fix: Change the sharder to return error instead of panicking for no shards

Cargo.lock

@@ -4945,6 +4945,8 @@ dependencies = [
  "parking_lot 0.12.1",
  "rand",
  "siphasher",
+ "snafu",
+ "test_helpers",
  "workspace-hack",
 ]
 

ioxd_querier/src/rpc/namespace.rs

@@ -63,7 +63,7 @@ mod tests {
     async fn test_get_namespaces_empty() {
         let catalog = TestCatalog::new();
 
-        // QuerierDatabase::new panics if there are no sequencers in the catalog
+        // QuerierDatabase::new returns an error if there are no sequencers in the catalog
         catalog.create_sequencer(0).await;
 
         let catalog_cache = Arc::new(QuerierCatalogCache::new(
@@ -98,7 +98,7 @@ mod tests {
     async fn test_get_namespaces() {
         let catalog = TestCatalog::new();
 
-        // QuerierDatabase::new panics if there are no sequencers in the catalog
+        // QuerierDatabase::new returns an error if there are no sequencers in the catalog
         catalog.create_sequencer(0).await;
 
         let catalog_cache = Arc::new(QuerierCatalogCache::new(

ioxd_router/src/lib.rs

@@ -49,6 +49,9 @@ pub enum Error {
 
     #[error("Catalog DSN error: {0}")]
     CatalogDsn(#[from] clap_blocks::catalog_dsn::Error),
+
+    #[error("failed to initialize sharded cache: {0}")]
+    Sharder(#[from] sharder::Error),
 }
 
 pub type Result<T, E = Error> = std::result::Result<T, E>;
@@ -175,7 +178,7 @@ pub async fn create_router_server_type(
     let ns_cache = Arc::new(InstrumentedCache::new(
         Arc::new(ShardedCache::new(
             std::iter::repeat_with(|| Arc::new(MemoryNamespaceCache::default())).take(10),
-        )),
+        )?),
         &*metrics,
     ));
 
@@ -319,13 +322,12 @@ async fn init_write_buffer(
         "connected to write buffer topic",
     );
 
-    Ok(ShardedWriteBuffer::new(
+    Ok(ShardedWriteBuffer::new(JumpHash::new(
         shards
             .into_iter()
             .map(|id| Sequencer::new(id as _, Arc::clone(&write_buffer), &metrics))
-            .map(Arc::new)
+            .map(Arc::new),
-            .collect::<JumpHash<_>>(),
+    )?))
-    ))
 }
 
 /// Pre-populate `cache` with the all existing schemas in `catalog`.

querier/src/database.rs

@@ -30,6 +30,9 @@ pub enum Error {
     Catalog {
         source: iox_catalog::interface::Error,
     },
+
+    #[snafu(display("Sharder error: {source}"))]
+    Sharder { source: sharder::Error },
 }
 
 /// Database for the querier.
@@ -202,16 +205,15 @@ pub async fn create_sharder(catalog: &dyn Catalog) -> Result<JumpHash<Arc<KafkaP
         .map(|sequencer| sequencer.kafka_partition)
         .collect();
 
-    Ok(shards.into_iter().map(Arc::new).collect())
+    JumpHash::new(shards.into_iter().map(Arc::new)).context(SharderSnafu)
 }
 
 #[cfg(test)]
 mod tests {
-    use iox_tests::util::TestCatalog;
-
-    use crate::create_ingester_connection_for_testing;
-
     use super::*;
+    use crate::create_ingester_connection_for_testing;
+    use iox_tests::util::TestCatalog;
+    use test_helpers::assert_error;
 
     #[tokio::test]
     #[should_panic(
@@ -239,7 +241,6 @@ mod tests {
     }
 
     #[tokio::test]
-    #[should_panic(expected = "cannot initialise sharder with no shards")]
     async fn sequencers_in_catalog_are_required_for_startup() {
         let catalog = TestCatalog::new();
 
@@ -250,6 +251,7 @@ mod tests {
             usize::MAX,
         ));
 
+        assert_error!(
             QuerierDatabase::new(
                 catalog_cache,
                 catalog.metric_registry(),
@@ -258,14 +260,17 @@ mod tests {
                 create_ingester_connection_for_testing(),
                 QuerierDatabase::MAX_CONCURRENT_QUERIES_MAX,
             )
-        .await
+            .await,
-        .unwrap();
+            Error::Sharder {
+                source: sharder::Error::NoShards
+            },
+        );
     }
 
