投稿時間:2021-04-19 05:21:36 RSSフィード2021-04-19 05:00 分まとめ(25件)

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Program	[全てのタグ]の新着質問一覧｜teratail（テラテイル）	スプレッドシートにて、A1に特定の値を入力するとB2の値を削除し空白にする関数	https://teratail.com/questions/333977?rss=all	関数	2021-04-19 04:06:08
海外TECH	DEV Community	Product View Website Design | Using HTML CSS and JQuery	https://dev.to/alidevhash/product-view-website-design-using-html-css-and-jquery-56cl	Product View Website Design Using HTML CSS and JQueryProduct View Website Design Using HTML CSS and JQueryDemo gt	2021-04-18 19:51:32
海外TECH	DEV Community	Introduction to MySQL replication	https://dev.to/tutelaris/introduction-to-mysql-replication-97c	Introduction to MySQL replicationHello ultra devs ️Today I would like to talk about Replication and how it works in MySQL Let s start from the beginning If you know what replication is feel free to skip the next chapter What is replication Basically a replication mechanism means storing some copy of data on multiple machines How is it different from backups you may wonder Replication is a bit more than that When a backup is just a snapshot of the data in a certain time replication helps you to not only keep the copy of the data in real time ensuring availability but also facilitate the overload on the database providing both reading and writing to the client and therefore increase throughput Also replication helps you to distribute your data storage across the globe decreasing the response time for clients from different parts of the world In this article we will be talking about leader based replication and to continue our journey into this world it s required to introduce several terms Leader master part of the replication system eligible to write and read from the database Follower replica part of the replication system eligible only to read Basically leader is responsible for all inserts updates deletes and once these changes go through the leader it transfers these changes to all its followers that are responsible for reads and never writes Here is a simple example of single leader replication with two followers How it works in MySQL Ok now we know what replication is but how it actually works in MySQL How data got transferred from leader to followers and how MySQL keeps the consistency between them Imagine the situation that dev to is powered by MySQL You just wrote the article and clicked on the Publish button Here is what happens Data comes to the leader and get saved in the database The leader saves data changes in the special file called binary log Follower copies changes in binary log binlog to its own file called relay log Follower replays these changes from relay log to its own data As you can see to synchronize relay log with leader s binary log MySQL starts a worker thread that is called I O follower thread It s basically an ordinary client connection to the leader that starts reading its binary log Digging a bit into details we can ask a quite reasonable question in which format do binary log and relay log store the data Replication typesCurrently MySQL supports two types of replication Statement based replication Row based replication Statement based replicationSo as it s clear from the name statement based replication records the whole query that changed the state of the data in binlog So when a follower decides to synchronize its data with the leader it copies the query and replays it by executing this query and applying changes to its own data This kind of replication is very easy to implement and has multiple advantages It still works when the schema is different on the leader and the follower It s easy to audit and debug It requires not that much disk space Of course with great advantages comes great disadvantages Non deterministic functions With non deterministic functions it can come up with different data on leader and follower By non deterministic functions I mean function like the following CURRENT USER RAND IS FREE LOCK and so on Executing them first on leader and then on follower can lead to inconsistent data Performance penalty Imagine if you execute the following query INSERT INTO post statistics VALUES SELECT status AS statistics type COUNT id AS posts amount FROM posts GROUP BY status without having an index on the status field and after pressing Enter you just went for a tea a hypothetical situation I know you probably drink coffee The query got executed on leader consuming all available CPU and then follower picked up the baton copied the query to its relay log and cheerfully ate all CPU as well Triggers and stored routies Triggers and stored routines as well as Non deterministic functions can cause a lot of problems with different side effects on leader and follower So Statement based replication has its own advantages but big disadvantages Therefore not every database supports this type of replication but in the case of MySQL up until MySQL this type of replication