Class: AdmissionControlledResourceScheduler
- Inherits:
-
Object
- Object
- AdmissionControlledResourceScheduler
- Defined in:
- lib/rbvmomi/utils/admission_control.rb
Overview
An admission controlled resource scheduler for large scale vSphere deployments
While DRS (Dynamic Resource Scheduler) in vSphere handles CPU and Memory allocations within a single vSphere cluster, larger deployments require another layer of scheduling to make the use of multiple clusters transparent. So this class doesn’t replace DRS, but in fact works on top of it.
The scheduler in this class performs admission control to make sure clusters don’t get overloaded. It does so by adding additional metrics to the already existing CPU and Memory reservation system that DRS has. After admission control it also performs very basic initial placement. Note that in-cluster placement and load-balancing is left to DRS. Also note that no cross-cluster load balancing is done.
This class uses the concept of a Pod: A set of clusters that share a set of datastores. From a datastore perspective, we are free to place a VM on any host or cluster. So admission control is done at the Pod level first. Pods are automatically dicovered based on lists of clusters and datastores.
Admission control covers the following metrics:
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Host availability: If no hosts are available within a cluster or pod, admission is denied.
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Minimum free space: If a datastore falls below this free space percentage, admission to it will be denied. Admission to a pod is granted as long at least one datastore passes admission control.
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Maximum number of VMs: If a Pod exceeds a configured number of powered on VMs, admission is denied. This is a crude but effective catch-all metric in case users didn’t set proper individual CPU or Memory reservations or if the scalability limit doesn’t originate from CPU or Memory.
Placement after admission control:
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Cluster selection: A load metric based on a combination of CPU and Memory load is used to always select the “least loaded” cluster. The metric is very crude and only meant to do very rough load balancing. If DRS clusters are large enough, this is good enough in most cases though.
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Datastore selection: Right now NO intelligence is implemented here.
Usage: Instantiate the class, call make_placement_decision and then use the exposed computer (cluster), resource pool, vm_folder and datastore. Currently once computed, a new updated placement can’t be generated.
Instance Attribute Summary collapse
-
#rp ⇒ Object
readonly
Returns the value of attribute rp.
Instance Method Summary collapse
-
#computers ⇒ Array
Returns the candidate computers (aka clusters).
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#datacenter ⇒ RbVmomi::VIM::Datacenter
Returns the used Datacenter.
-
#datastore(placementHint = nil) ⇒ RbVmomi::VIM::Datastore
Returns the datastore to be used for placement.
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#datastores ⇒ Array
Returns the candidate datastores.
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#filtered_pods ⇒ Array
Returns the list of pods that pass admission control.
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#initialize(vim, opts = {}) ⇒ AdmissionControlledResourceScheduler
constructor
A new instance of AdmissionControlledResourceScheduler.
- #log(x) ⇒ Object
-
#make_placement_decision(opts = {}) ⇒ Object
Runs the placement algorithm and populates all the various properties as a side effect.
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#pick_computer(placementhint = nil) ⇒ RbVmomi::VIM::ClusterComputeResource
Returns the computer (aka cluster) to be used for placement.
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#pod_datastores(pod) ⇒ Array
Returns all candidate datastores for a given pod.
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#pod_vms(pod) ⇒ Hash
Returns all VMs residing with a pod.
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#pods ⇒ Array
Returns the candidate pods.
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#vm_folder ⇒ RbVmomi::VIM::Folder
Returns the used VM folder.
Constructor Details
#initialize(vim, opts = {}) ⇒ AdmissionControlledResourceScheduler
Returns a new instance of AdmissionControlledResourceScheduler.
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# File 'lib/rbvmomi/utils/admission_control.rb', line 50 def initialize vim, opts = {} @vim = vim @datacenter = opts[:datacenter] @datacenter_path = opts[:datacenter_path] @vm_folder = opts[:vm_folder] @vm_folder_path = opts[:vm_folder_path] @rp_path = opts[:rp_path] @computers = opts[:computers] @computer_names = opts[:computer_names] @datastores = opts[:datastores] @datastore_paths = opts[:datastore_paths] @max_vms_per_pod = opts[:max_vms_per_pod] @min_ds_free = opts[:min_ds_free] @service_docs_url = opts[:service_docs_url] @pc = @vim.serviceContent.propertyCollector @root_folder = @vim.serviceContent.rootFolder @logger = opts[:logger] end |
Instance Attribute Details
#rp ⇒ Object (readonly)
Returns the value of attribute rp.
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# File 'lib/rbvmomi/utils/admission_control.rb', line 48 def rp @rp end |
Instance Method Details
#computers ⇒ Array
Returns the candidate computers (aka clusters). If not set yet, uses the computer_names to look them up.
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# File 'lib/rbvmomi/utils/admission_control.rb', line 133 def computers if !@computers @computers = @computer_names.map do |name| computer = datacenter.find_compute_resource(name) [computer, computer.stats] end end @computers end |
#datacenter ⇒ RbVmomi::VIM::Datacenter
Returns the used Datacenter. If not set yet, uses the datacenter_path to lookup the datacenter.
