change the default warm_ip_target back to one, add config check

README.md

@@ -290,7 +290,7 @@ Type: Integer
 
 Default: None
 
-Specifies the number of free IP addresses that the `ipamd` daemon should attempt to keep available for pod assignment on the node. Setting this to a non-positive value is the same as setting this to 0.
+Specifies the number of free IP addresses that the `ipamd` daemon should attempt to keep available for pod assignment on the node. Setting this to a non-positive value is the same as setting this to 0 or not setting the variable.
 With `ENABLE_PREFIX_DELEGATION` set to `true` then `ipamd` daemon will check if the existing (/28) prefixes are enough to maintain the
 `WARM_IP_TARGET` if it is not sufficient then more prefixes will be attached.
 

cmd/aws-vpc-cni/main.go

@@ -83,7 +83,7 @@ const (
 	defaultEnPrefixDelegation    = false
 	defaultIPCooldownPeriod      = 30
 	defaultDisablePodV6          = false
-	defaultWarmIPTarget          = 1
+	defaultWarmIPTarget          = 0
 	defaultMinIPTarget           = 0
 	defaultWarmPrefixTarget      = 0
 
@@ -389,24 +389,27 @@ func validateEnvVars() bool {
 	prefixDelegationEn := utils.GetBoolAsStringEnvVar(envEnPrefixDelegation, defaultEnPrefixDelegation)
 	warmIPTarget, err, input := utils.GetIntFromStringEnvVar(envWarmIPTarget, defaultWarmIPTarget)
 	if err != nil {
-		log.Errorf("error when trying to get envWarmIPTarget: %s; input is %v", err, input)
+		log.Errorf("error when trying to get env WARM_IP_TARGET: %s; input is %v", err, input)
 		return false
 	}
 	warmPrefixTarget, err, input := utils.GetIntFromStringEnvVar(envWarmPrefixTarget, defaultWarmPrefixTarget)
 	if err != nil {
-		log.Errorf("error when trying to get envWarmPrefixTarget: %s; input is %v", err, input)
+		log.Errorf("error when trying to get env WARM_PREFIX_TARGET: %s; input is %v", err, input)
 		return false
 	}
 	minimumIPTarget, err, input := utils.GetIntFromStringEnvVar(envMinIPTarget, defaultMinIPTarget)
 	if err != nil {
-		log.Errorf("error when trying to get envMinIPTarget: %s; input is %v", err, input)
+		log.Errorf("error when trying to get env MINIMUM_IP_TARGET: %s; input is %v", err, input)
 		return false
 	}
 
 	// Note that these string values should probably be cast to integers, but the comparison for values greater than 0 works either way
 	if prefixDelegationEn && (warmIPTarget <= 0 && warmPrefixTarget <= 0 && minimumIPTarget <= 0) {
 		log.Errorf("Setting WARM_PREFIX_TARGET = 0 is not supported while WARM_IP_TARGET/MINIMUM_IP_TARGET is not set. Please configure either one of the WARM_{PREFIX/IP}_TARGET or MINIMUM_IP_TARGET env variables")
 		return false
+	} else if warmIPTarget <= 0 && minimumIPTarget > 0 {
+		log.Errorf("Setting WARM_IP_TARGET = 0 is not supported while MINIMUM_IP_TARGET is set, as it leads to no new ENIs being allocated after minimum threshold is meet, please configure properly")
+		return false
 	}
 	return true
 }