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commit dee6298f15cdec390e1cacba7f82f9e173e55ec7
Author: Benoit Tellier <btell...@linagora.com>
AuthorDate: Thu Jul 23 11:23:06 2020 +0700

    JAMES-3343 EventSourcing system to validate BlobStore StorageStrategy 
configuration
---
 .../guice/cassandra-rabbitmq-guice/pom.xml         |  11 ++
 ...obStoreConfigurationValidationStartUpCheck.java |  62 +++++++++++
 .../modules/blobstore/BlobStoreModulesChooser.java |  35 +++++-
 .../validation/EventsourcingStorageStrategy.java   |  53 +++++++++
 .../validation/RegisterStorageStrategy.java        |  35 ++++++
 .../RegisterStorageStrategyCommandHandler.java     |  53 +++++++++
 .../validation/StorageStrategyAggregate.java       | 106 ++++++++++++++++++
 .../validation/StorageStrategyChanged.java         |  51 +++++++++
 .../validation/StorageStrategyChangedDTO.java      | 108 ++++++++++++++++++
 .../validation/StorageStrategyModule.java          |  36 ++++++
 ...orageStrategyValidationEventSourcingSystem.java |  60 ++++++++++
 ...oreConfigurationValidationStartUpCheckTest.java | 124 +++++++++++++++++++++
 .../validation/StorageStrategyChangedDTOTest.java  |  79 +++++++++++++
 ...eStrategyValidationEventSourcingSystemTest.java | 100 +++++++++++++++++
 14 files changed, 911 insertions(+), 2 deletions(-)

diff --git a/server/container/guice/cassandra-rabbitmq-guice/pom.xml 
b/server/container/guice/cassandra-rabbitmq-guice/pom.xml
index a4c6c5f..3fc2aa9 100644
--- a/server/container/guice/cassandra-rabbitmq-guice/pom.xml
+++ b/server/container/guice/cassandra-rabbitmq-guice/pom.xml
@@ -122,6 +122,17 @@
         </dependency>
         <dependency>
             <groupId>${james.groupId}</groupId>
+            <artifactId>event-sourcing-event-store-cassandra</artifactId>
+            <type>test-jar</type>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>${james.groupId}</groupId>
+            <artifactId>event-sourcing-event-store-memory</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>${james.groupId}</groupId>
             <artifactId>james-server-cassandra-guice</artifactId>
         </dependency>
         <dependency>
diff --git 
a/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/BlobStoreConfigurationValidationStartUpCheck.java
 
b/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/BlobStoreConfigurationValidationStartUpCheck.java
new file mode 100644
index 0000000..4eace03
--- /dev/null
+++ 
b/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/BlobStoreConfigurationValidationStartUpCheck.java
@@ -0,0 +1,62 @@
+/****************************************************************
+ * Licensed to the Apache Software Foundation (ASF) under one   *
+ * or more contributor license agreements.  See the NOTICE file *
+ * distributed with this work for additional information        *
+ * regarding copyright ownership.  The ASF licenses this file   *
+ * to you under the Apache License, Version 2.0 (the            *
+ * "License"); you may not use this file except in compliance   *
+ * with the License.  You may obtain a copy of the License at   *
+ *                                                              *
+ * http://www.apache.org/licenses/LICENSE-2.0                   *
+ *                                                              *
+ * Unless required by applicable law or agreed to in writing,   *
+ * software distributed under the License is distributed on an  *
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY       *
+ * KIND, either express or implied.  See the License for the    *
+ * specific language governing permissions and limitations      *
+ * under the License.                                           *
+ ***************************************************************/
+
+package org.apache.james.modules.blobstore;
+
+import javax.inject.Inject;
+
+import org.apache.james.lifecycle.api.StartUpCheck;
+import 
org.apache.james.modules.blobstore.validation.EventsourcingStorageStrategy;
+
+import com.google.common.annotations.VisibleForTesting;
+
+public class BlobStoreConfigurationValidationStartUpCheck implements 
StartUpCheck {
+    private static final String BLOB_STORE_CONFIGURATION_VALIDATION = 
"blobStore-configuration-validation";
+    private final BlobStoreConfiguration blobStoreConfiguration;
+    private final EventsourcingStorageStrategy eventsourcingStorageStrategy;
+
+    @VisibleForTesting
+    @Inject
+    BlobStoreConfigurationValidationStartUpCheck(BlobStoreConfiguration 
blobStoreConfiguration, EventsourcingStorageStrategy 
eventsourcingStorageStrategy) {
+        this.blobStoreConfiguration = blobStoreConfiguration;
+        this.eventsourcingStorageStrategy = eventsourcingStorageStrategy;
+    }
+
+    @Override
+    public CheckResult check() {
+        try {
+            
eventsourcingStorageStrategy.registerStorageStrategy(blobStoreConfiguration.storageStrategy());
+            return CheckResult.builder()
+                .checkName(BLOB_STORE_CONFIGURATION_VALIDATION)
+                .resultType(ResultType.GOOD)
+                .build();
+        } catch (IllegalStateException e) {
+            return CheckResult.builder()
+                .checkName(BLOB_STORE_CONFIGURATION_VALIDATION)
+                .resultType(ResultType.BAD)
+                .description(e.getMessage())
+                .build();
+        }
+    }
+
+    @Override
+    public String checkName() {
+        return BLOB_STORE_CONFIGURATION_VALIDATION;
+    }
+}
diff --git 
a/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/BlobStoreModulesChooser.java
 
b/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/BlobStoreModulesChooser.java
index 323f6c5..20bdf8f 100644
--- 
a/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/BlobStoreModulesChooser.java
+++ 
b/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/BlobStoreModulesChooser.java
@@ -26,6 +26,12 @@ import org.apache.james.blob.api.DumbBlobStore;
 import org.apache.james.blob.cassandra.CassandraDumbBlobStore;
 import org.apache.james.blob.cassandra.cache.CachedBlobStore;
 import org.apache.james.blob.objectstorage.ObjectStorageBlobStore;
+import org.apache.james.eventsourcing.Event;
+import org.apache.james.eventsourcing.eventstore.cassandra.dto.EventDTO;
+import org.apache.james.eventsourcing.eventstore.cassandra.dto.EventDTOModule;
+import org.apache.james.lifecycle.api.StartUpCheck;
+import 
org.apache.james.modules.blobstore.validation.EventsourcingStorageStrategy;
+import org.apache.james.modules.blobstore.validation.StorageStrategyModule;
 import org.apache.james.modules.mailbox.CassandraBlobStoreDependenciesModule;
 import org.apache.james.modules.objectstorage.ObjectStorageDependenciesModule;
 import org.apache.james.server.blob.deduplication.DeDuplicationBlobStore;
@@ -36,6 +42,9 @@ import com.google.common.annotations.VisibleForTesting;
 import com.google.common.collect.ImmutableList;
 import com.google.inject.AbstractModule;
 import com.google.inject.Module;
+import com.google.inject.Scopes;
+import com.google.inject.TypeLiteral;
+import com.google.inject.multibindings.Multibinder;
 import com.google.inject.name.Names;
 
 public class BlobStoreModulesChooser {
@@ -59,10 +68,32 @@ public class BlobStoreModulesChooser {
         }
     }
 
+    static class StoragePolicyConfigurationSanityEnforcementModule extends 
AbstractModule {
+        private BlobStoreConfiguration choosingConfiguration;
+
+        
StoragePolicyConfigurationSanityEnforcementModule(BlobStoreConfiguration 
choosingConfiguration) {
+            this.choosingConfiguration = choosingConfiguration;
+        }
+
+        @Override
+        protected void configure() {
+            Multibinder<EventDTOModule<? extends Event, ? extends EventDTO>> 
eventDTOModuleBinder = Multibinder.newSetBinder(binder(), new 
TypeLiteral<EventDTOModule<? extends Event, ? extends EventDTO>>() {});
+            
eventDTOModuleBinder.addBinding().toInstance(StorageStrategyModule.STORAGE_STRATEGY);
+
+            
bind(BlobStoreConfiguration.class).toInstance(choosingConfiguration);
+            bind(EventsourcingStorageStrategy.class).in(Scopes.SINGLETON);
+
+            Multibinder.newSetBinder(binder(), StartUpCheck.class)
+                .addBinding()
+                .to(BlobStoreConfigurationValidationStartUpCheck.class);
+        }
+    }
+
     @VisibleForTesting
     public static List<Module> chooseModules(BlobStoreConfiguration 
choosingConfiguration) {
-        ImmutableList.Builder<Module> moduleBuilder = 
ImmutableList.<Module>builder().add(
-            
chooseDumBlobStoreModule(choosingConfiguration.getImplementation()));
+        ImmutableList.Builder<Module> moduleBuilder = 
ImmutableList.<Module>builder()
+            
.add(chooseDumBlobStoreModule(choosingConfiguration.getImplementation()))
+            .add( new 
StoragePolicyConfigurationSanityEnforcementModule(choosingConfiguration));
 
         //TODO JAMES-3028 add the storage policy module for all implementation 
and unbind the ObjectStorageBlobStore
         if (choosingConfiguration.getImplementation() == 
BlobStoreConfiguration.BlobStoreImplName.CASSANDRA) {
diff --git 
a/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/EventsourcingStorageStrategy.java
 
b/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/EventsourcingStorageStrategy.java
new file mode 100644
index 0000000..5e3cec2
--- /dev/null
+++ 
b/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/EventsourcingStorageStrategy.java
@@ -0,0 +1,53 @@
+/****************************************************************
+ * Licensed to the Apache Software Foundation (ASF) under one   *
+ * or more contributor license agreements.  See the NOTICE file *
+ * distributed with this work for additional information        *
+ * regarding copyright ownership.  The ASF licenses this file   *
+ * to you under the Apache License, Version 2.0 (the            *
+ * "License"); you may not use this file except in compliance   *
+ * with the License.  You may obtain a copy of the License at   *
+ *                                                              *
+ *   http://www.apache.org/licenses/LICENSE-2.0                 *
+ *                                                              *
+ * Unless required by applicable law or agreed to in writing,   *
+ * software distributed under the License is distributed on an  *
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY       *
+ * KIND, either express or implied.  See the License for the    *
+ * specific language governing permissions and limitations      *
+ * under the License.                                           *
+ ****************************************************************/
+
+package org.apache.james.modules.blobstore.validation;
+
+import javax.inject.Inject;
+
+import org.apache.james.eventsourcing.EventSourcingSystem;
+import org.apache.james.eventsourcing.Subscriber;
+import org.apache.james.eventsourcing.eventstore.EventStore;
+import org.apache.james.server.blob.deduplication.StorageStrategy;
+
+import com.google.common.base.Preconditions;
+import com.google.common.collect.ImmutableSet;
+
+import reactor.core.publisher.Mono;
+
+public class EventsourcingStorageStrategy {
+
+    private static final ImmutableSet<Subscriber> NO_SUBSCRIBER = 
ImmutableSet.of();
+
+    private final EventSourcingSystem eventSourcingSystem;
+
+    @Inject
+    public EventsourcingStorageStrategy(EventStore eventStore) {
+        this.eventSourcingSystem = EventSourcingSystem.fromJava(
+            ImmutableSet.of(new 
RegisterStorageStrategyCommandHandler(eventStore)),
+            NO_SUBSCRIBER,
+            eventStore);
+    }
+
+    public void registerStorageStrategy(StorageStrategy newStorageStrategy) {
+        Preconditions.checkNotNull(newStorageStrategy);
+
+        Mono.from(eventSourcingSystem.dispatch(new 
RegisterStorageStrategy(newStorageStrategy))).block();
+    }
+}
diff --git 
a/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/RegisterStorageStrategy.java
 