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# File 'lib/rbvmomi/utils/admission_control.rb', line 104 def datacenter if !@datacenter @datacenter = @root_folder.traverse(@datacenter_path, RbVmomi::VIM::Datacenter) raise "datacenter #{@datacenter_path} not found" if !@datacenter end @datacenter end |
#datastore(placementHint = nil) ⇒ RbVmomi::VIM::Datastore
Returns the datastore to be used for placement. If not set yet, picks a datastore without much intelligence, as long as it passes admission control.
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# File 'lib/rbvmomi/utils/admission_control.rb', line 326 def datastore placementHint = nil return @datastore if @datastore pod_datastores = pick_computer.datastore & datastores eligible = pod_datastores.select do |ds| min_ds_free = @min_ds_free if min_ds_free && min_ds_free > 0 ds_sum = @datastore_props[ds]['summary'] free_percent = ds_sum.freeSpace.to_f * 100 / ds_sum.capacity free_percent > min_ds_free else true end end raise "Couldn't find any eligible datastore. Admission control should have prevented this" if eligible.length == 0 if placementHint && placementHint > 0 @datastore = eligible[placementHint % eligible.length] else @datastore = eligible.first end @datastore end |
#datastores ⇒ Array
Returns the candidate datastores. If not set yet, uses the datastore_paths to lookup the datastores under the datacenter. As a side effect, also looks up properties about all the datastores
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# File 'lib/rbvmomi/utils/admission_control.rb', line 116 def datastores if !@datastores @datastores = @datastore_paths.map do |path| ds = datacenter.datastoreFolder.traverse(path, RbVmomi::VIM::Datastore) raise "datastore #{path} not found" if !ds ds end end @datastore_props = @pc.collectMultiple(@datastores, 'summary', 'name') if !@datastore_props @datastores end |
#filtered_pods ⇒ Array
Returns the list of pods that pass admission control. If not set yet, performs admission control to compute the list. If no pods passed the admission control, an exception is thrown.
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# File 'lib/rbvmomi/utils/admission_control.rb', line 215 def filtered_pods # This function applies admission control and returns those pods that have # passed admission control. An exception is thrown if access was denied to # all pods. if !@filtered_pods log 'Performing admission control:' @filtered_pods = self.pods.select do |pod| # Gather some statistics about the pod ... on_vms = pod_vms(pod).select{ |k, v| v['runtime.powerState'] == 'poweredOn' } num_pod_vms = on_vms.length pod_datastores = self.pod_datastores(pod) log "Pod: #{pod.map{ |x| x.name }.join(', ')}" log " #{num_pod_vms} VMs" pod_datastores.each do |ds| ds_sum = @datastore_props[ds]['summary'] @datastore_props[ds]['free_percent'] = ds_sum.freeSpace.to_f * 100 / ds_sum.capacity end pod_datastores.each do |ds| ds_props = @datastore_props[ds] ds_name = ds_props['name'] free = ds_props['free_percent'] free_gb = ds_props['summary'].freeSpace.to_f / 1024**3 free_str = '%.2f GB (%.2f%%)' % [free_gb, free] log " Datastore #{ds_name}: #{free_str} free" end # Admission check: VM limit denied = false max_vms = @max_vms_per_pod if max_vms && max_vms > 0 if num_pod_vms > max_vms err = "VM limit (#{max_vms}) exceeded on this Pod" denied = true end end # Admission check: Free space on datastores min_ds_free = @min_ds_free if min_ds_free && min_ds_free > 0 # We need at least one datastore with enough free space low_list = pod_datastores.select do |ds| @datastore_props[ds]['free_percent'] <= min_ds_free end if low_list.length == pod_datastores.length dsNames = low_list.map{ |ds| @datastore_props[ds]['name'] }.join(', ') err = "Datastores #{dsNames} below minimum free disk space (#{min_ds_free}%)" denied = true end end # Admission check: Hosts are available if !denied hosts_available = pod.any? do |computer| stats = Hash[self.computers][computer] stats[:totalCPU] > 0 && stats[:totalMem] > 0 end if !hosts_available err = 'No hosts are current available in this pod' denied = true end end if denied log " Admission DENIED: #{err}" else log ' Admission granted' end !denied end end if @filtered_pods.length == 0 log "Couldn't find any Pod with enough resources." log "Check #{@service_docs_url} to see which other Pods you may be able to use" if @service_docs_url raise 'Admission denied' end @filtered_pods end |
#log(x) ⇒ Object
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# File 'lib/rbvmomi/utils/admission_control.rb', line 73 def log x if @logger @logger.info x else puts "#{Time.now}: #{x}" end end |
#make_placement_decision(opts = {}) ⇒ Object
Runs the placement algorithm and populates all the various properties as a side effect. Run this first, before using the other functions of this class.