was the only one supported Row based replicationCompare to Statement based replication Row based replication stores the actual data changes in binary log but not the query So when a follower replicates the data it doesn t execute the query but applies the changes to each record it was applied to on leader Let s consider the advantages of this approach Less CPU intensive If we execute the query described in Statement based replication chapter follower does not replay this query but copy the value and apply the change to its own data record So the query gets executed once and doesn t consume all available CPU Helps to find data inconsistency Since Row based replication stores the changes only when follower replays these changes and tries to apply to the data that exists on leader but doesn t exist on follower it throws the error Meanwhile statement based replication proceeds with what it has and keeps the inconsistency hidden complicating the ability to find the point of failure and fix it No non deterministic behavior Compare to statement based replication if you execute the query that has Non deterministic functions it ends up with the same result for both leader and follower Looks nice that s what we were expecting from replication right But along with the advantages come disadvantages High disk space consumption Yeah we just talked about Less CPU consuming for this replication but this doesn t work for all queries Imagine if you have the following statement UPDATE posts SET status draft WHERE status published Considering the fact that the posts table has about of Published posts this query becomes quite expensive since it requires storing of changes in binary replication log files Does not allow different schemas Sometimes it might be useful when you have different schemas on leader and follower I don t know about these cases but they definitely exist As it was described above row based replication throws an error in case of data inconsistency caused by different schemas Statement is not included in the binary log It can be not a problem at all until you try to debug or audit what s going on and what query caused damage to your database Row based replication makes it hard to analyze Now we are fluent in replication process language Everything is clear Hold on on the picture of replication example we can see one leader and two followers Can we do things differently ️‍ ️ MySQL supported topologies Single leader replicationThis type of replication is the most common one It is useful when you have a lot of reads but not that many writes You can distribute users reads among followers load balancing them and therefore providing better response time With this replication topology you can easily add one more follower to it Also this topology prevents a lot of problems that multiple leaders topology have will be described in Leader leader replication since it has only one leader Leader leader replicationAs it is visible from the picture this topology involves two leaders This topology is useful when you have different data centers in different locations and you need to provide fast writes to both regions But with this advantage comes a great cost Suppose we have a table post statistics and you just realized that the number of posts with Published status is triple more than it s actually written in table and you decide to fix the situation So you connect to MySQL and execute the following query UPDATE posts statistics SET posts amount posts amount WHERE status published Meanwhile somebody from a different part of the world just published his her first post just like me and triggered the following query to be executed UPDATE posts statistics SET posts amount posts amount Suppose the original number of posts was k Due to replication lag databases ended up with two different numbers and And no errors were thrown This is a big disadvantage of this topology and in practice it brings more problems than advantages But if you ended up with this topology it s better to add few more replicas to it Active passive leader leader replicationIn Active passive leader leader replication topology one server takes the role of the leader and another one takes the role of the follower But in comparison to the ordinary leader follower topology it allows you to swap easily the leader responsibility from one server to another It s useful in many cases For example if you execute ALTER TABLE that locks the whole table for reads and writes you can stop the replication process easily swap leader responsibility execute ALTER TABLE on the passive server then swap the responsibility back restore replication process and execute ALTER TABLE on the remaining server It can help you to keep your service alive while executing that expensive query Other topologiesThere are many other topologies that are supported by MySQL Replication Ring topology Tree of pyramid topologyAnd many others You can choose the