autoscaling_enter_standby.sh

autoscaling_enter_standby() {
    local instance_id=$1
    local asg_name=${2}

    msg "Checking if this instance has already been moved in the Standby state"
    local instance_state=$(get_instance_state_asg $instance_id)
    if [ $? != 0 ]; then
        msg "Unable to get this instance's lifecycle state."
        return 1
    fi

    if [ "$instance_state" == "Standby" ]; then
        msg "Instance is already in Standby; nothing to do."
        return 0
    fi

    if [ "$instance_state" == "Pending:Wait" ]; then
        msg "Instance is Pending:Wait; nothing to do."
        return 0
    fi

    if [ "$HANDLE_PROCS" = "true" ]; then
        msg "Checking ASG ${asg_name} suspended processes"
        check_suspended_processes

        # Suspend troublesome processes while deploying
        suspend_processes
    fi

    msg "Checking to see if Lambda has added item to DynamoDB table"
    wait_for_dynamodb_record

    msg "Checking to see if ASG ${asg_name} will let us decrease desired capacity"
    local min_desired=$($AWS_CLI autoscaling describe-auto-scaling-groups \
        --auto-scaling-group-name "${asg_name}" \
        --query 'AutoScalingGroups[0].[MinSize, DesiredCapacity]' \
        --output text)

    local min_cap=$(echo $min_desired | awk '{print $1}')
    local desired_cap=$(echo $min_desired | awk '{print $2}')

    if [ -z "$min_cap" -o -z "$desired_cap" ]; then
        msg "Unable to determine minimum and desired capacity for ASG ${asg_name}."
        msg "Attempting to put this instance into standby regardless."
        set_flag "asgmindecremented" "false"
    elif [ $min_cap == $desired_cap -a $min_cap -gt 0 ]; then
        local new_min=$(($min_cap - 1))
        msg "Decrementing ASG ${asg_name}'s minimum size to $new_min"
        msg $($AWS_CLI autoscaling update-auto-scaling-group \
            --auto-scaling-group-name "${asg_name}" \
            --min-size $new_min)
        if [ $? != 0 ]; then
            msg "Failed to reduce ASG ${asg_name}'s minimum size to $new_min. Cannot put this instance into Standby."
            return 1
        else
            msg "ASG ${asg_name}'s minimum size has been decremented, creating flag in file $FLAGFILE"
            # Create a "flag" denote that the ASG min has been decremented
            set_flag "asgmindecremented" "true"
        fi
    else
        msg "No need to decrement ASG ${asg_name}'s minimum size"
        set_flag "asgmindecremented" "false"
    fi

    msg "Putting instance $instance_id into Standby"
    $AWS_CLI autoscaling enter-standby \
        --instance-ids $instance_id \
        --auto-scaling-group-name "${asg_name}" \
        --should-decrement-desired-capacity
    if [ $? != 0 ]; then
        msg "Failed to put instance $instance_id into Standby for ASG ${asg_name}."
        return 1
    fi

    msg "Waiting for move to Standby to finish"
    wait_for_state "autoscaling" $instance_id "Standby"
    if [ $? != 0 ]; then
        local wait_timeout=$(($WAITER_INTERVAL * $WAITER_ATTEMPTS))
        msg "Instance $instance_id did not make it to standby after $wait_timeout seconds"
        return 1
    fi

    return 0
}