Merge pull request #277 from Microsoft/feature/ssl_exception_retry

 #270 Retry transient ssl exceptions

sdk/mobile-center/src/androidTest/java/com/microsoft/azure/mobile/ingestion/http/HttpUtilsAndroidTest.java

@@ -9,6 +9,10 @@
 import java.net.SocketException;
 import java.net.SocketTimeoutException;
 import java.net.UnknownHostException;
+import java.security.cert.CertPathValidatorException;
+
+import javax.net.ssl.SSLException;
+import javax.net.ssl.SSLHandshakeException;
 
 import static com.microsoft.azure.mobile.ingestion.http.HttpUtils.isRecoverableError;
 import static junit.framework.Assert.assertFalse;
@@ -39,5 +43,11 @@ public void isRecoverableErrorTest() {
         assertFalse(isRecoverableError(new HttpException(413)));
         assertTrue(isRecoverableError(new HttpException(429)));
         assertTrue(isRecoverableError(new HttpException(401)));
+        assertTrue(isRecoverableError(new SSLException("Write error: ssl=0x59c28f90: I/O error during system call, Connection timed out")));
+        assertFalse(isRecoverableError(new SSLHandshakeException("java.security.cert.CertPathValidatorException: Trust anchor for certification path not found.")));
+        assertFalse(isRecoverableError(new SSLException(null, new CertPathValidatorException("Trust anchor for certification path not found."))));
+        assertFalse(isRecoverableError(new SSLException("java.lang.RuntimeException: Unexpected error: java.security.InvalidAlgorithmParameterException: the trustAnchors parameter must be non-empty")));
+        assertTrue(isRecoverableError(new SSLException("Read error: ssl=0x9dd07200: I/O error during system call, Connection reset by peer")));
+        assertTrue(isRecoverableError(new SSLException("SSL handshake aborted: ssl=0x1cc160: I/O error during system call, Connection reset by peer")));
     }
 }

sdk/mobile-center/src/main/java/com/microsoft/azure/mobile/ingestion/http/HttpUtils.java

@@ -6,29 +6,60 @@
 import java.io.InterruptedIOException;
 import java.net.SocketException;
 import java.net.UnknownHostException;
+import java.util.regex.Pattern;
 
+import javax.net.ssl.SSLException;
+
+/**
+ * HTTP utilities.
+ */
 public final class HttpUtils {
 
+    /**
+     * Types of exception that can be retried, no matter what the details are. Sub-classes are included.
+     */
     private static final Class[] RECOVERABLE_EXCEPTIONS = {
             EOFException.class,
             InterruptedIOException.class,
             SocketException.class,
             UnknownHostException.class
     };
 
+    /**
+     * Some transient exceptions can only be detected by interpreting the message...
+     */
+    private static Pattern CONNECTION_ISSUE_PATTERN = Pattern.compile("connection (time|reset)");
+
     @VisibleForTesting
     HttpUtils() {
     }
 
+    /**
+     * Check whether an exception/error describes a recoverable error or not.
+     *
+     * @param t exception or error.
+     * @return true if the exception/error should be retried, false otherwise.
+     */
     public static boolean isRecoverableError(Throwable t) {
+
+        /* Check HTTP exception details. */
         if (t instanceof HttpException) {
             HttpException exception = (HttpException) t;
             int code = exception.getStatusCode();
             return code >= 500 || code == 408 || code == 429 || code == 401;
         }
+
+        /* Check for a generic exception to retry. */
         for (Class<?> type : RECOVERABLE_EXCEPTIONS)
             if (type.isAssignableFrom(t.getClass()))
                 return true;
+
+        /* Check corner cases. */
+        if (t instanceof SSLException) {
+            String message = t.getMessage();
+            if (message != null && CONNECTION_ISSUE_PATTERN.matcher(message.toLowerCase()).find())
+                return true;
+        }
         return false;
     }
 }