Add customizable logging system

README.md

@@ -79,3 +79,46 @@ public class MyClass {
 
 To find usage documentation, visit our docs for [Local Bucketing](https://docs.devcycle.com/docs/sdk/server-side-sdks/java-local).
 
+## Logging
+
+The DevCycle SDK logs to **stdout** by default and does not require any specific logging package. To integrate with your 
+own logging system, such as Java Logging or SLF4J, you can create a wrapper that implements the `IDVCLogger` interface. 
+Then you can set the logger into the Java Server SDK setting the Custom Logger property in the options object used to 
+initialize the client.
+
+```java
+
+```java
+// Create your logging wrapper
+IDVCLogger loggingWrapper = new IDVCLogger() {
+    @Override
+    public void debug(String message) {
+        // Your logging implementation here
+    }
+
+    @Override
+    public void info(String message) {
+        // Your logging implementation here
+    }
+
+    @Override
+    public void warn(String message) {
+        // Your logging implementation here
+    }
+
+    @Override
+    public void error(String message) {
+        // Your logging implementation here
+    }
+};
+
+// Set the logger in the options before creating the DVCLocalClient
+DVCLocalOptions options = DVCLocalOptions.builder().customLogger(loggingWrapper).build();
+DVCLocalClient dvcClient = new DVCLocalClient("YOUR_DVC_SERVER_SDK_KEY", options);
+
+// Or for DVCCloudClient
+DVCCloudOptions options = DVCCloudOptions.builder().customLogger(loggingWrapper).build();
+DVCCloudClient dvcClient = new DVCCloudClient("YOUR_DVC_SERVER_SDK_KEY", options);
+```
+
+You can also disable all logging by setting the custom logger to `new SimpleDVCLogger(SimpleDVCLogger.Level.OFF)`.

src/main/java/com/devcycle/sdk/server/cloud/api/DVCCloudClient.java

@@ -3,6 +3,7 @@
 import com.devcycle.sdk.server.cloud.model.DVCCloudOptions;
 import com.devcycle.sdk.server.common.api.IDVCApi;
 import com.devcycle.sdk.server.common.exception.DVCException;
+import com.devcycle.sdk.server.common.logging.DVCLogger;
 import com.devcycle.sdk.server.common.model.*;
 import com.devcycle.sdk.server.common.model.Variable.TypeEnum;
 import com.fasterxml.jackson.annotation.JsonInclude;
@@ -37,6 +38,11 @@ public DVCCloudClient(String sdkKey, DVCCloudOptions options) {
       throw new IllegalArgumentException("Invalid environment key provided. Please call initialize with a valid server environment key");
     }
 
+    if(options.getCustomLogger() != null)
+    {
+        DVCLogger.setCustomLogger(options.getCustomLogger());
+    }
+
     this.dvcOptions = options;
     api = new DVCCloudApiClient(sdkKey, options).initialize();
     OBJECT_MAPPER.setSerializationInclusion(JsonInclude.Include.NON_NULL);

src/main/java/com/devcycle/sdk/server/cloud/model/DVCCloudOptions.java

@@ -1,5 +1,6 @@
 package com.devcycle.sdk.server.cloud.model;
 
+import com.devcycle.sdk.server.common.logging.IDVCLogger;
 import com.devcycle.sdk.server.common.model.IDVCOptions;
 
 import lombok.Builder;
@@ -14,5 +15,8 @@ public class DVCCloudOptions {
     @Builder.Default
     private String baseURLOverride = null;
 
