impl: backend design change

README.md

@@ -183,12 +183,6 @@ Snapshot Count:
 Snapshot Restore:
     kvs_tool -o snapshotrestore -s 1
 
-Get KVS Filename:
-    kvs_tool -o getkvsfilename -s 1
-
-Get Hash Filename:
-    kvs_tool -o gethashfilename -s 1
-
 ---------------------------------------
 
 Create Test Data:

docs/class_diagram.puml

@@ -0,0 +1,124 @@
+@startuml Persistency class diagram
+
+package "kvs_builder" {
+    ~class KvsInner {
+        ~parameters: KvsParameters
+        ~data: KvsData
+    }
+
+    +class KvsBuilder {
+        {static} -KVS_POOL: list<KvsInner>
+        -parameters: KvsParameters
+
+        +new(instance_id: InstanceId): KvsBuilder
+        {static} +max_instances(): usize
+        +defaults(mode: KvsDefaults): KvsBuilder
+        +kvs_load(mode: KvsLoad): KvsBuilder
+        +backend_parameters(parameters: KvsMap): KvsBuilder
+        +build(): Kvs
+    }
+
+    KvsInner <-- KvsBuilder
+}
+
+package "kvs_api" {
+    +interface KvsApi {
+        +reset()
+        +reset_key(key: string)
+        +get_all_keys(): list<string>
+        +key_exists(key: string): bool
+        +get_value(key: string): KvsValue
+        +get_value_as<T>(key: string): T
+        +get_default_value(key: string): KvsValue
+        +is_value_default(key: string): bool
+        +set_value<T>(key: string, value: T)
+        +remove_key(key: string)
+        +flush()
+        +snapshot_count(): usize
+        +snapshot_max_count(): usize
+        +snapshot_restore(snapshot_id: SnapshotId)
+    }
+}
+
+package "kvs" {
+    +class Kvs {
+        -data: KvsData
+        -parameters: KvsParameters
+        -backend: KvsBackend
+
+        ~new(data: KvsData, parameters: KvsParameters, backend: KvsBackend): Kvs
+        +parameters(): KvsParameters
+
+        +reset()
+        +reset_key(key: string)
+        +get_all_keys(): list<string>
+        +key_exists(key: string): bool
+        +get_value(key: string): KvsValue
+        +get_value_as<T>(key: string): T
+        +get_default_value(key: string): KvsValue
+        +is_value_default(key: string): bool
+        +set_value<T>(key: string, value: T)
+        +remove_key(key: string)
+        +flush()
+        +snapshot_count(): usize
+        +snapshot_max_count(): usize
+        +snapshot_restore(snapshot_id: SnapshotId)
+    }
+}
+
+KvsApi <|.. Kvs
+KvsBuilder -- Kvs
+
+package "kvs_backend_registry" {
+    +class KvsBackendRegistry {
+        {static} -REGISTERED_BACKENDS: map<string, KvsBackendFactory>
+
+        {static} ~from_name(name: string) -> Result<&Box<dyn KvsBackendFactory>, ErrorCode>
+        {static} ~from_parameters(parameters: KvsMap) -> Result<&Box<dyn KvsBackendFactory>, ErrorCode>
+
+        {static} +register(backend_factory: KvsBackendFactory)
+    }
+}
+
+KvsBackendRegistry .. KvsBuilder
+
+package "kvs_backend" {
+    +interface KvsBackend {
+        +load_kvs(instance_id: InstanceId, snapshot_id: SnapshotId): KvsMap
+        +load_defaults(instance_id: InstanceId): KvsMap
+        +flush(instance_id: InstanceId, kvs_map: KvsMap)
+        +snapshot_count(instance_id: InstanceId): usize
+        +snapshot_max_count(): usize
+        +snapshot_restore(instance_id: InstanceId, snapshot_id: SnapshotId): KvsMap
+    }
+
+    +interface KvsBackendFactory {
+        +create(parameters: KvsMap): KvsBackend
+    }
+}
+
+package "json_backend" {
+    ~class JsonBackend {
+        +load_kvs(instance_id: InstanceId, snapshot_id: SnapshotId): KvsMap
+        +load_defaults(instance_id: InstanceId): KvsMap
+        +flush(instance_id: InstanceId, kvs_map: KvsMap)
+        +snapshot_count(instance_id: InstanceId): usize
+        +snapshot_max_count(): usize
+        +snapshot_restore(instance_id: InstanceId, snapshot_id: SnapshotId): KvsMap
+    }
+
+    ~class JsonBackendFactory {
+        +create(parameters: KvsMap): KvsBackend
+    }
+}
+
+KvsBackend <-- Kvs
+
+KvsBackendRegistry --> KvsBackendFactory
+KvsBackendFactory -- KvsBackend
+
+KvsBackend <|.. JsonBackend
+KvsBackendFactory <|.. JsonBackendFactory
+JsonBackendFactory -- JsonBackend
+
+@enduml

