371 lines
10 KiB
TeX
371 lines
10 KiB
TeX
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\documentclass[aspectratio=169]{beamer}
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% \usepackage[frenchb]{babel}
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\AtBeginSection[]{
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\begin{frame}
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\vfill
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\centering
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\begin{beamercolorbox}[sep=8pt,center,shadow=true,rounded=true]{title}
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\usebeamerfont{title}\insertsectionhead\par%
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}
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\title{Garage}
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\subtitle{a lightweight and robust geo-distributed data storage system}
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\author{Alex Auvolat, Deuxfleurs}
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\date{SEED webinar, 2024-01-12}
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\begin{document}
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% \begin{frame}
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% \centering
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% \includegraphics[width=.3\linewidth]{../../sticker/Garage.png}
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% \vspace{1em}
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%
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% {\large\bf Alex Auvolat, Deuxfleurs Association}
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% \vspace{1em}
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%
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% \url{https://garagehq.deuxfleurs.fr/}
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%
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% %Matrix channel: \texttt{\#garage:deuxfleurs.fr}
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% \end{frame}
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\begin{frame}
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%\frametitle{Who I am}
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\begin{columns}[t]
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\begin{column}{.2\textwidth}
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\centering
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\adjincludegraphics[width=.4\linewidth, valign=t]{assets/alex.jpg}
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\end{column}
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\begin{column}{.6\textwidth}
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\textbf{Alex Auvolat}\\
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Member of Deuxfleurs, lead developer of Garage
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\end{column}
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\begin{column}{.2\textwidth}
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~
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\end{column}
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\end{columns}
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\vspace{.5em}
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\begin{columns}[t]
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\begin{column}{.2\textwidth}
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\centering
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\adjincludegraphics[width=.6\linewidth, valign=t]{../../logo/garage-notext.png}
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\end{column}
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\begin{column}{.6\textwidth}
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\\\textbf{Garage}\\
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A self-hosted alternative to S3 for object storage
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\end{column}
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\begin{column}{.2\textwidth}
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~
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\end{column}
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\end{columns}
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\vspace{2em}
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\begin{columns}[t]
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\begin{column}{.2\textwidth}
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\centering
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\adjincludegraphics[width=.5\linewidth, valign=t]{assets/deuxfleurs.pdf}
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\end{column}
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\begin{column}{.6\textwidth}
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\textbf{Deuxfleurs}\\
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A non-profit self-hosting collective,\\
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member of the CHATONS network
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\end{column}
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\begin{column}{.2\textwidth}
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\centering
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\adjincludegraphics[width=.7\linewidth, valign=t]{assets/logo_chatons.png}
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\end{column}
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\end{columns}
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\end{frame}
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\begin{frame}
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\frametitle{Stable vs Resilient}
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\hspace{1em}
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\begin{minipage}{7cm}
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\textbf{Building a "stable" system:}
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\vspace{1em}
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Enterprise-grade systems typically employ:
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\vspace{1em}
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\begin{itemize}
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\item RAID
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\item Redundant power grid + UPS
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\item Redundant Internet connections
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\item Low-latency links
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\item ...
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\end{itemize}
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\vspace{1em}
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$\to$ costly, only worth at DC scale\\
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$\to$ still risk of DC-level incident...
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\end{minipage}
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\hfill
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\begin{minipage}{7cm}
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\textbf{Building a \underline{resilient} system:}
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\vspace{1em}
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An alternative, cheaper way:
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\vspace{1em}
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\begin{itemize}
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\item Commodity hardware \\(e.g. old desktop PCs)
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\vspace{.5em}
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\item Commodity Internet \\(e.g. FTTB, FTTH) and power grid
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\vspace{.5em}
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\item \textbf{Geographical redundancy} \\(multi-site replication)
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\end{itemize}
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\vspace{1.5em}
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\end{minipage}
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\hspace{1em}
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\end{frame}
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\begin{frame}
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\frametitle{Example: our infrastructure at Deuxfleurs}
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\only<1>{
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\begin{center}
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\includegraphics[width=.8\linewidth]{assets/neptune.jpg}
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\end{center}
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}
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\only<2>{
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\begin{center}
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\includegraphics[width=.8\linewidth]{assets/atuin.jpg}
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\end{center}
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}
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\only<3>{
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\begin{center}
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\includegraphics[width=.8\linewidth]{assets/inframap_jdll2023.pdf}
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\end{center}
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}
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\end{frame}
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\begin{frame}
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\frametitle{Object storage: simpler than file systems}
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\begin{minipage}{6cm}
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Only two operations:
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\vspace{1em}
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\begin{itemize}
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\item Put an object at a key
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\vspace{1em}
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\item Retrieve an object from its key
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\end{itemize}
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\vspace{1em}
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{\footnotesize (and a few others)}
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\vspace{1em}
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Sufficient for many applications!