+    @Builder.Default
+    private IDVCLogger customLogger = null;
+
     public static class DVCCloudOptionsBuilder implements IDVCOptions { }
 }

src/main/java/com/devcycle/sdk/server/common/logging/DVCLogger.java

@@ -0,0 +1,42 @@
+package com.devcycle.sdk.server.common.logging;
+/**
+ * DVCLogger is a simple central entrypoint for the SDK to log messages without pinning the SDK to a
+ * specific logging framework. By default it logs to stdout but can e overriden by calling setCustomLogger()
+ */
+public class DVCLogger {
+    private static IDVCLogger logger = new SimpleDVCLogger(SimpleDVCLogger.Level.INFO);
+    public static void setCustomLogger(IDVCLogger logger) {
+        DVCLogger.logger = logger;
+    }
+
+    public static void debug(String message) {
+        if(logger != null){
+            logger.debug(message);
+        }
+    }
+
+    public static void info(String message) {
+        if(logger != null) {
+            logger.info(message);
+        }
+    }
+
+    public static void warning(String message) {
+        if(logger != null) {
+            logger.warning(message);
+        }
+    }
+
+    public static void error(String message) {
+            if(logger != null) {
+                logger.error(message);
+            }
+    }
+
+    public static void error(String message, Throwable t) {
+            if(logger != null) {
+                logger.error(message, t);
+            }
+    }
+}
+

src/main/java/com/devcycle/sdk/server/common/logging/IDVCLogger.java

@@ -0,0 +1,13 @@
+package com.devcycle.sdk.server.common.logging;
+
+/**
+ * A simple interface for logging inside the SDK. Implement this interface and pass it to the SDK to override the
+ * default behavior. Use this interface to integrate with an existing logging framework such as Java Logging, Log4j or SLF4J
+ */
+public interface IDVCLogger {
+    void debug(String message);
+    void info(String message);
+    void warning(String message);
+    void error(String message);
+    void error(String message, Throwable t);
+}

src/main/java/com/devcycle/sdk/server/common/logging/SimpleDVCLogger.java

@@ -0,0 +1,54 @@
+package com.devcycle.sdk.server.common.logging;
+
+/**
+ * Basic implementation of IDVCLogger that logs to stdout with some basic log level filtering.
+ */
+public class SimpleDVCLogger implements IDVCLogger {
+    public enum Level {
+        DEBUG,
+        INFO,
+        WARNING,
+        ERROR,
+        OFF,
+    }
+    private Level level;
+    public SimpleDVCLogger(Level level) {
+        this.level = level;
+    }
+
+    @Override
+    public void debug(String message) {
+        if(this.level.ordinal() == Level.DEBUG.ordinal())
+        {
+            System.out.println(message);
+        }
+    }
+
+    @Override
+    public void info(String message) {
+        if(this.level.ordinal() <= Level.INFO.ordinal()) {
+            System.out.println(message);
+        }
+    }
+
+    @Override
+    public void warning(String message) {
+        if(this.level.ordinal() <= Level.WARNING.ordinal()) {
+            System.out.println(message);
+        }
+    }
+
+    @Override
+    public void error(String message) {
+        if(this.level.ordinal() <= Level.ERROR.ordinal()) {
+            System.out.println(message);
+        }
+    }
+
+    @Override
+    public void error(String message, Throwable t) {
+        if(this.level.ordinal() <= Level.ERROR.ordinal()) {
+            System.out.println(message);
+        }
+    }
+}

src/main/java/com/devcycle/sdk/server/common/model/PlatformData.java

@@ -1,5 +1,6 @@
 package com.devcycle.sdk.server.common.model;
 
+import com.devcycle.sdk.server.common.logging.DVCLogger;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonValue;
 import com.fasterxml.jackson.core.JsonProcessingException;
@@ -11,11 +12,12 @@
 
 import java.net.InetAddress;
 import java.net.UnknownHostException;
+import java.util.logging.Level;
+import java.util.logging.Logger;
 
