feat: flagd in-process provider

providers/flagd/CONTRIBUTING.md

@@ -1,8 +1,12 @@
 # flagd Provider for OpenFeature
 
+Given below is the architecture of the provider implementation.
+
+![img.png](architecture.png)
+
 ## Building
 
-`mvn compile` will pull the `schemas` submodule, and build the gRPC/protobug resources.
+`mvn compile` will pull the `schemas` and `sync` submodule, and build the gRPC resources.
 Note that in some editors, you will need to disable some automatic compilation options to prevent your editor from cleaning them.
 In vscode for instance, the following settings are recommended:
 

providers/flagd/README.md

@@ -17,8 +17,13 @@ A feature flag daemon with a Unix philosophy.
 
 ## Usage
 
-The `FlagdProvider` communicates with flagd via the gRPC protocol. Instantiate a new FlagdProvider instance, and
-configure the OpenFeature SDK to use it:
+### Remote resolver
+
+This is the default mode of operation of the provider. 
+In this mode, `FlagdProvider` communicates with [flagd](https://github.com/open-feature/flagd) via the gRPC protocol.
+Flag evaluations happens remotely at the connected flagd instance.
+
+Instantiate a new FlagdProvider instance, and configure the OpenFeature SDK to use it:
 
 ```java
 // Create a flagd instance with default options
@@ -27,26 +32,43 @@ FlagdProvider flagd = new FlagdProvider();
 OpenFeatureAPI.getInstance().setProvider(flagd);
 ```
 
+### In-process resolver
+
+This mode perform flag evaluations locally(in-process). Flag configurations for evaluations are obtained via gRPC protocol using [sync protobuf schema](https://buf.build/open-feature/flagd/file/main:sync/v1/sync_service.proto) service definition.
+
+Consider following example to create a `FlagdProvider` with in-process evaluations,
+
+```java
+FlagdProvider flagdProvider = new FlagdProvider(
+        FlagdOptions.builder()
+                .resolverType(Config.ResolverType.IN_PROCESS)
+                .build());
+```
+
+In the above example, in-process handlers attempt to connect to a sync service on address `localhost:8013` to obtain flag configurations
+
+### Configuration options
+
 Options can be defined in the constructor or as environment variables, with constructor options having the highest
 precedence.
 
 Default options can be overridden through a `FlagdOptions` based constructor or set to be picked up from the environment
 variables.
 
-### Supported environmental variables
-
-| Option name           | Environment variable name      | Type    | Default   | Values       |
-|-----------------------|--------------------------------|---------|-----------|--------------|
-| host                  | FLAGD_HOST                     | string  | localhost |              |
-| port                  | FLAGD_PORT                     | number  | 8013      |              |
-| tls                   | FLAGD_TLS                      | boolean | false     |              |
-| socketPath            | FLAGD_SOCKET_PATH              | string  | null      |              |
-| certPath              | FLAGD_SERVER_CERT_PATH         | string  | null      |              |
-| cache                 | FLAGD_CACHE                    | string  | lru       | lru,disabled |
-| maxCacheSize          | FLAGD_MAX_CACHE_SIZE           | int     | 1000      |              |
-| maxEventStreamRetries | FLAGD_MAX_EVENT_STREAM_RETRIES | int     | 5         |              |
-| retryBackoffMs        | FLAGD_RETRY_BACKOFF_MS         | int     | 1000      |              |
-| deadline              | FLAGD_DEADLINE_MS              | int     | 500       |              |
+Given below are the supported configurations. Note that some configurations are only applicable for remote resolver.
+
+| Option name           | Environment variable name      | Type & Values          | Default   | Compatible resolver |
+|-----------------------|--------------------------------|------------------------|-----------|---------------------|
+| host                  | FLAGD_HOST                     | String                 | localhost | Remote & In-process |
+| port                  | FLAGD_PORT                     | int                    | 8013      | Remote & In-process |
+| tls                   | FLAGD_TLS                      | boolean                | false     | Remote & In-process |
+| socketPath            | FLAGD_SOCKET_PATH              | String                 | null      | Remote & In-process |
+| certPath              | FLAGD_SERVER_CERT_PATH         | String                 | null      | Remote & In-process |
+| cache                 | FLAGD_CACHE                    | String - lru, disabled | lru       | Remote              |
+| maxCacheSize          | FLAGD_MAX_CACHE_SIZE           | int                    | 1000      | Remote              |
+| maxEventStreamRetries | FLAGD_MAX_EVENT_STREAM_RETRIES | int                    | 5         | Remote              |
+| retryBackoffMs        | FLAGD_RETRY_BACKOFF_MS         | int                    | 1000      | Remote              |
+| deadline              | FLAGD_DEADLINE_MS              | int                    | 500       | Remote              |
 
