@ -91,7 +91,7 @@ A **Compressed-Flag** value of 1 indicates that the binary octet sequence of **M
For requests, **EOS** (end-of-stream) is indicated by the presence of the END_STREAM flag on the last received DATA frame. In scenarios where the **Request** stream needs to be closed but no data remains to be sent implementations MUST send an empty DATA frame with this flag set.
While the protocol does not require a user-agent to function it is recommended that clients provide a structured user-agent string that provides a basic description of the calling library, version & platform to facilitate issue diagnosis in heterogeneous environments. The following structure is recommended to library developers
Unless explicitly defined to be, gRPC Calls are not assumed to be idempotent. Specifically:
@ -186,15 +186,15 @@ Unless explicitly defined to be, gRPC Calls are not assumed to be idempotent. S
* Calls that are marked as idempotent may be sent multiple times.
####HTTP2 Transport Mapping
####HTTP2 Transport Mapping
#####Stream Identification
#####Stream Identification
All GRPC calls need to specify an internal ID. We will use HTTP2 stream-ids as call identifiers in this scheme. NOTE: These id’s are contextual to an open HTTP2 session and will not be unique within a given process that is handling more than one HTTP2 session nor can they be used as GUIDs.
#####Data Frames
#####Data Frames
DATA frame boundaries have no relation to **Length-Prefixed-Message** boundaries and implementations should make no assumptions about their alignment.
#####Errors
#####Errors
When an application or runtime error occurs during an RPC a **Status** and **Status-Message** are delivered in **Trailers**.
INADEQUATE_SECURITY| PERMISSION_DENIED … with additional detail indicating that permission was denied as protocol is not secure enough for call.
#####Security
#####Security
The HTTP2 specification mandates the use of TLS 1.2 or higher when TLS is used with HTTP2. It also places some additional constraints on the allowed ciphers in deployments to avoid known-problems as well as requiring SNI support. It is also expected that HTTP2 will be used in conjunction with proprietary transport security mechanisms about which the specification can make no meaningful recommendations.
#####Connection Management
######GOAWAY Frame
#####Connection Management
######GOAWAY Frame
Sent by servers to clients to indicate that they will no longer accept any new streams on the associated connections. This frame includes the id of the last successfully accepted stream by the server. Clients should consider any stream initiated after the last successfully accepted stream as UNAVAILABLE and retry the call elsewhere. Clients are free to continue working with the already accepted streams until they complete or the connection is terminated.
Servers should send GOAWAY before terminating a connection to reliably inform clients which work has been accepted by the server and is being executed.
######PING Frame
######PING Frame
Both clients and servers can send a PING frame that the peer must respond to by precisely echoing what they received. This is used to assert that the connection is still live as well as providing a means to estimate end-to-end latency. If a server initiated PING does not receive a response within the deadline expected by the runtime all outstanding calls on the server will be closed with a CANCELLED status. An expired client initiated PING will cause all calls to be closed with an UNAVAILABLE status. Note that the frequency of PINGs is highly dependent on the network environment, implementations are free to adjust PING frequency based on network and application requirements.
######Connection failure
######Connection failure
If a detectable connection failure occurs on the client all calls will be closed with an UNAVAILABLE status. For servers open calls will be closed with a CANCELLED status.
Craig Tiller
8 years ago