b/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/RegisterStorageStrategy.java
new file mode 100644
index 0000000..2b439b5
--- /dev/null
+++ 
b/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/RegisterStorageStrategy.java
@@ -0,0 +1,35 @@
+/****************************************************************
+ * Licensed to the Apache Software Foundation (ASF) under one   *
+ * or more contributor license agreements.  See the NOTICE file *
+ * distributed with this work for additional information        *
+ * regarding copyright ownership.  The ASF licenses this file   *
+ * to you under the Apache License, Version 2.0 (the            *
+ * "License"); you may not use this file except in compliance   *
+ * with the License.  You may obtain a copy of the License at   *
+ *                                                              *
+ *   http://www.apache.org/licenses/LICENSE-2.0                 *
+ *                                                              *
+ * Unless required by applicable law or agreed to in writing,   *
+ * software distributed under the License is distributed on an  *
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY       *
+ * KIND, either express or implied.  See the License for the    *
+ * specific language governing permissions and limitations      *
+ * under the License.                                           *
+ ****************************************************************/
+
+package org.apache.james.modules.blobstore.validation;
+
+import org.apache.james.eventsourcing.Command;
+import org.apache.james.server.blob.deduplication.StorageStrategy;
+
+public class RegisterStorageStrategy implements Command {
+    private final StorageStrategy storageStrategy;
+
+    public RegisterStorageStrategy(StorageStrategy storageStrategy) {
+        this.storageStrategy = storageStrategy;
+    }
+
+    public StorageStrategy getStorageStrategy() {
+        return storageStrategy;
+    }
+}
diff --git 
a/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/RegisterStorageStrategyCommandHandler.java
 
b/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/RegisterStorageStrategyCommandHandler.java
new file mode 100644
index 0000000..ddd69ff
--- /dev/null
+++ 
b/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/RegisterStorageStrategyCommandHandler.java
@@ -0,0 +1,53 @@
+/****************************************************************
+ * Licensed to the Apache Software Foundation (ASF) under one   *
+ * or more contributor license agreements.  See the NOTICE file *
+ * distributed with this work for additional information        *
+ * regarding copyright ownership.  The ASF licenses this file   *
+ * to you under the Apache License, Version 2.0 (the            *
+ * "License"); you may not use this file except in compliance   *
+ * with the License.  You may obtain a copy of the License at   *
+ *                                                              *
+ *   http://www.apache.org/licenses/LICENSE-2.0                 *
+ *                                                              *
+ * Unless required by applicable law or agreed to in writing,   *
+ * software distributed under the License is distributed on an  *
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY       *
+ * KIND, either express or implied.  See the License for the    *
+ * specific language governing permissions and limitations      *
+ * under the License.                                           *
+ ****************************************************************/
+
+package org.apache.james.modules.blobstore.validation;
+
+import java.util.List;
+
+import org.apache.james.eventsourcing.AggregateId;
+import org.apache.james.eventsourcing.CommandHandler;
+import org.apache.james.eventsourcing.Event;
+import org.apache.james.eventsourcing.eventstore.EventStore;
+import org.reactivestreams.Publisher;
+
+import reactor.core.publisher.Mono;
+
+public class RegisterStorageStrategyCommandHandler implements 
CommandHandler<RegisterStorageStrategy> {
+    static final String STORAGE_STRATEGY_CONFIGURATION_AGGREGATE_KEY = 
"BlobStoreStorageStrategyConfiguration";
+    public static final AggregateId AGGREGATE_ID = () -> 
STORAGE_STRATEGY_CONFIGURATION_AGGREGATE_KEY;
+
+    private final EventStore eventStore;
+
+    public RegisterStorageStrategyCommandHandler(EventStore eventStore) {
+        this.eventStore = eventStore;
+    }
+
+    @Override
+    public Class<RegisterStorageStrategy> handledClass() {
+        return RegisterStorageStrategy.class;
+    }
+
+    @Override
+    public Publisher<List<? extends Event>> handle(RegisterStorageStrategy 
command) {
+        return Mono.from(eventStore.getEventsOfAggregate(AGGREGATE_ID))
+            .map(history -> StorageStrategyAggregate.load(AGGREGATE_ID, 
history))
+            .map(aggregate -> aggregate.registerStorageStrategy(command));
+    }
+}
diff --git 
a/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/StorageStrategyAggregate.java
 
b/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/StorageStrategyAggregate.java
new file mode 100644
index 0000000..e949bd4
--- /dev/null
+++ 
b/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/StorageStrategyAggregate.java
@@ -0,0 +1,106 @@
+/****************************************************************
+ * Licensed to the Apache Software Foundation (ASF) under one   *
+ * or more contributor license agreements.  See the NOTICE file *
+ * distributed with this work for additional information        *
+ * regarding copyright ownership.  The ASF licenses this file   *
+ * to you under the Apache License, Version 2.0 (the            *
+ * "License"); you may not use this file except in compliance   *
+ * with the License.  You may obtain a copy of the License at   *
+ *                                                              *
+ *   http://www.apache.org/licenses/LICENSE-2.0                 *
+ *                                                              *
+ * Unless required by applicable law or agreed to in writing,   *
+ * software distributed under the License is distributed on an  *
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY       *
+ * KIND, either express or implied.  See the License for the    *
+ * specific language governing permissions and limitations      *
+ * under the License.                                           *
+ ****************************************************************/
+
+package org.apache.james.modules.blobstore.validation;
+
+import static 
org.apache.james.server.blob.deduplication.StorageStrategy.DEDUPLICATION;
+import static 
org.apache.james.server.blob.deduplication.StorageStrategy.PASSTHROUGH;
+
+import java.util.List;
+import java.util.Optional;
+
+import org.apache.james.eventsourcing.AggregateId;
+import org.apache.james.eventsourcing.Event;
+import org.apache.james.eventsourcing.eventstore.History;
+import org.apache.james.server.blob.deduplication.StorageStrategy;
+
+import com.google.common.collect.ImmutableList;
+
+public class StorageStrategyAggregate {
+    static class State {
+        static State initial() {
+            return new State(Optional.empty());
+        }
+
+        static State forStorageStrategy(StorageStrategy storageStrategy) {
+            return new State(Optional.of(storageStrategy));
+        }
+
+        private final Optional<StorageStrategy> storageStrategy;
+
+        State(Optional<StorageStrategy> storageStrategy) {
+            this.storageStrategy = storageStrategy;
+        }
+
+        public Optional<StorageStrategy> getStorageStrategy() {
+            return storageStrategy;
+        }
+
+        public boolean holds(StorageStrategy storageStrategy) {
+            return 
this.storageStrategy.filter(storageStrategy::equals).isPresent();
+        }
+
+        public boolean isAssignable(StorageStrategy storageStrategy) {
+            if (holds(DEDUPLICATION) && storageStrategy.equals(PASSTHROUGH)) {
+                return false;
+            }
+            return true;
+        }
+    }
+
+    public static StorageStrategyAggregate load(AggregateId aggregateId, 
History history) {
+        return new StorageStrategyAggregate(aggregateId, history);
+    }
+
+    private final AggregateId aggregateId;
+    private final History history;
+    private State state;
+
+    public StorageStrategyAggregate(AggregateId aggregateId, History history) {
+        this.aggregateId = aggregateId;
+        this.history = history;
+
+        this.state = State.initial();
+        history.getEventsJava()
+            .forEach(this::apply);
+    }
+
+    public List<Event> registerStorageStrategy(RegisterStorageStrategy 
command) {
+        if (state.holds(command.getStorageStrategy())) {
+            return ImmutableList.of();
+        }
+
+        if (!state.isAssignable(command.getStorageStrategy())) {
+            throw new IllegalStateException(
+                String.format("Cannot use %s as a BlobStoreStorageStrategy 
when current BlobStoreStorageStrategy is %s",
+                    command.getStorageStrategy(),
+                    state.getStorageStrategy()));
+        }
+
+        return ImmutableList.of(new 
StorageStrategyChanged(history.getNextEventId(), aggregateId, 
command.getStorageStrategy()));
+    }
+
+    private void apply(Event event) {
+        if (event instanceof StorageStrategyChanged) {
+            StorageStrategyChanged changed = (StorageStrategyChanged) event;
+
+            this.state = 
State.forStorageStrategy(changed.getStorageStrategy());
+        }
+    }
+}
diff --git 
a/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/StorageStrategyChanged.java
 
