Added leaderless replication write conflict example.

CSSE6400 · Apr 16, 2024 · 1e5b56e · 1e5b56e
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Showing 35 changed files with 196 additions and 23 deletions.
diff --git a/slides/distributed2/diagrams/Async.png b/slides/distributed2/diagrams/Async.png
diff --git a/slides/distributed2/diagrams/AsyncLag.png b/slides/distributed2/diagrams/AsyncLag.png
diff --git a/slides/distributed2/diagrams/AvoidWriteConflict.png b/slides/distributed2/diagrams/AvoidWriteConflict.png
diff --git a/slides/distributed2/diagrams/FocusDB.png b/slides/distributed2/diagrams/FocusDB.png
diff --git a/slides/distributed2/diagrams/LeaderFollower.png b/slides/distributed2/diagrams/LeaderFollower.png
diff --git a/slides/distributed2/diagrams/LeaderFollowerSpread.png b/slides/distributed2/diagrams/LeaderFollowerSpread.png
diff --git a/slides/distributed2/diagrams/Leaderless.png b/slides/distributed2/diagrams/Leaderless.png
diff --git a/slides/distributed2/diagrams/LeaderlessCoordinator.png b/slides/distributed2/diagrams/LeaderlessCoordinator.png
diff --git a/slides/distributed2/diagrams/LeaderlessExampleBad.png b/slides/distributed2/diagrams/LeaderlessExampleBad.png
diff --git a/slides/distributed2/diagrams/LeaderlessExampleRead.png b/slides/distributed2/diagrams/LeaderlessExampleRead.png
diff --git a/slides/distributed2/diagrams/LeaderlessExampleWrite.png b/slides/distributed2/diagrams/LeaderlessExampleWrite.png
diff --git a/slides/distributed2/diagrams/LeaderlessExampleWrite.puml b/slides/distributed2/diagrams/LeaderlessExampleWrite.puml
@@ -57,7 +57,7 @@ note right of db3
   | 4321 | Lifelike Inflatable Elephant | 5 | $50.00 |
 end note
 
-Rel(client, db, "Rename Inflatable", $tags="browser")
+Rel_D(client, db, "Rename Inflatable", $tags="browser")
 Rel(client, db2, "Rename Inflatable", $tags="browser")
 
 Lay_L(db2, db3)

