Combine flour, cocoa, baking powder, salt and baking soda. In another bowl, combine eggs, water and vanilla, beat until thick. Add sugar gradually, beat well, combine wet and dry ingrediants, mix thoroughly. Grease and line with waxed paper, a jelly roll pan. pour in batter evenly and bake for 30 minutes at 350 degrees. Sprinkle heavily with confectioners sugar. Roll warm cake lengthwise with a towel, into a roll, cool, seam side down. Unroll cake, spread with filling, reroll and refrigerate, serve.