cbaines/guix-data-service
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Completely rework the way db connections are handled during requests

Browse source 
Previously, a connection was passed through the code handling the
request. When queries were performed, this could block the thread though,
potentially leaving the server unable to serve other requests.

Instead, this now runs queries in a pool of threads. This should remove the
possibility of blocking the threads used by the web server, and in doing so,
some of the queries have been parallelised.

I''m still not sure about the naming and syntax, but I think the functionality
is a sort of step forward.
This commit is contained in:
Christopher Baines 2020-10-03 21:35:31 +01:00
parent e2e55c69de
commit c3c9c07f9a
9 changed files with 1771 additions and 1366 deletions
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740
guix-data-service/web/compare/controller.scm
View file

@ -23,6 +23,8 @@
#:use-module (texinfo)
#:use-module (texinfo html)
#:use-module (texinfo plain-text)
#:use-module (guix-data-service utils)
#:use-module (guix-data-service database)
#:use-module (guix-data-service web sxml)
#:use-module (guix-data-service web util)
#:use-module (guix-data-service web render)
@ -48,35 +50,37 @@
(define (parse-build-status s)
s)
(define (parse-commit conn)
(lambda (s)
(if (guix-commit-exists? conn s)
s
(make-invalid-query-parameter
s "unknown commit"))))
(define (parse-commit s)
(if (parallel-via-thread-pool-channel
(with-thread-postgresql-connection
(lambda (conn)
(guix-commit-exists? conn s))))
s
(make-invalid-query-parameter
s "unknown commit")))
(define (parse-derivation conn)
(lambda (file-name)
(if (select-derivation-by-file-name conn file-name)
file-name
(make-invalid-query-parameter
file-name "unknown derivation"))))
(define (parse-derivation file-name)
(if (parallel-via-thread-pool-channel
(with-thread-postgresql-connection
(lambda (conn)
(select-derivation-by-file-name conn file-name))))
file-name
(make-invalid-query-parameter
file-name "unknown derivation")))
(define (compare-controller request
method-and-path-components
mime-types
body
conn)
body)
(match method-and-path-components
(('GET "compare")
(let* ((parsed-query-parameters
(parse-query-parameters
request
`((base_commit ,(parse-commit conn) #:required)
(target_commit ,(parse-commit conn) #:required)
`((base_commit ,parse-commit #:required)
(target_commit ,parse-commit #:required)
(locale ,identity #:default "en_US.UTF-8")))))
(render-compare mime-types
conn
parsed-query-parameters)))
(('GET "compare-by-datetime")
(let* ((parsed-query-parameters
@ -88,28 +92,25 @@
(target_datetime ,parse-datetime #:required)
(locale ,identity #:default "en_US.UTF-8")))))
(render-compare-by-datetime mime-types
conn
parsed-query-parameters)))
(('GET "compare" "derivation")
(let* ((parsed-query-parameters
(parse-query-parameters
request
`((base_derivation ,(parse-derivation conn) #:required)
(target_derivation ,(parse-derivation conn) #:required)))))
`((base_derivation ,parse-derivation #:required)
(target_derivation ,parse-derivation #:required)))))
(render-compare/derivation mime-types
conn
parsed-query-parameters)))
(('GET "compare" "derivations")
(let* ((parsed-query-parameters
(parse-query-parameters
request
`((base_commit ,(parse-commit conn) #:required)
(target_commit ,(parse-commit conn) #:required)
`((base_commit ,parse-commit #:required)
(target_commit ,parse-commit #:required)
(system ,parse-system #:multi-value)
(target ,parse-target #:multi-value)
(build_status ,parse-build-status #:multi-value)))))
(render-compare/derivations mime-types
conn
parsed-query-parameters)))
(('GET "compare-by-datetime" "derivations")
(let* ((parsed-query-parameters
@ -126,17 +127,15 @@
'((base_commit base_datetime)
