feat(api): add cpu utilization query and subscription

Adds a new query and subscription to the info resolver for CPU to get CPU utilization on Unraid.

- Adds `cpuUtilization` query to get a one-time snapshot of CPU load.
- Adds `cpuUtilizationSubscription` to get real-time updates on CPU load.
- Adds a `utilization` field to the `InfoCpu` type.
- Creates a generic `SubscriptionTrackerService` to manage polling for subscriptions, ensuring that polling only occurs when there are active subscribers.
- Creates a request-scoped `CpuDataService` to cache CPU load data within a single GraphQL request to improve performance.
- Updates tests to cover the new functionality.
- Adds detailed documentation to the `CpuLoad` object type.

api/src/unraid-api/graph/resolvers/info/cpu-data.service.ts

@@ -0,0 +1,14 @@
+import { Injectable, Scope } from '@nestjs/common';
+import { currentLoad, Systeminformation } from 'systeminformation';
+
+@Injectable({ scope: Scope.REQUEST })
+export class CpuDataService {
+    private cpuLoadData: Promise<Systeminformation.CurrentLoadData>;
+
+    public getCpuLoad(): Promise<Systeminformation.CurrentLoadData> {
+        if (!this.cpuLoadData) {
+            this.cpuLoadData = currentLoad();
+        }
+        return this.cpuLoadData;
+    }
+}

api/src/unraid-api/graph/resolvers/info/info.model.ts

@@ -117,6 +117,42 @@ export class InfoCpu extends Node {
 
     @Field(() => [String])
     flags!: string[];
+
+    @Field(() => Float, {
+        description: 'CPU utilization in percent',
+        nullable: true,
+    })
+    utilization?: number;
+}
+
+@ObjectType({ description: 'CPU load for a single core' })
+export class CpuLoad {
+    @Field(() => Float, { description: 'The total CPU load on a single core, in percent.' })
+    load!: number;
+
+    @Field(() => Float, { description: 'The percentage of time the CPU spent in user space.' })
+    loadUser!: number;
+
+    @Field(() => Float, { description: 'The percentage of time the CPU spent in kernel space.' })
+    loadSystem!: number;
+
+    @Field(() => Float, { description: 'The percentage of time the CPU spent on low-priority (niced) user space processes.' })
+    loadNice!: number;
+
+    @Field(() => Float, { description: 'The percentage of time the CPU was idle.' })
+    loadIdle!: number;
+
+    @Field(() => Float, { description: 'The percentage of time the CPU spent servicing hardware interrupts.' })
+    loadIrq!: number;
+}
+
+@ObjectType({ implements: () => Node })
+export class CpuUtilization extends Node {
+    @Field(() => Float)
+    load!: number;
+
+    @Field(() => [CpuLoad])
+    cpus!: CpuLoad[];
 }
 
 @ObjectType({ implements: () => Node })

api/src/unraid-api/graph/resolvers/info/info.resolver.spec.ts

@@ -6,8 +6,10 @@ import { beforeEach, describe, expect, it, vi } from 'vitest';
 
 import { DisplayService } from '@app/unraid-api/graph/resolvers/display/display.service.js';
 import { DockerService } from '@app/unraid-api/graph/resolvers/docker/docker.service.js';
+import { CpuDataService } from '@app/unraid-api/graph/resolvers/info/cpu-data.service.js';
 import { InfoResolver } from '@app/unraid-api/graph/resolvers/info/info.resolver.js';
 import { InfoService } from '@app/unraid-api/graph/resolvers/info/info.service.js';
+import { SubscriptionTrackerService } from '@app/unraid-api/graph/services/subscription-tracker.service.js';
 
 // Mock necessary modules
 vi.mock('fs/promises', () => ({
@@ -187,6 +189,19 @@ describe('InfoResolver', () => {
         generateDisplay: vi.fn().mockResolvedValue(mockDisplayData),
     };
 
+    const mockSubscriptionTrackerService = {
+        registerTopic: vi.fn(),
+        subscribe: vi.fn(),
+        unsubscribe: vi.fn(),
+    };
+
+    const mockCpuDataService = {
+        getCpuLoad: vi.fn().mockResolvedValue({
+            currentLoad: 10,
+            cpus: [],
+        }),
+    };
+
     beforeEach(async () => {
         const module: TestingModule = await Test.createTestingModule({
             providers: [
@@ -207,6 +222,14 @@ describe('InfoResolver', () => {
                     provide: CACHE_MANAGER,
                     useValue: mockCacheManager,
                 },
+                {
+                    provide: SubscriptionTrackerService,
+                    useValue: mockSubscriptionTrackerService,
+                },
+                {
+                    provide: CpuDataService,
+                    useValue: mockCpuDataService,
+                },
             ],
         }).compile();
 

