201 lines
11 KiB
Bash
Executable File
201 lines
11 KiB
Bash
Executable File
#!/bin/bash -
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# Author: Colin Johnson / colin@cloudavail.com
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# Date: 2012-08-11
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# Version 0.1
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# License Type: GNU GENERAL PUBLIC LICENSE, Version 3
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#
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#####
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#confirms that executables required for succesful script execution are available
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prerequisitecheck()
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{
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for prerequisite in basename grep cut as-describe-auto-scaling-groups as-update-auto-scaling-group elb-deregister-instances-from-lb as-terminate-instance-in-auto-scaling-group elb-describe-instance-health
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do
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#use of "hash" chosen as it is a shell builtin and will add programs to hash table, possibly speeding execution. Use of type also considered - open to suggestions.
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hash $prerequisite &> /dev/null
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if [[ $? == 1 ]] #has exits with exit status of 70, executable was not found
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then echo "In order to use $app_name, the executable \"$prerequisite\" must be installed." 1>&2 ; exit 70
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fi
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done
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}
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return_as_initial_maxsize()
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{
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if [[ $max_size_change -eq 1 ]]
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then echo "$asg_group_name had its max-size increased temporarily by 1 to a max-size of $asg_temporary_max_size. $app_name will now return the max-size of $asg_group_name to its original max-size of $asg_initial_max_size."
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#decrease max-size by 1
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as-update-auto-scaling-group $asg_group_name --region $region --max-size=$asg_initial_max_size
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fi
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}
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return_as_initial_desiredcapacity()
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{
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echo "$asg_group_name had its desired-capacity increased temporarily by 1 to a desired-capacity of $asg_temporary_desired_capacity. $app_name will now return the desired-capacity of $asg_group_name to its original desired-capacity of $asg_initial_desired_capacity."
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as-update-auto-scaling-group $asg_group_name --region $region --desired-capacity=$asg_initial_desired_capacity
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}
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#set application defaults
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app_name=`basename $0`
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elb_timeout=60
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region="us-east-1"
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#max_size_change is used as a "flag" to determine if the max-size of an Auto Scaling Group was changed
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max_size_change="0"
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inservice_time_allowed=300
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inservice_polling_time=10
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delimiter="%"
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#calls prerequisitecheck function to ensure that all executables required for script execution are available
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prerequisitecheck
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#handles options processing
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while getopts :a:t:r:i: opt
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do
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case $opt in
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a) asg_group_name="$OPTARG";;
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t) elb_timeout="$OPTARG";;
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r) region="$OPTARG";;
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i) inservice_time_allowed="$OPTARG";;
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*) echo "Error with Options Input. Cause of failure is most likely that an unsupported parameter was passed or a parameter was passed without a corresponding option." 1>&2 ; exit 64 ;;
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esac
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done
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#validate elb_timeout is number
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##code to be written
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if [[ -z $asg_group_name ]]
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then echo "You did not specify an Auto Scaling Group name. In order to use $app_name you must specify an Auto Scaling Group name using -a <autoscalingroupname>." 1>&2 ; exit 64
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fi
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#region validator
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case $region in
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us-east-1|us-west-2|us-west-1|eu-west-1|ap-southeast-1|ap-northeast-1|sa-east-1|ap-southeast-2) ;;
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*) echo "The \"$region\" region does not exist. You must specify a valid region (example: -r us-east-1 or -r us-west-2)." 1>&2 ; exit 64;;
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esac
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#creates variable containing Auto Scaling Group
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asg_result=`as-describe-auto-scaling-groups $asg_group_name --show-long --max-records 1000 --region $region --delimiter $delimiter`
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#validate Auto Scaling Group Exists
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#user response for Auto Scaling Group lookup - alerts user if Auto Scaling Group was not found.
