The stateless in the country are facing a desperate situation, according to Maalini Ramalo of the Development of Human Resources for Rural Areas, Malaysia (DHRRA).

“Stateless people are still people who were born in this country or who have been adopted by Malaysian parents. Malaysian families get affected, too, just because of a stateless person in their family.

“We need to support them through this period. It is unfortunate that the stateless are always left behind.”

本篇文章是個經驗分享文，作者分享使用 Docker 作為開發環境時值得注意的 Best practices，透過這些經驗分享希望能夠讓開發者少走一些冤枉路。

原文提出了 15 個經驗談，這邊幫大家節錄幾個，有興趣的可以點選原文瞭解更多!
1. One thing at a time
2. Be ephemeral
3. Utilize .dockerignore
4. Less is more
5. Secrets should be secret
6. PID 1 is your birth right
7. Share and Care
8. Vulnerability Scan
9. Tag like you mean it
10. Permissions are costly
11. Source of Truth
12. Always official
13. Don’t include debug
14. Use entry point script smartly
15. Size does matter

One thing at a time
建置 Image 的時候專注做好一件事情，每個 Image 應該有一個專心要解決的問題，譬如一個應用程式，一個小工具等。對於 Nginx 這類型的 Image 來說，應該沒有人會期望於裡面看到有 Apache 的應用程式吧?

Be ephemeral
這個主要探討的是該 Image 本身建置時應該要以 stateless 的概念去處理，未來不論是透過 docker 或是 Kubernetes 來管理部署時，Contaienr 都很有機會被重啟，每次的重啟都意味該容器是重新啟動。所以千萬不要讓你的 Image 變成多次重啟會導致應用程式出問題的形式，任何的這類型資料應該都要透過外部取得，不要塞到你的 Image 內

Utilize .dockerignore
善用 .dockerignore 這個檔案來將不必要的檔案從 build 過程給排除，使用方法與 .gitignore 類似。透過這個檔案的設定可以避免 docker build 的時候不會把一些過大或是完全不需要的檔案都送給 docker daemon，不當浪費時間也浪費空間。

Less is more
避免安裝任何無關或是非必要的套件到你的 image 中，特別是那些 "nice to have" 的理由。

註: 我個人是滿討厭把 Image 弄得很乾淨的，除錯什麼工具都沒有，連 ash/sh/busybox/bash 都沒有的 image 更是我討厭中的排行榜冠軍

Secrets should be secret
任何機密資訊都應該要於運行期間動態載入，而不是建置期間塞入。請使用其他工具譬如 Vault 來管理這些機密資訊，並且執行期間讓 Container 能夠存取到正確的值。

PID 1 is your birth right
Linux 環境下會使用 SIGTERN, SIGKILL 等相關的 Singal 來戳你的應用程式，請確保你運行的應用程式要能夠攔截這些訊號來處理並完成有效的 Graceful shutdown.

Share and Care
如果環境中有多個 Image 彼此有共享相同的工具與功能，與其每個 Image 都單獨建置維護不如建置一個 Base Image，接者讓所有要使用的 image 去載入使用即可。
透過這種方式可以讓整體的維護性與管理性更為簡單，每個 image 可以減少重複的程式碼，同時要升級時只要針對 base Image 處理即可。

https://medium.com/pradpoddar/avoid-costly-mistakes-using-advanced-docker-development-best-practices-acd812784109

📜 [專欄新文章] EIP2929, EIP2930 簡介
✍️ Anton Cheng
📥 歡迎投稿： https://medium.com/taipei-ethereum-meetup #徵技術分享文 #使用心得 #教學文 #medium

Opcode 加油Proposal，會不會讓以太坊變更貴呢

昨天在同事的推薦下發現了這個YouTube系列：Peep an EIP，也聽了Vitalik和Martin介紹EIP2929 + 2930的這一期。這兩個EIP都已經被列入下一次的硬分岔(Berlin Hardfork)，所以我就來寫個學習筆記。先打個預防針，本人對EVM可以說是非常不熟，但也希望藉著這個機會逼自己學習，如果有錯誤的話也希望懂的更多的各路大神可以不吝賜教。

