The protocol

infra/workers/tail/src/index.ts

@@ -4,16 +4,51 @@
  * https://developers.cloudflare.com/workers/observability/logging/tail-workers/
  */
 export default {
-    async tail(events: TailItems[], env: Env) {
+    async tail(events: TraceItem[], env: Env) {
         // If the tail worker itself throws an exception (it shouldn't, unless
         // Loki is down), we don't catch it so that it counts as an "error" in
         // the worker stats.
-        return handleTail(events, env.LOKI_URL);
+        return handleTail(events, env.LOKI_PUSH_URL);
     },
-} satisfies ExportedHander<Env>;
+} satisfies ExportedHandler<Env>;
 
 interface Env {
-    LOKI_URL: string;
+    LOKI_PUSH_URL: string;
 }
 
-const handleTail = (events: TailItems[], lokiURL: string) => {};
+const handleTail = async (events: TraceItem[], lokiPushURL: string) => {};
+
+/**
+ * Send a log entry to (Grafana) Loki
+ *
+ * For more details about the protocol, see
+ * https://grafana.com/docs/loki/latest/reference/loki-http-api/#ingest-logs
+ *
+ * @param tsNano Unix epoch in nanoseconds when the event occurred.
+ *
+ * @param logLine The message to log.
+ *
+ * @param lokiPushURL The URL of the Loki instance to push logs to. The
+ * credentials are part of the URL.
+ */
+const pushLogLine = async (
+    tsNano: number,
+    logLine: string,
+    lokiPushURL: string
+) =>
+    fetch(lokiPushURL, {
+        method: "POST",
+        headers: {
+            "Content-Type": "application/json",
+        },
+        body: JSON.stringify({
+            streams: [
+                {
+                    stream: {
+                        job: "cf-worker",
+                    },
+                    values: [[`${tsNano}`, logLine]],
+                },
+            ],
+        }),
+    });

infra/workers/tail/wrangler.toml

@@ -4,4 +4,4 @@ compatibility_date = "2024-06-14"
 
 [vars]
 # Added as a secret via the Cloudflare dashboard
-# LOKI_URL = "https://discord.com/api/webhooks/{webhook.id}/{webhook.token}"
+# LOKI_PUSH_URL = "https://{loki_base_url}>/loki/api/v1/push"