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guix-cuirass
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http: Process client connections really concurrently, again. 

This reinstates c47dfdf82b and fixes the
issues that led to the revert in
b71f0cdca5.

Before that, 'run-server' would force sequential processing of client
requests one after another.

* src/cuirass/http.scm (run-cuirass-server): Rewrite to use its own loop
instead of 'run-server'.  Spawn a database fiber.
(with-database-access): New macro.
(handle-build-request): Expect 'db-channel' and use 'with-database-access'.
(handle-builds-request): Likewise.
(url-handler): Likewise.
This commit is contained in:
Ludovic Courtès 2018-03-28 22:41:12 +02:00
parent e8543d7aa9
commit 8bdde878c7
1 changed files with 79 additions and 32 deletions
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111
src/cuirass/http.scm
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@ -22,12 +22,16 @@
#:use-module (cuirass database)
#:use-module (cuirass utils)
#:use-module (cuirass logging)
#:use-module (srfi srfi-11)
#:use-module (srfi srfi-26)
#:use-module (ice-9 match)
#:use-module (json)
#:use-module (web request)
#:use-module (web response)
#:use-module (web server)
#:use-module ((web server) #:hide (run-server))
#:use-module (web uri)
#:use-module (fibers)
#:use-module (fibers channels)
#:export (run-cuirass-server))
(define (build->hydra-build build)
@ -66,20 +70,28 @@
(#:releasename . #nil)
(#:buildinputs_builds . #nil)))
(define (handle-build-request db build-id)
"Retrieve build identified by BUILD-ID in DB and convert it to hydra
format. Return #f is not build was found."
(let ((build (db-get-build db build-id)))
(define-syntax-rule (with-database-access channel db exp ...)
"Evaluate EXP with DB bound to the database. Do that by passing EXP over to
CHANNEL for execution by the database fiber. This ensures that the database
handle is only ever accessed from on thread, the thread where the database
fiber runs (IOW, it creates a critical section.)"
(begin
(put-message channel (lambda (db) exp ...))
(get-message channel)))
(define (handle-build-request db-channel build-id)
"Retrieve build identified by BUILD-ID over DB-CHANNEL and convert it to
hydra format. Return #f is not build was found."
(let ((build (with-database-access db-channel db
(db-get-build db build-id))))
(and=> build build->hydra-build)))
(define (handle-builds-request db filters)
"Retrieve all builds matched by FILTERS in DB and convert them to hydra
format."
;; Since these requests can take several seconds (!), run them through
;; 'non-blocking'.
(let ((builds (non-blocking
(with-time-logging "builds request"
(db-get-builds db filters)))))
(define (handle-builds-request db-channel filters)
"Retrieve all builds matched by FILTERS in DB-CHANNEL and convert them to
Hydra format."
(let ((builds (with-database-access db-channel db
(with-time-logging "builds request"
(db-get-builds db filters)))))
(map build->hydra-build builds)))
(define (request-parameters request)
@ -112,10 +124,10 @@
(define (request-path-components request)
(split-and-decode-uri-path (uri-path (request-uri request))))
(define (url-handler request body db)
(define (url-handler request body db-channel)
(define* (respond response #:key body (db db))
(values response body db))
(define* (respond response #:key body (db-channel db-channel))
(values response body db-channel))
(define-syntax-rule (respond-json body ...)
(respond '((content-type . (application/json)))
@ -152,14 +164,18 @@
(request-path-components request)
'method-not-allowed)
(((or "jobsets" "specifications") . rest)
(respond-json (object->json-string (db-get-specifications db))))
(respond-json (object->json-string
(with-database-access db-channel db
(db-get-specifications db)))))
(("build" build-id)
(let ((hydra-build (handle-build-request db (string->number build-id))))
(let ((hydra-build (handle-build-request db-channel
(string->number build-id))))
(if hydra-build
(respond-json (object->json-string hydra-build))
(respond-build-not-found build-id))))
(("build" build-id "log" "raw")
(let ((build (db-get-build db (string->number build-id))))
(let ((build (with-database-access db-channel db
(db-get-build db (string->number build-id)))))
(if build
(match (assq-ref build #:outputs)
(((_ (#:path . (? string? output))) _ ...)
@ -186,7 +202,7 @@
(if valid-params?
;; Limit results to builds that are "done".
(respond-json (object->json-string
(handle-builds-request db
(handle-builds-request db-channel
`((status done)
,@params
(order finish-time)))))
@ -200,34 +216,65 @@
(object->json-string
;; Use the 'status+submission-time' order so that builds in
;; 'running' state appear before builds in 'scheduled' state.
(handle-builds-request db
(handle-builds-request db-channel
`((status pending)
,@params
(order status+submission-time)))))
(respond-json-with-error 500 "Parameter not defined!"))))
('method-not-allowed
;; 405 "Method Not Allowed"
(values (build-response #:code 405) #f db))
(values (build-response #:code 405) #f db-channel))
(_
(respond (build-response #:code 404)
#:body (string-append "Resource not found: "
(uri->string (request-uri request)))))))
(define* (run-cuirass-server db #:key (host "localhost") (port 8080))
(let* ((host-info (gethostbyname host))
(address (inet-ntop (hostent:addrtype host-info)
(car (hostent:addr-list host-info)))))
(let* ((host-info (gethostbyname host))
(address (inet-ntop (hostent:addrtype host-info)
(car (hostent:addr-list host-info))))
(db-channel (make-channel)))
(log-message "listening on ~A:~A" address port)
;; Spawn a fiber to process database queries sequentially. We need this
;; because guile-sqlite3 handles are not thread-safe (caching in
;; particular), and creating one new handle for each request would be
;; costly and may defeat statement caching.
(spawn-fiber
(lambda ()
(let loop ()
(match (get-message db-channel)
((? procedure? proc)
(put-message db-channel (proc db))))
(loop))))
;; Here we use our own web backend, call 'fiberized'. We cannot use the
;; 'fibers' backend that comes with Fibers 1.0.0 because it does its own
;; thread creations and calls 'run-fibers' by itself, which isn't
;; necessary here (and harmful).
;;
;; XXX: 'run-server' serializes client request processing, making sure
;; only one client is served at a time. This is not ideal, but processing
;; things concurrently would require having several database handles.
(run-server url-handler
'fiberized
`(#:host ,address #:port ,port)
db)))
;; In addition, we roll our own instead of using Guile's 'run-server' and
;; 'serve-one-client'. The key thing here is that we spawn a fiber to
;; process each client request and then directly go back waiting for the
;; next client (conversely, Guile's 'run-server' loop processes clients
;; one after another, sequentially.) We can do that because we don't
;; maintain any state across connections.
;;
;; XXX: We don't do 'call-with-sigint' like 'run-server' does.
(let* ((impl (lookup-server-impl 'fiberized))
(server (open-server impl `(#:host ,address #:port ,port))))
(let loop ()
(let-values (((client request body)
(read-client impl server)))
;; Spawn a fiber to handle REQUEST and reply to CLIENT.
(spawn-fiber
(lambda ()
(let-values (((response body state)
(handle-request (cut url-handler <> <> db-channel)
request body '())))
(write-client impl server client response body)))))
(loop)))))
;;; Local Variables:
;;; eval: (put 'with-database-access 'scheme-indent-function 2)
;;; End: