Stop using a pool of threads for database operations

Now that squee cooperates with suspendable ports, this is unnecessary. Use a
connection pool to still support running queries in parallel using multiple
connections.

1 files changed, 235 insertions, 277 deletions

diff --git a/guix-data-service/web/compare/controller.scm b/guix-data-service/web/compare/controller.scm
index 3d96aa4..6380651 100644
--- a/guix-data-service/web/compare/controller.scm
+++ b/guix-data-service/web/compare/controller.scm
@@ -30,6 +30,7 @@
   #:use-module (guix-data-service web util)
   #:use-module (guix-data-service web render)
   #:use-module (guix-data-service web query-parameters)
+  #:use-module (guix-data-service web controller)
   #:use-module (guix-data-service model utils)
   #:use-module (guix-data-service comparison)
   #:use-module (guix-data-service jobs load-new-guix-revision)
@@ -55,42 +56,38 @@
   s)
 
 (define (parse-commit s)
-  (parallel-via-thread-pool-channel
-   (with-thread-postgresql-connection
-    (lambda (conn)
-      (let* ((job-details
-              (select-job-for-commit conn s))
-             (job-state
-              (assq-ref job-details 'state)))
-        (if job-details
-            (cond
-             ((string=? job-state "succeeded")
-              s)
-             ((string=? job-state "queued")
-              (make-invalid-query-parameter
-               s
-               `("data unavailable, "
-                 (a (@ (href ,(string-append
-                               "/revision/" s)))
-                    "yet to process revision"))))
-             ((string=? job-state "failed")
-              (make-invalid-query-parameter
-               s
-               `("data unavailable, "
-                 (a (@ (href ,(string-append
-                               "/revision/" s)))
-                    "failed to process revision"))))
-             (else
-              (make-invalid-query-parameter
-               s "unknown job state")))
+  (with-resource-from-pool (connection-pool) conn
+    (let* ((job-details
+            (select-job-for-commit conn s))
+           (job-state
+            (assq-ref job-details 'state)))
+      (if job-details
+          (cond
+           ((string=? job-state "succeeded")
+            s)
+           ((string=? job-state "queued")
             (make-invalid-query-parameter
-             s "unknown commit")))))))
+             s
+             `("data unavailable, "
+               (a (@ (href ,(string-append
+                             "/revision/" s)))
+                  "yet to process revision"))))
+           ((string=? job-state "failed")
+            (make-invalid-query-parameter
+             s
+             `("data unavailable, "
+               (a (@ (href ,(string-append
+                             "/revision/" s)))
+                  "failed to process revision"))))
+           (else
+            (make-invalid-query-parameter
+             s "unknown job state")))
+          (make-invalid-query-parameter
+           s "unknown commit")))))
 
 (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))))
+  (if (with-resource-from-pool (connection-pool) conn
+        (select-derivation-by-file-name conn file-name))
       file-name
       (make-invalid-query-parameter
        file-name "unknown derivation")))
@@ -235,18 +232,16 @@
       (letpar& ((base-job
                  (match (assq-ref query-parameters 'base_commit)
                    (($ <invalid-query-parameter> value)
-                    (with-thread-postgresql-connection
-                     (lambda (conn)
-                       (and (string? value)
-                            (select-job-for-commit conn value)))))
+                    (with-resource-from-pool (connection-pool) conn
+                      (and (string? value)
+                           (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)
-                       (and (string? value)
-                            (select-job-for-commit conn value)))))
+                    (with-resource-from-pool (connection-pool) conn
+                      (and (string? value)
+                           (select-job-for-commit conn value))))
                    (_ #f))))
         (case (most-appropriate-mime-type
                '(application/json text/html)
@@ -281,28 +276,24 @@
                             #f
                             #f)))))
       (letpar& ((base-revision-id
-                 (with-thread-postgresql-connection
-                  (lambda (conn)
-                    (commit->revision-id
-                     conn
-                     (assq-ref query-parameters 'base_commit)))))
+                 (with-resource-from-pool (connection-pool) 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)))))
+                 (with-resource-from-pool (connection-pool) 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
-               (parallel-via-thread-pool-channel
-                (with-thread-postgresql-connection
-                 (lambda (conn)
-                   (package-differences-data conn
-                                             base-revision-id
-                                             target-revision-id)))))))
+               (with-resource-from-pool (connection-pool) 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))
@@ -313,20 +304,18 @@
                  (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