(target_commit target_datetime)))))
(render-compare-by-datetime/derivations mime-types
conn
parsed-query-parameters)))
(('GET "compare" "packages")
(let* ((parsed-query-parameters
(parse-query-parameters
request
`((base_commit ,(parse-commit conn) #:required)
(target_commit ,(parse-commit conn) #:required)))))
`((base_commit ,parse-commit #:required)
(target_commit ,parse-commit #:required)))))
(render-compare/packages mime-types
conn
parsed-query-parameters)))
parsed-query-parameters)))
(_ #f)))
(define (texinfo->variants-alist s)
@ -148,16 +147,7 @@
(plain . ,(stexi->plain-text stexi)))))
(define (render-compare mime-types
conn
query-parameters)
(define lint-warnings-locale-options
(map
(match-lambda
((locale)
locale))
(lint-warning-message-locales-for-revision
conn (assq-ref query-parameters 'target_commit))))
(if (any-invalid-query-parameters? query-parameters)
(case (most-appropriate-mime-type
'(application/json text/html)
@ -166,195 +156,79 @@
(render-json
'((error . "invalid query"))))
(else
(render-html
#:sxml (compare-invalid-parameters
query-parameters
(match (assq-ref query-parameters 'base_commit)
(($ <invalid-query-parameter> value)
(select-job-for-commit conn value))
(_ #f))
(match (assq-ref query-parameters 'target_commit)
(($ <invalid-query-parameter> value)
(select-job-for-commit conn value))
(_ #f))))))
(letpar& ((base-job
(match (assq-ref query-parameters 'base_commit)
(($ <invalid-query-parameter> value)
(with-thread-postgresql-connection
(lambda (conn)
(select-job-for-commit conn value))))
(_ #f)))
(target-job
(match (assq-ref query-parameters 'target_commit)
(($ <invalid-query-parameter> value)
(with-thread-postgresql-connection
(lambda (conn)
(select-job-for-commit conn value))))
(_ #f))))
(render-html
#:sxml (compare-invalid-parameters
query-parameters
base-job
target-job)))))
(let ((base-revision-id (commit->revision-id
conn
(assq-ref query-parameters 'base_commit)))
(target-revision-id (commit->revision-id
conn
(assq-ref query-parameters 'target_commit)))
(locale (assq-ref query-parameters 'locale)))
(letpar& ((base-revision-id
(with-thread-postgresql-connection
(lambda (conn)
(commit->revision-id
conn
(assq-ref query-parameters 'base_commit)))))
(target-revision-id
(with-thread-postgresql-connection
(lambda (conn)
(commit->revision-id
conn
(assq-ref query-parameters 'target_commit)))))
(locale
(assq-ref query-parameters 'locale)))
(let-values
(((base-packages-vhash target-packages-vhash)
(package-data->package-data-vhashes
(package-differences-data conn
base-revision-id
target-revision-id))))
(let* ((new-packages
(package-data-vhashes->new-packages base-packages-vhash
target-packages-vhash))
(removed-packages
(package-data-vhashes->removed-packages base-packages-vhash
target-packages-vhash))
(version-changes
(package-data-version-changes base-packages-vhash
target-packages-vhash))
(lint-warnings-data
(group-list-by-first-n-fields
2
(lint-warning-differences-data conn
base-revision-id
target-revision-id
locale)))
(channel-news-data
(channel-news-differences-data conn
base-revision-id
target-revision-id)))
(case (most-appropriate-mime-type
'(application/json text/html)
mime-types)
((application/json)
(render-json
`((channel-news . ,(list->vector
(map
(match-lambda
((commit tag title_text body_text change)
`(,@(if (null? commit)
'()
`((commit . ,commit)))
,@(if (null? tag)
'()
`((tag . ,tag)))
(title-text
. ,(map
(match-lambda
((lang . text)
(cons
lang
(texinfo->variants-alist text))))
title_text))
(body-text
. ,(map
(match-lambda
((lang . text)
(cons
lang
(texinfo->variants-alist text))))
body_text))
(change . ,change))))
channel-news-data)))
(new-packages . ,(list->vector new-packages))
(removed-packages . ,(list->vector removed-packages))
(version-changes . ,(list->vector
(map
(match-lambda
((name data ...)