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# File 'lib/rbvmomi/utils/admission_control.rb', line 355 def make_placement_decision opts = {} self.filtered_pods self.pick_computer opts[:placementHint] log "Selected compute resource: #{@computer.name}" @rp = @computer.resourcePool.traverse(@rp_path) raise "Resource pool #{@rp_path} not found" if !@rp log "Resource pool: #{@rp.pretty_path}" stats = @computer.stats if stats[:totalMem] > 0 && stats[:totalCPU] > 0 cpu_load = "#{(100*stats[:usedCPU])/stats[:totalCPU]}% cpu" mem_load = "#{(100*stats[:usedMem])/stats[:totalMem]}% mem" log "Cluster utilization: #{cpu_load}, #{mem_load}" end user_vms = vm_folder.inventory_flat('VirtualMachine' => %w(name storage)).select do |k, v| k.is_a?(RbVmomi::VIM::VirtualMachine) end numVms = user_vms.length unshared = user_vms.map do |vm, info| info['storage'].perDatastoreUsage.map{ |x| x.unshared }.inject(0, &:+) end.inject(0, &:+) log "User stats: #{numVms} VMs using %.2fGB of storage" % [unshared.to_f / 1024**3] @placement_hint = opts[:placement_hint] || (rand(100) + 1) datastore = self.datastore @placement_hint log "Datastore: #{datastore.name}" end |
#pick_computer(placementhint = nil) ⇒ RbVmomi::VIM::ClusterComputeResource
Returns the computer (aka cluster) to be used for placement. If not set yet, computs the least loaded cluster (using a metric that combines CPU and Memory load) that passes admission control.
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# File 'lib/rbvmomi/utils/admission_control.rb', line 299 def pick_computer placementhint = nil if !@computer # Out of the pods to which we have been granted access, pick the cluster # (aka computer) with the lowest CPU/Mem utilization for load balancing available = self.filtered_pods.flatten eligible = self.computers.select do |computer, stats| available.member?(computer) && stats[:totalCPU] > 0 and stats[:totalMem] > 0 end computer = nil if placementhint computer = eligible.map{ |x| x[0] }[placementhint % eligible.length] if eligible.length > 0 else computer, = eligible.min_by do |computer, stats| 2**(stats[:usedCPU].to_f/stats[:totalCPU]) + (stats[:usedMem].to_f/stats[:totalMem]) end end raise 'No clusters available, should have been prevented by admission control' if !computer @computer = computer end @computer end |
#pod_datastores(pod) ⇒ Array
Returns all candidate datastores for a given pod.
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# File 'lib/rbvmomi/utils/admission_control.rb', line 207 def pod_datastores pod pod.first.datastore & self.datastores end |
#pod_vms(pod) ⇒ Hash
Returns all VMs residing with a pod. Doesn’t account for templates. Does so very efficiently using a single API query.
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# File 'lib/rbvmomi/utils/admission_control.rb', line 166 def pod_vms pod # This function retrieves all VMs residing inside a pod filterSpec = RbVmomi::VIM.PropertyFilterSpec( objectSet: pod.map do |computer, stats| { obj: computer.resourcePool, selectSet: [ RbVmomi::VIM.TraversalSpec( name: 'tsFolder', type: 'ResourcePool', path: 'resourcePool', skip: false, selectSet: [ RbVmomi::VIM.SelectionSpec(name: 'tsFolder'), RbVmomi::VIM.SelectionSpec(name: 'tsVM'), ] ), RbVmomi::VIM.TraversalSpec( name: 'tsVM', type: 'ResourcePool', path: 'vm', skip: false, selectSet: [], ) ] } end, propSet: [ { type: 'ResourcePool', pathSet: ['name'] }, { type: 'VirtualMachine', pathSet: %w(runtime.powerState) } ] ) result = @vim.propertyCollector.RetrieveProperties(specSet: [filterSpec]) out = result.map { |x| [x.obj, Hash[x.propSet.map { |y| [y.name, y.val] }]] } out.select{ |obj, props| obj.is_a?(RbVmomi::VIM::VirtualMachine) } end |
#pods ⇒ Array
Returns the candidate pods. If not set, automatically computes the pods based on the list of computers (aka clusters) and datastores.
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# File 'lib/rbvmomi/utils/admission_control.rb', line 146 def pods if !@pods # A pod is defined as a set of clusters (aka computers) that share the same # datastore accessibility. Computing pods is done automatically using simple # set theory math. computersProps = @pc.collectMultiple(computers.map{ |x| x[0] }, 'datastore') @pods = computers.map do |computer, stats| computersProps[computer]['datastore'] & self.datastores end.uniq.map do |ds_list| computers.map{ |x| x[0] }.select do |computer| (computer.datastore & self.datastores) == ds_list end end end @pods end |
#vm_folder ⇒ RbVmomi::VIM::Folder
Returns the used VM folder. If not set yet, uses the vm_folder_path to lookup the folder. If it doesn’t exist, it is created. Collisions between multiple clients concurrently creating the same folder are handled.
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# File 'lib/rbvmomi/utils/admission_control.rb', line 85 def vm_folder retries = 1 begin @vm_folder ||= datacenter.vmFolder.traverse!(@vm_folder_path, RbVmomi::VIM::Folder) raise "VM folder #{@vm_folder_path} not found" if !@vm_folder rescue RbVmomi::Fault => fault if !fault.fault.is_a?(RbVmomi::VIM::DuplicateName) raise else retries -= 1 retry if retries >= 0 end end @vm_folder end |