 ### OpenTelemetry support
 

providers/flagd/pom.xml

@@ -71,6 +71,30 @@
             <version>1.57.2</version>
         </dependency>
 
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-databind</artifactId>
+            <version>2.15.2</version>
+        </dependency>
+
+        <dependency>
+            <groupId>io.github.jamsesso</groupId>
+            <artifactId>json-logic-java</artifactId>
+            <version>1.0.7</version>
+        </dependency>
+
+        <dependency>
+            <groupId>com.networknt</groupId>
+            <artifactId>json-schema-validator</artifactId>
+            <version>1.0.86</version>
+            <exclusions>
+                <exclusion>
+                    <groupId>org.apache.commons</groupId>
+                    <artifactId>commons-lang3</artifactId>
+                </exclusion>
+            </exclusions>
+        </dependency>
+
         <dependency>
             <!-- necessary for Java 9+ -->
             <groupId>org.apache.tomcat</groupId>
@@ -126,7 +150,7 @@
                         </configuration>
                     </execution>
                     <execution>
-                        <id>copy-protobuf-definition</id>
+                        <id>copy-schema-definition</id>
                         <phase>validate</phase>
                         <goals>
                             <goal>exec</goal>
@@ -140,6 +164,36 @@
                             </arguments>
                         </configuration>
                     </execution>
+                    <execution>
+                        <id>copy-sync-definition</id>
+                        <phase>validate</phase>
+                        <goals>
+                            <goal>exec</goal>
+                        </goals>
+                        <configuration>
+                            <!-- run: cp schemas/protobuf/sync/v1/sync_service.proto src/main/proto/ -->
+                            <executable>cp</executable>
+                            <arguments>
+                                <argument>schemas/protobuf/sync/v1/sync_service.proto</argument>
+                                <argument>src/main/proto/</argument>
+                            </arguments>
+                        </configuration>
+                    </execution>
+                    <execution>
+                        <id>copy-schema-json</id>
+                        <phase>validate</phase>
+                        <goals>
+                            <goal>exec</goal>
+                        </goals>
+                        <configuration>
+                            <!-- run: cp schemas/json/flagd-definitions.json src/main/resources/ -->
+                            <executable>cp</executable>
+                            <arguments>
+                                <argument>schemas/json/flagd-definitions.json</argument>
+                                <argument>src/main/resources/</argument>
+                            </arguments>
+                        </configuration>
+                    </execution>
                 </executions>
             </plugin>
 
