Bootstrap based Simulations Sample Clauses

Bootstrap based Simulations. In these simulations, we associated each service in the CarOnLine example with delay behaviors of one of the six web services mentioned previously. The associations are shown in Table II and the cumulative distribution functions of the observed response 0.9 GarageA GarageB AllCredit AllCreditPlus GoldInsure InsureAll InsurePlus 0.8 0.7 CDF 0.6 0.5 0.4 0.3 0.2 2000 4000 6000 8000 10000 12000 14000 delay (msec) times for each of the called services are shown in Figure 7. During any run of CarOnLine, the response time of a call is picked uniformly from the set of 20,000 delay values of its associated site. Since the response times of these services were measured from the client’s side, they include the network’s delay too. So we do not consider the explicit delays modeled by the sites NetGA, NetGB, NetC and NetCP , and give them zero delay each (if the contracts modeled only the performance from the server’s perspective, without accounting for the network, we could give delays to each of these sites according pings done to the web services). RESPONSE TIME ASSOCIATIONS FOR SITES IN CARONLINE Results using hard contracts: Consider the following “hard contract” policy—which is close to current state of practice. Contracts have the form of a certain quantile, e.g.: “the response time shall not exceed x ms in y% of the cases.” More precisely, let contracts of the orchestration with a Figure 7. Cumulative distribution function for the measured delays of the six web services. where δ is the response time of the orchestration and K is the max-plus combination the Ki’s, according to the orches- tration’s partial ordering of call events. By setting the delay contracts (maximum delay values) of each of the sites involved in CarOnLine to their 99.2% quantile values, we get the end-to-end orchestration delay bound to be K = 44, 243 ms, which can be guaranteed for 94.53% of the cases. Results using probabilistic soft contracts: We now com- pare the above results with our approach using probabilistic contracts. To this end, we performed 100,000 runs of the orchestration in the bootstrap mode. The empirical distribution of end-to-end delays of the orchestration is shown in Figure 8. The minimum delay observed in this case is 1,511 ms and the maximum is 369,559 ms. The 94.53% delay quantile of this distribution is 23,189 ms, to be compared with the more pessimistic value 44,243 of ms that we obtained using the usual approach.

Bootstrap based Simulations. As before, we asso- ciated each service in the CarOnLine example with delay behaviors of one of the six web services measured. The associations are the same as before, given in Table II. We Figure 8. Empirical distribution of end-to-end orchestration delays for 100000 simulations in the bootstrapping case. GarageA 2.678 GoldInsure 1.338 GarageB 0.835 InsureAll 0.835 AllCredit 0.297 InsurePlus 0.835 PARAMETER ν OF THE FITTED T LOCATION DISTRIBUTIONS Mode Soft contract 94.53% quantile Hard contract 94.53% quantile The results are summarized in Table IV. now have timeouts for the calls to sites GarageA and GarageB. The 99.2% delay quantiles for these two sites are 3,304 msec and 4,183 msec respectively. We perform simulations with different timeout values: 3,000, 4,000 and 5,000 msec. The results are given in Table V.