Backend Extension Mechanisms Guide

GoWind CMS provides multiple backend extension approaches, allowing custom business logic without modifying core code. This document introduces all extension mechanisms and their applicable scenarios.

1. Extension Approaches Overview

2. Extension Approaches Compared

Approach	Development Cost	Runtime Flexibility	Performance	Applicable Scenarios
New business module	High	No (requires compilation)	Best	Brand-new feature modules
Lua script	Low	Yes	Medium	Lightweight logic extensions
Event subscription	Low	Yes	High	Side-effect handling
Custom API	Medium	Yes	Medium	Aggregate endpoints/adapters
Scheduled tasks	Low	Yes	High	Periodic tasks
Middleware	Medium	No	High	Global request processing

3. Adding a Business Module

For the complete module addition workflow, see Full-Stack Practice: Adding a Content Type. Core steps:

4. Lua Script Extension

For details, see Lua Script Extension in Practice.

4.1 Quick Example

-- Register a custom API
api.register("GET", "/app/v1/posts/popular", function(ctx)
    local posts = db.query("SELECT * FROM posts WHERE status = 1 ORDER BY view_count DESC LIMIT 10")
    return json.encode({ items = posts })
end)

-- Event subscription
eventbus.subscribe("post.published", function(event)
    log.info("Post published: " .. event.PostId)
end)

5. Event Bus Extension

For details, see Event Bus Architecture.

5.1 Go Subscription

// Register a subscriber
bus.Subscribe("post.published", func(ctx context.Context, event interface{}) {
    e := event.(*eventbus.PostPublishedEvent)
    // Custom handling logic
})

5.2 Lua Subscription

eventbus.subscribe("post.published", function(event)
    -- Lua handling logic
end)

6. Custom Middleware

6.1 Middleware Example

// pkg/middleware/tenant_context.go
func TenantContext() middleware.Middleware {
    return func(handler middleware.Handler) middleware.Handler {
        return func(ctx context.Context, req interface{}) (interface{}, error) {
            // Extract the tenant ID from the JWT
            tenantId := ctx.Value(middleware.TenantIDKey{}).(uint32)

            // Inject it into the context
            ctx = context.WithValue(ctx, entgo.TenantKey{}, tenantId)

            return handler(ctx, req)
        }
    }
}

6.2 Registering Middleware

// app/admin/service/internal/server/rest_server.go
srv.Use(
    middleware.Logging(),
    middleware.Audit(),
    middleware.Auth(),           // JWT authentication
    middleware.TenantContext(),  // Tenant context
    middleware.Authz(authorizer),// Permission verification
)

7. Scheduled Task Extension

7.1 Asynq Scheduled Tasks

// app/core/service/internal/server/asynq_server.go
func RegisterScheduledTasks(scheduler *asynq.Scheduler) {
    scheduler.Register("0 3 * * *", asynq.NewTask(
        task.TypeCleanupExpiredData,
        jsonMustMarshal(task.CleanupExpiredDataPayload{
            EntityType: "posts",
            OlderThan:  time.Now().AddDate(0, 0, -30).Unix(),
        }),
    ))
}

7.2 Lua Scheduled Tasks

cron.register("0 2 * * *", function()
    -- Daily data statistics
    local stats = db.query("SELECT ...")
    redis.set("daily:stats", json.encode(stats))
end)

8. Extension Best Practices

8.1 Choosing an Extension Approach

8.2 Extension Security

Rule	Description
Lua sandbox	Restricts file system/network access
Event isolation	Subscriber panics do not affect the main flow
Permission checks	Extension APIs require authentication