`((name . ,name)
,@data)))
version-changes))))
#:extra-headers http-headers-for-unchanging-content))
(else
(render-html
#:sxml (compare query-parameters
(guix-revisions-cgit-url-bases
conn
(list base-revision-id
target-revision-id))
new-packages
removed-packages
version-changes
lint-warnings-data
lint-warnings-locale-options
channel-news-data)
#:extra-headers http-headers-for-unchanging-content))))))))
(define (render-compare-by-datetime mime-types
conn
query-parameters)
(if (any-invalid-query-parameters? query-parameters)
(case (most-appropriate-mime-type
'(application/json text/html)
mime-types)
((application/json)
(render-json
'((error . "invalid query"))))
(else
(render-html
#:sxml (compare-invalid-parameters
query-parameters
(match (assq-ref query-parameters 'base_commit)
(($ <invalid-query-parameter> value)
(select-job-for-commit conn value))
(_ #f))
(match (assq-ref query-parameters 'target_commit)
(($ <invalid-query-parameter> value)
(select-job-for-commit conn value))
(_ #f))))))
(let ((base-branch (assq-ref query-parameters 'base_branch))
(base-datetime (assq-ref query-parameters 'base_datetime))
(target-branch (assq-ref query-parameters 'target_branch))
(target-datetime (assq-ref query-parameters 'target_datetime))
(locale (assq-ref query-parameters 'locale)))
(let* ((base-revision-details
(select-guix-revision-for-branch-and-datetime conn
base-branch
base-datetime))
(lint-warnings-locale-options
(map
(match-lambda
((locale)
locale))
(lint-warning-message-locales-for-revision
conn (second base-revision-details))))
(base-revision-id
(first base-revision-details))
(target-revision-details
(select-guix-revision-for-branch-and-datetime conn
target-branch
target-datetime))
(target-revision-id
(first target-revision-details)))
(let-values
(((base-packages-vhash target-packages-vhash)
(package-data->package-data-vhashes
(package-differences-data conn
base-revision-id
target-revision-id))))
(let* ((new-packages
(package-data-vhashes->new-packages base-packages-vhash
target-packages-vhash))
(removed-packages
(package-data-vhashes->removed-packages base-packages-vhash
target-packages-vhash))
(version-changes
(package-data-version-changes base-packages-vhash
target-packages-vhash))
(lint-warnings-data
(group-list-by-first-n-fields
2
(lint-warning-differences-data conn
base-revision-id
target-revision-id
locale)))
(channel-news-data
(channel-news-differences-data conn
base-revision-id
target-revision-id)))
(parallel-via-thread-pool-channel
(with-thread-postgresql-connection
(lambda (conn)
(package-differences-data conn
base-revision-id
target-revision-id)))))))
(let ((new-packages
(package-data-vhashes->new-packages base-packages-vhash
target-packages-vhash))
(removed-packages
(package-data-vhashes->removed-packages base-packages-vhash
target-packages-vhash))
(version-changes
(package-data-version-changes base-packages-vhash
target-packages-vhash)))
(letpar& ((lint-warnings-data
(with-thread-postgresql-connection
(lambda (conn)
(group-list-by-first-n-fields
2
(lint-warning-differences-data conn
base-revision-id
target-revision-id
locale)))))
(channel-news-data
(with-thread-postgresql-connection
(lambda (conn)
(channel-news-differences-data conn
base-revision-id
target-revision-id)))))
(case (most-appropriate-mime-type
'(application/json text/html)
mime-types)
((application/json)
(render-json
`((revisions
. ((base
. ((commit . ,(second base-revision-details))
(datetime . ,(fifth base-revision-details))))
(target
. ((commit . ,(second target-revision-details))
(datetime . ,(fifth target-revision-details))))))
(channel-news . ,(list->vector
`((channel-news . ,(list->vector
(map
(match-lambda
((commit tag title_text body_text change)
@ -393,24 +267,202 @@
version-changes))))
#:extra-headers http-headers-for-unchanging-content))
(else
(render-html
#:sxml (compare `(,@query-parameters
(base_commit . ,(second base-revision-details))
(target_commit . ,(second target-revision-details)))
(guix-revisions-cgit-url-bases
conn
(list base-revision-id
target-revision-id))
new-packages
removed-packages
version-changes
