Move the introducer config reading code into _Config

src/allmydata/client.py

@@ -1,7 +1,6 @@
 import os, stat, time, weakref
 from base64 import urlsafe_b64encode
 from functools import partial
-from errno import ENOENT, EPERM
 
 # On Python 2 this will be the backported package:
 from configparser import NoSectionError
@@ -464,51 +463,13 @@ def create_introducer_clients(config, main_tub, _introducer_factory=None):
     # we return this list
     introducer_clients = []
 
-    introducers_yaml_filename = config.get_private_path("introducers.yaml")
+    introducers = config.get_introducer_configuration()
-    introducers_filepath = FilePath(introducers_yaml_filename)
 
-    try:
+    for petname, introducer_furl in introducers.items():
-        with introducers_filepath.open() as f:
-            introducers_yaml = yamlutil.safe_load(f)
-            if introducers_yaml is None:
-                raise EnvironmentError(
-                    EPERM,
-                    "Can't read '{}'".format(introducers_yaml_filename),
-                    introducers_yaml_filename,
-                )
-            introducers = introducers_yaml.get("introducers", {})
-            log.msg(
-                "found {} introducers in private/introducers.yaml".format(
-                    len(introducers),
-                )
-            )
-    except EnvironmentError as e:
-        if e.errno != ENOENT:
-            raise
-        introducers = {}
-
-    if "default" in introducers.keys():
-        raise ValueError(
-            "'default' introducer furl cannot be specified in introducers.yaml;"
-            " please fix impossible configuration."
-        )
-
-    # read furl from tahoe.cfg
-    tahoe_cfg_introducer_furl = config.get_config("client", "introducer.furl", None)
-    if tahoe_cfg_introducer_furl == "None":
-        raise ValueError(
-            "tahoe.cfg has invalid 'introducer.furl = None':"
-            " to disable it, use 'introducer.furl ='"
-            " or omit the key entirely"
-        )
-    if tahoe_cfg_introducer_furl:
-        introducers[u'default'] = {'furl':tahoe_cfg_introducer_furl}
-
-    for petname, introducer in introducers.items():
         introducer_cache_filepath = FilePath(config.get_private_path("introducer_{}_cache.yaml".format(petname)))
         ic = _introducer_factory(
             main_tub,
-            introducer['furl'].encode("ascii"),
+            introducer_furl.encode("ascii"),
             config.nickname,
             str(allmydata.__full_version__),
             str(_Client.OLDEST_SUPPORTED_VERSION),

src/allmydata/node.py

@@ -21,10 +21,13 @@ import types
 import errno
 import tempfile
 from base64 import b32decode, b32encode
+from errno import ENOENT, EPERM
+from warnings import warn
 
 # On Python 2 this will be the backported package.
 import configparser
 
+from twisted.python.filepath import FilePath
 from twisted.python import log as twlog
 from twisted.application import service
 from twisted.python.failure import Failure
@@ -37,6 +40,9 @@ from allmydata.util.assertutil import _assert
 from allmydata.util.fileutil import abspath_expanduser_unicode
 from allmydata.util.encodingutil import get_filesystem_encoding, quote_output
 from allmydata.util import configutil
+from allmydata.util.yamlutil import (
+    safe_load,
+)
 
 def _common_valid_config():
     return configutil.ValidConfiguration({
@@ -428,6 +434,65 @@ class _Config(object):
             os.path.join(self._basedir, *args)
         )
 
+    def get_introducer_configuration(self):
+        """
+        Get configuration for introducers.
+
+        :return {unicode: unicode}: A mapping from introducer petname to the
+            introducer's fURL.
+        """
+        introducers_yaml_filename = self.get_private_path("introducers.yaml")
+        introducers_filepath = FilePath(introducers_yaml_filename)
+
+        try:
+            with introducers_filepath.open() as f:
+                introducers_yaml = safe_load(f)
+                if introducers_yaml is None:
+                    raise EnvironmentError(
+                        EPERM,
+                        "Can't read '{}'".format(introducers_yaml_filename),
+                        introducers_yaml_filename,
+                    )
+                introducers = {
+                    petname: config["furl"]
+                    for petname, config
+                    in introducers_yaml.get("introducers", {}).items()
+                }
+                log.msg(
+                    "found {} introducers in private/introducers.yaml".format(
+                        len(introducers),
+                    )
+                )
+        except EnvironmentError as e:
+            if e.errno != ENOENT:
+                raise
+            introducers = {}
+
+        if "default" in introducers.keys():
+            raise ValueError(
+                "'default' introducer furl cannot be specified in introducers.yaml;"
+                " please fix impossible configuration."
+            )
+
+        # read furl from tahoe.cfg
+        tahoe_cfg_introducer_furl = self.get_config("client", "introducer.furl", None)
+        if tahoe_cfg_introducer_furl == "None":
+            raise ValueError(
+                "tahoe.cfg has invalid 'introducer.furl = None':"
+                " to disable it, use 'introducer.furl ='"
+                " or omit the key entirely"
+            )
+        if tahoe_cfg_introducer_furl:
+            warn(
+                "tahoe.cfg [client]introducer.furl is deprecated; "
+                "use private/introducers.yaml instead.",
+                category=DeprecationWarning,
+                stacklevel=-1,
+            )
+            introducers['default'] = tahoe_cfg_introducer_furl
+
+        return introducers
+
 
 def create_tub_options(config):
     """