Why Ama­zon should use two-phase com­mit

Work­ing for Atomikos, I use two-phase com­mit a lot. While I don't want to claim that it is a so­lu­tion to all prob­lems, I do find it frus­trat­ing to hear peo­ple pro­claim­ing that they don't use it be­cause it doesn't scale (or some oth­er rea­son).

Take, for in­stance, Wern­er Vo­gel's talk about the Ama­zon ar­chi­tec­ture. Once again, two-phase com­mit is re­ject­ed as a vi­able so­lu­tion/tech­nol­o­gy. Once again, I dis­agree.

Let me il­lus­trate my point with an ex­am­ple of what re­al­ly hap­pened to me re­cent­ly - af­ter or­der­ing a book at Ama­zon (iron­i­cal­ly;-). I can give sim­i­lar ex­am­ples with air­line tick­et reser­va­tions but those will have to wait un­til lat­er...

So what hap­pened re­al­ly? Well, I or­dered a book that I re­al­ly want­ed to have. I or­dered it on­line at Ama­zon... All went well, I checked out and paid by VISA. How­ev­er, that is where things start­ed to go wrong: while wait­ing for the book to be de­liv­ered, I sud­den­ly get an email from Ama­zon say­ing that... my or­der has been can­celed!

Canceled? Yes, but not in a way you would think: I still had to pay for the de­liv­ery by DHL (sor­ry, what is that?!). Yes sir, DHL claimed they had found no­body present at the de­liv­ery ad­dress. The de­liv­ery was at our of­fice ad­dress, so it is very un­like­ly that no­body be there in the first place. More­over, any couri­er ser­vice I know will leave a note that they passed by and at least set­tle for an al­ter­na­tive de­liv­ery. Not this time.

My con­clu­sion? DHL did not ar­rive at my place. On the Ama­zon or­der track­ing page, my or­der had not even left Ger­many (to be de­liv­ered where I live, in Bel­gium).

Now what will I re­mem­ber? I will re­mem­ber that Ama­zon let me down, ei­ther di­rect­ly or via DHL. I will also re­mem­ber to be very sus­pi­cious about peo­ple who say they don't need two-phase com­mit. Two-phase com­mit comes down to en­sur­ing agree­ment be­tween the dif­fer­ent par­ties in­volved in a trans­ac­tion. Clear­ly, there was no such thing in my case.