added utils/redis-copy.rb, a script that is able to copy data from one Redis server to another one on the fly.

utils/redis-copy.rb

@@ -0,0 +1,80 @@
+# redis-sha1.rb - Copyright (C) 2009 Salvatore Sanfilippo
+# BSD license, See the COPYING file for more information.
+#
+# Performs the SHA1 sum of the whole datset.
+# This is useful to spot bugs in persistence related code and to make sure
+# Slaves and Masters are in SYNC.
+#
+# If you hack this code make sure to sort keys and set elements as this are
+# unsorted elements. Otherwise the sum may differ with equal dataset.
+
+require 'rubygems'
+require 'redis'
+require 'digest/sha1'
+
+def redisCopy(opts={})
+    sha1=""
+    src = Redis.new(:host => opts[:srchost], :port => opts[:srcport])
+    dst = Redis.new(:host => opts[:dsthost], :port => opts[:dstport])
+    puts "Loading key names..."
+    keys = src.keys('*')
+    puts "Copying #{keys.length} keys..."
+    c = 0
+    keys.each{|k|
+        vtype = src.type?(k)
+        ttl = src.ttl(k).to_i if vtype != "none"
+
+        if vtype == "string"
+            dst[k] = src[k]
+        elsif vtype == "list"
+            list = src.lrange(k,0,-1)
+            if list.length == 0
+                # Empty list special case
+                dst.lpush(k,"")
+                dst.lpop(k)
+            else
+                list.each{|ele|
+                    dst.rpush(k,ele)
+                }
+            end
+        elsif vtype == "set"
+            set = src.smembers(k)
+            if set.length == 0
+                # Empty set special case
+                dst.sadd(k,"")
+                dst.srem(k,"")
+            else
+                set.each{|ele|
+                    dst.sadd(k,ele)
+                }
+            end
+        elsif vtype == "none"
+            puts "WARNING: key '#{k}' was removed in the meanwhile."
+        end
+
+        # Handle keys with an expire time set
+        if ttl != -1 and vtype != "none"
+            dst.expire(k,ttl)
+        end
+
+        c = c+1
+        if (c % 1000) == 0
+            puts "#{c}/#{keys.length} completed"
+        end
+    }
+    puts "DONE!"
+end
+
+if ARGV.length != 4
+    puts "Usage: redis-copy.rb <srchost> <srcport> <dsthost> <dstport>"
+    exit 1
+end
+puts "WARNING: it's up to you to FLUSHDB the destination host before to continue, press any key when ready."
+STDIN.gets
+srchost = ARGV[0]
+srcport = ARGV[1]
+dsthost = ARGV[2]
+dstport = ARGV[3]
+puts "Copying #{srchost}:#{srcport} into #{dsthost}:#{dstport}"
+redisCopy(:srchost => srchost, :srcport => srcport.to_i,
+          :dsthost => dsthost, :dstport => dstport.to_i)