It is trad, Amos. this from Contemplator :
William Cole lists this as an Irish song. It was well known in both Ireland and Scotland. Before Auld Lange Syne, this song was the most popular parting song in Scotland. It appears in Herd's Scots Songs and in the Scots Musical Museum (1803/4). It was printed on broadsides as early as 1770* and saw a resurgence of popularity in the late 1800s. Several copies of these broadsides can be found at the Bodleian Library.
The tune appears as early as the 1600s - in the Skene Manuscript and in the Guthrie Manuscript (c 1675). It is also in Playford's Original Scots Tunes (1700).**
The song is also known as Good Night and Joy Be With You All.
Sam Henry collected The Parting Glass in Ireland in 1938. In Folksongs of Britain and Ireland, Peter Kennedy relates it to the Manx song Te Traa Goll Thie (It's Time to Go Home).