put receiving in a transaction, to prevent the crazy duplicate index errors and hopefully fix federation visibility.

app/models/post.rb

@@ -83,8 +83,8 @@ class Post < ActiveRecord::Base
     #exists_locally?
     #you know about it, and it is mutable
     #you know about it, and it is not mutable
-
-    local_post = Post.where(:guid => self.guid).first
+    self.class.transaction do
+      local_post = self.class.where(:guid => self.guid).first
       if local_post && local_post.author_id == self.author_id
         known_post = user.find_visible_post_by_id(self.guid, :key => :guid)
         if known_post
@@ -112,6 +112,7 @@ class Post < ActiveRecord::Base
         Rails.logger.info("event=receive payload_type=#{self.class} update=true status=abort sender=#{self.diaspora_handle} reason='update not from post owner' existing_post=#{self.id}")
       end
     end
+  end
 
   def activity_streams?
     false

lib/diaspora/relayable.rb

@@ -36,6 +36,7 @@ module Diaspora
     end
 
     def receive(user, person)
+      self.class.transaction do
         object = self.class.where(:guid => self.guid).first || self
 
         unless object.parent.author == user.person || object.verify_parent_author_signature
@@ -51,7 +52,7 @@ module Diaspora
 
         #dispatch object DOWNSTREAM, received it via UPSTREAM
         unless user.owns?(object)
-        object.save!
+          object.save 
           Postzord::Dispatch.new(user, object).post
         end
 
@@ -60,6 +61,7 @@ module Diaspora
           object
         end
       end
+    end
 
     def after_receive(user, person)
       self