Use compare and set to make thread safe

Author: dave-fn

core/auth/src/main/java/software/amazon/awssdk/auth/credentials/ProfileCredentialsProvider.java

@@ -17,6 +17,7 @@
 
 import java.util.Objects;
 import java.util.Optional;
+import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Consumer;
 import java.util.function.Supplier;
 import software.amazon.awssdk.annotations.SdkPublicApi;
@@ -49,10 +50,10 @@ public final class ProfileCredentialsProvider
                SdkAutoCloseable,
                ToCopyableBuilder<ProfileCredentialsProvider.Builder, ProfileCredentialsProvider> {
 
-    private AwsCredentialsProvider credentialsProvider;
+    private final AtomicReference<AwsCredentialsProvider> credentialsProvider = new AtomicReference<>();
     private final RuntimeException loadException;
     private final Supplier<ProfileFile> profileFile;
-    private volatile ProfileFile currentProfileFile;
+    private final AtomicReference<ProfileFile> currentProfileFile = new AtomicReference<>();
     private final String profileName;
     private final Supplier<ProfileFile> defaultProfileFileLoader;
 
@@ -116,32 +117,21 @@ public AwsCredentials resolveCredentials() {
             throw loadException;
         }
 
+        ProfileFile current = currentProfileFile.get();
         ProfileFile cachedOrRefreshedProfileFile = refreshProfileFile();
-        if (isNewProfileFile(cachedOrRefreshedProfileFile)) {
-            currentProfileFile = cachedOrRefreshedProfileFile;
+        if (!Objects.equals(current, cachedOrRefreshedProfileFile)
+            && currentProfileFile.compareAndSet(current, cachedOrRefreshedProfileFile)) {
             handleProfileFileReload(cachedOrRefreshedProfileFile);
         }
 
-        return credentialsProvider.resolveCredentials();
-    }
-
-    private void handleProfileFileReload(ProfileFile profileFile) {
-        credentialsProvider = createCredentialsProvider(profileFile, profileName);
-    }
-
-    private ProfileFile refreshProfileFile() {
-        return profileFile.get();
-    }
-
-    private boolean isNewProfileFile(ProfileFile profileFile) {
-        return !Objects.equals(currentProfileFile, profileFile);
+        return credentialsProvider.get().resolveCredentials();
     }
 
     @Override
     public String toString() {
         return ToString.builder("ProfileCredentialsProvider")
                        .add("profileName", profileName)
-                       .add("profileFile", currentProfileFile)
+                       .add("profileFile", currentProfileFile.get())
                        .build();
     }
 
@@ -155,6 +145,14 @@ public void close() {
         IoUtils.closeIfCloseable(credentialsProvider, null);
     }
 
+    private void handleProfileFileReload(ProfileFile profileFile) {
+        credentialsProvider.set(createCredentialsProvider(profileFile, profileName));
+    }
+
+    private ProfileFile refreshProfileFile() {
+        return profileFile.get();
+    }
+
     @Override
     public Builder toBuilder() {
         return new BuilderImpl(this);

core/auth/src/main/java/software/amazon/awssdk/auth/token/credentials/ProfileTokenProvider.java

@@ -17,6 +17,7 @@
 
 import java.util.Objects;
 import java.util.Optional;
+import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Supplier;
 import software.amazon.awssdk.annotations.SdkPublicApi;
 import software.amazon.awssdk.annotations.SdkTestInternalApi;
@@ -38,10 +39,11 @@
  */
 @SdkPublicApi
 public final class ProfileTokenProvider implements SdkTokenProvider, SdkAutoCloseable {
-    private SdkTokenProvider tokenProvider;
+
+    private final AtomicReference<SdkTokenProvider> tokenProvider = new AtomicReference<>();
     private final RuntimeException loadException;
     private final Supplier<ProfileFile> profileFile;
-    private volatile ProfileFile currentProfileFile;
+    private final AtomicReference<ProfileFile> currentProfileFile = new AtomicReference<>();
     private final String profileName;
 
     /**
@@ -100,20 +102,21 @@ public SdkToken resolveToken() {
             throw loadException;
         }
 
+        ProfileFile current = currentProfileFile.get();
         ProfileFile cachedOrRefreshedProfileFile = refreshProfileFile();
-        if (isNewProfileFile(cachedOrRefreshedProfileFile)) {
-            currentProfileFile = cachedOrRefreshedProfileFile;
+        if (!Objects.equals(current, cachedOrRefreshedProfileFile)
+            && currentProfileFile.compareAndSet(current, cachedOrRefreshedProfileFile)) {
             handleProfileFileReload(cachedOrRefreshedProfileFile);
         }
 
-        return tokenProvider.resolveToken();
+        return tokenProvider.get().resolveToken();
     }
 
     @Override
     public String toString() {
         return ToString.builder("ProfileTokenProvider")
                        .add("profileName", profileName)
-                       .add("profileFile", currentProfileFile)
+                       .add("profileFile", currentProfileFile.get())
                        .build();
     }
 
@@ -135,17 +138,13 @@ private SdkTokenProvider createTokenProvider(ProfileFile profileFile, String pro
     }
 
     private void handleProfileFileReload(ProfileFile profileFile) {
-        tokenProvider = createTokenProvider(profileFile, profileName);
+        tokenProvider.set(createTokenProvider(profileFile, profileName));
     }
 
     private ProfileFile refreshProfileFile() {
         return profileFile.get();
     }
 
-    private boolean isNewProfileFile(ProfileFile profileFile) {
-        return !Objects.equals(currentProfileFile, profileFile);
-    }
-
     /**
      * A builder for creating a custom {@link ProfileTokenProvider}.
      */