Adding utility to calculate max-pods for kubelet (awslabs#706)

files/max-pods-calculator.sh

@@ -0,0 +1,151 @@
+#!/bin/bash
+
+set -o pipefail
+set -o nounset
+set -o errexit
+
+err_report() {
+    echo "Exited with error on line $1"
+}
+trap 'err_report $LINENO' ERR
+
+function print_help {
+    echo "usage: $0 <instance(s)> [options]"
+    echo "Calculates maxPods value to be used when starting up the kubelet."
+    echo "-h,--help print this help."
+    echo "--instance-type Specify the instance type to calculate max pods value."
+    echo "--instance-type-from-imds Use this flag if the instance type should be fetched from IMDS."
+    echo "--cni-version Specify the version of the CNI (example - 1.7.5)."
+    echo "--cni-custom-networking-enabled Use this flag to indicate if CNI custom networking mode has been enabled."
+    echo "--cni-prefix-delegation-enabled Use this flag to indicate if CNI prefix delegation has been enabled."
+    echo "--cni-max-eni specify how many ENIs should be used for prefix delegation. Defaults to using all ENIs per instance."
+}
+
+POSITIONAL=()
+
+while [[ $# -gt 0 ]]; do
+    key="$1"
+    case $key in
+        -h|--help)
+            print_help
+            exit 1
+            ;;
+        --instance-type)
+            INSTANCE_TYPE=$2
+            shift
+            shift
+            ;;
+        --instance-type-from-imds)
+            INSTANCE_TYPE_FROM_IMDS=true
+            shift
+            ;;
+        --cni-version)
+            CNI_VERSION=$2
+            shift
+            shift
+            ;;
+        --cni-custom-networking-enabled)
+            CNI_CUSTOM_NETWORKING_ENABLED=true
+            shift
+            ;;
+        --cni-prefix-delegation-enabled)
+            CNI_PREFIX_DELEGATION_ENABLED=true
+            shift
+            ;;
+        --cni-max-eni)
+            CNI_MAX_ENI=$2
+            shift
+            shift
+            ;;
+        *)    # unknown option
+            POSITIONAL+=("$1") # save it in an array for later
+            shift # past argument
+            ;;
+    esac
+done
+
+CNI_VERSION="${CNI_VERSION:-}"
+CNI_CUSTOM_NETWORKING_ENABLED="${CNI_CUSTOM_NETWORKING_ENABLED:-false}"
+CNI_PREFIX_DELEGATION_ENABLED="${CNI_PREFIX_DELEGATION_ENABLED:-false}"
+CNI_MAX_ENI="${CNI_MAX_ENI:-}"
+INSTANCE_TYPE="${INSTANCE_TYPE:-}"
+INSTANCE_TYPE_FROM_IMDS="${INSTANCE_TYPE_FROM_IMDS:-false}"
+
+PREFIX_DELEGATION_SUPPORTED=false
+IPS_PER_PREFIX=16
+
+if [ "$INSTANCE_TYPE_FROM_IMDS" = true ]; then
+    TOKEN=$(curl -m 10 -X PUT -H "X-aws-ec2-metadata-token-ttl-seconds: 600" -s "http://169.254.169.254/latest/api/token")
+    export AWS_DEFAULT_REGION=$(curl -s --retry 5 -H "X-aws-ec2-metadata-token: $TOKEN" http://169.254.169.254/latest/dynamic/instance-identity/document | jq .region -r)
+    INSTANCE_TYPE=$(curl -m 10 -H "X-aws-ec2-metadata-token: $TOKEN" -s http://169.254.169.254/latest/meta-data/instance-type)
+elif [ -z "$INSTANCE_TYPE" ];
+    # There's no reasonable default for an instanceType so force one to be provided to the script.
+    then echo "You must specify an instance type to calculate max pods value."
+    exit 1
+fi
+
+if [ -z "$CNI_VERSION" ];
+    then echo "You must specify a CNI Version to use. Example - 1.7.5"
+    exit 1
+fi
+
+calculate_max_ip_addresses_prefix_delegation() {
+    enis=$1
+    instance_max_eni_ips=$2
+    echo $(($enis * (($instance_max_eni_ips - 1) * $IPS_PER_PREFIX ) + 2))
+}
+
+calculate_max_ip_addresses_secondary_ips() {
+    enis=$1
+    instance_max_eni_ips=$2
+    echo $(($enis * ($instance_max_eni_ips - 1) + 2))
+}
+
+min_number() {
+    printf "%s\n" "$@" | sort -g | head -n1
+}
+
+
+VERSION_SPLIT=(${CNI_VERSION//./ })
+CNI_MAJOR_VERSION="${VERSION_SPLIT[0]}"
+CNI_MINOR_VERSION="${VERSION_SPLIT[1]}"
+if [[ "$CNI_MAJOR_VERSION" -gt 1 ]] || ([[ "$CNI_MAJOR_VERSION" = 1 ]] && [[ "$CNI_MINOR_VERSION" -gt 8 ]]); then
+    PREFIX_DELEGATION_SUPPORTED=true
+fi
+
+DESCRIBE_INSTANCES_RESULT=$(aws ec2 describe-instance-types --instance-type $INSTANCE_TYPE --query 'InstanceTypes[0].{Hypervisor: Hypervisor, EniCount: NetworkInfo.MaximumNetworkInterfaces, PodsPerEniCount: NetworkInfo.Ipv4AddressesPerInterface, CpuCount: VCpuInfo.DefaultVCpus'})
+
+HYPERVISOR_TYPE=$(echo $DESCRIBE_INSTANCES_RESULT | jq -r '.Hypervisor' )
+IS_NITRO=false
+if [[ "$HYPERVISOR_TYPE" == "nitro" ]]; then
+    IS_NITRO=true
+fi
+INSTANCE_MAX_ENIS=$(echo $DESCRIBE_INSTANCES_RESULT | jq -r '.EniCount' )
+INSTANCE_MAX_ENIS_IPS=$(echo $DESCRIBE_INSTANCES_RESULT | jq -r '.PodsPerEniCount' )
+
+if [ -z "$CNI_MAX_ENI" ] ; then
+    enis_for_pods=$INSTANCE_MAX_ENIS
+else
+    enis_for_pods="$(min_number $CNI_MAX_ENI $INSTANCE_MAX_ENIS)"
+fi
+
+if [ "$CNI_CUSTOM_NETWORKING_ENABLED" = true ] ; then
+    enis_for_pods=$((enis_for_pods-1))
+fi
+
+
+if [ "$IS_NITRO" = true ] && [ "$CNI_PREFIX_DELEGATION_ENABLED" = true ] && [ "$PREFIX_DELEGATION_SUPPORTED" = true ]; then
+    max_pods=$(calculate_max_ip_addresses_prefix_delegation $enis_for_pods $INSTANCE_MAX_ENIS_IPS)
+else
+    max_pods=$(calculate_max_ip_addresses_secondary_ips $enis_for_pods $INSTANCE_MAX_ENIS_IPS)
+fi
+
+# Limit the total number of pods that can be launched on any instance type based on the vCPUs on that instance type.
+MAX_POD_CEILING_FOR_LOW_CPU=110
+MAX_POD_CEILING_FOR_HIGH_CPU=250
+CPU_COUNT=$(echo $DESCRIBE_INSTANCES_RESULT | jq -r '.CpuCount' )
+if [ "$CPU_COUNT" -gt 30 ] ; then
+    echo $(min_number $MAX_POD_CEILING_FOR_HIGH_CPU $max_pods)
+else
+    echo $(min_number $MAX_POD_CEILING_FOR_LOW_CPU $max_pods)
+fi