b/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/StorageStrategyChanged.java
new file mode 100644
index 0000000..b33236a
--- /dev/null
+++ 
b/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/StorageStrategyChanged.java
@@ -0,0 +1,51 @@
+/****************************************************************
+ * Licensed to the Apache Software Foundation (ASF) under one   *
+ * or more contributor license agreements.  See the NOTICE file *
+ * distributed with this work for additional information        *
+ * regarding copyright ownership.  The ASF licenses this file   *
+ * to you under the Apache License, Version 2.0 (the            *
+ * "License"); you may not use this file except in compliance   *
+ * with the License.  You may obtain a copy of the License at   *
+ *                                                              *
+ *   http://www.apache.org/licenses/LICENSE-2.0                 *
+ *                                                              *
+ * Unless required by applicable law or agreed to in writing,   *
+ * software distributed under the License is distributed on an  *
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY       *
+ * KIND, either express or implied.  See the License for the    *
+ * specific language governing permissions and limitations      *
+ * under the License.                                           *
+ ****************************************************************/
+
+package org.apache.james.modules.blobstore.validation;
+
+import org.apache.james.eventsourcing.AggregateId;
+import org.apache.james.eventsourcing.Event;
+import org.apache.james.eventsourcing.EventId;
+import org.apache.james.server.blob.deduplication.StorageStrategy;
+
+public class StorageStrategyChanged implements Event {
+    private final EventId eventId;
+    private final AggregateId aggregateId;
+    private final StorageStrategy storageStrategy;
+
+    public StorageStrategyChanged(EventId eventId, AggregateId aggregateId, 
StorageStrategy storageStrategy) {
+        this.eventId = eventId;
+        this.aggregateId = aggregateId;
+        this.storageStrategy = storageStrategy;
+    }
+
+    @Override
+    public EventId eventId() {
+        return eventId;
+    }
+
+    @Override
+    public AggregateId getAggregateId() {
+        return aggregateId;
+    }
+
+    public StorageStrategy getStorageStrategy() {
+        return storageStrategy;
+    }
+}
diff --git 
a/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/StorageStrategyChangedDTO.java
 
