#questdb
, and I'm over the moon. We met at Hazelcast back in 2015, and some of my best memories include working together on the Hazelcast core team.
@AndreyPechkurov
: You're a true trend-setter, no doubt! 😂😂
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@howie_hua
1. Multiplying by 10 is easy, so start with 16x10 = 160
2. Add half of it. So the result is 160 + 160/2 = 160 + 80
3. Realize it's (2x8 + 1x8)x10 = (3x8)x10 = 24x10 = 240
4. Show off on Twitter!
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I was a Hazelcast contributor before joining as a full time engineer. I still remember the joy when my first PR was merged!
If you would like to contribute to Hazelcast then a Jet connector is a good start. For example a Twitter Sink should be easy!
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Java Tip: java.util.HexFormat is a nice addition in JDK17.
Helpful to quickly visualize the content of various buffers, etc.
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@gunnarmorling
@thomaswue
@quananh1999
@TheMukel
Thank you so much for organizing this challenge! Not only it's been a great fun, but I also learned a ton.
The idea of keeping everything in open and encourage folks to learn from each other, that was just brilliant!
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I needed a map-like structure with lock-free readers and a single writer. The writer was allowed to block.
I was so proud of the protocol I come-up with. Only to realize the basic idea is the same as described here:
Well, worse things happen at sea 🤷♂️
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I'm volunteering at the Fast and Streaming Data devroom at FOSDEM. My amazing
#questdb
colleague
@supercoco9
is there too.
Stop by to learn something new or just to say Hi!
Also, finally, I get to meet
@FawazGhali
. Hazelcast will always have a special place in my heart!
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The chain of disk lies:
1. SSD lies to OS: It's persisted, trust me🤞
2. (Mac)OS to a database: fsync is completed you are safe 😉
3. MongoDB to a business app: D stands for durability, right😇?
Plot twist: The business app is so buggy that nobody cares anyway🙊
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Nothing extraordinary to be seen here; it's just
@AndreyPechkurov
casually improving
#QuestDB
aggregation query performance by 1-2 orders of magnitude. Business as usual, move along.
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Maven plugin to build Rust Cargo crates within a Java Maven project:
We use it to implement native bits of
#questdb
in Rust.
It's still early and contributions are very welcome!
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I have a massive respect for antirez and his work. Benchmarketing is an ugly discipline, but RedisLabs’s benchmarks are unprofessional and misleading. See flawed Elasticsearch benchmark: and Hazelcast:
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@trif
Aby to fungovalo, tak je při dočasném vzdálení se z pokoje potřeba pověsit cedulku “Nerušit”. Jinak chybějící pivo pokojská odhalí, nahradí a započítá!
#lessonlearned
#notevenashamed
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Cache invalidation really is one of the hardest problems in computer science:
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JVM native methods usually don't obstruct safepoints, but there are exceptions.
Here a pointer from malloc() is passed to GetByteArrayRegion, which is running the vm_state and it may obstruct safepoints. Possibly for a long time.
Why? Lazy allocations➡️Page Fault➡️Suffering
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Confession: I still use "ifconfig" and "route" when poking a Linux network config.
I tried to switch to iproute2 multiple times, but "the old way" is too deep under my skin. With iproute2 I always have to re-learn it from scratch.
Am I stupid, lazy or just getting old? :)
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I showed Lemmings to my 6yo. The DOS version from 1991.
She saw the pixalated graphics and went: "I like it, because it looks a bit like Minecraft."🙈
Also:I still remember first few levels. After 30 years. How is that even possible? My memory is bad, but I remember game lvls🤦
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I just published 2nd part of my investigation: LockSupport.parkNanos() Under the Hood and the Curious Case of Parking, Part II: Behavior on Windows
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Company heuristics:
1. 'Innovation departments' imply a lack of real innovation.
2. 'Agile' in job titles signals a rigid culture.
3. Too many 'strategy' meetings? There's no strategy!
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I use debuggers. Especially when working with unknown or complex code.
Attaching a debugger to tests is my way to learn how stuff works inside. I thought everyone was doing it that way 🤔
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Has anyone already tried
#1BRC
with CUDA?
I see most solutions use SWAR/SIMD to find semicolons. I wonder if there is an opportunity to load the entire input into VRAM, use CUDA to find all semicolons super fast and then just iterate over them.
PS: I know nothing about CUDA🤷♂️
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I was today years old when I had to study differences between cgroups v1 and v2 wrt to kernel dirty pages tracking.
This is a good read about v2:
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Good read about Memory Access Ordering Model:
Bonus: Have a look at this little piggie:
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I used to think I needed an external display, keyboard & other crap to work.
Today after lunch I had difficulties focusing on work. So I went for a walk.
I end-up working from a local "community garden". The whole afternoon. It was freaking fantastic! Fresh air does miracles.
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The same here, no Devoxx for me this year :(
I have some sugar coating tho: I can now turn the talk into a blog post. Chances are it'll work better as a blog anyway.
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I just noticed this little badge in my GitHub profile🦚
I guess I can stop hacking now, this is the peak! :)
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Me before checking JDK LongAdder impl: "It's just a thread-local register + on demand sum, how hard it could be?"
Me while looking at its src: "Kill me, please!"
G̶o̶t̶o̶ Labelled Break included.
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"Look ma, I can trade pointer chasing for memory allocations and still win in (some) benchmarks."
Seriously, this was quite a rollercoaster. I had a subtle bug causing perf. degradation. After fixing the bug it looks like a win in many situations. 😅😎
Today in QuestDB:
@jerrinot
is cooking something fancy. That's a specialized single string key hash table. The idea is to avoid redundant allocations and memcpy and, instead, put pointers to mmapped memory in the entries. The mem footprint is much lower and the table is faster.
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