ApolloFederation-网关中的子图健康检查

1. 在 Apollo Server 中，使用 FederatedSchemaAdapter 将 GraphQL schema 转换为 FederatedSchemaAdapter，然后将其传递给 Apollo Gateway。

const { ApolloServer } = require('apollo-server');
const { buildFederatedSchema } = require('@apollo/federation');
const { FederatedSchemaAdapter } = require('@apollo/federation/dist/composition');

const schema = buildFederatedSchema([...]);

const federatedSchema = new FederatedSchemaAdapter(schema);

const server = new ApolloServer({
  gateway: new ApolloGateway({
    schema: federatedSchema,
    // ...
  }),
  // ...
});

server.listen().then(({ url }) => {
  console.log(`Server ready at ${url}`);
});

2. 使用 Apollo Gateway 提供的 onSchemaChange 事件，检查每个子图是否可用，如果不可用则抛出错误。以下是示例代码。

const { ApolloGateway } = require('@apollo/gateway');

const gateway = new ApolloGateway({
  serviceList: [...],
});

gateway.onSchemaChange(({ serviceList }) => {
  serviceList.forEach(async (service) => {
    const result = await service.checkHealth();
    if (result.status === 'fail' || !result.schema) {
      throw new Error(`Service ${service.name} is unavailable`);
    }
  });
});

app.use(gateway.getMiddleware());