 @Data
 @Builder
 @JsonInclude(JsonInclude.Include.NON_NULL)
-
 public class PlatformData {
     public PlatformData(String platform, String platformVersion, SdkTypeEnum sdkType, String sdkVersion, String hostname) {
         this.platform = platform;
@@ -25,7 +27,7 @@ public PlatformData(String platform, String platformVersion, SdkTypeEnum sdkType
         try {
             this.hostname = hostname != null ? hostname : InetAddress.getLocalHost().getHostName();
         } catch (UnknownHostException e) {
-            System.out.println("Error getting hostname: " + e.getMessage());
+            DVCLogger.warning("Error getting system hostname: " + e.getMessage());
             this.hostname = "";
         }
     }
@@ -64,7 +66,7 @@ public String toString() {
             mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
             platformDataString = mapper.writeValueAsString(platformData);
         } catch (JsonProcessingException e) {
-            System.out.println("Error reading platformData: " + e.getMessage());
+            DVCLogger.warning("Error reading platformData: " + e.getMessage());
         }
         return platformDataString;
     }

src/main/java/com/devcycle/sdk/server/local/api/DVCLocalClient.java

@@ -10,6 +10,7 @@
 import com.devcycle.sdk.server.local.protobuf.SDKVariable_PB;
 import com.devcycle.sdk.server.local.protobuf.VariableForUserParams_PB;
 import com.devcycle.sdk.server.local.protobuf.VariableType_PB;
+import com.devcycle.sdk.server.common.logging.DVCLogger;
 import com.devcycle.sdk.server.local.utils.ProtobufUtils;
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
@@ -27,7 +28,6 @@ public final class DVCLocalClient {
 
   private EventQueueManager eventQueueManager;
 
-
   public DVCLocalClient(String sdkKey) {
     this(sdkKey, DVCLocalOptions.builder().build());
   }
@@ -40,8 +40,12 @@ public DVCLocalClient(String sdkKey, DVCLocalOptions dvcOptions) {
       throw new IllegalArgumentException("Invalid SDK key provided. Please call initialize with a valid server SDK key");
     }
 
+    if(dvcOptions.getCustomLogger() != null) {
+      DVCLogger.setCustomLogger(dvcOptions.getCustomLogger());
+    }
+
     if(!isValidRuntime()){
-        System.out.println("Invalid architecture. The DVCLocalClient requires a 64-bit, x86 runtime environment.");
+      DVCLogger.warning("Invalid architecture. The DVCLocalClient requires a 64-bit, x86 runtime environment.");
     }
 
     localBucketing.setPlatformData(PlatformData.builder().build().toString());
@@ -51,7 +55,7 @@ public DVCLocalClient(String sdkKey, DVCLocalOptions dvcOptions) {
     try {
       eventQueueManager = new EventQueueManager(sdkKey, localBucketing, dvcOptions);
     } catch (Exception e) {
-      System.out.printf("Error creating event queue due to error: %s%n", e.getMessage());
+      DVCLogger.warning("Error creating event queue due to error: " + e.getMessage());
     }
   }
 
@@ -81,7 +85,7 @@ public Map<String, Feature> allFeatures(User user) {
     try {
       bucketedUserConfig = localBucketing.generateBucketedConfig(sdkKey, user);
     } catch (JsonProcessingException e) {
-      System.out.printf("Unable to parse JSON for allFeatures due to error: %s%n", e.getMessage());
+      DVCLogger.info("Unable to parse JSON for allFeatures due to error: " + e.getMessage());
       return Collections.emptyMap();
     }
     return bucketedUserConfig.features;
@@ -130,11 +134,11 @@ public <T> Variable<T> variable(User user, String key, T defaultValue) {
             .build();
 