api/src/unraid-api/graph/resolvers/info/info.resolver.ts

@@ -1,4 +1,12 @@
-import { Query, ResolveField, Resolver, Subscription } from '@nestjs/graphql';
+import { OnModuleInit } from '@nestjs/common';
+import {
+    Parent,
+    Query,
+    Resolver,
+    Subscription,
+    ResolveField,
+} from '@nestjs/graphql';
+import { PubSub } from 'graphql-subscriptions';
 
 import { Resource } from '@unraid/shared/graphql.model.js';
 import {
@@ -6,10 +14,18 @@ import {
     AuthPossession,
     UsePermissions,
 } from '@unraid/shared/use-permissions.directive.js';
-import { baseboard as getBaseboard, system as getSystem } from 'systeminformation';
+import {
+    baseboard as getBaseboard,
+    system as getSystem,
+} from 'systeminformation';
 
-import { createSubscription, PUBSUB_CHANNEL } from '@app/core/pubsub.js';
 import { getMachineId } from '@app/core/utils/misc/get-machine-id.js';
+import {
+    createSubscription,
+    PUBSUB_CHANNEL,
+    pubsub,
+} from '@app/core/pubsub.js';
+
 import { DisplayService } from '@app/unraid-api/graph/resolvers/display/display.service.js';
 import {
     Baseboard,
@@ -22,16 +38,40 @@ import {
     Os,
     System,
     Versions,
+    CpuUtilization,
 } from '@app/unraid-api/graph/resolvers/info/info.model.js';
+import { CpuDataService } from '@app/unraid-api/graph/resolvers/info/cpu-data.service.js';
 import { InfoService } from '@app/unraid-api/graph/resolvers/info/info.service.js';
+import { SubscriptionTrackerService } from '@app/unraid-api/graph/services/subscription-tracker.service.js';
+
+const CPU_UTILIZATION = 'CPU_UTILIZATION';
 
 @Resolver(() => Info)
-export class InfoResolver {
+export class InfoResolver implements OnModuleInit {
+    private cpuPollingTimer: NodeJS.Timeout;
+
     constructor(
         private readonly infoService: InfoService,
-        private readonly displayService: DisplayService
+        private readonly displayService: DisplayService,
+        private readonly subscriptionTracker: SubscriptionTrackerService,
+        private readonly cpuDataService: CpuDataService
     ) {}
 
+    onModuleInit() {
+        this.subscriptionTracker.registerTopic(
+            CPU_UTILIZATION,
+            () => {
+                this.cpuPollingTimer = setInterval(async () => {
+                    const payload = await this.infoService.generateCpuLoad();
+                    pubsub.publish(CPU_UTILIZATION, { cpuUtilization: payload });
+                }, 1000);
+            },
+            () => {
+                clearInterval(this.cpuPollingTimer);
+            }
+        );
+    }
+
     @Query(() => Info)
     @UsePermissions({
         action: AuthActionVerb.READ,
@@ -116,4 +156,57 @@ export class InfoResolver {
     public async infoSubscription() {
         return createSubscription(PUBSUB_CHANNEL.INFO);
     }
+
+    @Query(() => CpuUtilization)
+    @UsePermissions({
+        action: AuthActionVerb.READ,
+        resource: Resource.INFO,
+        possession: AuthPossession.ANY,
+    })
+    public async cpuUtilization(): Promise<CpuUtilization> {
+        const { currentLoad: load, cpus } = await this.cpuDataService.getCpuLoad();
+        return {
+            id: 'info/cpu-load',
+            load,
+            cpus,
+        };
+    }
+
+    @Subscription(() => CpuUtilization, {
+        name: 'cpuUtilization',
+        resolve: (value) => value.cpuUtilization,
+    })
+    @UsePermissions({
+        action: AuthActionVerb.READ,
+        resource: Resource.INFO,
+        possession: AuthPossession.ANY,
+    })
+    public async cpuUtilizationSubscription() {
+        const iterator = createSubscription(CPU_UTILIZATION);
+
+        return {
+            [Symbol.asyncIterator]: () => {
+                this.subscriptionTracker.subscribe(CPU_UTILIZATION);
+                return iterator[Symbol.asyncIterator]();
+            },
+            return: () => {
+                this.subscriptionTracker.unsubscribe(CPU_UTILIZATION);
+                return iterator.return();
+            },
+        };
+    }
+}
+
+@Resolver(() => InfoCpu)
+export class InfoCpuResolver {
+    constructor(private readonly cpuDataService: CpuDataService) {}
+
+    @ResolveField(() => Number, {
+        description: 'CPU utilization in percent',
+        nullable: true,
+    })
+    public async utilization(@Parent() cpu: InfoCpu): Promise<number> {
+        const { currentLoad } = await this.cpuDataService.getCpuLoad();
+        return currentLoad;
+    }
 }

api/src/unraid-api/graph/resolvers/info/info.service.ts

@@ -1,6 +1,14 @@
 import { Injectable } from '@nestjs/common';
 