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if [[ $asg_result = "No AutoScalingGroups found" ]]
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then echo "The Auto Scaling Group named \"$asg_group_name\" does not exist in the region named \"$region\". You must specify an Auto Scaling Group that exists." 1>&2 ; exit 64
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fi
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#validate - the pipeline of echo -e "$asg_result" | grep -c "AUTO-SCALING-GROUP" must only return one group found - in the case below - more than one group has been found
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if [[ `echo -e "$asg_result" | grep -c "^AUTO-SCALING-GROUP"` > 1 ]]
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then echo "More than one Auto Scaling Group found. As more than one Auto Scaling Group has been found, $app_name does not know which Auto Scaling Group should have Instances terminated." 1>&2 ; exit 64
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fi
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#validate - the pipeline of echo -e "$asg_result" | grep -c "AUTO-SCALING-GROUP" must only return one group found
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if [[ `echo -e "$asg_result" | grep -c "^AUTO-SCALING-GROUP"` < 1 ]]
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then echo "No Auto Scaling Group was found. Because no Auto Scaling Group has been found, $app_name does not know which Auto Scaling Group should have Instances terminated." 1>&2 ; exit 64
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fi
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#confirms that certain Auto Scaling processes are not suspended. For certain processes, the "Suspending Processing" state prevents the termination of Auto Scaling Group instances and thus prevents aws-ha-release from running properly.
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necessary_processes=(RemoveFromLoadBalancerLowPriority Terminate Launch HealthCheck AddToLoadBalancer)
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for process in "${necessary_processes[@]}"
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do
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if [[ `echo -e "$asg_result" | grep -c "SUSPENDED-PROCESS$delimiter$process"` > 0 ]]
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then echo "Scaling Process $process for the Auto Scaling Group $asg_group_name is currently suspended. $app_name will now exit as Scaling Processes ${necessary_processes[@]} are required for $app_name to run properly." 1>&2 ; exit 77
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fi
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done
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#gets Auto Scaling Group max-size
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asg_initial_max_size=`echo $asg_result | grep ^AUTO-SCALING-GROUP | cut -d "$delimiter" -f 9`
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asg_temporary_max_size=$(($asg_initial_max_size+1))
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#gets Auto Scaling Group desired-capacity
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asg_initial_desired_capacity=`echo "$asg_result" | grep ^AUTO-SCALING-GROUP | cut -d "$delimiter" -f 10`
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asg_temporary_desired_capacity=$((asg_initial_desired_capacity+1))
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#gets list of Auto Scaling Group Instances - these Instances will be terminated
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asg_instance_list=`echo "$asg_result" | grep ^INSTANCE | cut -d "$delimiter" -f 2`
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#builds an array of load balancers
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IFS=',' read -a asg_elbs <<< `echo "$asg_result" | grep ^AUTO-SCALING-GROUP | cut -d "$delimiter" -f 6`
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#if the max-size of the Auto Scaling Group is zero there is no reason to run
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if [[ $asg_initial_max_size -eq 0 ]]
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then echo "$asg_group_name has a max-size of 0. As the Auto Scaling Group \"$asg_group_name\" has no active Instances there is no reason to run." ; exit 79
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fi
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#echo a list of Instances that are slated for termination
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echo -e "The list of Instances in Auto Scaling Group $asg_group_name that will be terminated is below:\n$asg_instance_list"
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as_processes_to_suspend="ReplaceUnhealthy,AlarmNotification,ScheduledActions,AZRebalance"
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as-suspend-processes $asg_group_name --processes $as_processes_to_suspend --region $region
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#if the desired-capacity of an Auto Scaling Group group is greater than or equal to the max-size of an Auto Scaling Group, the max-size must be increased by 1 to cycle instances while maintaining desired-capacity. This is particularly true of groups of 1 instance (where we'd be removing all instances if we cycled).
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if [[ $asg_initial_desired_capacity -ge $asg_initial_max_size ]]
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then echo "$asg_group_name has a max-size of $asg_initial_max_size. In order to recycle instances max-size will be temporarily increased by 1 to max-size $asg_temporary_max_size."
