Add talk made on 2023-01-18 #482
2 changed files with 51 additions and 22 deletions
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@ -187,7 +187,7 @@
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\vspace{1em}
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\item Folder hierarchies
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\vspace{1em}
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\item Other requirements of the POSIX spec
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\item Other requirements of the POSIX spec (e.g.~locks)
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\end{itemize}
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\vspace{1em}
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Coordination in a distributed system is costly
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@ -291,7 +291,7 @@
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\frametitle{Key-value stores, upgraded: the Dynamo model}
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\textbf{Two keys:}
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\begin{itemize}
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\item Partition key: used to divide data into partitions (shards)
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\item Partition key: used to divide data into partitions {\small (a.k.a.~shards)}
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\item Sort key: used to identify items inside a partition
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\end{itemize}
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@ -326,7 +326,7 @@
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\begin{frame}
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\frametitle{Key-value stores, upgraded: the Dynamo model}
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\begin{itemize}
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\item Data with different partition keys is stored independantly,\\
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\item Data with different partition keys is stored independently,\\
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on a different set of nodes\\
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\vspace{.5em}
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$\to$ no easy way to list all partition keys\\
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@ -520,7 +520,7 @@
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\vspace{1em}
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Require \textbf{additionnal assumptions} such as a fault detector or a strong RNG\\
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Require \textbf{additional assumptions} such as a fault detector or a strong RNG\\
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(FLP impossibility theorem)
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\end{minipage}
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\hfill
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@ -608,7 +608,7 @@
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$\to$ the API is equivalent to consensus/total ordering of messages\\
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$\to$ the API cannot be implemented in a weakly consistent system
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\vspace{2em}
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\item \textbf{This API can be implemented using only weak primitives}\\
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\item<2-> \textbf{This API can be implemented using only weak primitives}\\
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(e.g. in the asynchronous message passing model with no further assumption)\\
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$\to$ the API is strictly weaker than consensus\\
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$\to$ we can implement it in Garage!
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@ -648,13 +648,13 @@
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\begin{itemize}
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\item Any \textbf{conflict-free replicated data type} (CRDT)
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\vspace{1em}
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\item Non-transactional key-value stores such as S3 are equivalent to a simple CRDT:\\
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a \textbf{last-writer-wins registry}
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\item<2-> Non-transactional key-value stores such as S3 are equivalent to a simple CRDT:\\
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a map of \textbf{last-writer-wins registers} (each key is its own CRDT)
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\vspace{1em}
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\item \textbf{Read-after-write consistency} can be implemented
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\item<3-> \textbf{Read-after-write consistency} can be implemented
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using quorums on read and write operations
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\vspace{1em}
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\item \textbf{Monotonicity of reads} can be implemented with repair-on-read\\
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\item<4-> \textbf{Monotonicity of reads} can be implemented with repair-on-read\\
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(makes reads more costly, not implemented in Garage)
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\end{itemize}
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\end{frame}
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@ -735,7 +735,7 @@
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\vspace{1em}
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\textbf{Algorithm $read()$:}
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\textbf{Algorithm $monotonic\_read()$:} {\small (a.k.a. repair-on-read)}
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\begin{enumerate}
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\item Broadcast $read()$ to all nodes
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\item Wait for $k > n/2$ nodes to reply with values $x_1, \dots, x_k$
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@ -754,10 +754,10 @@
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\begin{itemize}
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\item We rely on quorums $k > n/2$ within each partition:\\
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$$n=3,~~~~~~~k\ge 2$$
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\item When rebalancing, the set of nodes responsible for a partition can change:\\
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\item<2-> When rebalancing, the set of nodes responsible for a partition can change:\\
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$$\{n_A, n_B, n_C\} \to \{n_A, n_D, n_E\}$$
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\vspace{.01em}
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\item During the rebalancing, $D$ and $E$ don't yet have the data,\\
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\item<3-> During the rebalancing, $D$ and $E$ don't yet have the data,\\
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~~~~~~~~~~~~~~~~~~~and $B$ and $C$ want to get rid of the data to free up space\\
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\vspace{.2em}
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$\to$ quorums only within the new set of nodes don't work\\
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@ -769,7 +769,7 @@
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\section{Going further than the S3 API}
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\begin{frame}
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\frametitle{Further plans for Garage}