lint-warnings-data
lint-warnings-locale-options
channel-news-data)
#:extra-headers http-headers-for-unchanging-content)))))))))
(letpar& ((lint-warnings-locale-options
(map
(match-lambda
((locale)
locale))
(with-thread-postgresql-connection
(lambda (conn)
(lint-warning-message-locales-for-revision
conn
(assq-ref query-parameters 'target_commit))))))
(cgit-url-bases
(with-thread-postgresql-connection
(lambda (conn)
(guix-revisions-cgit-url-bases
conn
(list base-revision-id
target-revision-id))))))
(render-html
#:sxml (compare query-parameters
cgit-url-bases
new-packages
removed-packages
version-changes
lint-warnings-data
lint-warnings-locale-options
channel-news-data)
#:extra-headers http-headers-for-unchanging-content))))))))))
(define (render-compare-by-datetime mime-types
query-parameters)
(if (any-invalid-query-parameters? query-parameters)
(case (most-appropriate-mime-type
'(application/json text/html)
mime-types)
((application/json)
(render-json
'((error . "invalid query"))))
(else
(letpar& ((base-job
(match (assq-ref query-parameters 'base_commit)
(($ <invalid-query-parameter> value)
(with-thread-postgresql-connection
(lambda (conn)
(select-job-for-commit conn value))))
(_ #f)))
(target-job
(match (assq-ref query-parameters 'target_commit)
(($ <invalid-query-parameter> value)
(with-thread-postgresql-connection
(lambda (conn)
(select-job-for-commit conn value))))
(_ #f))))
(render-html
#:sxml (compare-invalid-parameters
query-parameters
base-job
target-job)))))
(let ((base-branch (assq-ref query-parameters 'base_branch))
(base-datetime (assq-ref query-parameters 'base_datetime))
(target-branch (assq-ref query-parameters 'target_branch))
(target-datetime (assq-ref query-parameters 'target_datetime))
(locale (assq-ref query-parameters 'locale)))
(letpar& ((base-revision-details
(with-thread-postgresql-connection
(lambda (conn)
(select-guix-revision-for-branch-and-datetime
conn
base-branch
base-datetime))))
(target-revision-details
(with-thread-postgresql-connection
(lambda (conn)
(select-guix-revision-for-branch-and-datetime
conn
target-branch
target-datetime)))))
(letpar& ((lint-warnings-locale-options
(map
(match-lambda
((locale)
locale))
(with-thread-postgresql-connection
(lambda (conn)
(lint-warning-message-locales-for-revision
conn
(second base-revision-details)))))))
(let ((base-revision-id
(first base-revision-details))
(target-revision-id
(first target-revision-details)))
(let-values
(((base-packages-vhash target-packages-vhash)
(package-data->package-data-vhashes
(parallel-via-thread-pool-channel
(with-thread-postgresql-connection
(lambda (conn)
(package-differences-data conn
base-revision-id
target-revision-id)))))))
(let* ((new-packages
(package-data-vhashes->new-packages base-packages-vhash
target-packages-vhash))
(removed-packages
(package-data-vhashes->removed-packages base-packages-vhash
target-packages-vhash))
(version-changes
(package-data-version-changes base-packages-vhash
target-packages-vhash))
(channel-news-data
(parallel-via-thread-pool-channel
(with-thread-postgresql-connection
(lambda (conn)
(channel-news-differences-data conn
base-revision-id
target-revision-id))))))
(case (most-appropriate-mime-type
'(application/json text/html)
mime-types)
((application/json)
(render-json
`((revisions
. ((base
. ((commit . ,(second base-revision-details))
(datetime . ,(fifth base-revision-details))))
(target
. ((commit . ,(second target-revision-details))
(datetime . ,(fifth target-revision-details))))))
(channel-news . ,(list->vector
(map
(match-lambda
((commit tag title_text body_text change)
`(,@(if (null? commit)
'()
`((commit . ,commit)))
,@(if (null? tag)
'()
`((tag . ,tag)))
(title-text
. ,(map
(match-lambda
((lang . text)
(cons
lang
(texinfo->variants-alist text))))
title_text))
(body-text
. ,(map
(match-lambda
((lang . text)
(cons
lang
(texinfo->variants-alist text))))
body_text))
(change . ,change))))
channel-news-data)))
(new-packages . ,(list->vector new-packages))
(removed-packages . ,(list->vector removed-packages))
(version-changes . ,(list->vector
(map
(match-lambda
((name data ...)