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\end{minipage}
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\hfill
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\begin{minipage}{8cm}
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\begin{center}
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\vspace{2em}
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\includegraphics[height=6em]{../2020-12-02_wide-team/img/Amazon-S3.jpg}
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\hspace{2em}
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\includegraphics[height=5em]{assets/minio.png}
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\vspace{2em}
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\includegraphics[height=6em]{../../logo/garage_hires_crop.png}
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\end{center}
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\vspace{1em}
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\end{minipage}
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\end{frame}
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\begin{frame}
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\frametitle{The data model of object storage}
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Object storage is basically a key-value store:
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\vspace{1em}
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\begin{center}
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\begin{tabular}{|l|p{8cm}|}
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\hline
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\textbf{Key: file path + name} & \textbf{Value: file data + metadata} \\
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\hline
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\hline
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\texttt{index.html} &
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\texttt{Content-Type: text/html; charset=utf-8} \newline
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\texttt{Content-Length: 24929} \newline
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\texttt{<binary blob>} \\
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\hline
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\texttt{img/logo.svg} &
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\texttt{Content-Type: text/svg+xml} \newline
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\texttt{Content-Length: 13429} \newline
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\texttt{<binary blob>} \\
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\hline
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\texttt{download/index.html} &
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\texttt{Content-Type: text/html; charset=utf-8} \newline
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\texttt{Content-Length: 26563} \newline
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\texttt{<binary blob>} \\
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\hline
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\end{tabular}
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\end{center}
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\end{frame}
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\begin{frame}
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\frametitle{Implementation: consensus vs weak consistency}
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\hspace{1em}
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\begin{minipage}{7cm}
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\textbf{Consensus-based systems:}
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\vspace{1em}
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\begin{itemize}
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\item \textbf{Leader-based:} a leader is elected to coordinate
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all reads and writes
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\vspace{1em}
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\item Allows for \textbf{sequential reasoning}:
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program as if running on a single machine
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\vspace{1em}
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\item Serializability is one of the \\
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\textbf{strongest consistency guarantees}
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\vspace{1em}
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\item \textbf{Costly}, the leader is a bottleneck;
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leader elections on failure take time
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\end{itemize}
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\end{minipage}
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\hfill
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\begin{minipage}{7cm} \visible<2->{
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\textbf{Weakly consistent systems:}
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\vspace{1em}
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\begin{itemize}
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\item \textbf{Nodes are equivalent}, any node
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can originate a read or write operation
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\vspace{1em}
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\item \textbf{Operations must be independent},
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conflicts are resolved after the fact
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\vspace{1em}
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\item Strongest achievable consistency:\\
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\textbf{read-after-write consistency}\\(using quorums)
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\vspace{1em}
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\item \textbf{Fast}, no single bottleneck;\\
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works transparently with offline nodes
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\end{itemize}
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} \end{minipage}
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\hspace{1em}
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\end{frame}
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\begin{frame}
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\frametitle{Why avoid consensus?}
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Consensus can be implemented reasonably well in practice, so why avoid it?
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\vspace{2em}
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\begin{itemize}
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\item \textbf{Software complexity:} RAFT and PAXOS are complex beasts;\\
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harder to prove, harder to reason about
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\vspace{1.5em}
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\item \textbf{Performance issues:}
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\vspace{1em}
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\begin{itemize}
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\item Taking a decision may take an \textbf{arbitrary number of steps} (in adverse scenarios)
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\vspace{1em}
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\item The leader is a \textbf{bottleneck} for all requests;\\
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even in leaderless approaches, \textbf{all nodes must process all operations in order}
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\vspace{1em}
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\item Particularly \textbf{sensitive to higher latency} between nodes
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\end{itemize}
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\end{itemize}
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\end{frame}
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\begin{frame}
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\frametitle{Objective: the right level of consistency for Garage}
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\underline{Constraints:} slow network (geographical distance), node unavailability/crashes\\
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\underline{Objective:} maximize availability, maintain an \emph{appropriate level of consistency}\\
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\vspace{1em}
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\begin{enumerate}
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\item<2-> \textbf{Weak consistency for most things}\\
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\vspace{1em}
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\underline{Example:} \texttt{PutObject}\\
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\vspace{.5em}
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If two clients write the same
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object at the same time, one of the two is implicitly overwritten.
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No need to coordinate, use a \emph{last-writer-wins register}.
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\vspace{1em}
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\item<3-> \textbf{Stronger consistency only when necessary}\\
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\vspace{1em}
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\underline{Example:} \texttt{CreateBucket}\\
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\vspace{.5em}
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A bucket is a reserved name in a shared namespace,
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two clients should be prevented from both creating the same bucket
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(\emph{mutual exclusion}).
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\end{enumerate}
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\end{frame}
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\begin{frame}
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\frametitle{The possibility of \emph{leaderless consensus}}
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Currently, Garage \emph{only has weak consistency}. Is fast, but \texttt{CreateBucket} is broken!
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\visible<2->{
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\vspace{1em}
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Leaderless consensus (Antoniadis et al., 2023) alleviates issues with RAFT and PAXOS:
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\vspace{1em}
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\begin{itemize}
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\item \textbf{No leader.} All nodes participate equally at each time step,
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and different nodes can be unavailable at different times without issues.
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\\ \vspace{.5em} $\to$ better tolerance to the high latency (remove bottleneck issue)
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\\ $\to$ tolerates crash transparently
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\vspace{1em}
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\item \textbf{Simpler formalization.} The algorithm is very simple to express and to analyze in mathematical terms.
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\end{itemize}
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}
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\visible<3->{
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\vspace{1em}
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One of the possible subjects for this PhD:
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\\$\to$ \emph{integration of leaderless consensus in Garage} + testing + perf eval, etc.
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}
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\end{frame}
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\begin{frame}
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\begin{center}
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\includegraphics[width=.25\linewidth]{../../logo/garage_hires.png}\\
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\vspace{-1em}
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\url{https://garagehq.deuxfleurs.fr/}\\
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\url{mailto:garagehq@deuxfleurs.fr}\\
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\texttt{\#garage:deuxfleurs.fr} on Matrix
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\vspace{1.5em}
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\includegraphics[width=.06\linewidth]{assets/rust_logo.png}
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\includegraphics[width=.13\linewidth]{assets/AGPLv3_Logo.png}
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\end{center}
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\end{frame}
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\end{document}
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%% vim: set ts=4 sw=4 tw=0 noet spelllang=en :
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