config: Add a new option connect_timeout

connect_timeout can be used to increase the time Spack waits for the
server to answer. This can be used to work around slow connections or
servers.

Fixes #14700

lib/spack/spack/config.py

@@ -97,6 +97,7 @@
 config_defaults = {
     'config': {
         'debug': False,
+        'connect_timeout': 10,
         'verify_ssl': True,
         'checksum': True,
         'dirty': False,

lib/spack/spack/fetch_strategy.py

@@ -326,11 +326,15 @@ def _fetch_from_url(self, url):
             '-D',
             '-',  # print out HTML headers
             '-L',  # resolve 3xx redirects
-            # Timeout if can't establish a connection after 10 sec.
-            '--connect-timeout', '10',
             url,
         ]
 
+        connect_timeout = spack.config.get('config:connect_timeout')
+
+        if connect_timeout > 0:
+            # Timeout if can't establish a connection after n sec.
+            curl_args.extend(['--connect-timeout', str(connect_timeout)])
+
         if not spack.config.get('config:verify_ssl'):
             curl_args.append('-k')
 

lib/spack/spack/schema/config.py

@@ -55,6 +55,7 @@
             },
             'source_cache': {'type': 'string'},
             'misc_cache': {'type': 'string'},
+            'connect_timeout': {'type': 'integer', 'minimum': 0},
             'verify_ssl': {'type': 'boolean'},
             'suppress_gpg_warnings': {'type': 'boolean'},
             'install_missing_compilers': {'type': 'boolean'},