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#increase max-size by 1
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as-update-auto-scaling-group $asg_group_name --region $region --max-size=$asg_temporary_max_size
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#sets the flag that max-size has been changed
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max_size_change="1"
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fi
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#increase groups desired capacity to allow for instance recycling without decreasing available instances below initial capacity
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echo "$asg_group_name is currently at $asg_initial_desired_capacity desired-capacity. $app_name will increase desired-capacity by 1 to desired-capacity $asg_temporary_desired_capacity."
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as-update-auto-scaling-group $asg_group_name --region $region --desired-capacity=$asg_temporary_desired_capacity
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#and begin recycling instances
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for instance_selected in $asg_instance_list
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do
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all_instances_inservice=0
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#the while loop below sleeps for the auto scaling group to have an InService capacity that is equal to the desired-capacity + 1
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while [[ $all_instances_inservice -eq 0 ]]
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do
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if [[ $inservice_time_taken -gt $inservice_time_allowed ]]
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then echo "During the last $inservice_time_allowed seconds the InService capacity of the $asg_group_name Auto Scaling Group did not meet the Auto Scaling Group's desired capacity of $asg_temporary_desired_capacity." 1>&2
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echo "Because we can't be sure that instances created by this script are healthy, settings that were changed are being left as is. Settings that were changed:"
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if [[ $max_size_change -eq 1 ]]
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then echo "max size was increased by $max_size_change"
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fi
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echo "desired capacity was increased by 1"
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echo "AutoScaling processes \"$as_processes_to_suspend\" were suspended."
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exit 79
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fi
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for index in "${!asg_elbs[@]}"
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do
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inservice_instance_list=`elb-describe-instance-health ${asg_elbs[$index]} --region $region --show-long | grep InService`
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inservice_instance_count=`echo "$inservice_instance_list" | wc -l`
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if [ $index -eq 0 ]
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then [ $inservice_instance_count -eq $asg_temporary_desired_capacity ] && all_instances_inservice=1 || all_instances_inservice=0
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else
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[[ ($all_instances_inservice -eq 1) && ($inservice_instance_count -eq $asg_temporary_desired_capacity) ]] && all_instances_inservice=1 || all_instances_inservice=0
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fi
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done
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#sleeps a particular amount of time
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sleep $inservice_polling_time
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inservice_time_taken=$(($inservice_time_taken+$inservice_polling_time))
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echo $inservice_instance_count "Instances are InService status. $asg_temporary_desired_capacity Instances are required to terminate the next instance. $inservice_time_taken seconds have elapsed while waiting for an Instance to reach InService status."
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#if any status in $elbinstancehealth != "InService" repeat
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done
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#if the
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echo "$asg_group_name has reached a desired-capacity of $asg_temporary_desired_capacity. $app_name can now remove an Instance from service."
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inservice_instance_count=0
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inservice_time_taken=0
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#remove instance from ELB - this ensures no traffic will be directed at an instance that will be terminated
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echo "Instance $instance_selected will now be deregistered from ELBs \"${asg_elbs[@]}.\""
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for elb in "${asg_elbs[@]}"
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do
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elb-deregister-instances-from-lb $elb --region $region --instances $instance_selected > /dev/null
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done
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#sleep for "elb_timeout" seconds so that the instance can complete all processing before being terminated
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sleep $elb_timeout
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#terminates a pre-existing instance within the autoscaling group
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echo "Instance $instance_selected will now be terminated. By terminating this Instance, the actual capacity will be decreased to 1 under desired-capacity."
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as-terminate-instance-in-auto-scaling-group --region $region --instance $instance_selected --no-decrement-desired-capacity --force > /dev/null
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done
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#return max-size to initial size
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return_as_initial_maxsize
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#return temporary desired-capacity to initial desired-capacity
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return_as_initial_desiredcapacity
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as-resume-processes $asg_group_name --region $region
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