amazon adapter: bid on a slot-level

[nickjacob]

re-structuring amazon adapter to allow integration w/ prebid line items + creative rendering. By default this uses the existing amznslots k-v pair, but if the user overrides the adserverTargeting (to use the default), it can use a CPM.

In order to do this, I added a callback system so that the publisher can modify the bid after it's created (so they can add site-specific/proprietary information).

On the publisher side, the integration with amazon would require something like:

pbjs.bidderSettings = {
  amazon: {
    // override the bidder settings
    usesGenericKeys: true,
  }
};

pbjs.que.push(function () {

  pbjs.events.on('beforeAddBidResponse', function (code, bidResponse) {
    if (!bidResponse || bidResponse.bidderCode !== 'amazon') return;
    // ....code to generate an actual CPM....
    bidResponse.cpm = cpm;
  });

});

I know that exposing this functionality to publishers is a challenge; by using callbacks I wanted to add flexibility without affecting the current architecture—in our integration (@ aplus), we really want to be able to serve amazon through the same line items/creatives.

this uses the following algorithm (the current one selects the first unit bidded on):

1. Sort the bids by size
2. for each size
   1. order the bids for that size by bid - take the highest
   2. pick a unit (random) from available units for that size (remove from further amazon bidding)
   3. register bid on that unit @ the size

A callback could be added there (at step 3) to give the publisher more control. As far as I know the above is the same logic as DFP when the keys are set as page targeting. Feedback on this approach would be great. thanks!

[mkendall07]

This looks like a promising approach. I'd like to get @Heray feedback on this before approving the PR.

[mkendall07]

I like this approach to the event handling. Did you write this yourself or get it from another library?

[nickjacob]

wrote it myself; based on node.js EventEmitter api (use a similar but more object-oriented impl. on aplus)

[mkendall07]

Awesome! I think we can probably extend this to use for all the event handling in prebid.js if we tweak it a bit. I'll play with it a bit...

[Heray]

You guys are badass