+                       (with-resource-from-pool (connection-pool) conn
+                         (group-list-by-first-n-fields
+                          2
+                          (lint-warning-differences-data conn
                                                          base-revision-id
-                                                         target-revision-id)))))
+                                                         target-revision-id
+                                                         locale))))
+                      (channel-news-data
+                       (with-resource-from-pool (connection-pool) conn
+                         (channel-news-differences-data conn
+                                                        base-revision-id
+                                                        target-revision-id))))
               (case (most-appropriate-mime-type
                      '(application/json text/html)
                      mime-types)
@@ -412,18 +401,16 @@
                              (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
+                             (with-resource-from-pool (connection-pool) conn
+                               (lint-warning-message-locales-for-revision
                                 conn
-                                (list base-revision-id
-                                      target-revision-id))))))
+                                (assq-ref query-parameters 'target_commit)))))
+                           (cgit-url-bases
+                            (with-resource-from-pool (connection-pool) conn
+                              (guix-revisions-cgit-url-bases
+                               conn
+                               (list base-revision-id
+                                     target-revision-id)))))
                    (render-html
                     #:sxml (compare query-parameters
                                     'revision
@@ -463,29 +450,26 @@
             (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))))
+                   (with-resource-from-pool (connection-pool) 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)))))))
+                   (with-resource-from-pool (connection-pool) conn
+                     (select-guix-revision-for-branch-and-datetime
+                      conn
+                      target-branch
+                      target-datetime))))
+          (let ((lint-warnings-locale-options
+                 (map
+                  (match-lambda
+                    ((locale)
+                     locale))
+                  (with-resource-from-pool (connection-pool) conn
+                    (lint-warning-message-locales-for-revision
+                     conn
+                     (second base-revision-details))))))
             (let ((base-revision-id
                    (first base-revision-details))
                   (target-revision-id
@@ -493,12 +477,10 @@
               (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)))))))
+                      (with-resource-from-pool (connection-pool) 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))
@@ -509,12 +491,10 @@
                         (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))))))
+                        (with-resource-from-pool (connection-pool) conn
+                          (channel-news-differences-data conn
+                                                         base-revision-id
+                                                         target-revision-id))))
                   (case (most-appropriate-mime-type
                          '(application/json text/html)
                          mime-types)
@@ -567,32 +547,29 @@
                       #: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)))
-                                      'datetime
-                                      (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)
+                      #:sxml (compare
+                              `(,@query-parameters
+                                (base_commit . ,(second base-revision-details))
+                                (target_commit . ,(second target-revision-details)))
+                              'datetime
+                              (with-resource-from-pool (connection-pool) conn
+                                (guix-revisions-cgit-url-bases
+                                 conn
+                                 (list base-revision-id
+                                       target-revision-id)))
+                              new-packages
+                              removed-packages
+                              version-changes
+                              (group-list-by-first-n-fields
+                               2
+                               (with-resource-from-pool (connection-pool) 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
@@ -612,12 +589,11 @@
 
       (let ((base-derivation    (assq-ref query-parameters 'base_derivation))
             (target-derivation  (assq-ref query-parameters 'target_derivation)))
-        (letpar& ((data
-                   (with-thread-postgresql-connection
-                    (lambda (conn)
-                      (derivation-differences-data conn
-                                                   base-derivation
-                                                   target-derivation)))))
+        (let ((data
+               (with-resource-from-pool (connection-pool) conn
