Reduce impact of CDS rate-limiting issues.

This will at least allow users with > RateLimit contacts to perform a successful sync. More work needs to be done here in the future to handle this better.

app/src/main/java/org/thoughtcrime/securesms/contacts/sync/ContactDiscoveryV2.java

@@ -26,7 +26,10 @@ import java.security.KeyStoreException;
 import java.security.NoSuchAlgorithmException;
 import java.security.SignatureException;
 import java.security.cert.CertificateException;
+import java.util.ArrayList;
 import java.util.Collections;
+import java.util.HashSet;
+import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import java.util.UUID;
@@ -38,6 +41,8 @@ class ContactDiscoveryV2 {
 
   private static final String TAG = Log.tag(ContactDiscoveryV2.class);
 
+  private static final int MAX_NUMBERS = 20_500;
+
   @WorkerThread
   static DirectoryResult getDirectoryResult(@NonNull Context context,
                                             @NonNull Set<String> databaseNumbers,
@@ -47,7 +52,14 @@ class ContactDiscoveryV2 {
     Set<String>                        allNumbers        = SetUtil.union(databaseNumbers, systemNumbers);
     FuzzyPhoneNumberHelper.InputResult inputResult       = FuzzyPhoneNumberHelper.generateInput(allNumbers, databaseNumbers);
     Set<String>                        sanitizedNumbers  = sanitizeNumbers(inputResult.getNumbers());
+    Set<String>                        ignoredNumbers    = new HashSet<>();
 
+    if (sanitizedNumbers.size() > MAX_NUMBERS) {
+      Set<String> randomlySelected = randomlySelect(sanitizedNumbers, MAX_NUMBERS);
+
+      ignoredNumbers   = SetUtil.difference(sanitizedNumbers, randomlySelected);
+      sanitizedNumbers = randomlySelected;
+    }
 
     SignalServiceAccountManager accountManager = ApplicationDependencies.getSignalServiceAccountManager();
     KeyStore                    iasKeyStore    = getIasKeyStore(context);
@@ -56,7 +68,7 @@ class ContactDiscoveryV2 {
       Map<String, UUID>                     results      = accountManager.getRegisteredUsers(iasKeyStore, sanitizedNumbers, BuildConfig.CDS_MRENCLAVE);
       FuzzyPhoneNumberHelper.OutputResultV2 outputResult = FuzzyPhoneNumberHelper.generateOutputV2(results, inputResult);
 
-      return new DirectoryResult(outputResult.getNumbers(), outputResult.getRewrites());
+      return new DirectoryResult(outputResult.getNumbers(), outputResult.getRewrites(), ignoredNumbers);
     } catch (SignatureException | UnauthenticatedQuoteException | UnauthenticatedResponseException | Quote.InvalidQuoteFormatException e) {
       Log.w(TAG, "Attestation error.", e);
       throw new IOException(e);
@@ -77,6 +89,13 @@ class ContactDiscoveryV2 {
     }).collect(Collectors.toSet());
   }
 
+  private static @NonNull Set<String> randomlySelect(@NonNull Set<String> numbers, int max) {
+    List<String> list = new ArrayList<>(numbers);
+    Collections.shuffle(list);
+
+    return new HashSet<>(list.subList(0, max));
+  }
+
   private static KeyStore getIasKeyStore(@NonNull Context context) {
     try {
       TrustStore contactTrustStore = new IasTrustStore(context);

app/src/main/java/org/thoughtcrime/securesms/contacts/sync/DirectoryHelper.java

@@ -235,6 +235,7 @@ public class DirectoryHelper {
     Set<RecipientId>         inactiveIds   = Stream.of(allNumbers)
                                                    .filterNot(activeNumbers::contains)
                                                    .filterNot(n -> result.getNumberRewrites().containsKey(n))
+                                                   .filterNot(n -> result.getIgnoredNumbers().contains(n))
                                                    .map(recipientDatabase::getOrInsertFromE164)
                                                    .collect(Collectors.toSet());
 
@@ -468,12 +469,15 @@ public class DirectoryHelper {
   static class DirectoryResult {
     private final Map<String, UUID>   registeredNumbers;
     private final Map<String, String> numberRewrites;
+    private final Set<String>         ignoredNumbers;
 
     DirectoryResult(@NonNull Map<String, UUID> registeredNumbers,
-                    @NonNull Map<String, String> numberRewrites)
+                    @NonNull Map<String, String> numberRewrites,
+                    @NonNull Set<String> ignoredNumbers)
     {
       this.registeredNumbers = registeredNumbers;
       this.numberRewrites    = numberRewrites;
+      this.ignoredNumbers    = ignoredNumbers;
     }
 
 
@@ -484,6 +488,10 @@ public class DirectoryHelper {
     @NonNull Map<String, String> getNumberRewrites() {
       return numberRewrites;
     }
+
+    @NonNull Set<String> getIgnoredNumbers() {
+      return ignoredNumbers;
+    }
   }
 
   private static class UnlistedResult {