mongo-tail: Rewrite with Mongo Ruby driver 2.2

bin/mongo-tail

@@ -8,11 +8,11 @@ require 'json'
 require 'mongo'
 
 TailConfig = {
-  :d => 'fluent',
-  :c => 'out_mongo_backup',
-  :h => 'localhost',
-  :p => 27017,
-  :n => 10
+  d: 'fluent',
+  c: 'out_mongo_backup',
+  h: 'localhost',
+  p: 27017,
+  n: 10
 }
 
 OptionParser.new { |opt|
@@ -28,51 +28,58 @@ OptionParser.new { |opt|
   opt.parse!(ARGV)
 }
 
+def get_client_options(conf)
+  client_options = {}
+  client_options[:database] = conf[:d]
+  client_options
+end
+
+def get_collection_options
+  collection_options = {}
+  collection_options[:capped] = true
+  collection_options
+end
+
 def get_capped_collection(conf)
-  db = Mongo::MongoClient.new(conf[:h], conf[:p]).db(conf[:d])
-  if db.collection_names.include?(conf[:c])
-    collection = db.collection(conf[:c])
-    if collection.capped?
-      collection
-    else
-      puts "#{conf[:c]} is not capped. mongo-tail can not tail normal collection."
-    end
+  client_options = get_client_options(conf)
+  collection_options = get_collection_options
+  client = Mongo::Client.new(["#{conf[:h]}:#{conf[:p]}"], client_options)
+  collection = client["#{conf[:c]}", collection_options]
+  if collection.capped?
+    collection
   else
-    puts "#{conf[:c]} not found: server = #{conf[:h]}:#{conf[:p]}"
+    puts "#{conf[:c]} is not capped. mongo-tail can not tail normal collection."
   end
 end
 
-def create_cursor_conf(collection, conf)
+def create_skip_number(collection, conf)
   skip = collection.count - conf[:n]
-  cursor_conf = {}
-  cursor_conf[:skip] = skip if skip > 0
-  cursor_conf
+  skip
 end
 
 def tail_n(collection, conf)
-  collection.find({}, create_cursor_conf(collection, conf)).each { |doc|
+  collection.find().skip(create_skip_number(collection, conf)).each {|doc|
     puts doc.to_json
   }
 end
 
 def tail_forever(collection, conf)
-  cursor_conf = create_cursor_conf(collection, conf)
-  cursor_conf[:tailable] = true
-
-  cursor = Mongo::Cursor.new(collection, cursor_conf)
   loop {
-    # TODO: Check more detail of cursor state if needed
-    cursor = Mongo::Cursor.new(collection, cursor_conf) unless cursor.alive?
+    option['_id'] = {'$gt' => BSON::ObjectId(@last_id)} if @last_id
 
-    if doc = cursor.next_document
-      STDOUT.puts doc.to_json
-      STDOUT.flush
+    documents = collection.find(option)
+    if documents.count >= 1
+      documents.each {|doc|
+        STDOUT.puts doc.to_json
+        STDOUT.flush
+        if id = doc.delete('_id')
+          @last_id = id.to_s
+        end
+      }
     else
       sleep 1
     end
   }
-rescue
-  # ignore Mongo::OperationFailuer at CURSOR_NOT_FOUND
 end
 
 exit unless collection = get_capped_collection(TailConfig)