The manual that came with your Glock states;
Your GLOCK pistol should be field stripped, cleaned and lubricated as follows:
1. Wwhen brand new, before the first time it is fired, plus
2. At least once a month, plus
3. After each time it is fired, plus
4. As required. This will be determined by the pistols exposure to adverse conditions such as rain, snow, perspiration, salt water, dirt, dust, lint, etc. Additionally, the pistol should be cleaned and inspected if it has been dropped or if any defects are suspected or malfunctions experienced.
Lots of folks will tell you its not necessary to clean your Glock pistol it will work just fine, they may be right but I would suggest following what is written and issued with your pistol.