src/rust/rust_kvs/examples/backend_registration.rs

@@ -0,0 +1,111 @@
+//! Example for custom backend registration.
+//! - Implementation of `KvsBackend` traits.
+//! - Registration of custom backend.
+//! - Creation of KVS instance utilizing custom backend.
+
+use rust_kvs::prelude::*;
+use tempfile::tempdir;
+
+/// Mock backend implementation.
+/// Only `load_kvs` is implemented.
+struct MockBackend;
+
+impl KvsBackend for MockBackend {
+    fn load_kvs(
+        &self,
+        _instance_id: InstanceId,
+        _snapshot_id: SnapshotId,
+    ) -> Result<KvsMap, ErrorCode> {
+        println!("`load_kvs` used");
+        Ok(KvsMap::new())
+    }
+
+    fn load_defaults(&self, _instance_id: InstanceId) -> Result<KvsMap, ErrorCode> {
+        unimplemented!()
+    }
+
+    fn flush(&self, _instance_id: InstanceId, _kvs_map: &KvsMap) -> Result<(), ErrorCode> {
+        unimplemented!()
+    }
+
+    fn snapshot_count(&self, _instance_id: InstanceId) -> usize {
+        unimplemented!()
+    }
+
+    fn snapshot_max_count(&self) -> usize {
+        unimplemented!()
+    }
+
+    fn snapshot_restore(
+        &self,
+        _instance_id: InstanceId,
+        _snapshot_id: SnapshotId,
+    ) -> Result<KvsMap, ErrorCode> {
+        unimplemented!()
+    }
+}
+
+/// Mock backend factory implementation.
+struct MockBackendFactory;
+
+impl KvsBackendFactory for MockBackendFactory {
+    fn create(&self, _parameters: &KvsMap) -> Result<Box<dyn KvsBackend>, ErrorCode> {
+        Ok(Box::new(MockBackend))
+    }
+}
+
+fn main() -> Result<(), ErrorCode> {
+    // Temporary directory.
+    let dir = tempdir()?;
+    let dir_string = dir.path().to_string_lossy().to_string();
+
+    // Register `MockBackendFactory`.
+    KvsBackendRegistry::register("mock", || Box::new(MockBackendFactory))?;
+
+    // Build KVS instance with mock backend.
+    {
+        let instance_id = InstanceId(0);
+        let parameters = KvsMap::from([("name".to_string(), KvsValue::String("mock".to_string()))]);
+        let builder = KvsBuilder::new(instance_id)
+            .backend_parameters(parameters)
+            .defaults(KvsDefaults::Ignored);
+        let kvs = builder.build()?;
+
+        println!(
+            "KVS instance with mock backend - parameters: {:?}",
+            kvs.parameters()
+        );
+    }
+
+    // Build KVS instance with JSON backend - default parameters.
+    {
+        let instance_id = InstanceId(1);
+        let builder = KvsBuilder::new(instance_id).defaults(KvsDefaults::Ignored);
+        let kvs = builder.build()?;
+
+        println!(
+            "KVS instance with default JSON backend - parameters: {:?}",
+            kvs.parameters()
+        );
+    }
+
+    // Build KVS instance with JSON backend - `working_dir` set.
+    {
+        let instance_id = InstanceId(2);
+        let parameters = KvsMap::from([
+            ("name".to_string(), KvsValue::String("json".to_string())),
+            ("working_dir".to_string(), KvsValue::String(dir_string)),
+        ]);
+        let builder = KvsBuilder::new(instance_id)
+            .backend_parameters(parameters)
+            .defaults(KvsDefaults::Ignored);
+        let kvs = builder.build()?;
+
+        println!(
+            "KVS instance with JSON backend - parameters: {:?}",
+            kvs.parameters()
+        );
+    }
+
+    Ok(())
+}

src/rust/rust_kvs/examples/basic.rs

@@ -11,6 +11,10 @@ fn main() -> Result<(), ErrorCode> {
     // Temporary directory.
     let dir = tempdir()?;
     let dir_string = dir.path().to_string_lossy().to_string();
+    let backend_parameters = KvsMap::from([
+        ("name".to_string(), KvsValue::String("json".to_string())),
+        ("working_dir".to_string(), KvsValue::String(dir_string)),
+    ]);
 
     // Instance ID for KVS object instances.
     let instance_id = InstanceId(0);
@@ -20,7 +24,7 @@ fn main() -> Result<(), ErrorCode> {
         // `kvs_load` is explicitly set to `KvsLoad::Optional`, but this is the default value.
         // KVS files are not required.
         let builder = KvsBuilder::new(instance_id)
-            .dir(dir_string.clone())
+            .backend_parameters(backend_parameters.clone())
             .kvs_load(KvsLoad::Optional);
         let kvs = builder.build()?;
 
