// Copyright 2025 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// SPDX-License-Identifier: Apache-2.0
// This sample demonstrates durable streaming, which allows clients to reconnect
// to in-progress or completed streams using a stream ID.
//
// Start the server:
//
// go run .
//
// Test streaming (get a stream ID back in X-Genkit-Stream-Id header):
//
// curl -N -i -H "Accept: text/event-stream" \
// -d '{"data": 5}' \
// http://localhost:8080/countdown
//
// Subscribe to an existing stream using the stream ID from the previous response:
//
// curl -N -H "Accept: text/event-stream" \
// -H "X-Genkit-Stream-Id: <stream-id-from-above>" \
// -d '{"data": 5}' \
// http://localhost:8080/countdown
//
// The subscription will replay any buffered chunks and then continue with live updates.
// If the stream has already completed, all chunks plus the final result are returned.
package main
import (
"context"
"fmt"
"log"
"net/http"
"time"
"github.com/firebase/genkit/go/core/x/streaming"
"github.com/firebase/genkit/go/genkit"
"github.com/firebase/genkit/go/plugins/server"
)
func main() {
ctx := context.Background()
g := genkit.Init(ctx)
type CountdownChunk struct {
Count int `json:"count"`
Message string `json:"message"`
Timestamp string `json:"timestamp"`
}
// Define a streaming flow that counts down with delays.
countdown := genkit.DefineStreamingFlow(g, "countdown",
func(ctx context.Context, count int, sendChunk func(context.Context, CountdownChunk) error) (string, error) {
if count <= 0 {
count = 5
}
for i := count; i > 0; i-- {
select {
case <-ctx.Done():
return "", ctx.Err()
case <-time.After(1 * time.Second):
}
chunk := CountdownChunk{
Count: i,
Message: fmt.Sprintf("T-%d...", i),
Timestamp: time.Now().Format(time.RFC3339),
}
if err := sendChunk(ctx, chunk); err != nil {
return "", err
}
}
return "Liftoff!", nil
})
// Set up HTTP server with durable streaming enabled.
// Completed streams are kept for 10 minutes before cleanup (while server is running).
mux := http.NewServeMux()
mux.HandleFunc("POST /countdown", genkit.Handler(countdown,
genkit.WithStreamManager(streaming.NewInMemoryStreamManager(streaming.WithTTL(10*time.Minute))),
))
log.Fatal(server.Start(ctx, "127.0.0.1:8080", mux))
}