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\frametitle{Using Garage for everything}
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\begin{center}
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\only<1>{\includegraphics[width=.8\linewidth]{assets/slideB1.png}}%
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\only<2>{\includegraphics[width=.8\linewidth]{assets/slideB2.png}}%
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@ -821,10 +821,10 @@
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\begin{itemize}
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\item If we keep only $x_1$ or $x'_1$, we risk \textbf{loosing application data}
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\vspace{1.5em}
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\item Values are opaque binary blobs, \textbf{K2V cannot resolve conflicts} by itself\\
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\item<2-> Values are opaque binary blobs, \textbf{K2V cannot resolve conflicts} by itself\\
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(e.g. by implementing a CRDT)
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\vspace{1.5em}
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\item Solution: \textbf{we keep both!}\\
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\item<3-> Solution: \textbf{we keep both!}\\
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$\to$ the value of the key is now $\{x_1, x'_1\}$\\
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$\to$ the client application can decide how to resolve conflicts on the next read
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\end{itemize}
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@ -837,13 +837,13 @@
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\begin{itemize}
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\item $read()$ returns \textbf{a set of values} and an associated \textbf{causality token}\\
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\vspace{1.5em}
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\item When calling $write()$, the client sends \textbf{the causality token from its last read}
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\item<2-> When calling $write()$, the client sends \textbf{the causality token from its last read}
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\vspace{1.5em}
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\item The causality token represents the set of values \textbf{already seen by the client}\\
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\item<3-> The causality token represents the set of values \textbf{already seen by the client}\\
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$\to$ those values are the \textbf{causal past} of the write operation\\
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$\to$ K2V can keep concurrent values and overwrite all ones in the causal past
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\vspace{1.5em}
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\item Internally, the causality token is \textbf{a vector clock}
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\item<4-> Internally, the causality token is \textbf{a vector clock}
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\end{itemize}
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\end{frame}
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@ -854,8 +854,28 @@
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\end{center}
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\end{frame}
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\begin{frame}
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\frametitle{Aerogramme data model}
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\begin{center}
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\only<1>{\includegraphics[width=.4\linewidth]{assets/aerogramme_datatype.drawio.pdf}}%
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\only<2->{\includegraphics[width=.9\linewidth]{assets/aerogramme_keys.drawio.pdf}\vspace{1em}}%
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\end{center}
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\visible<3->{Aerogramme encrypts all stored values for privacy\\
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(Garage server administrators can't read your mail)}
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\end{frame}
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\begin{frame}
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\frametitle{Different deployment scenarios}
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\begin{center}
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\only<1>{\includegraphics[width=.9\linewidth]{assets/aerogramme_components1.drawio.pdf}}%
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\only<2>{\includegraphics[width=.9\linewidth]{assets/aerogramme_components2.drawio.pdf}}%
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\end{center}
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\end{frame}
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\begin{frame}
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\frametitle{A new model for building resilient software}
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How to build an application using only Garage as a data store:
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\vspace{1em}
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\begin{enumerate}
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\item Design a data model suited to K2V\\
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{\footnotesize (see Cassandra docs on porting SQL data models to Cassandra)}
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\item Store opaque binary blobs to provide End-to-End Encryption\\
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\end{itemize}
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\vspace{1em}
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\item Store big blobs (files) using the S3 API
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\item<2-> Store big blobs (files) using the S3 API
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\vspace{1em}
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\item Let Garage manage sharding, replication, failover, etc.
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\item<3-> Let Garage manage sharding, replication, failover, etc.
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\end{enumerate}
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\end{frame}
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\section{Conclusion}
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\begin{frame}
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\frametitle{Research perspectives}
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\frametitle{Perspectives}
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\begin{itemize}
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\item TODO
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\item Fix the consistency issue when rebalancing
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\vspace{1em}
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\item Write about Garage's architecture and properties,\\
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and about our proposed architecture for (E2EE) apps over K2V+S3
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\vspace{1em}
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\item Continue developing Garage; finish Aerogramme; build new applications...
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\vspace{1em}
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\item Anything else?
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\end{itemize}
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\end{frame}
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