client: Implement gRFC A6: configurable client-side retry support (#2111)

rpc_util.go

@@ -162,10 +162,15 @@ type callInfo struct {
 	creds                 credentials.PerRPCCredentials
 	contentSubtype        string
 	codec                 baseCodec
+	disableRetry          bool
+	maxRetryRPCBufferSize int
 }
 
 func defaultCallInfo() *callInfo {
-	return &callInfo{failFast: true}
+	return &callInfo{
+		failFast:              true,
+		maxRetryRPCBufferSize: 256 * 1024, // 256KB
+	}
 }
 
 // CallOption configures a Call before it starts or extracts information from
@@ -415,6 +420,27 @@ func (o CustomCodecCallOption) before(c *callInfo) error {
 }
 func (o CustomCodecCallOption) after(c *callInfo) {}
 
+// MaxRetryRPCBufferSize returns a CallOption that limits the amount of memory
+// used for buffering this RPC's requests for retry purposes.
+//
+// This API is EXPERIMENTAL.
+func MaxRetryRPCBufferSize(bytes int) CallOption {
+	return MaxRetryRPCBufferSizeCallOption{bytes}
+}
+
+// MaxRetryRPCBufferSizeCallOption is a CallOption indicating the amount of
+// memory to be used for caching this RPC for retry purposes.
+// This is an EXPERIMENTAL API.
+type MaxRetryRPCBufferSizeCallOption struct {
+	MaxRetryRPCBufferSize int
+}
+
+func (o MaxRetryRPCBufferSizeCallOption) before(c *callInfo) error {
+	c.maxRetryRPCBufferSize = o.MaxRetryRPCBufferSize
+	return nil
+}
+func (o MaxRetryRPCBufferSizeCallOption) after(c *callInfo) {}
+
 // The format of the payload: compressed or not?
 type payloadFormat uint8