Berlin without hardfork. (By Claudio Schwarz on Unsplash)

EIP2929: Gas cost increases for state access opcodes

乍看之下這是一個極為恐怖的Proposal。在Gas已經高到爆炸的2021年，理論上不應該再通過這種「加油」類的方案。不過不用緊張，其實這個EIP真正改變的是第一次access的價格，如果一筆交易內要執行一樣Opcode動作輛次，那麼gas cost 將降低為100。

Increases gas cost for SLOAD, *CALL, BALANCE, EXT* and SELFEDESTRUCT when used for the first time in a transaction.

大家都知道，合約最終會被Compile成一堆Opcode，這些Opcode也是用來計算最終交易手續費的依據：理論上越是花時間的的Opcode，應該要收越高的手續費。

但是一直以來，state access opcode 太便宜都是一個已知的問題：在2016年的上海DOS攻擊中，其中幾個攻擊的手法就是透過惡意交易大量讀取帳戶資訊、大量的創造合約再銷毀，或是不斷用 EXTCODESIZE 來讀合約大小等等，讓Client必須花大量的IO資源處理交易(需要讀寫disk的動作特別慢)，最終使Client程式Crash或是延長出塊時間。儘管大部分的弱點已經透過EIP150中大量提升gas cost獲得改善（還有其後的EIP1884），但在EIP2929中，也引用的這篇Paper的數據：現在replay所有以太坊上的交易，當時那些惡意交易中的worst case還會需要~80秒才能完成。這跟以太坊所定義的13秒出塊時間有著很大的差距，也代表這個潛在的攻擊是可行的。

透過增加這些opcode所需要的gas cost，可以降低每個區塊最大可能的讀取數。以下是偷抄Vitalik PPT 的數據：(12,500,000 為gas limit上限)

Pre-EIP 2929:

BALANCE spam: 12,500,000 / (400 cost + 320 address size + 50 boilerplate) = 16,233 accesses per block

CALL spam: 12,500,000 / (700 + 320 + 50) = 11,682 accesses per block

SLOAD spam: 12,500,000 gas / (800 + 25 boilerplate) = 15,151 accesses per block (but of a smaller tree)

Post-EIP 2929:

BALANCE spam: 12,500,000 / (2,600 + 320 + 50) = 4,280 accesses per block

CALL spam: 12,500,000 / (2,600 + 320 + 50) = 4,280 accesses per block

SLOAD spam: 12,500,000 / (2,100 + 25) = 5,882 accesses per block

說實在的這個數據的解釋也很廢話，就是把Opcode變得用貴，能Spam的數量越少。平均來說Gas cost 變高3倍，所以之前worst case的80秒執行時間可以被下降到大概 ~27秒。

SSTORE changes

在實作層，EVM會維繫一個本筆交易讀取過所有交易的 Set。每次有尚未讀取過的slot時，就會先收取一筆 CLOD_SLOAD_COST (2100) ，然後把這個slot加入這個set中，下次讀寫就會比較便宜。

對於已經讀取過的Slot，再次寫入的Opcode SSTORE 之gas cost為會降低為

5000 — COLD_SLOAD_COST (2100) = 2900

簡單的說，單純只操作一次 SSTORE 的總gas 會維持一樣在 5000 。但如果這個slot是之前有讀過的，則寫入的gas cost就會降低。近一步來說，一個 x += 100 ，其實會變得更便宜:

Pre-EIP-2929: 800 SLOAD + 5000 SSTORE = 5800
Post-EIP-2929: 2100 SLOAD + 2900 warm SSTORE = 5000

其他Side effects

這個改動除了降低了最高能夠spam的次數以外，也降低了以太坊想要做到stateless client，理論上最大的witness 大小。其實這裡的原理跟前面很類似，下圖的表格比較的是目前使用hexary tree所需要的witness大小：若12.5M的區塊全部塞滿該Opcode的witness，理論上最大會佔多少空間。在EIP2929之後由於gas cost增加，就壓縮了最大可能的witness size.