     if (!isInitialized()) {
-      System.out.println("Variable called before DVCClient has initialized, returning default value");
+      DVCLogger.info("Variable called before DVCClient has initialized, returning default value");
       try {
         eventQueueManager.queueAggregateEvent(Event.builder().type("aggVariableDefaulted").target(key).build(), null);
       } catch (Exception e) {
-        System.out.printf("Unable to parse aggVariableDefaulted event for Variable %s due to error: %s", key, e.toString());
+        DVCLogger.error("Unable to parse aggVariableDefaulted event for Variable " + key + " due to error: " + e, e);
       }
       return defaultVariable;
     }
@@ -157,13 +161,13 @@ public <T> Variable<T> variable(User user, String key, T defaultValue) {
       } else {
         SDKVariable_PB sdkVariable = SDKVariable_PB.parseFrom(variableData);
         if(sdkVariable.getType() != pbVariableType) {
-          System.out.printf("Variable type mismatch, returning default value");
+          DVCLogger.info("Variable type mismatch, returning default value");
           return defaultVariable;
         }
         return ProtobufUtils.createVariable(sdkVariable, defaultValue);
       }
     } catch (Exception e) {
-      System.out.printf("Unable to evaluate Variable %s due to error: %s", key, e);
+      DVCLogger.error("Unable to evaluate Variable " + key + " due to error: " + e, e);
     }
     return defaultVariable;
   }
@@ -185,7 +189,7 @@ public Map<String, BaseVariable> allVariables(User user) {
     try {
       bucketedUserConfig = localBucketing.generateBucketedConfig(sdkKey, user);
     } catch (JsonProcessingException e) {
-      System.out.printf("Unable to parse JSON for allVariables due to error: %s%n", e.getMessage());
+      DVCLogger.info("Unable to parse JSON for allVariables due to error: " + e.getMessage());
       return Collections.emptyMap();
     }
     return bucketedUserConfig.variables;
@@ -207,14 +211,14 @@ public void track(User user, Event event) {
     try {
       eventQueueManager.queueEvent(user, event);
     } catch (Exception e) {
-      System.out.printf("Failed to queue event due to error: %s%n", e.getMessage());
+      DVCLogger.warning("Failed to queue event due to error: " + e.getMessage());
     }
   }
 
   public void setClientCustomData(Map<String,Object> customData) {
     if (!isInitialized())
     {
-     System.out.println("SetClientCustomData called before DVCClient has initialized");
+      DVCLogger.info("SetClientCustomData called before DVCClient has initialized");
      return;
     }
 
@@ -224,7 +228,7 @@ public void setClientCustomData(Map<String,Object> customData) {
         String customDataJSON = mapper.writeValueAsString(customData);
         localBucketing.setClientCustomData(this.sdkKey, customDataJSON);
       } catch(Exception e) {
-        System.out.printf("Failed to set custom data: %s%n", e.getMessage());
+        DVCLogger.error("Failed to set custom data due to error: " + e.getMessage(), e);
       }
     }
   }

src/main/java/com/devcycle/sdk/server/local/bucketing/LocalBucketing.java

@@ -1,5 +1,6 @@
 package com.devcycle.sdk.server.local.bucketing;
 
+import com.devcycle.sdk.server.common.logging.DVCLogger;
 import com.devcycle.sdk.server.common.model.User;
 import com.devcycle.sdk.server.common.model.Variable;
 import com.devcycle.sdk.server.local.model.BucketedUserConfig;
@@ -20,6 +21,8 @@
 import java.text.SimpleDateFormat;
 import java.util.*;
 import java.util.concurrent.atomic.AtomicReference;
+import java.util.logging.Level;
+import java.util.logging.Logger;
 
 import static io.github.kawamuray.wasmtime.WasmValType.F64;
 import static io.github.kawamuray.wasmtime.WasmValType.I32;
@@ -38,6 +41,8 @@ public class LocalBucketing {
     private final int WASM_OBJECT_ID_STRING = 1;
     private final int WASM_OBJECT_ID_UINT8ARRAY = 9;
 
+    private Logger logger = Logger.getLogger(LocalBucketing.class.getName());
+
     public LocalBucketing() {
         OBJECT_MAPPER.setSerializationInclusion(JsonInclude.Include.NON_NULL);
 
@@ -76,7 +81,7 @@ private Collection<Extern> setImportsOnLinker() {
 
         Func consoleLogFn = WasmFunctions.wrap(store, I32, (addr) -> {
             String message = readWasmString(((Number) addr).intValue());
-            System.out.println(message);
+            DVCLogger.warning("WASM error: " + message);
         });
         linker.define("env", "console.log", Extern.fromFunc(consoleLogFn));