feat(core): Default encoding/decoding limits (#1335)

* feat(core): Default encoding/decoding limits

This PR adds new defaults for both client and server max
encoding/decoding message size limits. By default, the max message
decoding size is `4MB` and the max message encoding size is
`usize::MAX`.

This is follow up work from https://github.com/hyperium/tonic/pull/1274

BREAKING: Default max message encoding/decoding limits

* update generated code

tonic/src/codec/decode.rs

@@ -1,5 +1,5 @@
 use super::compression::{decompress, CompressionEncoding};
-use super::{DecodeBuf, Decoder, DEFAULT_MAX_MESSAGE_SIZE, HEADER_SIZE};
+use super::{DecodeBuf, Decoder, DEFAULT_MAX_RECV_MESSAGE_SIZE, HEADER_SIZE};
 use crate::{body::BoxBody, metadata::MetadataMap, Code, Status};
 use bytes::{Buf, BufMut, BytesMut};
 use futures_core::Stream;
@@ -174,7 +174,9 @@ impl StreamingInner {
             };
 
             let len = self.buf.get_u32() as usize;
-            let limit = self.max_message_size.unwrap_or(DEFAULT_MAX_MESSAGE_SIZE);
+            let limit = self
+                .max_message_size
+                .unwrap_or(DEFAULT_MAX_RECV_MESSAGE_SIZE);
             if len > limit {
                 return Err(Status::new(
                     Code::OutOfRange,

tonic/src/codec/encode.rs

@@ -1,5 +1,5 @@
 use super::compression::{compress, CompressionEncoding, SingleMessageCompressionOverride};
-use super::{EncodeBuf, Encoder, DEFAULT_MAX_MESSAGE_SIZE, HEADER_SIZE};
+use super::{EncodeBuf, Encoder, DEFAULT_MAX_SEND_MESSAGE_SIZE, HEADER_SIZE};
 use crate::{Code, Status};
 use bytes::{BufMut, Bytes, BytesMut};
 use futures_core::{Stream, TryStream};
@@ -141,7 +141,7 @@ fn finish_encoding(
     buf: &mut BytesMut,
 ) -> Result<Bytes, Status> {
     let len = buf.len() - HEADER_SIZE;
-    let limit = max_message_size.unwrap_or(DEFAULT_MAX_MESSAGE_SIZE);
+    let limit = max_message_size.unwrap_or(DEFAULT_MAX_SEND_MESSAGE_SIZE);
     if len > limit {
         return Err(Status::new(
             Code::OutOfRange,

tonic/src/codec/mod.rs

@@ -30,7 +30,8 @@ const HEADER_SIZE: usize =
     std::mem::size_of::<u32>();
 
 // The default maximum uncompressed size in bytes for a message. Defaults to 4MB.
-const DEFAULT_MAX_MESSAGE_SIZE: usize = 4 * 1024 * 1024;
+const DEFAULT_MAX_RECV_MESSAGE_SIZE: usize = 4 * 1024 * 1024;
+const DEFAULT_MAX_SEND_MESSAGE_SIZE: usize = usize::MAX;
 
 /// Trait that knows how to encode and decode gRPC messages.
 pub trait Codec {

tonic/src/lib.rs

@@ -53,6 +53,14 @@
 //! to build even more feature rich clients and servers. This module also provides the ability to
 //! enable TLS using [`rustls`], via the `tls` feature flag.
 //!
+//! # Code generated client/server configuration
+//!
+//! ## Max Message Size
+//!
+//! Currently, both servers and clients can be configured to set the max message encoding and
+//! decoding size. This will ensure that an incoming gRPC message will not exahust the systems
+//! memory. By default, the decoding message limit is `4MB` and the encoding limit is `usize::MAX`.
+//!
 //! [gRPC]: https://grpc.io
 //! [`tonic`]: https://github.com/hyperium/tonic
 //! [`tokio`]: https://docs.rs/tokio