b/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/StorageStrategyChangedDTO.java
new file mode 100644
index 0000000..37a6208
--- /dev/null
+++ 
b/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/StorageStrategyChangedDTO.java
@@ -0,0 +1,108 @@
+/****************************************************************
+ * Licensed to the Apache Software Foundation (ASF) under one   *
+ * or more contributor license agreements.  See the NOTICE file *
+ * distributed with this work for additional information        *
+ * regarding copyright ownership.  The ASF licenses this file   *
+ * to you under the Apache License, Version 2.0 (the            *
+ * "License"); you may not use this file except in compliance   *
+ * with the License.  You may obtain a copy of the License at   *
+ *                                                              *
+ * http://www.apache.org/licenses/LICENSE-2.0                   *
+ *                                                              *
+ * Unless required by applicable law or agreed to in writing,   *
+ * software distributed under the License is distributed on an  *
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY       *
+ * KIND, either express or implied.  See the License for the    *
+ * specific language governing permissions and limitations      *
+ * under the License.                                           *
+ ***************************************************************/
+
+package org.apache.james.modules.blobstore.validation;
+
+import java.util.Objects;
+
+import org.apache.james.eventsourcing.EventId;
+import org.apache.james.eventsourcing.eventstore.cassandra.dto.EventDTO;
+import org.apache.james.server.blob.deduplication.StorageStrategy;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonIgnore;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.google.common.base.Preconditions;
+
+class StorageStrategyChangedDTO implements EventDTO {
+
+    static StorageStrategyChangedDTO from(StorageStrategyChanged 
storageStrategyChanged, String type) {
+        Preconditions.checkNotNull(storageStrategyChanged);
+
+        StorageStrategy storageStrategy = 
storageStrategyChanged.getStorageStrategy();
+        return new StorageStrategyChangedDTO(
+                storageStrategyChanged.eventId().serialize(),
+                storageStrategyChanged.getAggregateId().asAggregateKey(),
+                type,
+                storageStrategy.name());
+    }
+
+    static StorageStrategyChangedDTO from(StorageStrategyChanged 
storageStrategyChanged) {
+        return from(storageStrategyChanged, StorageStrategyModule.TYPE_NAME);
+    }
+
+    private final int eventId;
+    private final String aggregateKey;
+    private final String type;
+    private final String storageStrategy;
+
+    @JsonCreator
+    StorageStrategyChangedDTO(
+            @JsonProperty("eventId") int eventId,
+            @JsonProperty("aggregateKey") String aggregateKey,
+            @JsonProperty("type") String type,
+            @JsonProperty("storageStrategy") String storageStrategy) {
+        this.eventId = eventId;
+        this.aggregateKey = aggregateKey;
+        this.type = type;
+        this.storageStrategy = storageStrategy;
+    }
+
+    @JsonIgnore
+    public StorageStrategyChanged toEvent() {
+        return new StorageStrategyChanged(
+            EventId.fromSerialized(eventId),
+            () -> aggregateKey,
+            StorageStrategy.valueOf(storageStrategy));
+    }
+
+    public int getEventId() {
+        return eventId;
+    }
+
+    public String getAggregateKey() {
+        return aggregateKey;
+    }
+
+    public String getType() {
+        return type;
+    }
+
+    public String getStorageStrategy() {
+        return storageStrategy;
+    }
+
+    @Override
+    public final boolean equals(Object o) {
+        if (o instanceof StorageStrategyChangedDTO) {
+            StorageStrategyChangedDTO that = (StorageStrategyChangedDTO) o;
+
+            return Objects.equals(this.eventId, that.eventId)
+                && Objects.equals(this.aggregateKey, that.aggregateKey)
+                && Objects.equals(this.type, that.type)
+                && Objects.equals(this.storageStrategy, that.storageStrategy);
+        }
+        return false;
+    }
+
+    @Override
+    public final int hashCode() {
+        return Objects.hash(eventId, aggregateKey, type, storageStrategy);
+    }
+}
diff --git 
a/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/StorageStrategyModule.java
 
b/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/StorageStrategyModule.java
new file mode 100644
index 0000000..6607810
--- /dev/null
+++ 
b/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/StorageStrategyModule.java
@@ -0,0 +1,36 @@
+/****************************************************************
+ * Licensed to the Apache Software Foundation (ASF) under one   *
+ * or more contributor license agreements.  See the NOTICE file *
+ * distributed with this work for additional information        *
+ * regarding copyright ownership.  The ASF licenses this file   *
+ * to you under the Apache License, Version 2.0 (the            *
+ * "License"); you may not use this file except in compliance   *
+ * with the License.  You may obtain a copy of the License at   *
+ *                                                              *
+ *   http://www.apache.org/licenses/LICENSE-2.0                 *
+ *                                                              *
+ * Unless required by applicable law or agreed to in writing,   *
+ * software distributed under the License is distributed on an  *
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY       *
+ * KIND, either express or implied.  See the License for the    *
+ * specific language governing permissions and limitations      *
+ * under the License.                                           *
+ ****************************************************************/
+
+package org.apache.james.modules.blobstore.validation;
+
+import org.apache.james.eventsourcing.eventstore.cassandra.dto.EventDTOModule;
+
+public interface StorageStrategyModule {
+
+    String TYPE_NAME = "storage-strategy-changed";
+
+    EventDTOModule<StorageStrategyChanged, StorageStrategyChangedDTO> 
STORAGE_STRATEGY =
+        EventDTOModule
+            .forEvent(StorageStrategyChanged.class)
+            .convertToDTO(StorageStrategyChangedDTO.class)
+            .toDomainObjectConverter(StorageStrategyChangedDTO::toEvent)
+            .toDTOConverter(StorageStrategyChangedDTO::from)
+            .typeName(TYPE_NAME)
+            .withFactory(EventDTOModule::new);
+}
\ No newline at end of file
diff --git 
a/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/StorageStrategyValidationEventSourcingSystem.java
 
b/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/StorageStrategyValidationEventSourcingSystem.java
new file mode 100644
index 0000000..7024599
--- /dev/null
+++ 
b/server/container/guice/cassandra-rabbitmq-guice/src/main/java/org/apache/james/modules/blobstore/validation/StorageStrategyValidationEventSourcingSystem.java
@@ -0,0 +1,60 @@
+/****************************************************************
+ * Licensed to the Apache Software Foundation (ASF) under one   *
+ * or more contributor license agreements.  See the NOTICE file *
+ * distributed with this work for additional information        *
+ * regarding copyright ownership.  The ASF licenses this file   *
+ * to you under the Apache License, Version 2.0 (the            *
+ * "License"); you may not use this file except in compliance   *
+ * with the License.  You may obtain a copy of the License at   *
+ *                                                              *
+ *   http://www.apache.org/licenses/LICENSE-2.0                 *
+ *                                                              *
+ * Unless required by applicable law or agreed to in writing,   *
+ * software distributed under the License is distributed on an  *
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY       *
+ * KIND, either express or implied.  See the License for the    *
+ * specific language governing permissions and limitations      *
+ * under the License.                                           *
+ ****************************************************************/
+
+package org.apache.james.modules.blobstore.validation;
+
+import javax.inject.Inject;
+
+import org.apache.james.eventsourcing.EventSourcingSystem;
+import org.apache.james.eventsourcing.eventstore.EventStore;
+import org.apache.james.lifecycle.api.StartUpCheck;
+import org.apache.james.lifecycle.api.StartUpCheck.CheckResult;
+import org.apache.james.modules.blobstore.BlobStoreConfiguration;
+
+import com.google.common.collect.ImmutableSet;
+
+import reactor.core.publisher.Mono;
+
+public class StorageStrategyValidationEventSourcingSystem {
+    public static final String CHECK = 
"blobstore-storage-strategy-configuration-check";
+    private final EventSourcingSystem eventSourcingSystem;
+
+    @Inject
+    public StorageStrategyValidationEventSourcingSystem(EventStore eventStore) 
{
+        this.eventSourcingSystem = EventSourcingSystem.fromJava(
+            ImmutableSet.of(new 
RegisterStorageStrategyCommandHandler(eventStore)),
+            ImmutableSet.of(),
+            eventStore);
+    }
+
+    public CheckResult validate(BlobStoreConfiguration blobStoreConfiguration) 
{
+        return Mono.from(eventSourcingSystem.dispatch(new 
RegisterStorageStrategy(blobStoreConfiguration.storageStrategy())))
+            .thenReturn(CheckResult.builder()
+                .checkName(CHECK)
+                .resultType(StartUpCheck.ResultType.GOOD)
+                .build())
+            .onErrorResume(IllegalStateException.class,
+                e -> Mono.just(CheckResult.builder()
+                    .checkName(CHECK)
+                    .resultType(StartUpCheck.ResultType.BAD)
+                    .description(e.getMessage())
+                    .build()))
+            .block();
+    }
+}
diff --git 
a/server/container/guice/cassandra-rabbitmq-guice/src/test/java/org/apache/james/modules/blobstore/BlobStoreConfigurationValidationStartUpCheckTest.java
 