+                 (derivation-differences-data conn
+                                              base-derivation
+                                              target-derivation))))
           (case (most-appropriate-mime-type
                  '(application/json text/html)
                  mime-types)
@@ -655,9 +631,8 @@
                              ((? string? value) value)
                              (_ #f))
                            (lambda (commit)
-                             (with-thread-postgresql-connection
-                              (lambda (conn)
-                                (select-job-for-commit conn commit))))))
+                             (with-resource-from-pool (connection-pool) conn
+                               (select-job-for-commit conn commit)))))
                    (target-job
                     (and=> (match (assq-ref query-parameters 'target_commit)
                              (($ <invalid-query-parameter> value)
@@ -665,9 +640,8 @@
                              ((? string? value) value)
                              (_ #f))
                            (lambda (commit)
-                             (with-thread-postgresql-connection
-                              (lambda (conn)
-                                (select-job-for-commit conn commit)))))))
+                             (with-resource-from-pool (connection-pool) conn
+                               (select-job-for-commit conn commit))))))
            (render-json
             `((error . "invalid query")
               (query_parameters
@@ -690,14 +664,14 @@
               (target_job . ,target-job)))))
         (else
          (letpar& ((systems
-                    (with-thread-postgresql-connection
-                     list-systems))
+                    (call-with-resource-from-pool (connection-pool)
+                      list-systems))
                    (targets
-                    (with-thread-postgresql-connection
-                     valid-targets))
+                    (call-with-resource-from-pool (connection-pool)
+                      valid-targets))
                    (build-server-urls
-                    (with-thread-postgresql-connection
-                     select-build-server-urls-by-id)))
+                    (call-with-resource-from-pool (connection-pool)
+                      select-build-server-urls-by-id)))
          (render-html
           #:sxml (compare/package-derivations
                   query-parameters
@@ -718,19 +692,18 @@
             (after-name     (assq-ref query-parameters 'after_name))
             (limit-results  (assq-ref query-parameters 'limit_results)))
         (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
-                       #:build-change build-change
-                       #:after-name after-name
-                       #:limit-results limit-results))))
+                   (with-resource-from-pool (connection-pool) conn
+                     (package-derivation-differences-data
+                      conn
+                      (commit->revision-id conn base-commit)
+                      (commit->revision-id conn target-commit)
+                      #:systems systems
+                      #:targets targets
+                      #:build-change build-change
+                      #:after-name after-name
+                      #:limit-results limit-results)))
                   (build-server-urls
-                   (with-thread-postgresql-connection
+                   (with-resource-from-pool (connection-pool) conn
                     select-build-server-urls-by-id)))
           (let ((names-and-versions
                  (package-derivation-data->names-and-versions data)))
@@ -755,11 +728,11 @@
                        . ,derivation-changes))))
                   (else
                    (letpar& ((systems
-                              (with-thread-postgresql-connection
-                               list-systems))
+                              (call-with-resource-from-pool (connection-pool)
+                                list-systems))
                              (targets
-                              (with-thread-postgresql-connection
-                               valid-targets)))
+                              (call-with-resource-from-pool (connection-pool)
+                                valid-targets)))
                      (render-html
                       #:sxml (compare/package-derivations
                               query-parameters
@@ -784,11 +757,11 @@
           #:sxml (compare/package-derivations
                   query-parameters
                   'datetime
-                  (parallel-via-thread-pool-channel
-                   (with-thread-postgresql-connection list-systems))
+                  (call-with-resource-from-pool (connection-pool)
+                    list-systems)
                   (valid-targets->options
-                   (parallel-via-thread-pool-channel
-                    (with-thread-postgresql-connection valid-targets)))
+                   (call-with-resource-from-pool (connection-pool)
+                     valid-targets))
                   build-status-strings
                   '()
                   '()
@@ -807,30 +780,27 @@
             (limit-results  (assq-ref query-parameters 'limit_results)))
         (letpar&
             ((base-revision-details
-              (with-thread-postgresql-connection