這裡單純只比較增加gas cost後，對於max witness size的影響。影片中有提到其他許多方法旨在減少Witness bytes，包括使用binary tree而不是hexary tree，以及用Code Merklization等等。這些其他方法也能夠降低最後的Max Witness size，但跟這個EIP沒有直接相關。不過可以注意的一點是，這些其他在witness size上面的優化跟 gas cost 所帶來的優化的效果是可以相乘的，例如 SLOAD，更改gas price已經能夠讓max size 縮小2.6倍，若是改用Binary tree可以將 Witness bytes降低到 288 bytes，就會是再3~倍的優化。

對用戶的影響

依照Martin Swende 給出的數據，這個EIP對於一般交易的影響僅有提高0.3~0.4%。理由很簡單，雖然第一次access storage變貴了，但是後面幾次讀寫就會變得便宜。大部分應用的程式邏輯都是類似的幾個變數進行讀寫，因此可能有不少的動作反而會變得更便宜。一個最簡單的例子就是ERC20 Transfer，兩個餘額的 +=和 -= 都會變便宜，所以總共的花費也是變便宜的。

這其中也會對於Solidity的開發pattern有著一定程度的影響，我目前想到的影響可能有兩個：

由於多次的storage access變便宜，永遠cache state variables不再是一個最佳策略。以前我們會盡量想辦法減少寫入state storage的次數，現在可能會基於coding style考量減少一些的memory cache。

之前寫合約都會盡量避免external call，甚至會寫一些一次把所有 variable都回傳回來的笨函示，來避免多次的external calls。這有一部分原因是因為每次external call都會需要使用到 EXTCODESIZE 這個Opcode所以很貴。但如果 EXT 系列的Opcode也變得越call越便宜，那麼這個一次全部call 回來cache 住的pattern也可能改變。

以上兩個想法都還沒有經過實證，如果之後看到更有證據的分析的話，也會來這裡分享。

EIP2930: Optional access lists

EIP2929可能會影響一些鏈上的合約，因為有些合約有hardcode external call的gas 上限。對於這方面的問題，EIP2930提出一個新的交易類型，讓交易中多帶一個access list，即所有這筆交易即將讀寫的storage slot，並且先幫忙付掉第一次讀寫的gas，而真正交易讀寫該storage時，只會被要求付100 gas。

這不但可以避免這次EIP2929帶來的副作用，也可以被使用在其他因為gas price 改變的硬分岔升級而壞掉的合約，例如在EIP1184 增加 SLOAD gas price 時影響到的 Aragon 和Kyber 等等。儘管當時升級前各大專案都有幫助用戶提出migration 方案，但如果有人曾經卡錢在裡面，也可以Follow一下這次柏林Hardfork。

小結

新的一年就用一篇簡單的文章來開頭。最近發現自己以前的學習習慣有點亂無章法，所以新年整理了reading list，逼自己做筆記，順便發想一些想要寫的主題。今年的期許就是學更多Ethereum底層一點的知識，當然還有上層一點Defi的知識。也歡迎大家分享一下自己都是怎麼follow這麼多東西的><

EIP2929, EIP2930 簡介 was originally published in Taipei Ethereum Meetup on Medium, where people are continuing the conversation by highlighting and responding to this story.

👏 歡迎轉載分享鼓掌

(originally shot on 2nd August 2019)

UNICEF Malaysia Ambassador, Lisa Surihani and I travel to The Netherlands to attend a Summer Course on Statelessness.

During our 5 day course, Lisa and I were asked to present a short presentation about "“Communications and awareness-raising around statelessness”.