diff --git a/slides/distributed2/diagrams/LeaderlessExampleWriteConflict1.png b/slides/distributed2/diagrams/LeaderlessExampleWriteConflict1.png
diff --git a/slides/distributed2/diagrams/LeaderlessExampleWriteConflict1.puml b/slides/distributed2/diagrams/LeaderlessExampleWriteConflict1.puml
@@ -0,0 +1,67 @@
+@startuml LeaderlessExampleWriteConflict1
+
+left to right direction
+
+!include https://raw.githubusercontent.com/plantuml-stdlib/C4-PlantUML/master/C4_Dynamic.puml
+
+!define DEVICONS https://raw.githubusercontent.com/tupadr3/plantuml-icon-font-sprites/master/devicons
+!include DEVICONS/laravel.puml
+!include DEVICONS/javascript.puml
+!include DEVICONS/mysql.puml
+!include DEVICONS/chrome.puml
+
+!define AWSPuml https://raw.githubusercontent.com/awslabs/aws-icons-for-plantuml/v11.1/dist
+!includeurl AWSPuml/AWSCommon.puml
+!includeurl AWSPuml/Database/RDS.puml
+!includeurl AWSPuml/Compute/EC2.puml
+!includeurl AWSPuml/Compute/EC2AutoScaling.puml
+!includeurl AWSPuml/NetworkingContentDelivery/ElasticLoadBalancing.puml
+!includeurl AWSPuml/Storage/SimpleStorageService.puml
+' make orange
+AddContainerTag("AWS", $borderColor="#ff9900", $bgColor="#ffffff", $fontColor="#000000")
+
+AddContainerTag("browser", $bgColor="#bcddfc", $fontColor="#000000")
+AddContainerTag("database", $bgColor="#ccfddd", $fontColor="#000000", $borderColor="#cccccc")
+
+skinparam roundcorner 20
+skinparam Padding 20
+skinparam NoteBorderColor transparent
+skinparam NoteBackgroundColor #FDDDCC
+' skinparam NoteFontColor white
+
+UpdateElementStyle(node, $borderColor="#cccccc", $fontColor="#5c5c5c")
+UpdateElementStyle(container, $bgColor="#5388cb")
+
+hide stereotype
+
+Container(client1, "Customer", "")
+Container(client2, "Fulfillment Centre", "")
+
+ContainerDb(db, "Replica 1", "Container: Cassandra", $tags="database")
+note right of db
+  |= product_id |= name |= stock |= price |
+  | 1234 | Nicholas Cage Reversable Pillow | 20 | $10.00 |
+  | 4321 | Lifelike Inflatable Elephant | 5 | $50.00 |
+end note
+
+ContainerDb(db2, "Replica 2", "Container: Cassandra", $tags="database")
+note right of db2
+  |= product_id |= name |= stock |= price |
+  | 1234 | Nicholas Cage Reversable Pillow | 20 | $10.00 |
+  | 4321 | Lifelike Inflatable Elephant | 5 | $50.00 |
+end note
+
+ContainerDb(db3, "Replica 3", "Container: Cassandra", $tags="database")
+note right of db3
+  |= product_id |= name |= stock |= price |
+  | 1234 | Nicholas Cage Reversable Pillow | 20 | $10.00 |
+  | 4321 | Lifelike Inflatable Elephant | 5 | $50.00 |
+end note
+
+Rel(client1, db2, "Query Product 1234", $tags="browser")
+Rel_D(client1, db, "Query Product 1234", $tags="browser")
+
+Lay_L(db2, db3)
+Lay_U(db3, client2)
+
+@enduml
diff --git a/slides/distributed2/diagrams/LeaderlessExampleWriteConflict2.png b/slides/distributed2/diagrams/LeaderlessExampleWriteConflict2.png
diff --git a/slides/distributed2/diagrams/LeaderlessExampleWriteConflict2.puml b/slides/distributed2/diagrams/LeaderlessExampleWriteConflict2.puml
@@ -0,0 +1,73 @@
+@startuml LeaderlessExampleWriteConflict2
+
+left to right direction
+
+!include https://raw.githubusercontent.com/plantuml-stdlib/C4-PlantUML/master/C4_Dynamic.puml
+
+!define DEVICONS https://raw.githubusercontent.com/tupadr3/plantuml-icon-font-sprites/master/devicons
+!include DEVICONS/laravel.puml
+!include DEVICONS/javascript.puml
+!include DEVICONS/mysql.puml
+!include DEVICONS/chrome.puml
+
+!define AWSPuml https://raw.githubusercontent.com/awslabs/aws-icons-for-plantuml/v11.1/dist
+!includeurl AWSPuml/AWSCommon.puml
+!includeurl AWSPuml/Database/RDS.puml
+!includeurl AWSPuml/Compute/EC2.puml
+!includeurl AWSPuml/Compute/EC2AutoScaling.puml
+!includeurl AWSPuml/NetworkingContentDelivery/ElasticLoadBalancing.puml
+!includeurl AWSPuml/Storage/SimpleStorageService.puml
+' make orange
+AddContainerTag("AWS", $borderColor="#ff9900", $bgColor="#ffffff", $fontColor="#000000")
+
+AddContainerTag("browser", $bgColor="#bcddfc", $fontColor="#000000")
