Lufthansa pilot union has voted to have their 10th strike this year that will ground roughly half of its long-haul flights on December 4, 2014.
Lufthansa has listed the flights that will be affected due to its strike on its website that you can access here.
Note that there will be a spillover of this strike that will effect flights to Germany on December 5 if the incoming flight has not operated.
Lufthansa is required to rebook you on other airlines, even outside of the Lufthansa Group, to get you to the final destination and duty to provide care such as meals and hotel vouchers.
The EC 261/2004 monetary compensation due to cancellations doesn’t apply when a flight is canned due to a strike.
Check if your upcoming Lufthansa flight is operating this week and rebook if required. Lufthansa is hesitant to book on other airlines beyond their own, but the airline is required by law to do it, however.