Connection pooling

As explained in Elixir in Action, Third Edition

A database connection pool is a bounded collection of reusable database connections managed to constrain simultaneous database operations.

Connection pooling bounds concurrency when an underlying resource, such as database or disk I/O, cannot handle unbounded simultaneous operations. Requests reach one coordinating process and are quickly delegated to a fixed set of workers. section 7.3.4

A practical pool design:

• Create several worker processes and retain their PIDs in coordinator state. section 7.3.4
• Select a worker for each request using round-robin distribution or a key-based strategy. section 7.3.4 section 7.3.5
• Route identical keys to the same worker when per-key synchronization is required. section 7.3.5
• Keep the public database interface unchanged while forwarding get and store operations internally. section 7.3.5

Figure 7.4 Pooling database operations

Visualizes how a coordinating database process distributes operations across pooled workers. section 7.3.4

How Elixir in Action, Third Edition covers it

How deep it goes

Explains coordinator state, worker delegation, distribution strategies, stable key routing, and interface preservation.

Examples

Uses three workers, PID maps, stable key selection, and Todo.Database forwarding get and store requests.

What it assumes

Assumes familiarity with Elixir processes, GenServer callbacks, PIDs, and request forwarding.

What you can do after

Build a three-worker database pool while preserving the existing public interface and per-key synchronization.

How it connects

Connects processes, GenServer, concurrency, load distribution, and synchronization.

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Also explained in

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  PostgreSQL Mistakes and How to Avoid ThemConnection pooling is a technique that reuses a bounded set of database connections to serve a larger number of client requests.
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  100 Go Mistakes and How to Avoid ThemA database connection pool is a managed collection of reusable database connections that are allocated to operations and returned for later use.
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  ASP.NET Core in Action, 3eConnection pooling is the reuse of established network connections across multiple client requests to reduce connection-setup overhead.

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Related concepts

• database connectionuses · A database connection is an active communication channel or session through which software sends operations to and receives results from a database system.
• connection poolerimplemented by · A connection pooler is software that maintains reusable database connections and assigns them to application requests as needed.

This explainer was generated by Manning's knowledge graph from the text of Elixir in Action, Third Edition. The section links point to the parts of the book it draws on.