6 files changed, 66 insertions, 11 deletions
diff --git a/src/objective-c/GRPCClient/GRPCCall.h b/src/objective-c/GRPCClient/GRPCCall.h
index b9e741dfa8..7645bb1d34 100644
--- a/src/objective-c/GRPCClient/GRPCCall.h
+++ b/src/objective-c/GRPCClient/GRPCCall.h
@@ -155,6 +155,18 @@ typedef NS_ENUM(NSUInteger, GRPCErrorCode) {
 };
 
 /**
+ * Safety remark of a gRPC method as defined in RFC 2616 Section 9.1
+ */
+typedef NS_ENUM(NSUInteger, GRPCCallSafety) {
+  /** Signal that there is no guarantees on how the call affects the server state. */
+  GRPCCallSafetyDefault = 0,
+  /** Signal that the call is idempotent. gRPC is free to use PUT verb. */
+  GRPCCallSafetyIdempotentRequest = 1,
+  /** Signal that the call is cacheable and will not affect server state. gRPC is free to use GET verb. */
+  GRPCCallSafetyCacheableRequest = 2,
+};
+
+/**
  * Keys used in |NSError|'s |userInfo| dictionary to store the response headers and trailers sent by
  * the server.
  */
@@ -233,6 +245,14 @@ extern id const kGRPCTrailersKey;
  */
 - (void)cancel;
 
+/**
+ * Set the call flag for a specific host path.
+ *
+ * Host parameter should not contain the scheme (http:// or https://), only the name or IP addr
+ * and the port number, for example @"localhost:5050".
+ */
++ (void)setCallSafety:(GRPCCallSafety)callSafety host:(NSString *)host path:(NSString *)path;
+
 // TODO(jcanizales): Let specify a deadline. As a category of GRXWriter?
 @end
 
diff --git a/src/objective-c/GRPCClient/GRPCCall.m b/src/objective-c/GRPCClient/GRPCCall.m
index b5d8309787..43204345f5 100644
--- a/src/objective-c/GRPCClient/GRPCCall.m
+++ b/src/objective-c/GRPCClient/GRPCCall.m
@@ -47,6 +47,7 @@
 
 NSString * const kGRPCHeadersKey = @"io.grpc.HeadersKey";
 NSString * const kGRPCTrailersKey = @"io.grpc.TrailersKey";
+static NSMutableDictionary *callFlags;
 
 @interface GRPCCall () <GRXWriteable>
 // Make them read-write.
@@ -106,6 +107,29 @@ NSString * const kGRPCTrailersKey = @"io.grpc.TrailersKey";
 // TODO(jcanizales): If grpc_init is idempotent, this should be changed from load to initialize.
 + (void)load {
   grpc_init();
+  callFlags = [NSMutableDictionary dictionary];
+}
+
++ (void)setCallSafety:(GRPCCallSafety)callSafety host:(NSString *)host path:(NSString *)path {
+  NSString *hostAndPath = [NSString stringWithFormat:@"%@/%@", host, path];
+  switch (callSafety) {
+    case GRPCCallSafetyDefault:
+      callFlags[hostAndPath] = @0;
+      break;
+    case GRPCCallSafetyIdempotentRequest:
+      callFlags[hostAndPath] = @GRPC_INITIAL_METADATA_IDEMPOTENT_REQUEST;
+      break;
+    case GRPCCallSafetyCacheableRequest:
+      callFlags[hostAndPath] = @GRPC_INITIAL_METADATA_CACHEABLE_REQUEST;
+      break;
+    default:
+      break;
+  }
+}
+
++ (uint32_t)callFlagsForHost:(NSString *)host path:(NSString *)path {
+  NSString *hostAndPath = [NSString stringWithFormat:@"%@/%@", host, path];
+  return [callFlags[hostAndPath] intValue];
 }
 
 - (instancetype)init {
@@ -213,13 +237,9 @@ NSString * const kGRPCTrailersKey = @"io.grpc.TrailersKey";
         // don't want to throw, because the app shouldn't crash for a behavior
         // that's on the hands of any server to have. Instead we finish and ask
         // the server to cancel.
-        //
-        // TODO(jcanizales): No canonical code is appropriate for this situation
-        // (because it's just a client problem). Use another domain and an
-        // appropriately-documented code.
         [weakSelf finishWithError:[NSError errorWithDomain:kGRPCErrorDomain
-                                                      code:GRPCErrorCodeInternal
-                                                  userInfo:nil]];
+                                                      code:GRPCErrorCodeResourceExhausted
+                                                  userInfo:@{NSLocalizedDescriptionKey: @"Client does not have enough memory to hold the server response."}]];
         [weakSelf cancelCall];
         return;
       }
@@ -235,6 +255,7 @@ NSString * const kGRPCTrailersKey = @"io.grpc.TrailersKey";
 - (void)sendHeaders:(NSDictionary *)headers {
   // TODO(jcanizales): Add error handlers for async failures
   [_wrappedCall startBatchWithOperations:@[[[GRPCOpSendMetadata alloc] initWithMetadata:headers
+                                                                                  flags:[GRPCCall callFlagsForHost:_host path:_path]
                                                                                 handler:nil]]];
 }
 
