Add custom logger (#203)

https://linear.app/statsig/issue/SDK-86/custom-logger-for-java-server

Replace println() with a callback, default still prints out to console

Author: xinlili-statsig

src/main/kotlin/com/statsig/sdk/ErrorBoundary.kt

@@ -102,8 +102,7 @@ internal class ErrorBoundary(private val apiKey: String, private val options: St
             throw ex
         }
 
-        println("[Statsig]: An unexpected exception occurred.")
-        println(ex)
+        options.customLogger.warning("[Statsig]: An unexpected exception occurred: $ex")
 
         logException(tag, ex, configName)
     }

src/main/kotlin/com/statsig/sdk/Evaluator.kt

@@ -374,7 +374,7 @@ internal class Evaluator(
                 conditionFromString(condition.type)
             } catch (e: java.lang.IllegalArgumentException) {
                 errorBoundary.logException("evaluateCondition:condition", e)
-                println("[Statsig]: An exception was caught:  $e")
+                options.customLogger.warning("[Statsig]: An exception was caught:  $e")
                 null
             }
 
@@ -872,7 +872,7 @@ internal class Evaluator(
             false
         } catch (e: Exception) {
             errorBoundary.logException("versionCompareHelper", e)
-            println("[Statsig]: An exception was caught:  $e")
+            options.customLogger.warning("[Statsig]: An exception was caught:  $e")
             false
         }
     }

src/main/kotlin/com/statsig/sdk/SpecStore.kt

@@ -109,7 +109,7 @@ internal class SpecStore constructor(
             configString = gson.toJson(configSpecs)
         } catch (e: Exception) {
             errorBoundary.logException("fireRulesUpdatedCallback", e)
-            println("[Statsig]: An exception was caught:  $e")
+            options.customLogger.warning("[Statsig]: An exception was caught:  $e")
         }
 
         if (configString.isEmpty()) {
@@ -241,7 +241,7 @@ internal class SpecStore constructor(
             diagnostics.markEnd(KeyType.GET_ID_LIST, true, StepType.PROCESS, additionalMarker = Marker(url = list.url))
         } catch (e: Exception) {
             errorBoundary.logException("downloadIDList", e)
-            println("[Statsig]: An exception was caught:  $e")
+            options.customLogger.warning("[Statsig]: An exception was caught:  $e")
             diagnostics.markEnd(KeyType.GET_ID_LIST, false, StepType.NETWORK_REQUEST, additionalMarker = Marker(url = list.url))
         } finally {
             response?.close()
@@ -431,7 +431,7 @@ internal class SpecStore constructor(
             return gson.fromJson(specs, APIDownloadedConfigs::class.java)
         } catch (e: Exception) {
             errorBoundary.logException("parseConfigSpecs", e)
-            println("[Statsig]: An exception was caught:  $e")
+            options.customLogger.warning("[Statsig]: An exception was caught:  $e")
         }
         return null
     }
@@ -450,7 +450,7 @@ internal class SpecStore constructor(
             return configs
         } catch (e: Exception) {
             errorBoundary.logException("downloadConfigSpecs", e)
-            println("[Statsig]: An exception was caught:  $e")
+            options.customLogger.warning("[Statsig]: An exception was caught:  $e")
         } finally {
             response?.close()
         }

src/main/kotlin/com/statsig/sdk/Statsig.kt

@@ -639,7 +639,11 @@ class Statsig {
         private fun checkInitialized(): Boolean {
             val initialized = isInitialized()
             if (!initialized) {
-                println("Call and wait for initialize to complete before calling SDK methods.")
+                if (::statsigServer.isInitialized) {
+                    statsigServer.getCustomLogger().warning("Call and wait for initialize to complete before calling SDK methods.")
+                } else {
+                    println("Call and wait for initialize to complete before calling SDK methods.")
+                }
             }
             return initialized
         }

src/main/kotlin/com/statsig/sdk/StatsigNetwork.kt

@@ -215,7 +215,7 @@ internal class StatsigNetwork(
             diagnostics?.endNetworkRequestDiagnostics(diagnosticsKey, response.isSuccessful, response)
             return response
         } catch (e: Exception) {
-            println("[Statsig]: An exception was caught: $e")
+            options.customLogger.warning("[Statsig]: An exception was caught: $e")
             if (e is JsonParseException) {
                 errorBoundary.logException("postImpl", e)
             }
@@ -257,7 +257,7 @@ internal class StatsigNetwork(
                         }
                     }
                 } catch (e: Exception) {
-                    println("[Statsig]: An exception was caught: $e")
+                    options.customLogger.warning("[Statsig]: An exception was caught: $e")
                     if (e is JsonParseException) {
                         errorBoundary.logException("retryPostLogs", e)
                     }

src/main/kotlin/com/statsig/sdk/StatsigOptions.kt

@@ -4,6 +4,16 @@ private const val TIER_KEY: String = "tier"
 private const val DEFAULT_INIT_TIME_OUT_MS: Long = 3000L
 private const val CONFIG_SYNC_INTERVAL_MS: Long = 10 * 1000
 private const val ID_LISTS_SYNC_INTERVAL_MS: Long = 60 * 1000
+private val defaultLogger = object : LoggerInterface {
+
+    override fun warning(message: String) {
+        println(message)
+    }
+
+    override fun info(message: String) {
+        println(message)
+    }
+}
 
