Upgrade to Pro
— share decks privately, control downloads, hide ads and more …
Speaker Deck
Features
Speaker Deck
PRO
Sign in
Sign up for free
Search
Search
Distributed Elixir
Search
Maciej Kaszubowski
July 07, 2018
Programming
0
90
Distributed Elixir
Presentation about some of the tools for distributed programming in Elixir
Maciej Kaszubowski
July 07, 2018
Tweet
Share
More Decks by Maciej Kaszubowski
See All by Maciej Kaszubowski
Error-free Elixir
mkaszubowski
0
210
Modular Design in Elixir (ElixirConf EU 2019)
mkaszubowski
2
530
The Big Ball of Nouns
mkaszubowski
0
85
Modular Design in Elixir
mkaszubowski
1
320
Our three years with Elixir
mkaszubowski
0
180
Concurrency Basics for Elixir
mkaszubowski
0
92
Software Architecture
mkaszubowski
0
110
Let it crash - fault tolerance in Elixir/OTP
mkaszubowski
0
330
CRDTs - The science behind Phoenix Presence
mkaszubowski
2
230
Other Decks in Programming
See All in Programming
さきがけから振り返るアーキテクチャ刷新 / Reflecting on the Architectural Renewal from the Vanguard
nrslib
2
770
Javaの現状2024夏 / Java current status 2024 summer
kishida
4
1.4k
Rustのweb開発を助ける 便利なツール紹介
yuki0418
1
190
日付と正規化
megmogmog1965
0
140
Trial
cairolibrary720
1
130
最近追加した型の紹介とその振り返り
aki19035vc
0
170
コード生成を伴うLLMエージェント - 2024.07.18 Tokyo AI
smiyawaki0820
11
4.1k
社内 LT 会を発足し、アウトプット文化を醸成させるために考えたこと・やったこと / Starting internal LT meetings and fostering an output culture
mackey0225
3
120
APIのない大学ログインWebサービスをWKWebViewとJavaScriptでアプリ化した話
akidon0000
1
330
MIERUNE BBQにおけるユーザー中心設計()
mierune
PRO
1
110
Modern Angular: Renovation for Your Applications
manfredsteyer
PRO
0
140
12年前の『型システム入門』翻訳の思い出話
mame
11
1.2k
Featured
See All Featured
Building Applications with DynamoDB
mza
89
5.8k
The Illustrated Children's Guide to Kubernetes
chrisshort
39
47k
Code Review Best Practice
trishagee
58
16k
How to Create Impact in a Changing Tech Landscape [PerfNow 2023]
tammyeverts
34
1.9k
Creating an realtime collaboration tool: Agile Flush - .NET Oxford
marcduiker
16
1.6k
Fashionably flexible responsive web design (full day workshop)
malarkey
399
65k
10 Git Anti Patterns You Should be Aware of
lemiorhan
652
58k
How STYLIGHT went responsive
nonsquared
93
5k
How To Stay Up To Date on Web Technology
chriscoyier
784
250k
Facilitating Awesome Meetings
lara
46
5.8k
The Invisible Customer
myddelton
117
13k
Code Reviewing Like a Champion
maltzj
517
39k
Transcript
It’s scary out there
Organisational Matters
None
We’re 1 year old!
Summer break (probably)
We’re looking for speakers!
It’s scary out there Distributed Systems in Elixir Poznań Elixir
Meetup #8
None
Pid 1 Pid 2
Pid 1 Pid 2 Node A Node B
The basics
iex --name
[email protected]
--cookie cookie -S mix
Node.connect(:’
[email protected]
')
(DEMO)
#PID<0.94.0>
#PID<0.94.0> node identifier (relative to current node)
#PID<0.94.0> node identifier (relative to current node) 0 =a local
process
#PID<0.94.0> Process id node identifier (relative to current node)
How does it work?
