Fix mt issues (#178)

src/db/pool.cr

@@ -216,8 +216,10 @@ module DB
 
     private def build_resource : T
       resource = @factory.call
-      @total << resource
+      sync do
-      @idle << resource
+        @total << resource
+        @idle << resource
+      end
       resource
     end
 

src/db/pool_prepared_statement.cr

@@ -7,6 +7,7 @@ module DB
   class PoolPreparedStatement < PoolStatement
     # connections where the statement was prepared
     @connections = Set(WeakRef(Connection)).new
+    @mutex = Mutex.new
 
     def initialize(db : Database, query : String)
       super
@@ -20,35 +21,47 @@ module DB
     end
 
     protected def do_close
-      # TODO close all statements on all connections.
+      @mutex.synchronize do
-      # currently statements are closed when the connection is closed.
+        # TODO close all statements on all connections.
+        # currently statements are closed when the connection is closed.
 
-      # WHAT-IF the connection is busy? Should each statement be able to
+        # WHAT-IF the connection is busy? Should each statement be able to
-      # deallocate itself when the connection is free.
+        # deallocate itself when the connection is free.
-      @connections.clear
+        @connections.clear
+      end
     end
 
     # builds a statement over a real connection
     # the connection is registered in `@connections`
     private def build_statement : Statement
       clean_connections
-      conn, existing = @db.checkout_some(@connections)
+
+      conn, existing = @mutex.synchronize do
+        @db.checkout_some(@connections)
+      end
+
       begin
         stmt = conn.prepared.build(@query)
       rescue ex
         conn.release
         raise ex
       end
-      @connections << WeakRef.new(conn) unless existing
+      unless existing
+        @mutex.synchronize do
+          @connections << WeakRef.new(conn)
+        end
+      end
       stmt
     end
 
     private def clean_connections
-      # remove disposed or closed connections
+      @mutex.synchronize do
-      @connections.each do |ref|
+        # remove disposed or closed connections
-        conn = ref.value
+        @connections.each do |ref|
-        if !conn || conn.closed?
+          conn = ref.value
-          @connections.delete ref
+          if !conn || conn.closed?
+            @connections.delete ref
+          end
         end
       end
     end

src/db/string_key_cache.cr

@@ -1,21 +1,28 @@
 module DB
   class StringKeyCache(T)
     @cache = {} of String => T
+    @mutex = Mutex.new
 
     def fetch(key : String) : T
-      value = @cache.fetch(key, nil)
+      @mutex.synchronize do
-      value = @cache[key] = yield unless value
+        value = @cache.fetch(key, nil)
-      value
+        value = @cache[key] = yield unless value
+        value
+      end
     end
 
     def each_value
-      @cache.each do |_, value|
+      @mutex.synchronize do
-        yield value
+        @cache.each do |_, value|
+          yield value
+        end
       end
     end
 
     def clear
-      @cache.clear
+      @mutex.synchronize do
+        @cache.clear
+      end
     end
   end
 end