     #[tokio::test]
     async fn test_namespace() {
         let catalog = TestCatalog::new();
-        // QuerierDatabase::new panics if there are no sequencers in the catalog
+        // QuerierDatabase::new returns an error if there are no sequencers in the catalog
         catalog.create_sequencer(0).await;
 
         let catalog_cache = Arc::new(CatalogCache::new(
@@ -294,7 +299,7 @@ mod tests {
     #[tokio::test]
     async fn test_namespaces() {
         let catalog = TestCatalog::new();
-        // QuerierDatabase::new panics if there are no sequencers in the catalog
+        // QuerierDatabase::new returns an error if there are no sequencers in the catalog
         catalog.create_sequencer(0).await;
 
         let catalog_cache = Arc::new(CatalogCache::new(

querier/src/handler.rs

@@ -172,7 +172,7 @@ mod tests {
                 Arc::clone(&metric_registry),
                 usize::MAX,
             ));
-            // QuerierDatabase::new panics if there are no sequencers in the catalog
+            // QuerierDatabase::new returns an error if there are no sequencers in the catalog
             {
                 let mut repos = catalog.repositories().await;
 

router/benches/e2e.rs

@@ -35,11 +35,13 @@ fn init_write_buffer(n_sequencers: u32) -> ShardedWriteBuffer<JumpHash<Arc<Seque
 
     let shards: BTreeSet<_> = write_buffer.sequencer_ids();
     ShardedWriteBuffer::new(
+        JumpHash::new(
             shards
                 .into_iter()
                 .map(|id| Sequencer::new(id as _, Arc::clone(&write_buffer), &Default::default()))
-            .map(Arc::new)
+                .map(Arc::new),
-            .collect::<JumpHash<_>>(),
+        )
+        .expect("failed to init sharder"),
     )
 }
 
@@ -57,9 +59,12 @@ fn e2e_benchmarks(c: &mut Criterion) {
     let delegate = {
         let metrics = Arc::new(metric::Registry::new());
         let catalog: Arc<dyn Catalog> = Arc::new(MemCatalog::new(Arc::clone(&metrics)));
-        let ns_cache = Arc::new(ShardedCache::new(
+        let ns_cache = Arc::new(
+            ShardedCache::new(
                 iter::repeat_with(|| Arc::new(MemoryNamespaceCache::default())).take(10),
-        ));
+            )
+            .unwrap(),
+        );
 
         let write_buffer = init_write_buffer(1);
         let schema_validator =

router/benches/schema_validator.rs

@@ -42,9 +42,10 @@ fn bench(group: &mut BenchmarkGroup<WallTime>, tables: usize, columns_per_table:
     let metrics = Arc::new(metric::Registry::default());
 
     let catalog = Arc::new(MemCatalog::new(Arc::clone(&metrics)));
-    let ns_cache = Arc::new(ShardedCache::new(
+    let ns_cache = Arc::new(
-        iter::repeat_with(|| Arc::new(MemoryNamespaceCache::default())).take(10),
+        ShardedCache::new(iter::repeat_with(|| Arc::new(MemoryNamespaceCache::default())).take(10))
-    ));
+            .unwrap(),
+    );
     let validator = SchemaValidator::new(catalog, ns_cache, &*metrics);
 
     for i in 0..65_000 {

router/src/namespace_cache/sharded_cache.rs

@@ -12,10 +12,10 @@ pub struct ShardedCache<T> {
 impl<T> ShardedCache<T> {
     /// initialise a [`ShardedCache`] splitting the keyspace over the given
     /// instances of `T`.
-    pub fn new(shards: impl IntoIterator<Item = T>) -> Self {
+    pub fn new(shards: impl IntoIterator<Item = T>) -> Result<Self, sharder::Error> {
-        Self {
+        Ok(Self {
-            shards: JumpHash::new(shards),
+            shards: JumpHash::new(shards)?,
-        }
+        })
     }
 }
 
@@ -71,9 +71,12 @@ mod tests {
         // The number of shards to hash into.
         const SHARDS: usize = 10;
 
-        let cache = Arc::new(ShardedCache::new(
+        let cache = Arc::new(
+            ShardedCache::new(
                 iter::repeat_with(|| Arc::new(MemoryNamespaceCache::default())).take(SHARDS),
-        ));
+            )
+            .unwrap(),
+        );
 