Pid 1 Node A Pid 2 Node B
Pid 1 Node A Pid 2 Node B TCP Connection
send(pid2, msg) Pid 1 Node A Pid 2 Node B
TCP Connection
send(pid2, msg) Pid 1 Node A Pid 2 Node B
destination_node = node(pid) TCP Connection
send(pid2, msg) Pid 1 Node A Pid 2 Node B
destination_node = node(pid) :erlang.term_to_binary(msg) TCP Connection
send(pid2, msg) Pid 1 Node A Pid 2 Node B
destination_node = node(pid) :erlang.term_to_binary(msg) TCP Connection
send(pid2, msg) Pid 1 Node A Pid 2 Node B
destination_node = node(pid) :erlang.term_to_binary(msg) TCP Connection :erlang.binary_to_term(encode)
send(pid2, msg) Pid 1 Node A receive msg Pid 2
Node B destination_node = node(pid) :erlang.term_to_binary(msg) TCP Connection :erlang.binary_to_term(encode)
Distributed Systems?
Distributed Systems? Solved!
Well, not exactly…
Difficulties
Node A Node B
Node A Node B Node C
Node A Node B Node C Node D
None
A lot of messages
us-east-1 us-west-2
8 fallacies of distributed computing
fallacies of distributed computing 1. The network is reliable 2.
Latency is zero 3. Bandwidth is infinite 4. The network is secure 5. Topology doesn’t change 6. The is one administrator 7. Transport cost is zero 8. The network is homogenous
CAP THEOREM
CAP THEOREM us-west-2 us-east-1
CAP THEOREM us-west-2 us-east-1 Set X=5
CAP THEOREM us-west-2 us-east-1 Set X=5 Read X
CAP THEOREM us-west-2 us-east-1 Set X=5 Set X = 7
Consistency or Availability (under network partition)
Consistency or Speed In practice
Guarantees
Pid 1 Pid 2 Pid3 Guarantees m1, m2, m3 m4,
m5, m6 send(pid2, m1) send(pid2, m2) send(pid2, m3) send(pid2, m4) send(pid2, m5) send(pid2, m6)
Pid 1 Pid 2 Pid3 Guarantees m1, m2, m3 m4,
m5, m6 send(pid2, m1) send(pid2, m2) send(pid2, m3) send(pid2, m4) send(pid2, m5) send(pid2, m6) Ordering between two processes is preserved
Pid 1 Pid 2 Pid3 Guarantees m4, m5, m6 send(pid2,
m1) send(pid2, m2) send(pid2, m3) send(pid2, m4) send(pid2, m5) send(pid2, m6) m1, m2, m3 Delivery is not guaranteed
Pid 1 Pid 2 Pid3 Guarantees m1, m2, m3 m4,
m5, m6 send(pid2, m1) send(pid2, m2) send(pid2, m3) send(pid2, m4) send(pid2, m5) send(pid2, m6) Ordering between different processes is not guaranteed
[m1, m2, m3, m4, m5, m6]
[m1, m2, m3, m4, m5, m6] [m4, m5, m6, m1,
m2, m3]
[m1, m2, m3, m4, m5, m6] [m4, m5, m6, m1,
m2, m3] [m1, m4, m2, m5, m3, m6]
[m1, m2, m3, m4, m5, m6] [m4, m5, m6, m1,
m2, m3] [m1, m4, m2, m5, m3, m6] [m1, m2, m3]
[m1, m2, m3, m4, m5, m6] [m4, m5, m6, m1,
m2, m3] [m1, m4, m2, m5, m3, m6] [m1, m2, m3] [m1, m3, m5, m6]
[m1, m2, m3, m4, m5, m6] [m4, m5, m6, m1,
m2, m3] [m1, m4, m2, m5, m3, m6] [m1, m2, m3] [m1, m3, m5, m6] []
[m1, m2, m3, m4, m5, m6] [m4, m5, m6, m1,
m2, m3] [m1, m4, m2, m5, m3, m6] [m1, m2, m3] [m1, m3, m5, m6] [] [m1, m3, m2, m4, m5, m6]
[m1, m2, m3, m4, m5, m6] [m4, m5, m6, m1,
m2, m3] [m1, m4, m2, m5, m3, m6] [m1, m2, m3] [m1, m3, m5, m6] [] [m1, m3, m2, m4, m5, m6] [M3, M3]
Phoenix Request A User Logged In
Phoenix Request A Phoenix Request B User Logged In User
Logged OUT
Phoenix Request A Phoenix Request B User Logged In User
Logged OUT This Can arrive first
Unfortunately, things tend to work fine locally
The Tools
:global
Pid 1 Node A Node B Pid 2
Pid 1 Node A Node B Pid 2 :global.register_name(“global”, self())
Pid 1 Node A Node B Pid 2 :global.register_name(“global”, self())
Register PId1 as “global”
Pid 1 Node A Node B Pid 2 :global.register_name(“global”, self())
Register PId1 as “global” Sure
Pid 1 Node A Node B Pid 2 :global.register_name(“global”, self())
Register PId1 as “global” Sure :global.whereis_name(“global”) = pid1
Pid 1 Node A Node B Pid 2 :global.register_name(“global”, self())
:global.register_name(“global”, self()) ?