`((name . ,name)
,@data)))
version-changes))))
#:extra-headers http-headers-for-unchanging-content))
(else
(render-html
#:sxml (compare `(,@query-parameters
(base_commit . ,(second base-revision-details))
(target_commit . ,(second target-revision-details)))
(parallel-via-thread-pool-channel
(with-thread-postgresql-connection
(lambda (conn)
(guix-revisions-cgit-url-bases
conn
(list base-revision-id
target-revision-id)))))
new-packages
removed-packages
version-changes
(parallel-via-thread-pool-channel
(group-list-by-first-n-fields
2
(with-thread-postgresql-connection
(lambda (conn)
(lint-warning-differences-data
conn
base-revision-id
target-revision-id
locale)))))
lint-warnings-locale-options
channel-news-data)
#:extra-headers http-headers-for-unchanging-content)))))))))))
(define (render-compare/derivation mime-types
conn
query-parameters)
(if (any-invalid-query-parameters? query-parameters)
(case (most-appropriate-mime-type
@ -427,10 +479,12 @@
(let ((base-derivation (assq-ref query-parameters 'base_derivation))
(target-derivation (assq-ref query-parameters 'target_derivation)))
(let ((data
(derivation-differences-data conn
base-derivation
target-derivation)))
(letpar& ((data
(with-thread-postgresql-connection
(lambda (conn)
(derivation-differences-data conn
base-derivation
target-derivation)))))
(case (most-appropriate-mime-type
'(application/json text/html)
mime-types)
@ -446,7 +500,6 @@
#:extra-headers http-headers-for-unchanging-content)))))))
(define (render-compare/derivations mime-types
conn
query-parameters)
(define (derivations->alist derivations)
(map (match-lambda
@ -470,7 +523,8 @@
(render-html
#:sxml (compare/derivations
query-parameters
(valid-systems conn)
(parallel-via-thread-pool-channel
(with-thread-postgresql-connection valid-systems))
build-status-strings
'()))))
@ -479,41 +533,42 @@
(systems (assq-ref query-parameters 'system))
(targets (assq-ref query-parameters 'target))
(build-statuses (assq-ref query-parameters 'build_status)))
(let*
((data
(package-derivation-differences-data
conn
(commit->revision-id conn base-commit)
(commit->revision-id conn target-commit)
#:systems systems
#:targets targets))
(names-and-versions
(package-derivation-data->names-and-versions data)))
(let-values
(((base-packages-vhash target-packages-vhash)
(package-derivation-data->package-derivation-data-vhashes data)))
(let ((derivation-changes
(package-derivation-data-changes names-and-versions
base-packages-vhash
target-packages-vhash)))
(case (most-appropriate-mime-type
'(application/json text/html)
mime-types)
((application/json)
(render-json
derivation-changes
#:extra-headers http-headers-for-unchanging-content))
(else
(render-html
#:sxml (compare/derivations
query-parameters
(valid-systems conn)
build-status-strings
derivation-changes)
#:extra-headers http-headers-for-unchanging-content)))))))))
(letpar& ((data
(with-thread-postgresql-connection
(lambda (conn)
(package-derivation-differences-data
conn
(commit->revision-id conn base-commit)
(commit->revision-id conn target-commit)
#:systems systems
#:targets targets)))))
(let ((names-and-versions
(package-derivation-data->names-and-versions data)))
(let-values
(((base-packages-vhash target-packages-vhash)
(package-derivation-data->package-derivation-data-vhashes data)))
(let ((derivation-changes
(package-derivation-data-changes names-and-versions
base-packages-vhash
target-packages-vhash)))
(case (most-appropriate-mime-type
'(application/json text/html)
mime-types)
((application/json)
(render-json
derivation-changes
#:extra-headers http-headers-for-unchanging-content))
(else
(render-html
#:sxml (compare/derivations
query-parameters
(parallel-via-thread-pool-channel
(with-thread-postgresql-connection valid-systems))
build-status-strings
derivation-changes)
#:extra-headers http-headers-for-unchanging-content))))))))))
(define (render-compare-by-datetime/derivations mime-types
conn
query-parameters)
(define (derivations->alist derivations)
(map (match-lambda
@ -537,7 +592,8 @@
(render-html
#:sxml (compare-by-datetime/derivations
query-parameters
(valid-systems conn)
(parallel-via-thread-pool-channel
(with-thread-postgresql-connection valid-systems))
build-status-strings
'()
'()
@ -550,50 +606,58 @@
(systems (assq-ref query-parameters 'system))
(targets (assq-ref query-parameters 'target))