         // Build a set of namespace -> unique integer to validate the shard
         // mapping later.

router/tests/http.rs

@@ -83,17 +83,22 @@ impl TestContext {
 
         let shards: BTreeSet<_> = write_buffer.sequencer_ids();
         let sharded_write_buffer = ShardedWriteBuffer::new(
+            JumpHash::new(
                 shards
                     .into_iter()
                     .map(|id| Sequencer::new(id as _, Arc::clone(&write_buffer), &metrics))
-                .map(Arc::new)
+                    .map(Arc::new),
-                .collect::<JumpHash<_>>(),
+            )
+            .unwrap(),
         );
 
         let catalog: Arc<dyn Catalog> = Arc::new(MemCatalog::new(Arc::clone(&metrics)));
-        let ns_cache = Arc::new(ShardedCache::new(
+        let ns_cache = Arc::new(
+            ShardedCache::new(
                 iter::repeat_with(|| Arc::new(MemoryNamespaceCache::default())).take(10),
-        ));
+            )
+            .unwrap(),
+        );
 
         let ns_creator = NamespaceAutocreation::new(
             Arc::clone(&catalog),

sharder/Cargo.toml

@@ -8,6 +8,7 @@ data_types = { path = "../data_types" }
 mutable_batch = { path = "../mutable_batch" }
 parking_lot = "0.12"
 siphasher = "0.3"
+snafu = "0.7"
 workspace-hack = { path = "../workspace-hack"}
 
 [dev-dependencies]
@@ -15,6 +16,7 @@ criterion = { version = "0.3.4", features = ["async_tokio", "html_reports"] }
 hashbrown = "0.12"
 mutable_batch_lp = { path = "../mutable_batch_lp" }
 rand = "0.8.3"
+test_helpers = { path = "../test_helpers" }
 
 [[bench]]
 name = "sharder"

sharder/benches/sharder.rs

@@ -86,7 +86,7 @@ fn benchmark_sharder(
     table: &str,
     namespace: &DatabaseName<'_>,
 ) {
-    let hasher = JumpHash::new((0..num_buckets).map(Arc::new));
+    let hasher = JumpHash::new((0..num_buckets).map(Arc::new)).unwrap();
     let batch = MutableBatch::default();
 
     group.throughput(Throughput::Elements(1));

sharder/src/jumphash.rs

@@ -2,12 +2,20 @@ use super::Sharder;
 use data_types::{DatabaseName, DeletePredicate};
 use mutable_batch::MutableBatch;
 use siphasher::sip::SipHasher13;
+use snafu::{ensure, Snafu};
 use std::{
     fmt::Debug,
     hash::{Hash, Hasher},
     sync::Arc,
 };
 
+#[derive(Snafu, Debug)]
+#[allow(missing_docs)]
+pub enum Error {
+    #[snafu(display("Cannot initialize sharder with no shards"))]
+    NoShards,
+}
+
 /// A [`JumpHash`] maps operations for a given table in a given namespace
 /// consistently to the same shard, irrespective of the operation itself with
 /// near perfect distribution.
@@ -39,7 +47,7 @@ impl<T> JumpHash<T> {
     /// # Panics
     ///
     /// This constructor panics if the number of elements in `shards` is 0.
-    pub fn new(shards: impl IntoIterator<Item = T>) -> Self {
+    pub fn new(shards: impl IntoIterator<Item = T>) -> Result<Self, Error> {
         // A randomly generated static siphash key to ensure all router
         // instances hash the same input to the same u64 sharding key.
         //
@@ -50,15 +58,12 @@ impl<T> JumpHash<T> {
         ];
 
         let shards = shards.into_iter().collect::<Vec<_>>();
-        assert!(
+        ensure!(!shards.is_empty(), NoShardsSnafu,);
-            !shards.is_empty(),
-            "cannot initialise sharder with no shards"
-        );
 
-        Self {
+        Ok(Self {
             hasher: SipHasher13::new_with_key(&key),
             shards,
-        }
+        })
     }
 
     /// Return a slice of all the shards this instance is configured with,
@@ -102,12 +107,6 @@ impl<T> JumpHash<T> {
     }
 }
 
-impl<T> FromIterator<T> for JumpHash<T> {
-    fn from_iter<U: IntoIterator<Item = T>>(iter: U) -> Self {
-        Self::new(iter)
-    }
-}
-
 #[derive(Hash)]
 struct HashKey<'a> {
     table: &'a str,
@@ -169,17 +168,18 @@ where
 