(DEMO)
:global • single process registration (if everything works OK) •
Favours availability over consistency • Information stored locally (reading is fast) • Registration is blocking (may be slow)
:PG2
Pid1 Pid3 Pid2 [] [] []
Pid1 Pid3 Pid2 :pg2.create(“my_group”) [] [] []
Pid1 Pid3 Pid2 [] [] [] join join :pg2.join(“my_group”, self()
Pid1 Pid3 Pid2 [] [pid1] [] Monitor Monitor :pg2.join(“my_group”, self()
Pid1 Pid3 Pid2 [pid1] [pid1] [pid1] Monitor Monitor :pg2.join(“my_group”, self()
Pid1 Pid3 Pid2 [pid1] [pid1] [pid1]
Pid1 Pid3 Pid2 :pg2.join(“my_group”, self() [pid1] [pid1, pid2] [pid1]
Pid1 Pid3 Pid2 join :pg2.join(“my_group”, self() join [pid1, pid2] [pid1,
pid2] [pid1, pid2]
Pid1 Pid3 Pid2 [pid1] [pid2] [pid1]
Pid1 Pid3 Pid2 [pid1] [pid2] [pid1]
Pid1 Pid3 Pid2 [pid1] [pid2] [pid1]
Pid1 Pid3 Pid2 [pid1, pid2] [pid1, pid2] [pid1, pid2]
It will heal, but the state in inconsistent for some
time
What does it matter?
Node A Pg2 Pg2 Pg2 Node B Node C
Node A Pg2 Pg2 Pg2 Node B Node C Phoenix
Channels
Node A Pg2 Pg2 Pg2 Node B Node C Phoenix
Presence
Node A Pg2 Pg2 Pg2 Node B Node C Phoenix
Channels
:pg2 • Process groups • Favours availability over consistency •
Information stored locally (reading is fast) • Registration is blocking (may be slow)
Strongly consistent Solutions
Strongly consistent Solutions • Consensus - Raft, Paxos, ZAB •
Two-phase commit/THree-phase commit (2PC/3PC) • Read/Write quorums • Single database as a source of truth
Summary
Distributed Systems
Well, not exactly…
Asynchronous messages Distributed systems are all about
Really, there’s no magic
Just asynchronous messages between nodes
Just asynchronous messages between nodes & node failures
Just asynchronous messages between nodes & node failures & Communication
failures
Just asynchronous messages between nodes & node failures & Communication
failures & Network partitions
Tradeoffs Distributed systems are all about
Where to go next
Worth looking at • Riak_core • RAFT • Two-Phase Commit
(2PC) / Three-Phase Commit (3PC) • CRDTs • LASP and Partisan
Free online (click!) Elixir / Erlang
Free PDF (Click!) Distributed Systems
Theory (The hard stuff)
• https://raft.github.io/ (Raft Consensus) • http://learnyousomeerlang.com/distribunomicon • https://www.rgoarchitects.com/Files/fallacies.pdf (Fallacies of
distributed computing) • https://dzone.com/articles/better-explaining-cap-theorem (CAP Theorem) • https://medium.com/learn-elixir/message-order-and-delivery-guarantees-in-elixir- erlang-9350a3ea7541 (Elixir message delivery guarantees) • https://lasp-lang.readme.io/ (LASP) • https://arxiv.org/pdf/1802.02652.pdf (Partisan Paper) • https://bravenewgeek.com/tag/three-phase-commit/ (3PC)
We’re looking for speakers!
Thank You! Poznań Elixir Meetup #8