This 2nd episode shares how Lisa and I came about advocating the plight of stateless people in Malaysia - children in particular and how we used our social media platform to create the awareness amongst our peers and followers.

Please find time to watch this vlog, so you too can continue spreading the awareness about this and to mount pressure on our policy-makers in ending statelessness NOW!

Thank you Airbnb for comping our stay.

It truly means a lot that you helping our advocacy work in highlighting the plight of the stateless.

Everyone has the right to feel belonged. We should not rob them from their rights to live a life of dignity.

Airbnb's brand is built on the simple philosophy of belonging and this ties beautifully with UNCHR's #iBELONG Global Campaign to end statelessness by 2024, as well as my believe that everyone should have a home that they can truly call, a home.



Thanks for watching and please do not forget to subscribe!

Also follow me on my other social media channels:

Instagram
https://www.instagram.com/daphneiking/
Facebook
https://www.facebook.com/daphneiking/
Twitter
https://twitter.com/DaphCLPT

If you also need my profile and showreel, please visit:
joelebosi.wix.com/bedifulstory
Thanks for watching and please do not forget to subscribe!

Also follow me on my other social media channels:

Instagram
https://www.instagram.com/daphneiking/
Facebook
https://www.facebook.com/daphneiking/
Twitter
https://twitter.com/DaphCLPT

If you also need my profile and showreel, please visit:
joelebosi.wix.com/bedifulstory

(originally shot on 2nd August 2019)

UNICEF Malaysia Ambassador, Lisa Surihani and I travel to The Netherlands to attend a Summer Course on Statelessness.

Find out if we pass the friendship test as we travel, study AND live together in our quaint Airbnb house, just 15 minutes away from Tilburg University.

Thank you Airbnb for comping our stay.

It truly means a lot that you helping our advocacy work in highlighting the plight of the stateless.

Everyone has the right to feel belonged. We should not rob them from their rights to live a life of dignity.

Airbnb's brand is built on the simple philosophy of belonging and this ties beautifully with UNCHR's #iBELONG Global Campaign to end statelessness by 2024, as well as my believe that everyone should have a home that they can truly call, a home.



Thanks for watching and please do not forget to subscribe!

Also follow me on my other social media channels:

Instagram
https://www.instagram.com/daphneiking/
Facebook
https://www.facebook.com/daphneiking/
Twitter
https://twitter.com/DaphCLPT

If you also need my profile and showreel, please visit:
joelebosi.wix.com/bedifulstory
Thanks for watching and please do not forget to subscribe!

Also follow me on my other social media channels:

Instagram
https://www.instagram.com/daphneiking/
Facebook
https://www.facebook.com/daphneiking/
Twitter
https://twitter.com/DaphCLPT

If you also need my profile and showreel, please visit:
joelebosi.wix.com/bedifulstory

Everyone deserves a basic education. I made a trip down to Alor Setar, Kedah where my old childhood friend Sherril Netto has been doing some amazing work with the NTA School for Refugee Children. She co-founded this place over five years ago with two friends, Marianne and Dave Kameron when they were approached by the local Rohingya community for teachers so that their children could get a basic education, offering Marianne what little money they had for tuition.

The parents of children in the community had initially started teaching their kids in someone's house, then pooled enough money to rent a small, but roasting-hot shoplot with no fan or toilet facilities. Marianne started off volunteering as a teacher there, but soon realised conditions were not conducive to learning, and that's what sparked the effort to raise funds for the NTA School for Refugee Children, which is now just one of a number of projects they have under an umbrella organisation called Peaceworks, where they work with the local Rohingya community.

Find out more about what they do at
http://bit.ly/2wlWZOW
www.ntainaction.org
https://www.facebook.com/NTASE/
https://www.instagram.com/nta_imagery/

For more bits and bobs from me:
website l www.nadiaheng.com
blog l www.nadiaheng.com/3footuniverse
facebook l @official.nadiaheng
instagram l @nadiaheng