b/server/container/guice/cassandra-rabbitmq-guice/src/test/java/org/apache/james/modules/blobstore/BlobStoreConfigurationValidationStartUpCheckTest.java
new file mode 100644
index 0000000..81de1a4
--- /dev/null
+++ 
b/server/container/guice/cassandra-rabbitmq-guice/src/test/java/org/apache/james/modules/blobstore/BlobStoreConfigurationValidationStartUpCheckTest.java
@@ -0,0 +1,124 @@
+/****************************************************************
+ * Licensed to the Apache Software Foundation (ASF) under one   *
+ * or more contributor license agreements.  See the NOTICE file *
+ * distributed with this work for additional information        *
+ * regarding copyright ownership.  The ASF licenses this file   *
+ * to you under the Apache License, Version 2.0 (the            *
+ * "License"); you may not use this file except in compliance   *
+ * with the License.  You may obtain a copy of the License at   *
+ *                                                              *
+ * http://www.apache.org/licenses/LICENSE-2.0                   *
+ *                                                              *
+ * Unless required by applicable law or agreed to in writing,   *
+ * software distributed under the License is distributed on an  *
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY       *
+ * KIND, either express or implied.  See the License for the    *
+ * specific language governing permissions and limitations      *
+ * under the License.                                           *
+ ***************************************************************/
+
+package org.apache.james.modules.blobstore;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.Set;
+import java.util.stream.Stream;
+
+import org.apache.james.backends.cassandra.CassandraClusterExtension;
+import org.apache.james.backends.cassandra.components.CassandraModule;
+import 
org.apache.james.backends.cassandra.versions.CassandraSchemaVersionModule;
+import org.apache.james.eventsourcing.Event;
+import org.apache.james.eventsourcing.eventstore.EventStore;
+import org.apache.james.eventsourcing.eventstore.cassandra.CassandraEventStore;
+import 
org.apache.james.eventsourcing.eventstore.cassandra.CassandraEventStoreExtension;
+import 
org.apache.james.eventsourcing.eventstore.cassandra.CassandraEventStoreModule;
+import org.apache.james.eventsourcing.eventstore.cassandra.JsonEventSerializer;
+import org.apache.james.eventsourcing.eventstore.cassandra.dto.EventDTO;
+import org.apache.james.eventsourcing.eventstore.cassandra.dto.EventDTOModule;
+import org.apache.james.lifecycle.api.StartUpCheck;
+import 
org.apache.james.modules.blobstore.validation.EventsourcingStorageStrategy;
+import org.apache.james.modules.blobstore.validation.StorageStrategyModule;
+import org.apache.james.server.blob.deduplication.StorageStrategy;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+import com.google.common.collect.ImmutableSet;
+
+class BlobStoreConfigurationValidationStartUpCheckTest {
+    @RegisterExtension
+    static final CassandraClusterExtension CASSANDRA_CLUSTER = new 
CassandraClusterExtension(
+        CassandraModule.aggregateModules(
+            CassandraSchemaVersionModule.MODULE,
+            CassandraEventStoreModule.MODULE()));
+
+    private static final Set<EventDTOModule<? extends Event, ? extends 
EventDTO>> EVENT_DTO_MODULES = 
ImmutableSet.of(StorageStrategyModule.STORAGE_STRATEGY);
+
+
+    @RegisterExtension
+    CassandraEventStoreExtension eventStoreExtension = new 
CassandraEventStoreExtension(CASSANDRA_CLUSTER,
+            
JsonEventSerializer.forModules(EVENT_DTO_MODULES).withoutNestedType());
+
+    private static BlobStoreConfiguration DEDUPLICATION_STRATEGY = 
BlobStoreConfiguration
+            .builder()
+            .cassandra()
+            .disableCache()
+            .deduplication();
+    private static BlobStoreConfiguration PASSTHROUGH_STRATEGY = 
BlobStoreConfiguration
+            .builder()
+            .cassandra()
+            .disableCache()
+            .passthrough();
+
+    private EventsourcingStorageStrategy eventsourcingStorageStrategy;
+
+    @BeforeEach
+    void setUp(EventStore eventStore) {
+        eventsourcingStorageStrategy = new 
EventsourcingStorageStrategy(eventStore);
+    }
+
+    @ParameterizedTest
+    @MethodSource("storageStrategies")
+    void firstStartUpShouldReturnAGoodResult(BlobStoreConfiguration 
blobStoreConfiguration) {
+        BlobStoreConfigurationValidationStartUpCheck check = new 
BlobStoreConfigurationValidationStartUpCheck(blobStoreConfiguration, 
eventsourcingStorageStrategy);
+        
assertThat(check.check().getResultType()).isEqualTo(StartUpCheck.ResultType.GOOD);
+    }
+
+    @ParameterizedTest
+    @MethodSource("storageStrategies")
+    void 
startingUpTwiceWithTheStrategyShouldReturnGoodResults(BlobStoreConfiguration 
blobStoreConfiguration) {
+        BlobStoreConfigurationValidationStartUpCheck checkFirstStartUp = new 
BlobStoreConfigurationValidationStartUpCheck(blobStoreConfiguration, 
eventsourcingStorageStrategy);
+        
assertThat(checkFirstStartUp.check().getResultType()).isEqualTo(StartUpCheck.ResultType.GOOD);
+
+        BlobStoreConfigurationValidationStartUpCheck checkSecondStartUp = new 
BlobStoreConfigurationValidationStartUpCheck(blobStoreConfiguration, 
eventsourcingStorageStrategy);
+        
assertThat(checkSecondStartUp.check().getResultType()).isEqualTo(StartUpCheck.ResultType.GOOD);
+    }
+
+    @Test
+    void 
startingUpWithDeduplicationThenPassthroughTheStrategyShouldReturnABadResult() {
+        BlobStoreConfigurationValidationStartUpCheck checkFirstStartUp = new 
BlobStoreConfigurationValidationStartUpCheck(DEDUPLICATION_STRATEGY, 
eventsourcingStorageStrategy);
+        checkFirstStartUp.check();
+
+        BlobStoreConfigurationValidationStartUpCheck checkSecondStartUp = new 
BlobStoreConfigurationValidationStartUpCheck(PASSTHROUGH_STRATEGY, 
eventsourcingStorageStrategy);
+        
assertThat(checkSecondStartUp.check().getResultType()).isEqualTo(StartUpCheck.ResultType.BAD);
+    }
+
+    @Test
+    void 
startingUpWithPassthroughThenDeduplicationTheStrategyShouldReturnAGoodResult() {
+        BlobStoreConfigurationValidationStartUpCheck checkFirstStartUp = new 
BlobStoreConfigurationValidationStartUpCheck(PASSTHROUGH_STRATEGY, 
eventsourcingStorageStrategy);
+        checkFirstStartUp.check();
+
+        BlobStoreConfigurationValidationStartUpCheck checkSecondStartUp = new 
BlobStoreConfigurationValidationStartUpCheck(DEDUPLICATION_STRATEGY, 
eventsourcingStorageStrategy);
+        
assertThat(checkSecondStartUp.check().getResultType()).isEqualTo(StartUpCheck.ResultType.GOOD);
+    }
+
+    static Stream<Arguments> storageStrategies() {
+        return Stream.of(
+            Arguments.of(DEDUPLICATION_STRATEGY),
+            Arguments.of(PASSTHROUGH_STRATEGY)
+        );
+    }
+}
\ No newline at end of file
diff --git 
a/server/container/guice/cassandra-rabbitmq-guice/src/test/java/org/apache/james/modules/blobstore/validation/StorageStrategyChangedDTOTest.java
 
