From Array Suite Wiki
(Created page with "==Definition== Oscript parameter that tells the application whether or not Spot Instances should be used. When Spot Instances are used, you pay the Spot price that's in effec...")
Newer edit →
Revision as of 22:57, 14 January 2020
Oscript parameter that tells the application whether or not Spot Instances should be used. When Spot Instances are used, you pay the Spot price that's in effect for the time period your instances are running (more details here).
False (default - OnDemand instances are used) True (Spot instances are used)
Enable spot instances for all jobs
One method to enable spot instances through OmicSoft Server is to add this parameter to the [Cloud] options section in ArrayServer.cfg. Simply setting this parameter will request spot instances at the default max bid price (same as on-demand price) for any job that will run on Cloud.
Enabling spot instances in script
If the user wants to enable spot instances for an individual analysis, the user can set /EnableAWSSpot=True in the oscript's Options section. This will overwrite the default option specified in ArrayServer.cfg for the duration of these jobs. Please note, Oscripts supporting this flag can be found at the bottom of this page. Specifying spot instance price in script
Additionally, only in the oscript, in the Options section, when /EnableAWSSpot is set to True, user can also specify a spot price she is willing to pay, with parameter /SpotBidMaxPrice=x.xxxx. This will have an effect only for the duration of these jobs. If spot instances are more expensive at the time of the run, the oscript will fail.
e.g. /EnableAWSSpot=True /SpotBidMaxPrice=0.045
We explore two scenarios, starting from the assumption that user runs one spot instance for two hours, and after one hour, the current spot price doubles.
Description: User sets a valid spot price (i.e. higher than the current spot price). Parameters /EnableAWSSpot=True /SpotBidMaxPrice=0.045 Your spot price = $0.045 Spot price at start of run = $0.025 OnDemand price = $0.125 Spot price after one hour of run = $0.05 Outcome: You pay $0.025 for the first hour of run, then the instance is terminated by Amazon because your spot price is lower than Spot price after one hour run.
Description: User does not set any spot price. Parameters /EnableAWSSpot=True Your spot price = $0.125 (not specified by user, but Amazon will assume it is OnDemand price) Spot price at start of run = $0.025 OnDemand price = $0.125 Spot price after one hour of run = $0.05 Outcome: You pay $0.025 for the first hour of run and $0.05 for the second hour of run.
One has to consider that no matter what spot price you specify (or don't specify at all), you always pay the current spot price at the time of your run. So, it does not matter that in Scenario 1 user specified a smaller spot price than the one in Scenario 2, because in both situations, for the first hour of run, the charges were the same. More to this, in Scenario 1, user is at risk of having its instances terminated by Amazon and losing all work, if current spot price rises above user's initial spot price. On the other hand, if you do not specify any spot price, you are going to pay at most the OnDemand price.
Please note that all procs that can run on AWS Cloud will benefit from spot instances if EnableAWSSpot is set to True in ArrayServer.cfg.
In addition, the following list of procs support /EnableAWSSpot and /SpotBidMaxPrice as oscript parameters.
Price too low: if you see an instance creation error, you will be notified if attempt was unsuccessful because your bid was too low.
[00:00:40] Error occurred from OJobProcess.Run. Error message=Instance creation is not successful. Error=Your Spot request price of 0.3 is lower than the minimum required Spot request fulfillment price of 0.563.
Price is zero or negative: if you set the price to /SpotBidMaxPrice=0.0000 or /SpotBidMaxPrice=-0.5000, Amazon will set the default, OnDemand price for you.