+AddContainerTag("database", $bgColor="#ccfddd", $fontColor="#000000", $borderColor="#cccccc")
+
+skinparam roundcorner 20
+skinparam Padding 20
+skinparam NoteBorderColor transparent
+skinparam NoteBackgroundColor #FDDDCC
+' skinparam NoteFontColor white
+
+UpdateElementStyle(node, $borderColor="#cccccc", $fontColor="#5c5c5c")
+UpdateElementStyle(container, $bgColor="#5388cb")
+
+hide stereotype
+
+Container(client1, "Customer", "")
+Container(client2, "Fulfillment Centre", "")
+
+ContainerDb(db, "Replica 1", "Container: Cassandra", $tags="database")
+note right of db
+  |= product_id |= name |= stock |= price |
+  | 1234 | Nicholas Cage Reversable Pillow | 20 | $10.00 |
+  | 4321 | Lifelike Inflatable Elephant | 5 | $50.00 |
+end note
+
+ContainerDb(db2, "Replica 2", "Container: Cassandra", $tags="database")
+note right of db2
+  |= product_id |= name |= stock |= price |
+  | 1234 | Nicholas Cage Reversable Pillow | <color:red>19</color> | $10.00 |
+  | 4321 | Lifelike Inflatable Elephant | 5 | $50.00 |
+end note
+
+ContainerDb(db3, "Replica 3", "Container: Cassandra", $tags="database")
+note right of db3
+  |= product_id |= name |= stock |= price |
+  | 1234 | Nicholas Cage Reversable Pillow | 19 | $10.00 |
+  | 4321 | Lifelike Inflatable Elephant | 5 | $50.00 |
+end note
+
+' Rel_D(client1, db2, "Query Product 1234", $tags="browser")
+' Rel_D(client1, db, "Query Product 1234", $tags="browser")
+
+Rel_D(client2, db3, "Decrease Stock of Product 1234", $tags="browser")
+Rel_D(client2, db2, "Decrease Stock of Product 1234", $tags="browser")
+
+Rel_D(client1, db2, "Order 20 Items of 1234", $tags="browser")
+Rel_D(client1, db, "Order 20 Items of 1234", $tags="browser")
+Rel_U(db2, client1, "Error", $tags="browser")
+
+Lay_L(db2, db3)
+
+@enduml
diff --git a/slides/distributed2/diagrams/LeaderlessQuorum.png b/slides/distributed2/diagrams/LeaderlessQuorum.png
diff --git a/slides/distributed2/diagrams/MonotonicReads.png b/slides/distributed2/diagrams/MonotonicReads.png
diff --git a/slides/distributed2/diagrams/MultiLeader.png b/slides/distributed2/diagrams/MultiLeader.png
diff --git a/slides/distributed2/diagrams/Partitioning.png b/slides/distributed2/diagrams/Partitioning.png
diff --git a/slides/distributed2/diagrams/PartitioningExample.png b/slides/distributed2/diagrams/PartitioningExample.png
diff --git a/slides/distributed2/diagrams/PartitioningLB1.png b/slides/distributed2/diagrams/PartitioningLB1.png
diff --git a/slides/distributed2/diagrams/PartitioningLB2.png b/slides/distributed2/diagrams/PartitioningLB2.png
diff --git a/slides/distributed2/diagrams/PartitioningLB3.png b/slides/distributed2/diagrams/PartitioningLB3.png
diff --git a/slides/distributed2/diagrams/ReadYourWrites.png b/slides/distributed2/diagrams/ReadYourWrites.png
diff --git a/slides/distributed2/diagrams/ReadYourWritesExample.png b/slides/distributed2/diagrams/ReadYourWritesExample.png
diff --git a/slides/distributed2/diagrams/Replication.png b/slides/distributed2/diagrams/Replication.png
diff --git a/slides/distributed2/diagrams/ReplicationLag.png b/slides/distributed2/diagrams/ReplicationLag.png
diff --git a/slides/distributed2/diagrams/ResolveWriteConflict.png b/slides/distributed2/diagrams/ResolveWriteConflict.png
diff --git a/slides/distributed2/diagrams/Sahara.png b/slides/distributed2/diagrams/Sahara.png
diff --git a/slides/distributed2/diagrams/SaharaScaled.png b/slides/distributed2/diagrams/SaharaScaled.png
diff --git a/slides/distributed2/diagrams/Sync.png b/slides/distributed2/diagrams/Sync.png
diff --git a/slides/distributed2/diagrams/SyncVsAsync.png b/slides/distributed2/diagrams/SyncVsAsync.png
diff --git a/slides/distributed2/diagrams/WriteConflict.png b/slides/distributed2/diagrams/WriteConflict.png
diff --git a/slides/distributed2/main.tex b/slides/distributed2/main.tex
@@ -209,10 +209,13 @@
 {braewebb}%
 {}%
 {}%
+\note[item]<1->{Read user details.\vspace{1em}}
 
