Information Technology Reference
In-Depth Information
According to the budget constraints the algorithm constructs a scaling plan
that best fit the workflow computation requirements for the next hour. Algo-
rithm 1 presents the process of infrastructure scaling.
Algorithm 1.
Infrastructure scaling algorithm
1:
procedure
scaleInfrastructure:
2:
tasks ₐ
getTasksInThePeriod()
tasks running during the next hour
C
unbound
ₐ
estimateConsumption(
tasks
)
get unconstrained consumption
3:
4:
C
od
ₐ
scale(
C
unbound
,B
od
/cost
unbound
)
determine on-demand instances
C
unbound
ₐ C
unbound
− C
od
5:
6:
bidPrices ₐ
predictBidPrices()
invokes a bid price prediction method
C
s
ₐ
scale(
C
s
,B
s
/cost
s
)
determine spot instances
7:
8:
C
od
=
C
od
− R
9:
C
s
=
C
s
−
(
R − C
od
)
10:
for all
VMType
i
in
VMTypes
do
:
request instances
11:
requestInstance(
C
od
[
VMType
i
])
12:
requestSpotInstance(
C
s
[
VMType
i
]
, bidPrices
[
VMType
i
])
To generate the scaling plan, the algorithm starts by estimating the compu-
tation load for the next hour (lines 2 and 3). A consumption vector
C
unbound
=
{
represents the amount of instances necessary for each type for
the next hour with
unconstrained budget
. Each component
c
i
represents the
amount of instances of type
VMType
i
.
Each
c
i
value is estimated summing the computation hour portions for all
the tasks which prefer and instance of type
VMType
i
.Inthecaseof
running
tasks
, the computation load is set to the type of the instance where such task
is executing.
To generate the scaling plan, the algorithm computes two consumption vec-
tors,
C
od
and
C
s
(for on-demand and spot instances respectively) derived from
the unconstrained consumption vector
C
unbound
. This process is carried out in
two steps:
c
1
,c
2
,...,c
n
}
1. The consumption vector of
on-demand
instances
C
od
is determined fitting
the number of instances according to the available budget
B
od
.The
C
od
vec-
tor is obtained scaling the unconstrained consumption vector
C
unbound
by the
factor
B
od
/cost
od
,where
cost
od
is the total cost of acquiring all the instances
in
C
unbound
using the on-demand instance prices (line 4). A consumption
round(
C
·
r
)
r<
1
vector
C
is scaled by a factor
r>
0 as scale(
C,r
)=
1
,
round(
C
)
r
≥
r
is the product of a vector and a scalar and the round function
is applied to each element of the resulting vector.
2. In analogous manner, the consumption vector of
spot
instances
C
s
is de-
termined by scaling the remaining unconstrained instances:
C
unbound
−
where
C
·
C
od
(line 5). This new consumption vector is then scaled by the factor
B
s
/cost
s
