Idempotent Requests Implementation

Author: DrMimik

parse/src/main/java/com/parse/ParseException.java

@@ -102,6 +102,8 @@ public class ParseException extends Exception {
     public static final int FILE_DELETE_ERROR = 153;
     /** Error code indicating that the application has exceeded its request limit. */
     public static final int REQUEST_LIMIT_EXCEEDED = 155;
+    /** Error code indicating that the request was a duplicate and has been discarded due to idempotency rules. */
+    public static final int DUPLICATE_REQUEST = 159;
     /** Error code indicating that the provided event name is invalid. */
     public static final int INVALID_EVENT_NAME = 160;
     /** Error code indicating that the username is missing or empty. */

parse/src/main/java/com/parse/ParseRESTCommand.java

@@ -35,9 +35,10 @@ class ParseRESTCommand extends ParseRequest<JSONObject> {
     /* package */ static final String HEADER_OS_VERSION = "X-Parse-OS-Version";
 
     /* package */ static final String HEADER_INSTALLATION_ID = "X-Parse-Installation-Id";
+    /* package */ static final String HEADER_REQUEST_ID = "X-Parse-Request-Id";
     /* package */ static final String USER_AGENT = "User-Agent";
-    private static final String HEADER_SESSION_TOKEN = "X-Parse-Session-Token";
-    private static final String HEADER_MASTER_KEY = "X-Parse-Master-Key";
+    /* package */ static final String HEADER_SESSION_TOKEN = "X-Parse-Session-Token";
+    /* package */ static final String HEADER_MASTER_KEY = "X-Parse-Master-Key";
     private static final String PARAMETER_METHOD_OVERRIDE = "_method";
 
     // Set via Parse.initialize(Configuration)
@@ -215,6 +216,20 @@ protected void addAdditionalHeaders(ParseHttpRequest.Builder requestBuilder) {
         if (masterKey != null) {
             requestBuilder.addHeader(HEADER_MASTER_KEY, masterKey);
         }
+        try {
+            JSONObject jsonObject = jsonParameters != null ? new JSONObject(jsonParameters.toString()) : new JSONObject();
+            // using header names so we don't override a parameter with the same key name,
+            // using all headers to insure the requestId generated doesn't conflict with the rest of the users
+            if (installationId != null)
+                jsonObject.put(HEADER_INSTALLATION_ID, installationId);
+            if (sessionToken != null)
+                jsonObject.put(HEADER_SESSION_TOKEN, sessionToken);
+            if (masterKey != null)
+                jsonObject.put(HEADER_MASTER_KEY, masterKey);
+            requestBuilder.addHeader(HEADER_REQUEST_ID, ParseDigestUtils.md5(toDeterministicString(jsonObject)));
+        } catch (JSONException e) {
+            throw new RuntimeException(e.getMessage());
+        }
     }
 
     @Override

parse/src/test/java/com/parse/ParseRESTUserCommandTest.java

@@ -19,13 +19,17 @@
 import java.net.URL;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Random;
+
+import org.json.JSONArray;
 import org.json.JSONObject;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 import org.skyscreamer.jsonassert.JSONCompareMode;
 
 public class ParseRESTUserCommandTest {
+    private static final String ALLOWED_CHARACTERS = "0123456789qwertyuiopasdfghjklzxcvbnm";
 
     @Before
     public void setUp() throws MalformedURLException {
@@ -163,5 +167,44 @@ public void testOnResponseAsync() {
         assertEquals(200, command.getStatusCode());
     }
 
+    @Test
+    public void testRequestIdHeader() throws Exception {
+        JSONArray nestedJSONArray = new JSONArray().put(true).put(1).put("test");
+        JSONObject nestedJSON =
+            new JSONObject().put("bool", false).put("int", 2).put("string", "test");
+        String sessionToken = generateRandomString(32);
+        String installationId = generateRandomString(32);
+        String masterKey = generateRandomString(32);
+        JSONObject json =
+            new JSONObject()
+                .put("json", nestedJSON)
+                .put("jsonArray", nestedJSONArray)
+                .put("bool", true)
+                .put("int", 3)
+                .put("string", "test");
+
+        String jsonString = ParseRESTCommand.toDeterministicString(json);
+
+        JSONObject jsonAgain = new JSONObject(jsonString);
+        jsonAgain.put(ParseRESTCommand.HEADER_INSTALLATION_ID, installationId);
+        jsonAgain.put(ParseRESTCommand.HEADER_SESSION_TOKEN, sessionToken);
+        jsonAgain.put(ParseRESTCommand.HEADER_MASTER_KEY, masterKey);
+        ParseRESTCommand restCommand = new ParseRESTCommand.Builder().jsonParameters(json)
+            .installationId(installationId).sessionToken(sessionToken).masterKey(masterKey)
+            .build();
+
+        ParseHttpRequest.Builder builder = new ParseHttpRequest.Builder();
+        restCommand.addAdditionalHeaders(builder);
+        assertEquals(ParseDigestUtils.md5(ParseRESTCommand.toDeterministicString(jsonAgain)), builder.build().getHeader(ParseRESTCommand.HEADER_REQUEST_ID));
+    }
+
+    private static String generateRandomString(final int sizeOfRandomString) {
+        final Random random = new Random();
+        final StringBuilder sb = new StringBuilder(sizeOfRandomString);
+        for (int i = 0; i < sizeOfRandomString; ++i)
+            sb.append(ALLOWED_CHARACTERS.charAt(random.nextInt(ALLOWED_CHARACTERS.length())));
+        return sb.toString();
+    }
+
     // endregion
 }