config: add warnings on skipped URIs

There is a function `find_suitable_uri()` that basically looks for a
URI with non-zero address and port. This patch adds logging that should
ensure that it is easy to understand if a URI was skipped and why.
Note that additional logging is disabled by default and happens only
in sharding and replicaset configuration.

Closes #9644

NO_DOC=internal
NO_TEST=hard to test internal logging

changelogs/unreleased/gh-9644-verbose-uri-error.md

@@ -2,3 +2,5 @@
 
 * Added a subject URI to the error that is thrown on configuration
   verification (gh-9644).
+* Added a warning with the skipped (unsuitable) URI to replicaset
+  and sharding configuration (gh-9644).

src/box/lua/config/applier/box_cfg.lua

@@ -36,7 +36,8 @@ local function peer_uris(configdata)
         -- A user may configure a custom data flow using
         -- `replication.peers` option.
         if not is_anon then
-            local uri = instance_config:instance_uri(iconfig_def, 'peer')
+            local uri = instance_config:instance_uri(iconfig_def, 'peer',
+                {log_prefix = "replicaset dataflow configuration: "})
             if uri == nil then
                 log.info('%s: instance %q has no iproto.advertise.peer or ' ..
                     'iproto.listen URI suitable to create a client socket',

src/box/lua/config/configdata.lua

@@ -70,9 +70,10 @@ function methods.names(self)
     }
 end
 
-function methods._instance_uri(self, uri_type, opts)
+function methods._instance_uri(self, uri_type, opts, log_opts)
     assert(uri_type == 'peer' or uri_type == 'sharding')
-    return instance_config:instance_uri(choose_iconfig(self, opts), uri_type)
+    return instance_config:instance_uri(choose_iconfig(self, opts), uri_type,
+                                        log_opts)
 end
 
 -- Generate a part of a vshard configuration that relates to
@@ -95,7 +96,8 @@ function methods._instance_sharding(self, opts)
         return nil
     end
     local zone = self:get('sharding.zone', opts)
-    local uri = self:_instance_uri('sharding', opts)
+    local uri = self:_instance_uri('sharding', opts,
+                                   {log_prefix = "sharding configuration: "})
     if uri == nil then
         local err = 'No suitable URI provided for instance %q'
         error(err:format(opts.instance), 0)

src/box/lua/config/instance_config.lua

@@ -5,6 +5,7 @@ local uuid = require('uuid')
 local urilib = require('uri')
 local fio = require('fio')
 local file = require('internal.config.utils.file')
+local log = require('internal.config.utils.log')
 
 -- List of annotations:
 --
@@ -224,20 +225,29 @@ end
 --
 -- See the uri_is_suitable_to_connect() method in the instance
 -- schema object for details.
-local function find_suitable_uri_to_connect(listen)
+local function find_suitable_uri_to_connect(listen, opts)
+    local opts = opts or {}
+    assert(opts.log_prefix == nil or type(opts.log_prefix) == 'string')
+
     for _, u in ipairs(listen) do
         assert(u.uri ~= nil)
         local uri = urilib.parse(u.uri)
-        if uri ~= nil and uri_is_suitable_to_connect(uri) then
-            -- The urilib.format() call has the second optional
-            -- argument `write_password`. Let's assume that the
-            -- given URIs are to listen on them and so have no
-            -- user/password.
-            --
-            -- NB: We need to format the URI back to construct the
-            -- 'uri' field. urilib.parse() creates separate 'host'
-            -- and 'service'.
-            return urilib.format(uri), u.params
+        if uri ~= nil then
+            local ok, err = uri_is_suitable_to_connect(uri)
+            if ok then
+                -- The urilib.format() call has the second optional
+                -- argument `write_password`. Let's assume that the
+                -- given URIs are to listen on them and so have no
+                -- user/password.
+                --
+                -- NB: We need to format the URI back to construct the
+                -- 'uri' field. urilib.parse() creates separate 'host'
+                -- and 'service'.
+                return urilib.format(uri), u.params
+            elseif opts.log_prefix then
+                log.warn(("%sunsuitable URI %q: %s")
+                                :format(opts.log_prefix, u.uri, err))
+            end
         end
     end
     return nil
@@ -264,7 +274,7 @@ local function find_password(self, iconfig, username)
     return nil
 end
 
-local function instance_uri(self, iconfig, advertise_type)
+local function instance_uri(self, iconfig, advertise_type, opts)
     assert(advertise_type == 'peer' or advertise_type == 'sharding')
 
     -- An effective value of iproto.advertise.sharding defaults to
@@ -288,7 +298,7 @@ local function instance_uri(self, iconfig, advertise_type)
             return nil
         end
         uri = table.copy(uri)
-        uri.uri, uri.params = find_suitable_uri_to_connect(listen)
+        uri.uri, uri.params = find_suitable_uri_to_connect(listen, opts)
     end
     -- No URI found for the given instance.
     if uri.uri == nil then