Announcing Guile Knots

Summary

Guile Knots is a library providing higher-level patterns and building blocks for programming with Guile Fibers. I started developing it back in 2024, extracting code I'd written for the Guix Data Service and Guix Build Coordinator, making it possible to use this code in other services like the Bffe, Nar Herder and QA Frontpage. I started using Guile Fibers first for the Guix Data Service all the way back in 2019, and that was just because I copied the initial code from the Mumi project. There have definitely been some problems I've hit along the way, but using Fibers seems like a good fit for the software I've been writing in the past few years, and the functionality in Guile Knots is an essential part of that. To call out just some of the included functionality, the resource pools are a versatile tool, which can be used for database connections or limiting parallelism to give just a couple of examples. (let ((connection-pool (make-resource-pool (lambda () (open-postgresql-connection "web" postgresql-statement-timeout)) (floor (/ postgresql-connections 2)) #:name "web" #:idle-seconds 30 #:destructor (lambda (conn) (close-postgresql-connection conn "web")) #:add-resources-parallelism (floor (/ postgresql-connections 2)) #:default-max-waiters (floor (/ postgresql-connections 2)) #:default-checkout-timeout (/ postgresql-statement-timeout 1000)))) The thread pools are useful when threads are required, useful for interacting with SQLite for example. (let ((reader-thread-pool (make-fixed-size-thread-pool (min (max (current-processor-count) 32) 128) #:thread-initializer (lambda () (let ((db (db-open database-file #:write? #f))) (sqlite-exec db "PRAGMA busy_timeout = 5000;") (list db))) #:thread-destructor (lambda (db) (sqlite-close db)) #:thread-lifetime 50000 #:name "db read"))) Using suspendable ports you can do reliable I/O, and Guile Knots includes with-port-timeouts which supports timeouts both for plain suspendable ports and for fibers. (with-port-timeouts (lambda ()...