add plain Hash database support

Useful as a proof-of-concept and for benchmark base.

1 files changed, 75 insertions, 0 deletions

diff --git a/lib/metropolis/hash.rb b/lib/metropolis/hash.rb
new file mode 100644
index 0000000..698aef0
--- /dev/null
+++ b/lib/metropolis/hash.rb
@@ -0,0 +1,75 @@
+# -*- encoding: binary -*-
+require 'tempfile'
+
+# use a Ruby hash as a plain data store
+# It can unmarshal a hash from disk
+module Metropolis::Hash
+  include Metropolis::Common
+
+  def setup(opts)
+    super
+    if @path = opts[:path]
+      begin
+        @db = Marshal.load(File.open(@path, "rb") { |fp| fp.read })
+        Hash === @db or raise ArgumentError, "#@path is not a marshaled Hash"
+      rescue Errno::ENOENT
+        @db = {}
+      end
+    else
+      @db = {}
+    end
+    if @readonly
+      extend Metropolis::Common::RO
+    else
+      args = [ @db, @path, !!opts[:fsync] ]
+      @clean_proc = Metropolis::Hash.finalizer_callback(args)
+      ObjectSpace.define_finalizer(self, @clean_proc)
+    end
+  end
+
+  def close!
+    unless @readonly
+      @clean_proc.call
+      ObjectSpace.undefine_finalizer(self)
+    end
+    @db = @path = nil
+  end
+
+  def get(key)
+    value = @db[key] or return r(404)
+    [ 200, { 'Content-Length' => value.size.to_s }.merge!(@headers), [ value ] ]
+  end
+
+  def put(key, env)
+    value = env["rack.input"].read
+    case env['HTTP_X_TT_PDMODE']
+    when '1'
+      @db.exists?(key) and r(409)
+      @db[key] = value
+    when '2'
+      (tmp = @db[key] ||= "") << value
+    else
+      @db[key] = value
+    end
+    r(201)
+  end
+
+  def delete(key)
+    r(@db.delete(key) ? 200 : 404)
+  end
+
+  def self.finalizer_callback(data)
+    lambda {
+      db, path, fsync = data
+      dir = File.dirname(path)
+      tmp = Tempfile.new('hash_save', dir)
+      tmp.binmode
+      tmp.sync = true
+      tmp.write(Marshal.dump(db))
+      tmp.fsync if fsync
+      File.rename(tmp.path, path)
+      File.open(dir) { |d| d.fsync } if fsync
+      tmp.close!
+    }
+  end
+end