@@ -65,7 +69,7 @@ fn main() -> Result<(), ErrorCode> {
         // Build KVS instance for given instance ID and temporary directory.
         // `kvs_load` is set to `KvsLoad::Required` - KVS files must already exist from previous KVS instance.
         let builder = KvsBuilder::new(instance_id)
-            .dir(dir_string)
+            .backend_parameters(backend_parameters)
             .kvs_load(KvsLoad::Required);
         let kvs = builder.build()?;
 

src/rust/rust_kvs/examples/custom_types.rs

@@ -182,6 +182,10 @@ fn main() -> Result<(), ErrorCode> {
     // Temporary directory.
     let dir = tempdir()?;
     let dir_string = dir.path().to_string_lossy().to_string();
+    let backend_parameters = KvsMap::from([
+        ("name".to_string(), KvsValue::String("json".to_string())),
+        ("working_dir".to_string(), KvsValue::String(dir_string)),
+    ]);
 
     // Create initial example object.
     let object = Example {
@@ -218,7 +222,7 @@ fn main() -> Result<(), ErrorCode> {
     let kvs = KvsBuilder::new(InstanceId(0))
         .kvs_load(KvsLoad::Ignored)
         .defaults(KvsDefaults::Ignored)
-        .dir(dir_string)
+        .backend_parameters(backend_parameters)
         .build()?;
 
     // Serialize and set object.

src/rust/rust_kvs/examples/defaults.rs

@@ -34,6 +34,10 @@ fn main() -> Result<(), ErrorCode> {
     // Temporary directory.
     let dir = tempdir()?;
     let dir_string = dir.path().to_string_lossy().to_string();
+    let backend_parameters = KvsMap::from([
+        ("name".to_string(), KvsValue::String("json".to_string())),
+        ("working_dir".to_string(), KvsValue::String(dir_string)),
+    ]);
 
     // Instance ID for KVS object instances.
     let instance_id = InstanceId(0);
@@ -44,7 +48,7 @@ fn main() -> Result<(), ErrorCode> {
     // Build KVS instance for given instance ID and temporary directory.
     // `defaults` is set to `KvsDefaults::Required` - defaults are required.
     let builder = KvsBuilder::new(instance_id)
-        .dir(dir_string)
+        .backend_parameters(backend_parameters)
         .defaults(KvsDefaults::Required);
     let kvs = builder.build()?;
 

src/rust/rust_kvs/examples/snapshots.rs

@@ -6,9 +6,13 @@ use rust_kvs::prelude::*;
 use tempfile::tempdir;
 
 fn main() -> Result<(), ErrorCode> {
-    // Temporary directory.
+    // Temporary directory and common backend.
     let dir = tempdir()?;
     let dir_string = dir.path().to_string_lossy().to_string();
+    let backend_parameters = KvsMap::from([
+        ("name".to_string(), KvsValue::String("json".to_string())),
+        ("working_dir".to_string(), KvsValue::String(dir_string)),
+    ]);
 
     // Instance ID for KVS object instances.
     let instance_id = InstanceId(0);
@@ -17,7 +21,7 @@ fn main() -> Result<(), ErrorCode> {
         println!("-> `snapshot_count` and `snapshot_max_count` usage");
 
         // Build KVS instance for given instance ID and temporary directory.
-        let builder = KvsBuilder::new(instance_id).dir(dir_string.clone());
+        let builder = KvsBuilder::new(instance_id).backend_parameters(backend_parameters.clone());
         let kvs = builder.build()?;
 
         let max_count = kvs.snapshot_max_count() as u32;
@@ -38,7 +42,7 @@ fn main() -> Result<(), ErrorCode> {
         println!("-> `snapshot_restore` usage");
 
         // Build KVS instance for given instance ID and temporary directory.
-        let builder = KvsBuilder::new(instance_id).dir(dir_string.clone());
+        let builder = KvsBuilder::new(instance_id).backend_parameters(backend_parameters);
         let kvs = builder.build()?;
 
         let max_count = kvs.snapshot_max_count() as u32;

src/rust/rust_kvs/src/error_code.rs

@@ -85,6 +85,15 @@ pub enum ErrorCode {
 
     /// Instance parameters mismatch
     InstanceParametersMismatch,
+
+    /// Requested unknown backend
+    UnknownBackend,
+
+    /// Backend already registered
+    BackendAlreadyRegistered,
+
+    /// Invalid backend parameters.
+    InvalidBackendParameters,
 }
 
 impl From<std::io::Error> for ErrorCode {