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Indonesia is a mainly Muslim country so most people will be fasting over the next month.
Whilst there's nothing stopping non Muslims eating during daylight hours it is considered a little rude so I recommend you eat in places with curtains up so the locals can't see you.
Most restaurants will be open as normal but a lot will close until later in the day because they won't sell much the rest of the time so there's no point.
Chains such as McD just pull blinds down over the windows and open normally.

Most massage places and some karaoke joints will be closed if the usual pattern is followed because many are just fronts for prostitution. The real places will remain open, especially the ladies' only health spas.

The local extremist groups have been emboldened by the Ahok trial and they've already committed one set of murders in Jakarta so keep an eye out for people acting strangely, especially if they're carrying a backpack.
Pressure cooker bombs are the new weapon of choice so they should be easy enough to spot.
Armed coppers are patrolling potential targets such as churches but the extremists are like rats, they get everywhere and you can't get them all.

It is better if you eat and drink in private at your place of work if possible. Apart from showing respect for the Muslim staff it will do your reputation a lot of good.