@@ -166,57 +220,57 @@
 
     <profiles>
         <profile>
-        <!-- this profile handles running the flagd e2e tests -->
-        <id>e2e</id>
-        <properties>
-            <!-- run the e2e tests by clearing the exclusions -->
-            <testExclusions/>
-        </properties>  
-        <build>
-            <plugins>
-            <!-- pull the gherkin tests as a git submodule  -->
-            <plugin>
-                <groupId>org.codehaus.mojo</groupId>
-                <artifactId>exec-maven-plugin</artifactId>
-                <version>3.1.0</version>
-                <executions>
-                <execution>
-                    <id>update-test-harness-submodule</id>
-                    <phase>validate</phase>
-                    <goals>
-                    <goal>exec</goal>
-                    </goals>
-                    <configuration>
-                    <!-- run: git submodule update \-\-init \-\-recursive -->
-                    <executable>git</executable>
-                    <arguments>
-                        <argument>submodule</argument>
-                        <argument>update</argument>
-                        <argument>--init</argument>
-                        <argument>test-harness</argument>
-                    </arguments>
-                    </configuration>
-                </execution>
-                <execution>
-                    <id>copy-gherkin-tests</id>
-                    <phase>validate</phase>
-                    <goals>
-                    <goal>exec</goal>
-                    </goals>
-                    <configuration>
-                    <!-- copy the feature spec we want to test into resources so them can be easily loaded -->
-                    <!-- run: cp test-harness/features/evaluation.feature src/test/resources/features/ -->
-                    <executable>cp</executable>
-                    <arguments>
-                        <argument>test-harness/features/evaluation.feature</argument>
-                        <argument>src/test/resources/features/</argument>
-                    </arguments>
-                    </configuration>
-                </execution>
-                </executions>
-            </plugin>
-            </plugins>
-        </build>
+            <!-- this profile handles running the flagd e2e tests -->
+            <id>e2e</id>
+            <properties>
+                <!-- run the e2e tests by clearing the exclusions -->
+                <testExclusions/>
+            </properties>
+            <build>
+                <plugins>
+                    <!-- pull the gherkin tests as a git submodule  -->
+                    <plugin>
+                        <groupId>org.codehaus.mojo</groupId>
+                        <artifactId>exec-maven-plugin</artifactId>
+                        <version>3.1.0</version>
+                        <executions>
+                            <execution>
+                                <id>update-test-harness-submodule</id>
+                                <phase>validate</phase>
+                                <goals>
+                                    <goal>exec</goal>
+                                </goals>
+                                <configuration>
+                                    <!-- run: git submodule update \-\-init \-\-recursive -->
+                                    <executable>git</executable>
+                                    <arguments>
+                                        <argument>submodule</argument>
+                                        <argument>update</argument>
+                                        <argument>--init</argument>
+                                        <argument>test-harness</argument>
+                                    </arguments>
+                                </configuration>
+                            </execution>
+                            <execution>
+                                <id>copy-gherkin-tests</id>
+                                <phase>validate</phase>
+                                <goals>
+                                    <goal>exec</goal>
+                                </goals>
+                                <configuration>
+                                    <!-- copy the feature spec we want to test into resources so them can be easily loaded -->
+                                    <!-- run: cp test-harness/features/evaluation.feature src/test/resources/features/ -->
+                                    <executable>cp</executable>
+                                    <arguments>
+                                        <argument>test-harness/features/evaluation.feature</argument>
+                                        <argument>src/test/resources/features/</argument>
+                                    </arguments>
+                                </configuration>
+                            </execution>
+                        </executions>
+                    </plugin>
+                </plugins>
+            </build>
         </profile>
     </profiles>
 

providers/flagd/src/main/java/dev/openfeature/contrib/providers/flagd/Config.java

@@ -4,6 +4,7 @@
  * Helper class to hold configuration default values.
  */
 public final class Config {
+    static final ResolverType DEFAULT_RESOLVER_TYPE = ResolverType.FLAGD;
     static final String DEFAULT_PORT = "8013";
     static final String DEFAULT_TLS = "false";
     static final String DEFAULT_HOST = "localhost";
@@ -49,4 +50,19 @@ static int fallBackToEnvOrDefault(String key, int defaultValue) {
             return defaultValue;
         }
     }
+
+    /**
+     * flagd resolving type.
+     */
+    public enum ResolverType {
+        /**
+         * This is the default resolver type, which connects to flagd instance with flag evaluation gRPC contract.
+         */
+        FLAGD,
+        /**
+         * This is the in-process resolving type, where flags are fetched with flag sync gRPC contract and stored
+         * locally for in-process evaluation.
+         */
+        IN_PROCESS
+    }
 }

providers/flagd/src/main/java/dev/openfeature/contrib/providers/flagd/FlagdOptions.java

