feat(loki_client): handle absent logs gracefully

We have formatting code for it, but didn't use our Option=None path.

src/phoenix/inclusion_monitor/loki_client.rs

@@ -30,7 +30,7 @@ fn extract_date_time(json_map: &serde_json::Value, key: &str) -> anyhow::Result<
 /// Takes the payload logs response and extracts the first log line. We rely on the query being
 /// crafted in such a way that the oldest matching result is the one we're looking for.
 fn parse_payload_published_log(text: &str) -> anyhow::Result<Option<PayloadLogStats>> {
-    let payload_published_log: serde_json::Value = {
+    let payload_published_log: Option<serde_json::Value> = {
         let log_response_json: serde_json::Value = serde_json::from_str(text)
             .context("failed to parse payload log request body as JSON")?;
 
@@ -45,39 +45,45 @@ fn parse_payload_published_log(text: &str) -> anyhow::Result<Option<PayloadLogSt
             // Each of these lines is expected to contain parsed JSON values in the `stream` field and
             // raw values in the `values` field.
             .and_then(|line| line.get("stream"))
-            .context("failed to get stream from payload published log")
-            .cloned()?
+            .cloned()
     };
 
-    let received_at = extract_date_time(&payload_published_log, "timestampRequestStart")?;
-    let decoded_at = extract_date_time(&payload_published_log, "timestampAfterDecode")?;
-    let pre_publish_at = extract_date_time(&payload_published_log, "timestampBeforePublishing")?;
-    let post_publish_at = extract_date_time(&payload_published_log, "timestampAfterPublishing")?;
-    let decoded_at_slot_age_ms = payload_published_log["msIntoSlot"]
-        .as_str()
-        .and_then(|s| s.parse::<i64>().ok())
-        .context("failed to parse msIntoSlot as i64")?;
-
-    let pre_publish_duration_ms = pre_publish_at
-        .signed_duration_since(received_at)
-        .num_milliseconds();
-
-    let publish_duration_ms = post_publish_at
-        .signed_duration_since(pre_publish_at)
-        .num_milliseconds();
-
-    let request_download_duration_ms = decoded_at
-        .signed_duration_since(received_at)
-        .num_milliseconds();
-
-    let payload_log_stats = PayloadLogStats {
-        decoded_at_slot_age_ms,
-        pre_publish_duration_ms,
-        publish_duration_ms,
-        request_download_duration_ms,
-    };
-
-    Ok(Some(payload_log_stats))
+    match payload_published_log {
+        None => Ok(None),
+        Some(payload_published_log) => {
+            let received_at = extract_date_time(&payload_published_log, "timestampRequestStart")?;
+            let decoded_at = extract_date_time(&payload_published_log, "timestampAfterDecode")?;
+            let pre_publish_at =
+                extract_date_time(&payload_published_log, "timestampBeforePublishing")?;
+            let post_publish_at =
+                extract_date_time(&payload_published_log, "timestampAfterPublishing")?;
+            let decoded_at_slot_age_ms = payload_published_log["msIntoSlot"]
+                .as_str()
+                .and_then(|s| s.parse::<i64>().ok())
+                .context("failed to parse msIntoSlot as i64")?;
+
+            let pre_publish_duration_ms = pre_publish_at
+                .signed_duration_since(received_at)
+                .num_milliseconds();
+
+            let publish_duration_ms = post_publish_at
+                .signed_duration_since(pre_publish_at)
+                .num_milliseconds();
+
+            let request_download_duration_ms = decoded_at
+                .signed_duration_since(received_at)
+                .num_milliseconds();
+
+            let payload_log_stats = PayloadLogStats {
+                decoded_at_slot_age_ms,
+                pre_publish_duration_ms,
+                publish_duration_ms,
+                request_download_duration_ms,
+            };
+
+            Ok(Some(payload_log_stats))
+        }
+    }
 }
 
 pub struct LokiClient {