MiddlewareFunction = (topology, context) => MiddlewareResult
Defined in: packages/hoppity/src/types.ts:174
Middleware function that can modify the topology and optionally provide a callback.
Middleware functions are executed in the order they are added to the pipeline.
Each middleware receives the current topology and a context object for sharing state.
BrokerConfig
The current topology configuration
MiddlewareContext
Context object for sharing state between middleware
MiddlewareResult
- The modified topology and optional callback
// First middleware: sets up exchanges and shares info via context
const exchangeSetupMiddleware: MiddlewareFunction = (topology, context) => {
// Modify topology to add exchanges
const modifiedTopology = { ...topology };
// ... add exchanges ...
// Share exchange names with downstream middleware
context.data.exchangeNames = ['user-events', 'order-events'];
context.data.serviceName = 'user-service';
return { topology: modifiedTopology };
};
// Second middleware: uses context from previous middleware
const queueSetupMiddleware: MiddlewareFunction = (topology, context) => {
// Access data from previous middleware
const exchangeNames = context.data.exchangeNames || [];
const serviceName = context.data.serviceName;
// Check if required middleware has run
if (!context.middlewareNames.includes('exchangeSetupMiddleware')) {
throw new Error('exchangeSetupMiddleware must run before queueSetupMiddleware');
}
// Use the shared data to set up queues
const modifiedTopology = { ...topology };
// ... set up queues bound to the exchanges ...
return { topology: modifiedTopology };
};
