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Add polling support #2914

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merged 1 commit into from
Jun 27, 2019
Merged

Add polling support #2914

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46 changes: 45 additions & 1 deletion packages/apollo-gateway/src/index.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -52,13 +52,18 @@ function isLocalConfig(config: GatewayConfig): config is LocalGatewayConfig {
return 'localServiceList' in config;
}

export type SchemaChangeCallback = (schema: GraphQLSchema) => void;
export type Unsubscriber = () => void;

export class ApolloGateway implements GraphQLService {
public schema?: GraphQLSchema;
public isReady: boolean = false;
protected serviceMap: ServiceMap = Object.create(null);
protected config: GatewayConfig;
protected logger: Logger;
protected queryPlanStore?: InMemoryLRUCache<QueryPlan>;
private pollingTimer?: NodeJS.Timer;
private onSchemaChangeListeners = new Set<SchemaChangeCallback>();

constructor(config: GatewayConfig) {
this.config = {
Expand Down Expand Up @@ -124,11 +129,43 @@ export class ApolloGateway implements GraphQLService {
this.isReady = true;
}

public onSchemaChange(value: SchemaChangeCallback): Unsubscriber {
// TODO: if (!isRemoteGatewayConfig(this.config)) { throw new Error('onSchemaChange requires an Apollo Engine hosted service list definition.'); } (dependant on #2915)
this.onSchemaChangeListeners.add(value);
if (!this.pollingTimer) this.startPollingServices();

return () => {
this.onSchemaChangeListeners.delete(value);
if (this.onSchemaChangeListeners.size === 0 && this.pollingTimer) {
clearInterval(this.pollingTimer!);
this.pollingTimer = undefined;
}
};
}

private startPollingServices() {
if (this.pollingTimer) clearInterval(this.pollingTimer);

this.pollingTimer = setInterval(async () => {
const [services, isNewSchema] = await this.loadServiceDefinitions(
this.config,
);
if (!isNewSchema) {
this.logger.debug('No changes to gateway config');
return;
}
if (this.queryPlanStore) this.queryPlanStore.flush();
this.logger.debug('Gateway config has changed, updating schema');
this.createSchema(services);
this.onSchemaChangeListeners.forEach(listener => listener(this.schema!));
}, 10 * 1000);
}

protected createServices(services: ServiceEndpointDefinition[]) {
for (const serviceDef of services) {
if (!serviceDef.url && !isLocalConfig(this.config)) {
throw new Error(
`Service defintion for service ${serviceDef.name} is missing a url`,
`Service definition for service ${serviceDef.name} is missing a url`,
);
}
this.serviceMap[serviceDef.name] = this.config.buildService
Expand Down Expand Up @@ -234,6 +271,13 @@ export class ApolloGateway implements GraphQLService {
sizeCalculator: approximateObjectSize,
});
}

public async stop() {
if (this.pollingTimer) {
clearInterval(this.pollingTimer);
this.pollingTimer = undefined;
}
}
}

function approximateObjectSize<T>(obj: T): number {
Expand Down