fix(store): normalize trailing slashes in the S3 key prefix

mooncake-store/include/storage/distributed/s3_object_storage_adapter.h

@@ -17,6 +17,11 @@ struct S3ObjectStorageConfig {
 
     bool Validate() const;
     static S3ObjectStorageConfig FromEnvironment();
+    // Drops trailing '/' so "p", "p/" and "p///" name the same namespace.
+    // Every physical key is built as key_prefix + "/<area>/..."; a trailing
+    // slash would make LIST query "p//objects/" while PUT/GET land on the
+    // endpoint-normalized "p/objects/", hiding every object from ScanMeta.
+    static std::string NormalizeKeyPrefix(std::string prefix);
 };
 
 #ifdef HAVE_AWS_SDK

mooncake-store/src/storage/distributed/s3_object_storage_adapter.cpp

@@ -18,9 +18,15 @@ S3ObjectStorageConfig S3ObjectStorageConfig::FromEnvironment() {
     read("MOONCAKE_AWS_BUCKET_NAME", config.bucket);
     read("MOONCAKE_AWS_REGION", config.region);
     read("MOONCAKE_S3_KEY_PREFIX", config.key_prefix);
+    config.key_prefix = NormalizeKeyPrefix(std::move(config.key_prefix));
     return config;
 }
 
+std::string S3ObjectStorageConfig::NormalizeKeyPrefix(std::string prefix) {
+    while (!prefix.empty() && prefix.back() == '/') prefix.pop_back();
+    return prefix;
+}
+
 bool S3ObjectStorageConfig::Validate() const {
     // A durable namespace needs an explicit, credential-free HTTP(S) origin.
     // Reject it before any SDK request rather than mounting an unusable Store.
@@ -33,7 +39,9 @@ bool S3ObjectStorageConfig::Validate() const {
     const auto authority = endpoint.substr(scheme_end + 3);
     if (authority.empty() || authority.find('/') != std::string::npos)
         return false;
-    return !bucket.empty() && !region.empty() && !key_prefix.empty() &&
+    // A prefix of only slashes normalizes to empty: no owned namespace.
+    return !bucket.empty() && !region.empty() &&
+           !NormalizeKeyPrefix(key_prefix).empty() &&
            key_prefix.size() <= 909 &&
            key_prefix.find('\0') == std::string::npos &&
            bucket.find('\0') == std::string::npos &&
@@ -70,8 +78,19 @@ int Unhex(char c) {
 }
 }  // namespace
 
+namespace {
+// Configs built in code skip FromEnvironment; normalize on construction too so
+// PhysicalPrefix/WriterPrefix/DeletionIntentKey and the published durable
+// namespace always share one canonical prefix.
+S3ObjectStorageConfig Normalized(S3ObjectStorageConfig config) {
+    config.key_prefix =
+        S3ObjectStorageConfig::NormalizeKeyPrefix(std::move(config.key_prefix));
+    return config;
+}
+}  // namespace
+
 S3ObjectStorageAdapter::S3ObjectStorageAdapter(S3ObjectStorageConfig config)
-    : config_(std::move(config)) {}
+    : config_(Normalized(std::move(config))) {}
 
 S3ObjectStorageAdapter::~S3ObjectStorageAdapter() {
     helper_.reset();

mooncake-store/tests/object_storage_adapter_test.cpp

@@ -5,6 +5,7 @@
 
 #include <algorithm>
 #include <array>
+#include <cstdlib>
 #include <cstring>
 #include <filesystem>
 #include <limits>
@@ -731,4 +732,34 @@ TEST(S3ObjectStorageConfigTest, RequiresExplicitCredentialFreeOrigin) {
         EXPECT_TRUE(config.Validate()) << endpoint;
     }
 }
+
+// mint#1775: a trailing '/' on MOONCAKE_S3_KEY_PREFIX made ListKeys/ScanMeta
+// query "p//objects/" while PUT/GET used the endpoint-normalized
+// "p/objects/", so no provider ever re-registered an offloaded object.
+TEST(S3ObjectStorageConfigTest, KeyPrefixTrailingSlashesNameOneNamespace) {
+    for (const std::string prefix : {"p", "p/", "p///"}) {
+        EXPECT_EQ(S3ObjectStorageConfig::NormalizeKeyPrefix(prefix), "p")
+            << prefix;
+    }
+    EXPECT_EQ(S3ObjectStorageConfig::NormalizeKeyPrefix("a/b/"), "a/b");
+    EXPECT_EQ(S3ObjectStorageConfig::NormalizeKeyPrefix("/"), "");
+
+    ASSERT_EQ(setenv("MOONCAKE_S3_KEY_PREFIX", "mint-run-20261024//", 1), 0);
+    const auto config = S3ObjectStorageConfig::FromEnvironment();
+    ASSERT_EQ(unsetenv("MOONCAKE_S3_KEY_PREFIX"), 0);
+    EXPECT_EQ(config.key_prefix, "mint-run-20261024");
+}
+
+TEST(S3ObjectStorageConfigTest, RejectsPrefixThatIsOnlySlashes) {
+    S3ObjectStorageConfig config;
+    config.endpoint = "https://oss.example.test";
+    config.bucket = "bucket";
+    config.region = "region";
+    for (const std::string prefix : {"/", "///"}) {
+        config.key_prefix = prefix;
+        EXPECT_FALSE(config.Validate()) << prefix;
+    }
+    config.key_prefix = "isolated-prefix/";
+    EXPECT_TRUE(config.Validate());
+}
 }  // namespace mooncake