-               (lambda (conn)
-                 (select-guix-revision-for-branch-and-datetime conn
-                                                               base-branch
-                                                               base-datetime))))
+              (with-resource-from-pool (connection-pool) 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)))))
+              (with-resource-from-pool (connection-pool) 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
-                    #:build-change build-change
-                    #:after-name after-name
-                    #:limit-results limit-results)))))
+                (with-resource-from-pool (connection-pool) conn
+                  (package-derivation-differences-data
+                   conn
+                   (first base-revision-details)
+                   (first target-revision-details)
+                   #:systems systems
+                   #:targets targets
+                   #:build-change build-change
+                   #:after-name after-name
+                   #:limit-results limit-results))))
             (let ((names-and-versions
                    (package-derivation-data->names-and-versions data)))
               (let-values
@@ -859,15 +829,17 @@
                       #:sxml (compare/package-derivations
                               query-parameters
                               'datetime
-                              (parallel-via-thread-pool-channel
-                               (with-thread-postgresql-connection list-systems))
+                              (call-with-resource-from-pool
+                               (connection-pool)
+                               list-systems)
                               (valid-targets->options
-                               (parallel-via-thread-pool-channel
-                                (with-thread-postgresql-connection valid-targets)))
+                               (call-with-resource-from-pool
+                                (connection-pool)
+                                valid-targets))
                               build-status-strings
-                              (parallel-via-thread-pool-channel
-                               (with-thread-postgresql-connection
-                                select-build-server-urls-by-id))
+                              (call-with-resource-from-pool
+                               (connection-pool)
+                               select-build-server-urls-by-id)
                               derivation-changes
                               base-revision-details
                               target-revision-details))))))))))))
@@ -894,16 +866,14 @@
          (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))))
+                       (with-resource-from-pool (connection-pool) 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))))
+                       (with-resource-from-pool (connection-pool) conn
+                         (select-job-for-commit conn value)))
                       (_ #f))))
          (render-html
           #:sxml (compare-invalid-parameters
@@ -914,26 +884,22 @@
       (let ((base-commit    (assq-ref query-parameters 'base_commit))
             (target-commit  (assq-ref query-parameters 'target_commit)))
         (letpar& ((base-revision-id
-                   (with-thread-postgresql-connection
-                    (lambda (conn)
-                      (commit->revision-id
-                       conn
-                       base-commit))))
+                   (with-resource-from-pool (connection-pool) conn
+                     (commit->revision-id
+                      conn
+                      base-commit)))
                   (target-revision-id
-                   (with-thread-postgresql-connection
-                    (lambda (conn)
-                      (commit->revision-id
-                       conn
-                       target-commit)))))
+                   (with-resource-from-pool (connection-pool) conn
+                     (commit->revision-id
+                      conn
+                      target-commit))))
           (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)))))))
+                 (with-resource-from-pool (connection-pool) conn
+                   (package-differences-data conn
+                                             base-revision-id
+                                             target-revision-id)))))
             (case (most-appropriate-mime-type
                    '(application/json text/html)
                    mime-types)
@@ -967,10 +933,10 @@
           '((error . "invalid query"))))
         (else
          (letpar& ((systems
-                    (with-thread-postgresql-connection
+                    (with-resource-from-pool (connection-pool) conn
                      list-systems))
                    (build-server-urls
-                    (with-thread-postgresql-connection
+                    (with-resource-from-pool (connection-pool) conn
                      select-build-server-urls-by-id)))
          (render-html
           #:sxml (compare/system-test-derivations
@@ -986,26 +952,23 @@
             (target-commit  (assq-ref query-parameters 'target_commit))
             (system         (assq-ref query-parameters 'system)))
         (letpar& ((data
-                   (with-thread-postgresql-connection
-                    (lambda (conn)
