Change ConfigProvider to iterate from lowest to highest precedence so…

dd-smoke-tests/log-injection/src/main/java/datadog/smoketest/loginjection/BaseApplication.java

@@ -44,7 +44,8 @@ public void run() throws InterruptedException {
   }
 
   private static Object getLogInjectionEnabled() {
-    ConfigSetting configSetting = ConfigCollector.get().collect().get(LOGS_INJECTION_ENABLED);
+    ConfigSetting configSetting =
+        ConfigCollector.get().getAppliedConfigSetting(LOGS_INJECTION_ENABLED);
     if (configSetting == null) {
       return null;
     }

internal-api/src/main/java/datadog/trace/api/ConfigCollector.java

@@ -16,42 +16,58 @@ public class ConfigCollector {
   private static final AtomicReferenceFieldUpdater<ConfigCollector, Map> COLLECTED_UPDATER =
       AtomicReferenceFieldUpdater.newUpdater(ConfigCollector.class, Map.class, "collected");
 
-  private volatile Map<String, ConfigSetting> collected = new ConcurrentHashMap<>();
+  private volatile Map<String, Map<ConfigOrigin, ConfigSetting>> collected =
+      new ConcurrentHashMap<>();
 
   public static ConfigCollector get() {
     return INSTANCE;
   }
 
+  /**
+   * Records the latest ConfigSetting for the given key and origin, replacing any previous value for
+   * that (key, origin) pair.
+   */
   public void put(String key, Object value, ConfigOrigin origin) {
     ConfigSetting setting = ConfigSetting.of(key, value, origin);
-    collected.put(key, setting);
+    Map<ConfigOrigin, ConfigSetting> originMap =
+        collected.computeIfAbsent(key, k -> new ConcurrentHashMap<>());
+    originMap.put(origin, setting); // replaces any previous value for this origin
   }
 
+  public void put(String key, Object value, ConfigOrigin origin, int seqId) {
+    ConfigSetting setting = ConfigSetting.of(key, value, origin, seqId);
+    Map<ConfigOrigin, ConfigSetting> originMap =
+        collected.computeIfAbsent(key, k -> new ConcurrentHashMap<>());
+    originMap.put(origin, setting); // replaces any previous value for this origin
+  }
+
+  // TODO: Does this need a counterpart with seqId?
   public void putAll(Map<String, Object> keysAndValues, ConfigOrigin origin) {
-    // attempt merge+replace to avoid collector seeing partial update
-    Map<String, ConfigSetting> merged =
-        new ConcurrentHashMap<>(keysAndValues.size() + collected.size());
     for (Map.Entry<String, Object> entry : keysAndValues.entrySet()) {
-      ConfigSetting setting = ConfigSetting.of(entry.getKey(), entry.getValue(), origin);
-      merged.put(entry.getKey(), setting);
-    }
-    while (true) {
-      Map<String, ConfigSetting> current = collected;
-      current.forEach(merged::putIfAbsent);
-      if (COLLECTED_UPDATER.compareAndSet(this, current, merged)) {
-        break; // success
-      }
-      // roll back to original update before next attempt
-      merged.keySet().retainAll(keysAndValues.keySet());
+      put(entry.getKey(), entry.getValue(), origin);
     }
   }
 
   @SuppressWarnings("unchecked")
-  public Map<String, ConfigSetting> collect() {
+  public Map<String, Map<ConfigOrigin, ConfigSetting>> collect() {
     if (!collected.isEmpty()) {
       return COLLECTED_UPDATER.getAndSet(this, new ConcurrentHashMap<>());
     } else {
       return Collections.emptyMap();
     }
   }
+
+  /**
+   * Returns the {@link ConfigSetting} with the highest seq_id for the given key, or {@code null} if
+   * no setting exists for that key.
+   */
+  public ConfigSetting getHighestSeqIdConfig(String key) {
+    Map<ConfigOrigin, ConfigSetting> originMap = collected.get(key);
+    if (originMap == null || originMap.isEmpty()) {
+      return null;
+    }
+    return originMap.values().stream()
+        .max(java.util.Comparator.comparingInt(setting -> setting.seqId))
+        .orElse(null);
+  }
 }

internal-api/src/main/java/datadog/trace/api/ConfigSetting.java

@@ -11,19 +11,27 @@ public final class ConfigSetting {
   public final String key;
   public final Object value;
   public final ConfigOrigin origin;
+  public final int seqId;
+
+  public static final int DEFAULT_SEQ_ID = 1;
 
   private static final Set<String> CONFIG_FILTER_LIST =
       new HashSet<>(
           Arrays.asList("DD_API_KEY", "dd.api-key", "dd.profiling.api-key", "dd.profiling.apikey"));
 
   public static ConfigSetting of(String key, Object value, ConfigOrigin origin) {
-    return new ConfigSetting(key, value, origin);
+    return new ConfigSetting(key, value, origin, 0);
+  }
+
+  public static ConfigSetting of(String key, Object value, ConfigOrigin origin, int seqId) {
+    return new ConfigSetting(key, value, origin, seqId);
   }
 
-  private ConfigSetting(String key, Object value, ConfigOrigin origin) {
+  private ConfigSetting(String key, Object value, ConfigOrigin origin, int seqId) {
     this.key = key;
     this.value = CONFIG_FILTER_LIST.contains(key) ? "<hidden>" : value;
     this.origin = origin;
+    this.seqId = seqId;
   }
 
   public String normalizedKey() {
@@ -99,12 +107,15 @@ public boolean equals(Object o) {
     if (this == o) return true;
     if (o == null || getClass() != o.getClass()) return false;
     ConfigSetting that = (ConfigSetting) o;
-    return key.equals(that.key) && Objects.equals(value, that.value) && origin == that.origin;
+    return key.equals(that.key)
+        && Objects.equals(value, that.value)
+        && origin == that.origin
+        && seqId == that.seqId;
   }
 
   @Override
   public int hashCode() {
-    return Objects.hash(key, value, origin);
+    return Objects.hash(key, value, origin, seqId);
   }
 
   @Override
@@ -117,6 +128,8 @@ public String toString() {
         + stringValue()
         + ", origin="
         + origin
+        + ", seqId="
+        + seqId
         + '}';
   }
 }

internal-api/src/main/java/datadog/trace/bootstrap/config/provider/CapturedEnvironmentConfigSource.java

@@ -15,8 +15,15 @@ public CapturedEnvironmentConfigSource(CapturedEnvironment env) {
   }
 
   @Override
-  protected String get(String key) {
-    return env.getProperties().get(key);
+  protected String get(String key) throws ConfigSourceException {
+    Object value = env.getProperties().get(key);
+    if (value == null) {
+      return null;
+    }
+    if (!(value instanceof String)) {
+      throw new ConfigSourceException(value);
+    }
+    return (String) value;
   }
 
   @Override