b/server/container/guice/cassandra-rabbitmq-guice/src/test/java/org/apache/james/modules/blobstore/validation/StorageStrategyChangedDTOTest.java
new file mode 100644
index 0000000..668bb7d
--- /dev/null
+++ 
b/server/container/guice/cassandra-rabbitmq-guice/src/test/java/org/apache/james/modules/blobstore/validation/StorageStrategyChangedDTOTest.java
@@ -0,0 +1,79 @@
+/****************************************************************
+ * Licensed to the Apache Software Foundation (ASF) under one   *
+ * or more contributor license agreements.  See the NOTICE file *
+ * distributed with this work for additional information        *
+ * regarding copyright ownership.  The ASF licenses this file   *
+ * to you under the Apache License, Version 2.0 (the            *
+ * "License"); you may not use this file except in compliance   *
+ * with the License.  You may obtain a copy of the License at   *
+ *                                                              *
+ * http://www.apache.org/licenses/LICENSE-2.0                   *
+ *                                                              *
+ * Unless required by applicable law or agreed to in writing,   *
+ * software distributed under the License is distributed on an  *
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY       *
+ * KIND, either express or implied.  See the License for the    *
+ * specific language governing permissions and limitations      *
+ * under the License.                                           *
+ ***************************************************************/
+
+package org.apache.james.modules.blobstore.validation;
+
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+import org.apache.james.eventsourcing.EventId;
+import org.apache.james.server.blob.deduplication.StorageStrategy;
+import org.assertj.core.api.SoftAssertions;
+import org.junit.jupiter.api.Test;
+
+import nl.jqno.equalsverifier.EqualsVerifier;
+
+class StorageStrategyChangedDTOTest {
+
+    private static final int EVENT_ID_SERIALIZED = 10;
+    private static final EventId EVENT_ID = 
EventId.fromSerialized(EVENT_ID_SERIALIZED);
+    private static final String STORAGE_STRATEGY_AGGREGATE_KEY = "aggrKey";
+
+    @Test
+    void shouldMatchBeanContract() {
+        EqualsVerifier.forClass(StorageStrategyChangedDTO.class)
+            .verify();
+    }
+
+    @Test
+    void fromShouldThrowWhenStorageStrategyAddedIsNull() {
+        assertThatThrownBy(() -> StorageStrategyChangedDTO.from(null))
+            .isInstanceOf(NullPointerException.class);
+    }
+
+    @Test
+    void fromShouldReturnCorrespondingDTO() {
+        StorageStrategyChanged configurationChanged = new 
StorageStrategyChanged(
+            EVENT_ID,
+            () -> STORAGE_STRATEGY_AGGREGATE_KEY,
+            StorageStrategy.DEDUPLICATION);
+
+        StorageStrategyChangedDTO dto = 
StorageStrategyChangedDTO.from(configurationChanged);
+        SoftAssertions.assertSoftly(softly -> {
+            softly.assertThat(dto.getEventId()).isEqualTo(EVENT_ID_SERIALIZED);
+            
softly.assertThat(dto.getType()).isEqualTo(StorageStrategyModule.TYPE_NAME);
+            
softly.assertThat(dto.getStorageStrategy()).isEqualTo(StorageStrategy.DEDUPLICATION.name());
+        });
+    }
+
+    @Test
+    void toEventShouldReturnCorrespondingStorageStrategyChangedEvent() {
+        StorageStrategyChangedDTO dto = new StorageStrategyChangedDTO(
+            EVENT_ID_SERIALIZED,
+            STORAGE_STRATEGY_AGGREGATE_KEY,
+            StorageStrategyModule.TYPE_NAME,
+            StorageStrategy.DEDUPLICATION.name());
+        StorageStrategyChanged event = dto.toEvent();
+
+        SoftAssertions.assertSoftly(softly -> {
+            softly.assertThat(event.eventId()).isEqualTo(EVENT_ID);
+            
softly.assertThat(event.getAggregateId().asAggregateKey()).isEqualTo(STORAGE_STRATEGY_AGGREGATE_KEY);
+            
softly.assertThat(event.getStorageStrategy()).isEqualTo(StorageStrategy.DEDUPLICATION);
+        });
+    }
+}
diff --git 
a/server/container/guice/cassandra-rabbitmq-guice/src/test/java/org/apache/james/modules/blobstore/validation/StorageStrategyValidationEventSourcingSystemTest.java
 
