addContent(content: dbContent): Promise<void> {
   return this.contents.insert(content, {safe: true}).then<void, void>(
     () => {},
     err => {
       if (err.code != 11000) {
         //if not "document already exists"
         throw err;
       }
     },
   );
 }

 addHeader(header: dbHeader): Promise<void> {
   return this.headers.insert(header, {safe: true}).then<void, void>(
     () => {},
     err => {
       if (err.code != 11000) {
         //if not "document already exists"
         throw err;
       }
     },
   );
 }

 logRun(start: Date, end: Date): Promise<void> {
   var now = new Date();
   var day = now.toISOString().split('T')[0];
   return Promise.all([
     this.log.insert(
       {
         type: 'bot-run',
         start,
         end,
       },
       {safe: true},
     ),
     this.runsPerDay.update(
       {_id: day},
       {
         $inc: {
           runs: 1,
           totalDuration: start.getTime() - end.getTime(),
         },
       },
       {upsert: true},
     ),
   ]).then(() => {});
 }

 hasContent(id: string): Promise<boolean> {
   return this.headers
     .find({_id: id})
     .count()
     .then(result => !!result);
 }

 getHeaderByUrl(url: string): Promise<dbHeader> {
   return this.headers.findOne({url: url}) as any;
 }

 updateTopic(topic: dbTopic): Promise<void> {
   return this.topics
     .update({_id: topic._id}, topic, {upsert: true})
     .then(() => {});
 }