-                      (system-test-derivations-differences-data
-                       conn
-                       (commit->revision-id conn base-commit)
-                       (commit->revision-id conn target-commit)
-                       system))))
+                   (with-resource-from-pool (connection-pool) conn
+                     (system-test-derivations-differences-data
+                      conn
+                      (commit->revision-id conn base-commit)
+                      (commit->revision-id conn target-commit)
+                      system)))
                   (build-server-urls
-                   (with-thread-postgresql-connection
+                   (with-resource-from-pool (connection-pool) conn
                     select-build-server-urls-by-id))
                   (base-git-repositories
-                   (with-thread-postgresql-connection
-                    (lambda (conn)
-                      (git-repositories-containing-commit conn base-commit))))
+                   (with-resource-from-pool (connection-pool) conn
+                     (git-repositories-containing-commit conn base-commit)))
                   (target-git-repositories
-                   (with-thread-postgresql-connection
-                    (lambda (conn)
-                      (git-repositories-containing-commit conn target-commit))))
+                   (with-resource-from-pool (connection-pool) conn
+                     (git-repositories-containing-commit conn target-commit)))
                   (systems
-                   (with-thread-postgresql-connection
+                   (with-resource-from-pool (connection-pool) conn
                     list-systems)))
           (case (most-appropriate-mime-type
                  '(application/json text/html)
@@ -1040,10 +1003,10 @@
           '((error . "invalid query"))))
         (else
          (letpar& ((systems
-                    (with-thread-postgresql-connection
+                    (with-resource-from-pool (connection-pool) conn
                      list-systems))
                    (build-server-urls
-                    (with-thread-postgresql-connection
+                    (with-resource-from-pool (connection-pool) conn
                      select-build-server-urls-by-id)))
          (render-html
           #:sxml (compare/system-test-derivations
@@ -1062,42 +1025,37 @@
             (system         (assq-ref query-parameters 'system)))
         (letpar&
             ((base-revision-details
-              (with-thread-postgresql-connection
-               (lambda (conn)
-                 (select-guix-revision-for-branch-and-datetime conn
-                                                               base-branch
-                                                               base-datetime))))
+              (with-resource-from-pool (connection-pool) 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)))))
+              (with-resource-from-pool (connection-pool) conn
+                (select-guix-revision-for-branch-and-datetime conn
+                                                              target-branch
+                                                              target-datetime))))
           (letpar& ((data
-                     (with-thread-postgresql-connection
-                      (lambda (conn)
-                        (system-test-derivations-differences-data
-                         conn
-                         (first base-revision-details)
-                         (first target-revision-details)
-                         system))))
+                     (with-resource-from-pool (connection-pool) conn
+                       (system-test-derivations-differences-data
+                        conn
+                        (first base-revision-details)
+                        (first target-revision-details)
+                        system)))
                     (build-server-urls
-                     (with-thread-postgresql-connection
+                     (with-resource-from-pool (connection-pool) conn
                       select-build-server-urls-by-id))
                     (base-git-repositories
-                     (with-thread-postgresql-connection
-                      (lambda (conn)
-                        (git-repositories-containing-commit
-                         conn
-                         (second base-revision-details)))))
+                     (with-resource-from-pool (connection-pool) conn
+                       (git-repositories-containing-commit
+                        conn
+                        (second base-revision-details))))
                     (target-git-repositories
-                     (with-thread-postgresql-connection
-                      (lambda (conn)
-                        (git-repositories-containing-commit
-                         conn
-                         (second target-revision-details)))))
+                     (with-resource-from-pool (connection-pool) conn
+                       (git-repositories-containing-commit
+                        conn
+                        (second target-revision-details))))
                     (systems
-                     (with-thread-postgresql-connection
+                     (with-resource-from-pool (connection-pool) conn
                       list-systems)))
             (case (most-appropriate-mime-type
                    '(application/json text/html)