b/server/container/guice/cassandra-rabbitmq-guice/src/test/java/org/apache/james/modules/blobstore/validation/StorageStrategyValidationEventSourcingSystemTest.java
new file mode 100644
index 0000000..04a4753
--- /dev/null
+++ 
b/server/container/guice/cassandra-rabbitmq-guice/src/test/java/org/apache/james/modules/blobstore/validation/StorageStrategyValidationEventSourcingSystemTest.java
@@ -0,0 +1,100 @@
+/****************************************************************
+ * Licensed to the Apache Software Foundation (ASF) under one   *
+ * or more contributor license agreements.  See the NOTICE file *
+ * distributed with this work for additional information        *
+ * regarding copyright ownership.  The ASF licenses this file   *
+ * to you under the Apache License, Version 2.0 (the            *
+ * "License"); you may not use this file except in compliance   *
+ * with the License.  You may obtain a copy of the License at   *
+ *                                                              *
+ *   http://www.apache.org/licenses/LICENSE-2.0                 *
+ *                                                              *
+ * Unless required by applicable law or agreed to in writing,   *
+ * software distributed under the License is distributed on an  *
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY       *
+ * KIND, either express or implied.  See the License for the    *
+ * specific language governing permissions and limitations      *
+ * under the License.                                           *
+ ****************************************************************/
+
+package org.apache.james.modules.blobstore.validation;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.apache.james.eventsourcing.eventstore.History;
+import org.apache.james.eventsourcing.eventstore.memory.InMemoryEventStore;
+import org.apache.james.lifecycle.api.StartUpCheck;
+import org.apache.james.modules.blobstore.BlobStoreConfiguration;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import reactor.core.publisher.Mono;
+
+public class StorageStrategyValidationEventSourcingSystemTest {
+    private StorageStrategyValidationEventSourcingSystem testee;
+    private InMemoryEventStore eventStore;
+
+    @BeforeEach
+    void setUp() {
+        eventStore = new InMemoryEventStore();
+        testee = new StorageStrategyValidationEventSourcingSystem(eventStore);
+    }
+
+    @Test
+    void startingForTheFirstTimeShouldSucceedWhenPassThrough() {
+        StartUpCheck.CheckResult checkResult = 
testee.validate(BlobStoreConfiguration.builder().implementation(BlobStoreConfiguration.BlobStoreImplName.OBJECTSTORAGE)
+            .disableCache()
+            .passthrough());
+
+        
assertThat(checkResult.getResultType()).isEqualTo(StartUpCheck.ResultType.GOOD);
+    }
+
+    @Test
+    void startingForTheFirstTimeShouldSucceedWhenDeduplication() {
+        StartUpCheck.CheckResult checkResult = 
testee.validate(BlobStoreConfiguration.builder().implementation(BlobStoreConfiguration.BlobStoreImplName.OBJECTSTORAGE)
+            .disableCache()
+            .deduplication());
+
+        
assertThat(checkResult.getResultType()).isEqualTo(StartUpCheck.ResultType.GOOD);
+    }
+
+    @Test
+    void startingShouldSucceedWhenTurningOnDeduplication() {
+        
testee.validate(BlobStoreConfiguration.builder().implementation(BlobStoreConfiguration.BlobStoreImplName.OBJECTSTORAGE)
+            .disableCache()
+            .passthrough());
+
+        StartUpCheck.CheckResult checkResult = 
testee.validate(BlobStoreConfiguration.builder().implementation(BlobStoreConfiguration.BlobStoreImplName.OBJECTSTORAGE)
+            .disableCache()
+            .deduplication());
+
+        
assertThat(checkResult.getResultType()).isEqualTo(StartUpCheck.ResultType.GOOD);
+    }
+
+    @Test
+    void startingShouldFailWhenTurningOffDeduplication() {
+        
testee.validate(BlobStoreConfiguration.builder().implementation(BlobStoreConfiguration.BlobStoreImplName.OBJECTSTORAGE)
+            .disableCache()
+            .deduplication());
+
+        StartUpCheck.CheckResult checkResult = 
testee.validate(BlobStoreConfiguration.builder().implementation(BlobStoreConfiguration.BlobStoreImplName.OBJECTSTORAGE)
+            .disableCache()
+            .passthrough());
+
+        
assertThat(checkResult.getResultType()).isEqualTo(StartUpCheck.ResultType.BAD);
+    }
+
+    @Test
+    void validatingSeveralTimeTheSameStrategyShouldNotAddEventsToTheHistory() {
+        
testee.validate(BlobStoreConfiguration.builder().implementation(BlobStoreConfiguration.BlobStoreImplName.OBJECTSTORAGE)
+            .disableCache()
+            .deduplication());
+        
testee.validate(BlobStoreConfiguration.builder().implementation(BlobStoreConfiguration.BlobStoreImplName.OBJECTSTORAGE)
+            .disableCache()
+            .deduplication());
+
+        History history = 
Mono.from(eventStore.getEventsOfAggregate(RegisterStorageStrategyCommandHandler.AGGREGATE_ID)).block();
+
+        assertThat(history.getEventsJava()).hasSize(1);
+    }
+}
\ No newline at end of file


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