best topology that fits your purposes or create your own This is the list of the most common topologies used in MySQL SummaryReplication is a mechanism of having a consistent copy of the data storage It provides Data distribution Load balancing Backups High availability and failover Leader based replication consists of leader and follower Both of them have their own journal of changes binary log and relay log There are two types of replication Statement based replication It s represented in queries itself Row based replication It s represented in direct data changes There are multiple topologies for replication Leader follower topology Leader leader topology Leader leader active passive topology Ring topology Tree of Pyramids topology And many specialized topologies together with custom ones That s it Thank you for your attention I hope you liked this post	2021-04-18 19:12:19
海外科学	BBC News - Science & Environment	Nasa's Ingenuity Mars helicopter set for first flight	https://www.bbc.co.uk/news/science-environment-56704481	agency	2021-04-18 19:09:22
医療系	医療介護 CBnews	手術の外来化を図り、急性期らしさを追求すべき- 先が見えない時代の戦略的病院経営（145）	https://www.cbnews.jp/news/entry/20210416201849	千葉大学医学部附属病院	2021-04-19 05:00:00
ニュース	BBC News - Home	Uefa furious at football clubs' breakaway plan	https://www.bbc.co.uk/sport/football/56794673	Uefa furious at football clubs x breakaway planUefa and the Premier League have strongly condemned major European clubs including the big six from England signing up to a breakaway European Super League	2021-04-18 19:48:49
ニュース	BBC News - Home	Leicester City 1-0 Southampton: Kelechi Iheanacho earns Foxes first FA Cup final spot since 1969	https://www.bbc.co.uk/sport/football/56725449	Leicester City Southampton Kelechi Iheanacho earns Foxes first FA Cup final spot since Kelechi Iheanacho s goal settles a tight contest as Leicester edge past Southampton at Wembley to reach their first FA Cup final since	2021-04-18 19:38:42
ニュース	BBC News - Home	Russia will face 'consequences' if Navalny dies - US	https://www.bbc.co.uk/news/world-europe-56794744	medical	2021-04-18 19:47:33
ニュース	BBC News - Home	Table Mountain fire 'burns out of control' in Cape Town	https://www.bbc.co.uk/news/world-africa-56793317	library	2021-04-18 19:03:53
ニュース	BBC News - Home	Nasa's Ingenuity Mars helicopter set for first flight	https://www.bbc.co.uk/news/science-environment-56704481	agency	2021-04-18 19:09:22
ニュース	BBC News - Home	Welsh Ambulance Service crew dropped woman, 89, off at wrong house	https://www.bbc.co.uk/news/uk-wales-56794652	house	2021-04-18 19:27:42
ニュース	BBC News - Home	FA Cup: Kelechi Iheanacho slots Leicester ahead against Southampton	https://www.bbc.co.uk/sport/av/football/56795481	FA Cup Kelechi Iheanacho slots Leicester ahead against SouthamptonKelechi Iheanacho notches his tenth goal in seven games to give Leicester City the lead in their FA Cup semi final against Southampton	2021-04-18 19:03:30
ビジネス	ダイヤモンド・オンライン - 新着記事	【入山章栄・動画】人材ネットワークで「ハブ」になる人となれない人の決定的な差 - 入山章栄の世界標準の経営理論	https://diamond.jp/articles/-/264511	【入山章栄・動画】人材ネットワークで「ハブ」になる人となれない人の決定的な差入山章栄の世界標準の経営理論本連載では、この『世界標準の経営理論』のエッセンスを、著者の入山章栄氏自身が解説する。	2021-04-19 04:55:00
ビジネス	ダイヤモンド・オンライン - 新着記事	マッキンゼー流！R＆Dの変革こそ、日本企業の「救世主」になる理由【動画】 - 有料記事限定公開	https://diamond.jp/articles/-/268298	技術革新	2021-04-19 04:50:00
ビジネス	ダイヤモンド・オンライン - 新着記事	戦慄の業績二極化「K字型決算」が来る！コロナが生んだ業界内“新序列“を解明 - 戦慄のK字決算	https://diamond.jp/articles/-/268477		2021-04-19 04:45:00
ビジネス	ダイヤモンド・オンライン - 新着記事	1100兆円がうごめく「水素バブル」到来！脱炭素ブームで新エネルギー源に急浮上 - 1100兆円の水素バブル	https://diamond.jp/articles/-/268308	市場規模	2021-04-19 04:40:00
ビジネス	ダイヤモンド・オンライン - 新着記事	中学受験がコロナで10年ぶりに激化！今後の受験対策は「低年齢化」加速か - 今週の週刊ダイヤモンド　ここが見どころ	https://diamond.jp/articles/-/268405	片や、関西の塾関係者は、この首都圏の中学受験ブームが「年入試では西にも波及する」と予想する。	2021-04-19 04:35:00
ビジネス	ダイヤモンド・オンライン - 新着記事	各都道府県で最も年収が低い企業ランキング2020【トップ5】 - ニッポンなんでもランキング！	https://diamond.jp/articles/-/268646	都道府県	2021-04-19 04:30:00
ビジネス	ダイヤモンド・オンライン - 新着記事	各都道府県で最も年収が低い企業ランキング2020【全46社完全版】 - ニッポンなんでもランキング！	https://diamond.jp/articles/-/268645	都道府県	2021-04-19 04:30:00
ビジネス	ダイヤモンド・オンライン - 新着記事	JR西日本が「極上の赤身肉」を販売、その狙いとは - News&Analysis	https://diamond.jp/articles/-/268456	newsampampanalysisjr	2021-04-19 04:25:00
ビジネス	ダイヤモンド・オンライン - 新着記事	出世かなわず愚痴ばかり…「ひねくれベテラン社員」をよみがえらせる処方箋 - 組織の病気～成長を止める真犯人～　秋山進	https://diamond.jp/articles/-/268737	自分	2021-04-19 04:20:00
ビジネス	ダイヤモンド・オンライン - 新着記事	手取り月収50万円役員の妻が「生活費のため」に借金を重ねたワケ - “残念サラリーマン”のお金相談所	https://diamond.jp/articles/-/268736	専業主婦	2021-04-19 04:15:00
ビジネス	ダイヤモンド・オンライン - 新着記事	いつの間にか成長している人の秘密、「1行書くだけ日記」で可能に？ - 要約の達人　from flier	https://diamond.jp/articles/-/268288	fromflier	2021-04-19 04:10:00
ビジネス	ダイヤモンド・オンライン - 新着記事	ビッグデータがつくる治療から予防へのヘルスリテラシー - フロネシス　10年先を見据えてビジネスを組み立てる実践知	https://diamond.jp/articles/-/266077		2021-04-19 04:05:00
ビジネス	東洋経済オンライン	外資系管理職が｢プレーヤー｣を辞めない理由 ｢ジョブ型｣雇用で生き残る管理職の条件とは | リーダーシップ・教養・資格・スキル | 東洋経済オンライン	https://toyokeizai.net/articles/-/421815?utm_source=rss&utm_medium=http&utm_campaign=link_back	東洋経済オンライン	2021-04-19 04:30:00