services: web: Add support for configuring the nginx server names hash.

The nginx service can fail to start if the server names hash bucket size is
too small, which can happen on some systems, and when using QEMU, depending on
the CPU.

* gnu/services/web.scm (<nginx-configuration>): Add
  server-names-hash-bucket-size and server-names-hash-bucket-max-size.
  (default-nginx-config): Add support for the new hash bucket size parameters.
  (nginx-service, nginx-activation): Pass the new hash bucket size parameters
  through to the default-nginx-config procedure.
* doc/guix.texi (Web Services): Document the new hash bucket size parameters.

doc/guix.texi

@@ -14913,6 +14913,13 @@ This can be useful if you have an existing configuration file, or it's
 not possible to do what is required through the other parts of the
 nginx-configuration record.
 
+@item @code{server-names-hash-bucket-size} (default: @code{#f})
+Bucket size for the server names hash tables, defaults to @code{#f} to
+use the size of the processors cache line.
+
+@item @code{server-names-hash-bucket-max-size} (default: @code{#f})
+Maximum bucket size for the server names hash tables.
+
 @end table
 @end deffn
 

gnu/services/web.scm

@@ -38,6 +38,8 @@
             nginx-configuration-run-directory
             nginx-configuration-server-blocks
             nginx-configuration-upstream-blocks
+            nginx-configuration-server-names-hash-bucket-size
+            nginx-configuration-server-names-hash-bucket-max-size
             nginx-configuration-file
 
             <nginx-server-configuration>
@@ -141,6 +143,10 @@
                  (default '()))          ;list of <nginx-server-configuration>
   (upstream-blocks nginx-configuration-upstream-blocks
                    (default '()))      ;list of <nginx-upstream-configuration>
+  (server-names-hash-bucket-size nginx-configuration-server-names-hash-bucket-size
+                                 (default #f))
+  (server-names-hash-bucket-max-size nginx-configuration-server-names-hash-bucket-max-size
+                                     (default #f))
   (file          nginx-configuration-file         ;#f | string | file-like
                  (default #f)))
 
@@ -225,7 +231,9 @@ of index files."
         (cons head out)))
   (fold-right flatten1 '() lst))
 
-(define (default-nginx-config nginx log-directory run-directory server-list upstream-list)
+(define (default-nginx-config nginx log-directory run-directory server-list
+                              upstream-list server-names-hash-bucket-size
+                              server-names-hash-bucket-max-size)
   (apply mixed-text-file "nginx.conf"
          (flatten
           "user nginx nginx;\n"
@@ -239,6 +247,18 @@ of index files."
           "    scgi_temp_path " run-directory "/scgi_temp;\n"
           "    access_log " log-directory "/access.log;\n"
           "    include " nginx "/share/nginx/conf/mime.types;\n"
+          (if server-names-hash-bucket-size
+              (string-append
+               "    server_names_hash_bucket_size "
+               (number->string server-names-hash-bucket-size)
+               ";\n")
+              "")
+          (if server-names-hash-bucket-max-size
+              (string-append
+               "    server_names_hash_bucket_max_size "
+               (number->string server-names-hash-bucket-max-size)
+               ";\n")
+              "")
           "\n"
           (map emit-nginx-upstream-config upstream-list)
           (map emit-nginx-server-config server-list)
@@ -258,7 +278,8 @@ of index files."
 (define nginx-activation
   (match-lambda
     (($ <nginx-configuration> nginx log-directory run-directory server-blocks
-                              upstream-blocks file)
+                              upstream-blocks server-names-hash-bucket-size
+                              server-names-hash-bucket-max-size file)
      #~(begin
          (use-modules (guix build utils))
 
@@ -279,13 +300,16 @@ of index files."
          (system* (string-append #$nginx "/sbin/nginx")
                   "-c" #$(or file
                              (default-nginx-config nginx log-directory
-                               run-directory server-blocks upstream-blocks))
+                               run-directory server-blocks upstream-blocks
+                               server-names-hash-bucket-size
+                               server-names-hash-bucket-max-size))
                   "-t")))))
 
 (define nginx-shepherd-service
   (match-lambda
     (($ <nginx-configuration> nginx log-directory run-directory server-blocks
-                              upstream-blocks file)
+                              upstream-blocks server-names-hash-bucket-size
+                              server-names-hash-bucket-max-size file)
      (let* ((nginx-binary (file-append nginx "/sbin/nginx"))
             (nginx-action
              (lambda args
@@ -294,7 +318,9 @@ of index files."
                     (system* #$nginx-binary "-c"
                              #$(or file
                                    (default-nginx-config nginx log-directory
-                                     run-directory server-blocks upstream-blocks))
+                                     run-directory server-blocks upstream-blocks
+                                     server-names-hash-bucket-size
+                                     server-names-hash-bucket-max-size))
                              #$@args))))))
 
        ;; TODO: Add 'reload' action.