@@ -14,6 +14,7 @@
 import static dev.openfeature.contrib.providers.flagd.Config.DEFAULT_MAX_CACHE_SIZE;
 import static dev.openfeature.contrib.providers.flagd.Config.DEFAULT_MAX_EVENT_STREAM_RETRIES;
 import static dev.openfeature.contrib.providers.flagd.Config.DEFAULT_PORT;
+import static dev.openfeature.contrib.providers.flagd.Config.DEFAULT_RESOLVER_TYPE;
 import static dev.openfeature.contrib.providers.flagd.Config.DEFAULT_TLS;
 import static dev.openfeature.contrib.providers.flagd.Config.HOST_ENV_VAR_NAME;
 import static dev.openfeature.contrib.providers.flagd.Config.MAX_CACHE_SIZE_ENV_VAR_NAME;
@@ -33,6 +34,12 @@
 @SuppressWarnings("PMD.TooManyStaticImports")
 public class FlagdOptions {
 
+    /**
+     * flagd resolving type.
+     * */
+    @Builder.Default
+    private Config.ResolverType resolverType = DEFAULT_RESOLVER_TYPE;
+
     /**
      * flagd connection host.
      * */

providers/flagd/src/main/java/dev/openfeature/contrib/providers/flagd/FlagdProvider.java

@@ -1,7 +1,9 @@
 package dev.openfeature.contrib.providers.flagd;
 
-import dev.openfeature.contrib.providers.flagd.cache.CacheFactory;
-import dev.openfeature.contrib.providers.flagd.grpc.GrpcResolution;
+import dev.openfeature.contrib.providers.flagd.resolver.Resolver;
+import dev.openfeature.contrib.providers.flagd.resolver.grpc.GrpcResolver;
+import dev.openfeature.contrib.providers.flagd.resolver.grpc.cache.CacheFactory;
+import dev.openfeature.contrib.providers.flagd.resolver.process.InProcessResolver;
 import dev.openfeature.sdk.EvaluationContext;
 import dev.openfeature.sdk.EventProvider;
 import dev.openfeature.sdk.FeatureProvider;
@@ -42,7 +44,18 @@ public FlagdProvider() {
      * @param options {@link FlagdOptions} with
      */
     public FlagdProvider(final FlagdOptions options) {
-        this.flagResolver = new GrpcResolution(options, CacheFactory.getCache(options), this::getState, this::setState);
+        switch (options.getResolverType()) {
+            case IN_PROCESS:
+                this.flagResolver = new InProcessResolver(options, this::setState);
+                break;
+            case FLAGD:
+                this.flagResolver =
+                        new GrpcResolver(options, CacheFactory.getCache(options), this::getState, this::setState);
+                break;
+            default:
+                throw new IllegalStateException(
+                        String.format("Requested unsupported resolver type of %s", options.getResolverType()));
+        }
     }
 
     @Override

providers/flagd/src/main/java/dev/openfeature/contrib/providers/flagd/Resolver.java → providers/flagd/src/main/java/dev/openfeature/contrib/providers/flagd/resolver/Resolver.java

@@ -1,11 +1,11 @@
-package dev.openfeature.contrib.providers.flagd;
+package dev.openfeature.contrib.providers.flagd.resolver;
 
 import dev.openfeature.sdk.EvaluationContext;
 import dev.openfeature.sdk.ProviderEvaluation;
 import dev.openfeature.sdk.Value;
 
 /**
- * A generic contract flag resolving contract for flagd.
+ * A generic flag resolving contract for flagd.
  */
 public interface Resolver {
     void init() throws Exception;