(build-statuses (assq-ref query-parameters 'build_status)))
(let*
(letpar&
((base-revision-details
(select-guix-revision-for-branch-and-datetime conn
base-branch
base-datetime))
(with-thread-postgresql-connection
(lambda (conn)
(select-guix-revision-for-branch-and-datetime conn
base-branch
base-datetime))))
(target-revision-details
(select-guix-revision-for-branch-and-datetime conn
target-branch
target-datetime))
(data
(package-derivation-differences-data conn
(first base-revision-details)
(first target-revision-details)
#:systems systems
#:targets targets))
(names-and-versions
(package-derivation-data->names-and-versions data)))
(let-values
(((base-packages-vhash target-packages-vhash)
(package-derivation-data->package-derivation-data-vhashes data)))
(let ((derivation-changes
(package-derivation-data-changes names-and-versions
base-packages-vhash
target-packages-vhash)))
(case (most-appropriate-mime-type
'(application/json text/html)
mime-types)
((application/json)
(render-json
derivation-changes
#:extra-headers http-headers-for-unchanging-content))
(else
(render-html
#:sxml (compare-by-datetime/derivations
query-parameters
(valid-systems conn)
build-status-strings
base-revision-details
target-revision-details
derivation-changes)
#:extra-headers http-headers-for-unchanging-content)))))))))
(with-thread-postgresql-connection
(lambda (conn)
(select-guix-revision-for-branch-and-datetime conn
target-branch
target-datetime)))))
(letpar&
((data
(with-thread-postgresql-connection
(lambda (conn)
(package-derivation-differences-data
conn
(first base-revision-details)
(first target-revision-details)
#:systems systems
#:targets targets)))))
(let ((names-and-versions
(package-derivation-data->names-and-versions data)))
(let-values
(((base-packages-vhash target-packages-vhash)
(package-derivation-data->package-derivation-data-vhashes data)))
(let ((derivation-changes
(package-derivation-data-changes names-and-versions
base-packages-vhash
target-packages-vhash)))
(case (most-appropriate-mime-type
'(application/json text/html)
mime-types)
((application/json)
(render-json
derivation-changes
#:extra-headers http-headers-for-unchanging-content))
(else
(render-html
#:sxml (compare-by-datetime/derivations
query-parameters
(parallel-via-thread-pool-channel
(with-thread-postgresql-connection valid-systems))
build-status-strings
base-revision-details
target-revision-details
derivation-changes)
#:extra-headers http-headers-for-unchanging-content)))))))))))
(define (render-compare/packages mime-types
conn
query-parameters)
(define (package-data-vhash->json vh)
(delete-duplicates
@ -612,29 +676,49 @@
(render-json
'((error . "invalid query"))))
(else
(letpar& ((base-job
(match (assq-ref query-parameters 'base_commit)
(($ <invalid-query-parameter> value)
(with-thread-postgresql-connection
(lambda (conn)
(select-job-for-commit conn value))))
(_ #f)))
(target-job
(match (assq-ref query-parameters 'target_commit)
(($ <invalid-query-parameter> value)
(with-thread-postgresql-connection
(lambda (conn)
(select-job-for-commit conn value))))
(_ #f))))
(render-html
#:sxml (compare-invalid-parameters
query-parameters
(match (assq-ref query-parameters 'base_commit)
(($ <invalid-query-parameter> value)
(select-job-for-commit conn value))
(_ #f))
(match (assq-ref query-parameters 'target_commit)
(($ <invalid-query-parameter> value)
(select-job-for-commit conn value))
(_ #f))))))
base-job
target-job)))))
(let ((base-commit (assq-ref query-parameters 'base_commit))
(target-commit (assq-ref query-parameters 'target_commit)))
(let ((base-revision-id (commit->revision-id conn base-commit))
(target-revision-id (commit->revision-id conn target-commit)))
(letpar& ((base-revision-id
(with-thread-postgresql-connection
(lambda (conn)
(commit->revision-id
conn
base-commit))))
(target-revision-id
(with-thread-postgresql-connection
(lambda (conn)
(commit->revision-id
conn
target-commit)))))
(let-values
(((base-packages-vhash target-packages-vhash)
(package-data->package-data-vhashes
(package-differences-data conn
base-revision-id
target-revision-id))))
(parallel-via-thread-pool-channel
(with-thread-postgresql-connection
(lambda (conn)
(package-differences-data conn
base-revision-id
target-revision-id)))))))
(case (most-appropriate-mime-type
'(application/json text/html)
mime-types)