1. An application upgrade method performed by an application deployment server, the method comprising: receiving an application deployment request comprising a deployment package of a to-be-deployed application, wherein the deployment package describes a node template of the to-be-deployed application, an identifier of a deployed application to be upgraded by the to-be-deployed application, an identifier of a node template of the deployed application, an identifier of a first platform node template, and a version requirement of the first platform node template required by the node template of the to-be-deployed application; acquiring, according to the identifier of the deployed application, an identifier of a first platform node corresponding to the identifier of the first platform node template, and acquiring a version of the first platform node indicated by the identifier of the first platform node; wherein the to-be-deployed application runs based on a capability provided by the first platform node, and the first platform node is deployed prior to the to-be-deployed application according to the first platform node template; determining that the version of the first platform node is below the version requirement of the first platform node template required by the node template of the to-be-deployed application; acquiring a first platform node upgrade package that meets the version requirement in response to the determination result, wherein the first platform node upgrade package maintained by the application deployment server is acquired according to the version requirement of the first platform node template required by the node template of the to-be-deployed application; upgrading the first platform node indicated by the identifier of the first platform node by using the first platform node upgrade package; determining an identifier of a to-be-upgraded application node; and upgrading the application node after the first platform node is upgraded, wherein the application node is indicated by the identifier of the to-be-upgraded application node, and wherein the application node is upgraded using the deployment package carried in the application deployment request of the to-be-deployed application.