How To Download Node Js
Meridith Vicent
In addition, every kind of DOM node is represented by an interface based on Node. These include Attr, CharacterData (which Text, Comment, CDATASection and ProcessingInstruction are all based on), and DocumentType.
In some cases, a particular feature of the base Node interface may not apply to one of its child interfaces; in that case, the inheriting node may return null or throw an exception, depending on circumstances. For example, attempting to add children to a node type that cannot have children will throw an exception.
Returns a live NodeList containing all the children of this node (including elements, text and comments). NodeList being live means that if the children of the Node change, the NodeList object is automatically updated.
Returns a string containing the name of the Node. The structure of the name will differ with the node type. E.g. An HTMLElement will contain the name of the corresponding tag, like 'audio' for an HTMLAudioElement, a Text node will have the '#text' string, or a Document node will have the '#document' string.
Adds the specified childNode argument as the last child to the current node. If the argument referenced an existing node on the DOM tree, the node will be detached from its current position and attached at the new position.
If callback is provided, and it returns false when called, the current recursion level is aborted, and the function resumes execution at the last parent's level. This can be used to abort loops once a node has been found (such as searching for a text node which contains a certain string).
\n In addition, every kind of DOM node is represented by an interface based on\n Node. These include Attr, CharacterData\n (which Text, Comment, CDATASection and\n ProcessingInstruction are all based on), and DocumentType.\n
\n In some cases, a particular feature of the base Node interface may not\n apply to one of its child interfaces; in that case, the inheriting node may\n return null or throw an exception, depending on circumstances. For example,\n attempting to add children to a node type that cannot have children will throw an\n exception.\n
\n Returns a live NodeList containing all the children of this node\n (including elements, text and comments). NodeList being live means that\n if the children of the Node change, the NodeList object is\n automatically updated.\n
\n Returns a string containing the name of the Node. The\n structure of the name will differ with the node type. E.g. An\n HTMLElement will contain the name of the corresponding tag, like\n 'audio' for an HTMLAudioElement, a Text\n node will have the '#text' string, or a Document node will\n have the '#document' string.\n
\n Adds the specified childNode argument as the last child to the current node.\n If the argument referenced an existing node on the DOM tree, the node will be detached\n from its current position and attached at the new position.\n
\n If callback is provided, and it returns\n false when called, the current recursion level is aborted, and the function\n resumes execution at the last parent's level. This can be used to abort loops once a\n node has been found (such as searching for a text node which contains a certain string).\n
A third, optional dimension (altitude) can also be included: key:ele (abbrev. for "elevation"). A node can also be defined as part of a particular layer=* or level=*, where distinct features pass over or under one another; say, at a bridge.
Nodes can be used on their own to define point features. When used in this way, a node will normally have at least one tag to define its purpose. Nodes may have multiple tags and/or be part of a relation. For example, a telephone box may be tagged simply with amenity=telephone, or could also be tagged with operator=*.
Where ways intersect at the same altitude, the two ways must share a node (for example, a road junction). If highways or railways cross at different heights without connecting they should not share a node (e.g. highway intersection with a bridge=*). Where ways cross at different heights they should be tagged with different layer=* or level=* values, or be tagged with location=* 'overground' or 'underground'. There are some exceptions to this rule, roads across dams are by current definition required to share a node with the waterway crossing the dam.
You can constrain a Pod so that it isrestricted to run on particular node(s),or to prefer to run on particular nodes.There are several ways to do this and the recommended approaches all uselabel selectors to facilitate the selection.Often, you do not need to set any such constraints; thescheduler will automatically do a reasonable placement(for example, spreading your Pods across nodes so as not place Pods on a node with insufficient free resources).However, there are some circumstances where you may want to control which nodethe Pod deploys to, for example, to ensure that a Pod ends up on a node with an SSD attached to it,or to co-locate Pods from two different services that communicate a lot into the same availability zone.
Adding labels to nodes allows you to target Pods for scheduling on specificnodes or groups of nodes. You can use this functionality to ensure that specificPods only run on nodes with certain isolation, security, or regulatoryproperties.