 #[cfg(test)]
 mod tests {
+    use super::*;
     use data_types::TimestampRange;
     use hashbrown::HashMap;
-
+    use std::iter;
-    use super::*;
+    use test_helpers::assert_error;
 
     #[test]
     fn test_consistent_hashing() {
         const NUM_TESTS: usize = 10_000;
         const NUM_SHARDS: usize = 10;
 
-        let hasher = JumpHash::new(0..NUM_SHARDS);
+        let hasher = JumpHash::new(0..NUM_SHARDS).unwrap();
 
         // Create a HashMap<key, shard> to verify against.
         let mappings = (0..NUM_TESTS)
@@ -198,7 +198,7 @@ mod tests {
             .all(|(&key, &value)| hasher.hash(key) == value));
 
         // Reinitialise the hasher with the same (default) key
-        let hasher = JumpHash::new(0..NUM_SHARDS);
+        let hasher = JumpHash::new(0..NUM_SHARDS).unwrap();
 
         // And assert the mappings are the same
         assert!(mappings
@@ -206,7 +206,9 @@ mod tests {
             .all(|(&key, &value)| hasher.hash(key) == value));
 
         // Reinitialise the hasher with the a different key
-        let hasher = JumpHash::new(0..NUM_SHARDS).with_seed_key(&[42; 16]);
+        let hasher = JumpHash::new(0..NUM_SHARDS)
+            .unwrap()
+            .with_seed_key(&[42; 16]);
 
         // And assert the mappings are the NOT all same (some may be the same)
         assert!(!mappings
@@ -216,7 +218,7 @@ mod tests {
 
     #[test]
     fn test_sharder_impl() {
-        let hasher = JumpHash::new((0..10_000).map(Arc::new));
+        let hasher = JumpHash::new((0..10_000).map(Arc::new)).unwrap();
 
         let a = hasher.shard(
             "table",
@@ -261,7 +263,7 @@ mod tests {
 
     #[test]
     fn test_sharder_prefix_collision() {
-        let hasher = JumpHash::new((0..10_000).map(Arc::new));
+        let hasher = JumpHash::new((0..10_000).map(Arc::new)).unwrap();
         let a = hasher.shard(
             "a",
             &DatabaseName::try_from("bc").unwrap(),
@@ -289,7 +291,7 @@ mod tests {
     // strategy would that accounts for this mapping change.
     #[test]
     fn test_key_bucket_fixture() {
-        let hasher = JumpHash::new((0..1_000).map(Arc::new));
+        let hasher = JumpHash::new((0..1_000).map(Arc::new)).unwrap();
         let namespace = DatabaseName::try_from("bananas").unwrap();
 
         let mut batches = mutable_batch_lp::lines_to_batches("cpu a=1i", 42).unwrap();
@@ -308,7 +310,7 @@ mod tests {
 
     #[test]
     fn test_distribution() {
-        let hasher = JumpHash::new((0..100).map(Arc::new));
+        let hasher = JumpHash::new((0..100).map(Arc::new)).unwrap();
         let namespace = DatabaseName::try_from("bananas").unwrap();
 
         let mut mapping = HashMap::<_, usize>::new();
@@ -336,7 +338,7 @@ mod tests {
     fn test_delete_with_table() {
         let namespace = DatabaseName::try_from("bananas").unwrap();
 
-        let hasher = JumpHash::new((0..10_000).map(Arc::new));
+        let hasher = JumpHash::new((0..10_000).map(Arc::new)).unwrap();
 
         let predicate = DeletePredicate {
             range: TimestampRange::new(1, 2),
@@ -362,7 +364,7 @@ mod tests {
         let namespace = DatabaseName::try_from("bananas").unwrap();
 
         let shards = (0..10_000).map(Arc::new).collect::<Vec<_>>();
-        let hasher = JumpHash::new(shards.clone());
+        let hasher = JumpHash::new(shards.clone()).unwrap();
 
         let predicate = DeletePredicate {
             range: TimestampRange::new(1, 2),
@@ -373,4 +375,10 @@ mod tests {
 
         assert_eq!(got, shards);
     }
+
+    #[test]
+    fn no_shards() {
+        let shards: iter::Empty<i32> = iter::empty();
+        assert_error!(JumpHash::new(shards), Error::NoShards,);
+    }
 }