200 lines
6.7 KiB
HTML
200 lines
6.7 KiB
HTML
<!DOCTYPE html>
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<html><head>
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
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<meta http-equiv="content-type" content="text/html; charset=UTF-8">
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<link href="sqlite.css" rel="stylesheet">
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<title>SQLite Is Serverless</title>
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</head>
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<body>
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Small. Fast. Reliable.<br>Choose any three.
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<div class=fancy>
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<div class=nosearch>
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<div class="fancy_title">
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SQLite Is Serverless
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</div>
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</div>
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<h1 id="sqlite_is_serverless"><span>1. </span>SQLite Is Serverless</h1>
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<p>
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Most SQL database engines are implemented as a separate server process.
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Programs that want to access the database communicate with the server
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using some kind of interprocess communication (typically TCP/IP) to send
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requests to the server and to receive back results.
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SQLite does not work this way.
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With SQLite, the process that wants to access the database reads and
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writes directly from the database files on disk.
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There is no intermediary server process.
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</p>
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<p>
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There are advantages and disadvantages to being serverless.
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The main advantage is that there is no separate server process
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to install, setup, configure, initialize, manage, and troubleshoot.
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This is one reason why SQLite is a
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"<a href="zeroconf.html">zero-configuration</a>" database engine.
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Programs that use SQLite require no administrative support for
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setting up the database engine before they are run.
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Any program that is able to access the disk is able to use an SQLite database.
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</p>
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<p>
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On the other hand, a database engine that uses a server can
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provide better protection from bugs in the client
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application - stray pointers in a client cannot corrupt memory
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on the server.
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And because a server is a single persistent process,
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it is able to control database access with more precision,
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allowing for finer-grained locking and better concurrency.
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</p>
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<p>
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Most SQL database engines are client/server based.
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Of those that are serverless, SQLite is the only one
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known to this author that allows multiple applications
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to access the same database at the same time.
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</p>
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<h1 id="classic_serverless_vs_neo_serverless"><span>2. </span>Classic Serverless Vs. Neo-Serverless</h1>
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<p>
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<i>(This section was added on 2018-04-02)</i>
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</p><p>
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Recently, folks have begun to use the
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word "serverless" to mean something subtly different from its intended
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meaning in this document. Here are two possible definitions of "serverless":
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</p><ol>
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<li><p>
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<b>Classic Serverless:</b>
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The database engine runs within the same process, thread, and address space
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as the application. There is no message passing or network activity.
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</p></li><li><p>
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<b>Neo-Serverless:</b>
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The database engine runs in a separate namespace from the application,
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probably on a separate machine, but the database is provided as a
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turn-key service by the hosting provider, requires no management or
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administration by the application owners, and is so easy to use
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that the developers can think of the database as being serverless
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even if it really does use a server under the covers.
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</p></li></ol>
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<p>
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SQLite is an example of a classic serverless database engine.
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With SQLite, there are no other processes, threads, machines, or
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other mechanisms (apart from host computer OS and filesystem)
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to help provide database services or implementation. There really
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is no server.
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</p><p>
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<a href="https://docs.microsoft.com/en-us/azure/cosmos-db/serverless-computing-database">Microsoft Azure Cosmo DB</a>
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and
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<a href="https://aws.amazon.com/s3/">Amazon S3</a>
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are examples of a neo-serverless databases.
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These database are implemented by server processes running separately
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in the cloud.
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But the servers are maintained and administered by the ISP, not by
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the application developer.
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Application developers just use the service. Developers do not have to
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provision, configure, or manage database server instances, as all of that
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work is handled automatically by the service provider. Database servers
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do in fact exist, they are just hidden from the developers.
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</p><p>
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It is important to understand these two different definitions for
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"serverless".
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When a database claims to be "serverless",
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be sure to discern whether they mean "classic serverless"
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or "neo-serverless".
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</p>
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