 \only<2->{
 \includegraphics[width=0.3\textwidth]{diagrams/ReadYourWrites}
 }
+\note[item]<2->{Decide I don't like my name.\vspace{1em}}
+\note[item]<2->{Update name.\vspace{1em}}
 
 \only<3->{
 \tweet%
@@ -222,20 +225,16 @@
 {}%
 {}%
 }
+\note[item]<3->{Read user details.}
+
 \end{center}
 \end{frame}
-\note[itemize]{
-    \item Read user details
-    \item Decide I don't like my name
-    \item Update name
-    \item Read user details
-}
 
 \image{diagrams/ReadYourWritesExample}
 \note[itemize]{
     \item Typical interaction in simple Leader-Follower replication.
-    \item Write is to \textit{leader}.
-    \item Read is from \textit{follower}.
+    \item Write is to \highlight{leader}.
+    \item Read is from \highlight{follower}.
     \item \textit{Replication lag} means reading a field immediately after updating it \highlight{may} lead to reading \highlight{stale} data.
 }
 
@@ -254,6 +253,7 @@
 {My fist post}%
 {}%
 }
+\note[item]<1->{Misspell a tweet.\vspace{1em}}
 
 \only<2->{
 \tweet%
@@ -263,6 +263,7 @@
 {My first post}%
 {}%
 }
+\note[item]<2->{Correct spelling, and I see my \textit{updated} tweet.\vspace{1em}}
 
 \only<3->{
 \tweet%
@@ -272,13 +273,9 @@
 {My fist post}%
 {}%
 }
+\note[item]<3->{Other users may still see \textit{stale}, misspelt post.}
 \end{center}
 \end{frame}
-\note[enumerate]{
-    \item Misspell a tweet.
-    \item Correct spelling, and I see my \textit{updated} tweet.
-    \item Other users may still see \textit{stale}, misspelt post.
-}
 
 \image{diagrams/MonotonicReads}
 \note[itemize]{
@@ -305,14 +302,20 @@
 \point[Second approach]{Multi-leader Replication}
 
 \image[height=\textheight]{diagrams/MultiLeader}
+\note[itemize]{
+    \item Application can be partitioned to perform certain types of writes to a specific leader.
+    \item Reads are from replicas, as with Leader-Follower replication.
+}
 
 \point[Why multi-leader?]{
+\vspace{1em}
 \begin{itemize}[<+->]
     \item If you have multiple leaders,
-            you can write to any,
-            allowing \highlight{writes to scale}.
+          you can write to any,
+          allowing \highlight{writes to scale}.
+          \vspace{1em}
     \item A leader going down doesn't prevent writes,
-            giving \highlight{better fault-tolerance}.
+          giving \highlight{better fault-tolerance}.
 \end{itemize}
 }
 \note[itemize]{
@@ -328,7 +331,7 @@
 % }
 
 \questionanswer{What might go wrong?}{Write conflicts}
-\note{Write conflicts require the conflict to be resolved.}
+\note{Conflict needs to be \highlight{resolved}.}
 
 \image{diagrams/WriteConflict}
 \note[enumerate]{
@@ -352,17 +355,20 @@
     \item Custom resolution logic.
 \end{itemize}
 }
+\note{Yes, this can be \highlight{challenging}.}
 
 \image[height=\textheight]{diagrams/ResolveWriteConflict}
 
 \point[Resolving Conflicts]{
+\vspace{1em}
 \begin{description}
     \item[On Write] When a conflict is first noticed, take proactive resolution action.
+    \vspace{1em}
     \item[On Read] When a conflict is next read, ask for a resolution.
 \end{description} 
 }
 \note[itemize]{
-    \item Bucardo allows a perl script for on write resolution.
+    \item Bucardo allows a perl script for on write resolution.\vspace{1em}
     \item CouchDB prompts reads to resolve the conflict.
 }
 
@@ -392,13 +398,11 @@
 \point[How are changes propagated?]{
     \begin{itemize}[<+->]
         \item Read Repair
+        \note[item]<1->{Read Repair: Client detects stale data on read and writes updated data to that replica.\vspace{1em}}
         \item Anti-Entropy Process
+        \note[item]<2>{Anti-Entropy Process: Background process looks for stale or missing data and updates replicas.}
     \end{itemize}
 }
-\note[itemize]{
-    \item Read Repair: Client detects stale data on read and writes updated data to that replica.
-    \item Anti-Entropy Process: Background process looks for stale or missing data and updates replicas.
-}
 
 \question{How do we know it's consistent?}
 
@@ -457,6 +461,35 @@
     \end{tikzpicture}
 \end{center}
 \end{frame}
+\note[itemize]{
+    \item Graphical representation of previous equation. \vspace{3mm}
+    \item \textcolor{eq2}{\textbf{Orange}} inner group (\highlight{reads}), overlaps with \\ 
+           \textcolor{eq1}{\textbf{Blue}} inner group (\highlight{writes}). \vspace{3mm}
+    \item Showing how reads overlap writes via a quorum.
+}
+
+\questionanswer{What about write conflicts?}{Same problem as with Multi-leader replication.}
+
+\image{diagrams/LeaderlessExampleWriteConflict1}
+\note{
+  Same scenario as before:
+  \begin{enumerate}
+    \item Customer queries how many pillows are available.
+    \item Retrieves 20.
+  \end{enumerate}
+}
+
+\image{diagrams/LeaderlessExampleWriteConflict2}
+\note{Same scenario as before:}
+\note{
+  Same scenario as before:
+  \begin{enumerate}
+    \item Fulfilment centre finds faulty pillow and decreases inventory.
+    \item Customer orders 20 pillows, what they saw as the number available.
+    \item -1 Pillows?
+    \item How do we resolve this?
+  \end{enumerate}
+}
 
 \point[Summary]{
 \begin{itemize}[<+->]