If you use labels for node isolation, choose label keys that the kubeletcannot modify. This prevents a compromised node from setting those labels onitself so that the scheduler schedules workloads onto the compromised node.
nodeSelector is the simplest recommended form of node selection constraint.You can add the nodeSelector field to your Pod specification and specify thenode labels you want the target node to have.Kubernetes only schedules the Pod onto nodes that have each of the labels youspecify.
nodeSelector is the simplest way to constrain Pods to nodes with specificlabels. Affinity and anti-affinity expands the types of constraints you candefine. Some of the benefits of affinity and anti-affinity include:
If you specify multiple expressions in a single matchExpressions field associated with aterm in nodeSelectorTerms, then the Pod can be scheduled onto a node onlyif all the expressions are satisfied (expressions are ANDed).
You can specify a weight between 1 and 100 for each instance of thepreferredDuringSchedulingIgnoredDuringExecution affinity type. When thescheduler finds nodes that meet all the other scheduling requirements of the Pod, thescheduler iterates through every preferred rule that the node satisfies and adds thevalue of the weight for that expression to a sum.
If there are two possible nodes that match thepreferredDuringSchedulingIgnoredDuringExecution rule, one with thelabel-1:key-1 label and another with the label-2:key-2 label, the schedulerconsiders the weight of each node and adds the weight to the other scores forthat node, and schedules the Pod onto the node with the highest final score.
When configuring multiple scheduling profiles, you can associatea profile with a node affinity, which is useful if a profile only applies to a specific set of nodes.To do so, add an addedAffinity to the args field of the NodeAffinity pluginin the scheduler configuration. For example:
The addedAffinity is applied to all Pods that set .spec.schedulerName to foo-scheduler, in addition to theNodeAffinity specified in the PodSpec.That is, in order to match the Pod, nodes need to satisfy addedAffinity andthe Pod's .spec.NodeAffinity.
Inter-pod affinity and anti-affinity allow you to constrain which nodes yourPods can be scheduled on based on the labels of Pods already running on thatnode, instead of the node labels.
Inter-pod affinity and anti-affinity rules take the form "thisPod should (or, in the case of anti-affinity, should not) run in an X if that Xis already running one or more Pods that meet rule Y", where X is a topologydomain like node, rack, cloud provider zone or region, or similar and Y is therule Kubernetes tries to satisfy.
If the current Pod being scheduled is the first in a series that have affinity to themselves,it is allowed to be scheduled if it passes all other affinity checks. This is determined byverifying that no other pod in the cluster matches the namespace and selector of this pod,that the pod matches its own terms, and the chosen node matches all requested topologies.This ensures that there will not be a deadlock even if all the pods have inter-pod affinityspecified.
The affinity rule specifies that the scheduler is allowed to place the example Podon a node only if that node belongs to a specific zonewhere other Pods have been labeled with security=S1.For instance, if we have a cluster with a designated zone, let's call it "Zone V,"consisting of nodes labeled with topology.kubernetes.io/zone=V, the scheduler canassign the Pod to any node within Zone V, as long as there is at least one Pod withinZone V already labeled with security=S1. Conversely, if there are no Pods with security=S1labels in Zone V, the scheduler will not assign the example Pod to any node in that zone.
The anti-affinity rule specifies that the scheduler should try to avoid scheduling the Podon a node if that node belongs to a specific zonewhere other Pods have been labeled with security=S2.For instance, if we have a cluster with a designated zone, let's call it "Zone R,"consisting of nodes labeled with topology.kubernetes.io/zone=R, the scheduler should avoidassigning the Pod to any node within Zone R, as long as there is at least one Pod withinZone R already labeled with security=S2. Conversely, the anti-affinity rule does not impactscheduling into Zone R if there are no Pods with security=S2 labels.
One example use case is to ensure Pods go to the topology domain (node, zone, etc) where only Pods from the same tenant or team are scheduled in.In other words, you want to avoid running Pods from two different tenants on the same topology domain at the same time.
Inter-pod affinity and anti-affinity can be even more useful when they are used with higherlevel collections such as ReplicaSets, StatefulSets, Deployments, etc. Theserules allow you to configure that a set of workloads shouldbe co-located in the same defined topology; for example, preferring to place two relatedPods onto the same node.
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