Define limit on metadata size

Fixes grpc/grpc-common#273
pull/4047/head
Eric Anderson 10 years ago
parent 2e18fd6493
commit 5554738645
  1. 11
      doc/PROTOCOL-HTTP2.md

@ -52,10 +52,16 @@ HTTP2 requires that reserved headers, ones starting with ":" appear before all o
If **Timeout** is omitted a server should assume an infinite timeout. Client implementations are free to send a default minimum timeout based on their deployment requirements.
**Custom-Metadata** is an arbitrary set of key-value pairs defined by the application layer. Aside from transport limits on the total length of HTTP2 HEADERS the only other constraint is that header names starting with "grpc-" are reserved for future use.
**Custom-Metadata** is an arbitrary set of key-value pairs defined by the application layer. Header names starting with "grpc-" but not listed here are reserved for future GRPC use and should not be used by applications as **Custom-Metadata**.
Note that HTTP2 does not allow arbitrary octet sequences for header values so binary header values must be encoded using Base64 as per https://tools.ietf.org/html/rfc4648#section-4. Implementations MUST accept padded and un-padded values and should emit un-padded values. Applications define binary headers by having their names end with "-bin". Runtime libraries use this suffix to detect binary headers and properly apply base64 encoding & decoding as headers are sent and received.
Servers may limit the size of **Request-Headers**, with a default of 8 KiB
suggested. Implementations are encouraged to compute total header size like
HTTP/2's `SETTINGS_MAX_HEADER_LIST_SIZE`: the sum of all header fields, for each
field the sum of the uncompressed field name and value lengths plus 32, with
binary values' lengths being post-Base64.
The repeated sequence of **Length-Prefixed-Message** items is delivered in DATA frames
* **Length-Prefixed-Message** → Compressed-Flag Message-Length Message
@ -83,6 +89,9 @@ For responses end-of-stream is indicated by the presence of the END_STREAM flag
Implementations should expect broken deployments to send non-200 HTTP status codes in responses as well as a variety of non-GRPC content-types and to omit **Status** & **Status-Message**. Implementations must synthesize a **Status** & **Status-Message** to propagate to the application layer when this occurs.
Clients may limit the size of **Response-Headers**, **Trailers**, and
**Trailers-Only**, with a default of 8 KiB each suggested.
####Example
Sample unary-call showing HTTP2 framing sequence

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