 /**
  * A SAM for Java compatibility
@@ -13,6 +23,11 @@ fun interface RulesUpdatedCallback {
     fun accept(rules: String)
 }
 
+interface LoggerInterface {
+    fun warning(message: String)
+    fun info(message: String)
+}
+
 /**
  * An object of properties for initializing the sdk with advanced options
  * @property api the api endpoint to use for initialization and logging
@@ -30,6 +45,7 @@ class StatsigOptions(
     var rulesetsSyncIntervalMs: Long = CONFIG_SYNC_INTERVAL_MS,
     var idListsSyncIntervalMs: Long = ID_LISTS_SYNC_INTERVAL_MS,
     var dataStore: IDataStore? = null,
+    var customLogger: LoggerInterface = defaultLogger,
 ) {
     constructor(api: String) : this(api, DEFAULT_INIT_TIME_OUT_MS)
     constructor(initTimeoutMs: Long) : this(null, initTimeoutMs)

src/main/kotlin/com/statsig/sdk/StatsigServer.kt

@@ -167,6 +167,7 @@ sealed class StatsigServer {
     abstract fun shutdown()
 
     internal abstract suspend fun flush()
+    internal abstract fun getCustomLogger(): LoggerInterface
 
     companion object {
 
@@ -661,6 +662,10 @@ private class StatsigServerImpl() :
         logger.flush()
     }
 
+    override fun getCustomLogger(): LoggerInterface {
+        return options.customLogger
+    }
+
     private suspend fun getLayerImpl(user: StatsigUser, layerName: String, disableExposure: Boolean, onExposure: OnLayerExposure? = null): Layer {
         if (!isSDKInitialized()) {
             return Layer.empty(layerName)
@@ -748,11 +753,11 @@ private class StatsigServerImpl() :
 
     private fun isSDKInitialized(): Boolean {
         if (statsigJob.isCancelled || statsigJob.isCompleted) {
-            println("StatsigServer was shutdown")
+            options.customLogger.info("StatsigServer was shutdown")
             return false
         }
         if (!this::configEvaluator.isInitialized || !configEvaluator.isInitialized) { // If the server was never initialized
-            println("Must initialize a server before calling other APIs")
+            options.customLogger.warning("Must initialize a server before calling other APIs")
             return false
         }
         return true
@@ -803,7 +808,7 @@ private class StatsigServerImpl() :
             if (!t.name.equals(currentThread.name)) {
                 throw e
             }
-            println("[Statsig]: Shutting down Statsig because of unhandled exception from your server")
+            server.getCustomLogger().info("[Statsig]: Shutting down Statsig because of unhandled exception from your server")
             server.shutdown()
             throw e
         }

src/test/java/com/statsig/sdk/CustomLoggerTest.kt

@@ -0,0 +1,30 @@
+package com.statsig.sdk
+
+import kotlinx.coroutines.runBlocking
+import org.junit.Test
+
+class CustomLoggerTest {
+    val warningMessage = mutableListOf<String>()
+    val infoMessage = mutableListOf<String>()
+    val server = StatsigServer.create()
+    val fakeLogger = object : LoggerInterface {
+        override fun warning(message: String) {
+            println(message)
+            warningMessage.add(message)
+        }
+
+        override fun info(message: String) {
+            println(message)
+            infoMessage.add(message)
+        }
+    }
+
+    @Test
+    fun testExceptionLogger() = runBlocking {
+        server.initialize("server-secret", StatsigOptions(customLogger = fakeLogger))
+        assert(warningMessage.size == 2) // One from network one from gson
+        server.shutdown()
+        server.checkGate(StatsigUser("user_id"), "test_gate")
+        assert(infoMessage.size == 1)
+    }
+}

src/test/java/com/statsig/sdk/DiagnosticsTest.kt

@@ -14,6 +14,7 @@ import okhttp3.mockwebserver.RecordedRequest
 import org.junit.After
 import org.junit.Assert
 import org.junit.Before
+import org.junit.Rule
 import org.junit.Test
 import java.lang.StringBuilder
 
@@ -27,6 +28,9 @@ class DiagnosticsTest {
     lateinit var downloadConfigSpecsResponse: String
 
     private val user = StatsigUser("testUser")
+    @JvmField
+    @Rule
+    val retry = RetryRule(3)
 
     @Before
     fun setup() {

src/test/java/com/statsig/sdk/EvaluatorTest.java

@@ -29,6 +29,7 @@ public void testIP3Country() throws NoSuchFieldException, IllegalAccessException
 
         APIDownloadedConfigs configs = gson.fromJson(CONFIG_SPEC, APIDownloadedConfigs.class);
         specStore.setDownloadedConfigs(configs,false);
+        TestUtilJava.setInitReasonFromSpecStore(specStore, EvaluationReason.NETWORK);
 
         // IP Passes, but ID doesnt pass rollout percentage
         StatsigUser user = new StatsigUser("123");