scrubber: make scan-metadata enumerate relics & unreadable timelines

s3_scrubber/src/checks.rs

@@ -142,7 +142,7 @@ pub(crate) async fn branch_cleanup_and_check_errors(
                         .collect();
 
                     if !orphan_layers.is_empty() {
-                        result.errors.push(format!(
+                        result.warnings.push(format!(
                             "index_part.json does not contain layers from S3: {:?}",
                             orphan_layers
                                 .iter()
@@ -170,6 +170,7 @@ pub(crate) async fn branch_cleanup_and_check_errors(
                         ));
                     }
                 }
+                BlobDataParseResult::Relic => {}
                 BlobDataParseResult::Incorrect(parse_errors) => result.errors.extend(
                     parse_errors
                         .into_iter()
@@ -215,6 +216,8 @@ pub(crate) enum BlobDataParseResult {
         index_part_generation: Generation,
         s3_layers: HashSet<(LayerFileName, Generation)>,
     },
+    /// The remains of a deleted Timeline (i.e. an initdb archive only)
+    Relic,
     Incorrect(Vec<String>),
 }
 
@@ -245,6 +248,7 @@ pub(crate) async fn list_timeline_blobs(
     timeline_dir_target.delimiter = String::new();
 
     let mut index_parts: Vec<ObjectIdentifier> = Vec::new();
+    let mut initdb_archive: bool = false;
 
     let stream = stream_listing(s3_client, &timeline_dir_target);
     pin_mut!(stream);
@@ -258,6 +262,10 @@ pub(crate) async fn list_timeline_blobs(
                 tracing::info!("Index key {key}");
                 index_parts.push(obj)
             }
+            Some("initdb.tar.zst") => {
+                tracing::info!("initdb archive {key}");
+                initdb_archive = true;
+            }
             Some(maybe_layer_name) => match parse_layer_object_name(maybe_layer_name) {
                 Ok((new_layer, gen)) => {
                     tracing::info!("Parsed layer key: {} {:?}", new_layer, gen);
@@ -279,6 +287,16 @@ pub(crate) async fn list_timeline_blobs(
         }
     }
 
+    if index_parts.is_empty() && s3_layers.is_empty() && initdb_archive {
+        tracing::info!(
+            "Timeline is empty apart from initdb archive: expected post-deletion state."
+        );
+        return Ok(S3TimelineBlobData {
+            blob_data: BlobDataParseResult::Relic,
+            keys_to_remove: Vec::new(),
+        });
+    }
+
     // Choose the index_part with the highest generation
     let (index_part_object, index_part_generation) = match index_parts
         .iter()

s3_scrubber/src/lib.rs

@@ -86,7 +86,9 @@ impl S3Target {
         if new_self.prefix_in_bucket.is_empty() {
             new_self.prefix_in_bucket = format!("/{}/", new_segment);
         } else {
-            let _ = new_self.prefix_in_bucket.pop();
+            if new_self.prefix_in_bucket.ends_with('/') {
+                let _ = new_self.prefix_in_bucket.pop();
+            }
             new_self.prefix_in_bucket =
                 [&new_self.prefix_in_bucket, new_segment, ""].join(&new_self.delimiter);
         }

s3_scrubber/src/scan_metadata.rs

@@ -20,6 +20,14 @@ pub struct MetadataSummary {
     with_warnings: HashSet<TenantTimelineId>,
     with_garbage: HashSet<TenantTimelineId>,
     indices_by_version: HashMap<usize, usize>,
+    indices_with_generation: usize,
+    indices_without_generation: usize,
+
+    /// Timelines that couldn't even parse metadata and/or object keys: extremely damaged
+    invalid_count: usize,
+
+    /// Timelines with just an initdb archive, left behind after deletion.
+    relic_count: usize,
 
     layer_count: MinMaxHisto,
     timeline_size_bytes: MinMaxHisto,
@@ -39,6 +47,8 @@ impl MinMaxHisto {
     fn new() -> Self {
         Self {
             histo: histogram::Histogram::builder()
+                // Accomodate tenant sizes up to 32TiB
+                .maximum_value(32 * 1024 * 1024 * 1024 * 1024)
                 .build()
                 .expect("Bad histogram params"),
             min: u64::MAX,
@@ -90,6 +100,10 @@ impl MetadataSummary {
             with_warnings: HashSet::new(),
             with_garbage: HashSet::new(),
             indices_by_version: HashMap::new(),
+            indices_with_generation: 0,
+            indices_without_generation: 0,
+            invalid_count: 0,
+            relic_count: 0,
             layer_count: MinMaxHisto::new(),
             timeline_size_bytes: MinMaxHisto::new(),
             layer_size_bytes: MinMaxHisto::new(),
@@ -111,24 +125,35 @@ impl MetadataSummary {
 
     fn update_data(&mut self, data: &S3TimelineBlobData) {
         self.count += 1;
-        if let BlobDataParseResult::Parsed {
-            index_part,
-            index_part_generation: _,
-            s3_layers: _,
-        } = &data.blob_data
-        {
-            *self
-                .indices_by_version
-                .entry(index_part.get_version())
-                .or_insert(0) += 1;
+        match &data.blob_data {
+            BlobDataParseResult::Parsed {
+                index_part,
+                index_part_generation,
+                s3_layers: _,
+            } => {
+                *self
+                    .indices_by_version
+                    .entry(index_part.get_version())
+                    .or_insert(0) += 1;
 
-            if let Err(e) = self.update_histograms(index_part) {
-                // Value out of range?  Warn that the results are untrustworthy
-                tracing::warn!(
-                    "Error updating histograms, summary stats may be wrong: {}",
-                    e
-                );
+                // These statistics exist to track the transition to generations.  By early 2024 there should be zero
+                // generation-less timelines in the field and this check can be removed.
+                if index_part_generation.is_none() {
+                    self.indices_without_generation += 1;
+                } else {
+                    self.indices_with_generation += 1;
+                }
+
+                if let Err(e) = self.update_histograms(index_part) {
+                    // Value out of range?  Warn that the results are untrustworthy
+                    tracing::warn!(
+                        "Error updating histograms, summary stats may be wrong: {}",
+                        e
+                    );
+                }
             }
+            BlobDataParseResult::Incorrect(_) => self.invalid_count += 1,
+            BlobDataParseResult::Relic => self.relic_count += 1,
         }
     }
 
@@ -156,7 +181,10 @@ impl MetadataSummary {
 With errors: {1}
 With warnings: {2}
 With garbage: {3}
+Invalid: {9}
+Relics: {10}
 Index versions: {version_summary}
+Indices with/without generations: {7}/{8}
 Timeline size bytes: {4}
 Layer size bytes: {5}
 Timeline layer count: {6}
@@ -168,6 +196,10 @@ Timeline layer count: {6}
             self.timeline_size_bytes.oneline(),
             self.layer_size_bytes.oneline(),
             self.layer_count.oneline(),
+            self.indices_with_generation,
+            self.indices_without_generation,
+            self.invalid_count,
+            self.relic_count
         )
     }