-import { cpu, cpuFlags, mem, memLayout, osInfo, versions } from 'systeminformation';
+import {
+    cpu,
+    cpuFlags,
+    mem,
+    memLayout,
+    osInfo,
+    versions,
+    currentLoad,
+} from 'systeminformation';
 
 import { bootTimestamp } from '@app/common/dashboard/boot-timestamp.js';
 import { getUnraidVersion } from '@app/common/dashboard/get-unraid-version.js';
@@ -15,6 +23,7 @@ import {
     Os as InfoOs,
     MemoryLayout,
     Versions,
+    CpuUtilization,
 } from '@app/unraid-api/graph/resolvers/info/info.model.js';
 
 @Injectable()
@@ -91,4 +100,14 @@ export class InfoService {
             // These fields will be resolved by DevicesResolver
         } as Devices;
     }
+
+    async generateCpuLoad(): Promise<CpuUtilization> {
+        const { currentLoad: load, cpus } = await currentLoad();
+
+        return {
+            id: 'info/cpu-load',
+            load,
+            cpus,
+        };
+    }
 }

api/src/unraid-api/graph/resolvers/resolvers.module.ts

@@ -33,12 +33,16 @@ import { VarsResolver } from '@app/unraid-api/graph/resolvers/vars/vars.resolver
 import { VmMutationsResolver } from '@app/unraid-api/graph/resolvers/vms/vms.mutations.resolver.js';
 import { VmsResolver } from '@app/unraid-api/graph/resolvers/vms/vms.resolver.js';
 import { VmsService } from '@app/unraid-api/graph/resolvers/vms/vms.service.js';
+import { ServicesModule } from '@app/unraid-api/graph/services/services.module.js';
 import { ServicesResolver } from '@app/unraid-api/graph/services/services.resolver.js';
 import { SharesResolver } from '@app/unraid-api/graph/shares/shares.resolver.js';
 import { MeResolver } from '@app/unraid-api/graph/user/user.resolver.js';
+import { InfoCpuResolver } from '@app/unraid-api/graph/resolvers/info/info.resolver.js';
+import { CpuDataService } from '@app/unraid-api/graph/resolvers/info/cpu-data.service.js';
 
 @Module({
     imports: [
+        ServicesModule,
         ArrayModule,
         ApiKeyModule,
         AuthModule,
@@ -76,6 +80,8 @@ import { MeResolver } from '@app/unraid-api/graph/user/user.resolver.js';
         VmMutationsResolver,
         VmsResolver,
         VmsService,
+        InfoCpuResolver,
+        CpuDataService,
     ],
     exports: [ApiKeyModule],
 })

api/src/unraid-api/graph/services/services.module.ts

@@ -0,0 +1,8 @@
+import { Module } from '@nestjs/common';
+import { SubscriptionTrackerService } from './subscription-tracker.service';
+
+@Module({
+    providers: [SubscriptionTrackerService],
+    exports: [SubscriptionTrackerService],
+})
+export class ServicesModule {}

api/src/unraid-api/graph/services/subscription-tracker.service.ts

@@ -0,0 +1,44 @@
+import { Injectable } from '@nestjs/common';
+
+@Injectable()
+export class SubscriptionTrackerService {
+    private subscriberCounts = new Map<string, number>();
+    private topicHandlers = new Map<
+        string,
+        { onStart: () => void; onStop: () => void }
+    >();
+
+    public registerTopic(
+        topic: string,
+        onStart: () => void,
+        onStop: () => void
+    ): void {
+        this.topicHandlers.set(topic, { onStart, onStop });
+    }
+
+    public subscribe(topic: string): void {
+        const currentCount = this.subscriberCounts.get(topic) || 0;
+        this.subscriberCounts.set(topic, currentCount + 1);
+
+        if (currentCount === 0) {
+            const handlers = this.topicHandlers.get(topic);
+            if (handlers) {
+                handlers.onStart();
+            }
+        }
+    }
+
+    public unsubscribe(topic: string): void {
+        const currentCount = this.subscriberCounts.get(topic) || 1;
+        const newCount = currentCount - 1;
+
+        this.subscriberCounts.set(topic, newCount);
+
+        if (newCount === 0) {
+            const handlers = this.topicHandlers.get(topic);
+            if (handlers) {
+                handlers.onStop();
+            }
+        }
+    }
+}