GCP Pub/Sub

zero can publish to and subscribe from Google Cloud Pub/Sub through the unified PubSub client. Requests use OAuth2 bearer tokens (fetched via client-credentials), so there is no GCP SDK to link.

Configuration

PUBSUB_BACKEND=GCP          # or GOOGLE
GCP_PROJECT=my-gcp-project
GCP_SUBSCRIPTION=zero-sub
GCP_ENDPOINT=https://pubsub.googleapis.com
GCP_CLIENT_ID=
GCP_CLIENT_SECRET=
GCP_SCOPE=https://www.googleapis.com/auth/pubsub
# GCP_ACCESS_TOKEN=          # optional; bypasses the token fetch (workload identity / sidecar)

The subscription must already exist in your project.

Publish

try ctx.getPublisher().Publish("orders", "{\"id\":1}");

The subject is the Pub/Sub topic name.

Subscribe

pub fn onOrder(ctx: *Context, subject: []const u8, payload: []const u8) !void {
    // handle the message
}

try app.addPubSubSubscription("orders", onOrder);

zero polls the subscription, base64-decodes the payload, dispatches it to your hook, then acknowledges it.

Caveats

• The subscription must be created out-of-band; zero does not provision it.
• OAuth2 tokens are fetched with the client-credentials grant; set GCP_ACCESS_TOKEN to skip the fetch when a sidecar handles auth.

See the zero-redis example and the implementation in src/pubsub/gcp/gcppubsub.zig.