diff --git a/src/objective-c/GRPCClient/private/GRPCChannel.h b/src/objective-c/GRPCClient/private/GRPCChannel.h
index 40e78a92d6..5bada2dd50 100644
--- a/src/objective-c/GRPCClient/private/GRPCChannel.h
+++ b/src/objective-c/GRPCClient/private/GRPCChannel.h
@@ -59,8 +59,8 @@ struct grpc_channel_credentials;
  * Creates a secure channel to the specified @c host using Cronet as a transport mechanism.
  */
 #ifdef GRPC_COMPILE_WITH_CRONET
-+ (nullable GRPCChannel *)secureCronetChannelWithHost:(NSString *)host
-                                          channelArgs:(NSDictionary *)channelArgs;
++ (nullable GRPCChannel *)secureCronetChannelWithHost:(nonnull NSString *)host
+                                          channelArgs:(nonnull NSDictionary *)channelArgs;
 #endif
 /**
  * Creates a secure channel to the specified @c host using the specified @c credentials and
diff --git a/src/objective-c/GRPCClient/private/GRPCHost.m b/src/objective-c/GRPCClient/private/GRPCHost.m
index 9cd9593d17..f8634b448e 100644
--- a/src/objective-c/GRPCClient/private/GRPCHost.m
+++ b/src/objective-c/GRPCClient/private/GRPCHost.m
@@ -217,8 +217,10 @@ static NSMutableDictionary *kHostCache;
   }
 
   if (_responseSizeLimitOverride) {
-    args[@GRPC_ARG_MAX_MESSAGE_LENGTH] = _responseSizeLimitOverride;
+    args[@GRPC_ARG_MAX_RECEIVE_MESSAGE_LENGTH] = _responseSizeLimitOverride;
   }
+  // Use 10000ms initial backoff time for correct behavior on bad/slow networks  
+  args[@GRPC_ARG_INITIAL_RECONNECT_BACKOFF_MS] = @10000;
   return args;
 }
 
diff --git a/src/objective-c/GRPCClient/private/GRPCWrappedCall.h b/src/objective-c/GRPCClient/private/GRPCWrappedCall.h
index e37ed1b59f..52233c8242 100644
--- a/src/objective-c/GRPCClient/private/GRPCWrappedCall.h
+++ b/src/objective-c/GRPCClient/private/GRPCWrappedCall.h
@@ -45,6 +45,10 @@
 @interface GRPCOpSendMetadata : GRPCOperation
 
 - (instancetype)initWithMetadata:(NSDictionary *)metadata
+                         handler:(void(^)())handler;
+
+- (instancetype)initWithMetadata:(NSDictionary *)metadata
+                           flags:(uint32_t)flags
                          handler:(void(^)())handler NS_DESIGNATED_INITIALIZER;
 
 @end
diff --git a/src/objective-c/GRPCClient/private/GRPCWrappedCall.m b/src/objective-c/GRPCClient/private/GRPCWrappedCall.m
index 1339429660..627b6aa86d 100644
--- a/src/objective-c/GRPCClient/private/GRPCWrappedCall.m
+++ b/src/objective-c/GRPCClient/private/GRPCWrappedCall.m
@@ -64,16 +64,24 @@
 @implementation GRPCOpSendMetadata
 
 - (instancetype)init {
-  return [self initWithMetadata:nil handler:nil];
+  return [self initWithMetadata:nil flags:0 handler:nil];
 }
 
-- (instancetype)initWithMetadata:(NSDictionary *)metadata handler:(void (^)())handler {
+- (instancetype)initWithMetadata:(NSDictionary *)metadata
+                         handler:(void (^)())handler {
+  return [self initWithMetadata:metadata flags:0 handler:handler];
+}
+
+- (instancetype)initWithMetadata:(NSDictionary *)metadata
+                           flags:(uint32_t)flags
+                         handler:(void (^)())handler {
   if (self = [super init]) {
     _op.op = GRPC_OP_SEND_INITIAL_METADATA;
     _op.data.send_initial_metadata.count = metadata.count;
     _op.data.send_initial_metadata.metadata = metadata.grpc_metadataArray;
     _op.data.send_initial_metadata.maybe_compression_level.is_set = false;
     _op.data.send_initial_metadata.maybe_compression_level.level = 0;
+    _op.flags = flags;
     _handler = handler;
   }
   return self;