HTTP/3 and QPACK qlog event definitions

2.2.1. Raw packet and frame information

This document re-uses the definition of the RawInfo data class from [QLOG-MAIN].¶

Note:

As HTTP/3 does not use trailers in frames, each HTTP/3 frame header_length can be calculated as header_length = RawInfo:length - RawInfo:payload_length¶

Note:

In some cases, the length fields are also explicitly reflected inside of frame headers. For example, all HTTP/3 frames include their explicit payload lengths in the frame header. In these cases, those fields are intentionally preserved in the event definitions. Even though this can lead to duplicate data when the full RawInfo is logged, it allows a more direct mapping of the HTTP/3 specifications to qlog, making it easier for users to interpret. In this case, both fields MUST have the same value.¶

3.1.1. parameters_set

Importance: Base¶

This event contains HTTP/3 and QPACK-level settings, mostly those received from the HTTP/3 SETTINGS frame. All these parameters are typically set once and never change. However, they are typically set at different times during the connection, so there can be several instances of this event with different fields set.¶

Note that some settings have two variations (one set locally, one requested by the remote peer). This is reflected in the "owner" field. As such, this field MUST be correct for all settings included a single event instance. If you need to log settings from two sides, you MUST emit two separate event instances.¶

Note: we use the CDDL unwrap operator (~) here to make HTTPParameters into a re-usable list of fields. The unwrap operator copies the fields from the referenced type into the target type directly, extending the target with the unwrapped fields. TODO: explain this better + provide reference and maybe an example.¶

Definition:¶

HTTPParametersSet = {
    ? owner: Owner

    ~HTTPParameters

    ; qlog-specific
    ; indicates whether this implementation waits for a SETTINGS
    ; frame before processing requests
    ? waits_for_settings: bool
}

HTTPParameters = {
    ? max_header_list_size: uint64
    ? max_table_capacity: uint64
    ? blocked_streams_count: uint64

    ; additional settings for grease and extensions
    * text => uint64
}

Note: enabling server push is not explicitly done in HTTP/3 by use of a setting or parameter. Instead, it is communicated by use of the MAX_PUSH_ID frame, which should be logged using the frame_created and frame_parsed events below.¶

Additionally, this event can contain any number of unspecified fields. This is to reflect setting of for example unknown (greased) settings or parameters of (proprietary) extensions.¶

3.1.2. parameters_restored

Importance: Base¶

When using QUIC 0-RTT, HTTP/3 clients are expected to remember and reuse the server's SETTINGs from the previous connection. This event is used to indicate which HTTP/3 settings were restored and to which values when utilizing 0-RTT.¶

Definition:¶

HTTPParametersRestored = {

    ~HTTPParameters

}

Note that, like for parameters_set above, this event can contain any number of unspecified fields to allow for additional and custom settings.¶

3.1.3. stream_type_set

Importance: Base¶

Emitted when a stream's type becomes known. This is typically when a stream is opened and the stream's type indicator is sent or received.¶

Note: most of this information can also be inferred by looking at a stream's id, since id's are strictly partitioned at the QUIC level. Even so, this event has a "Base" importance because it helps a lot in debugging to have this information clearly spelled out.¶

Definition:¶

HTTPStreamTypeSet = {
    ? owner: Owner
    stream_id: uint64

    ? old: HTTPStreamType
    new: HTTPStreamType

    ; only when new === "push"
    ? associated_push_id: uint64
}

HTTPStreamType =  "data" /
                  "control" /
                  "push" /
                  "reserved" /
                  "qpack_encode" /
                  "qpack_decode"

3.1.4. frame_created

Importance: Core¶

HTTP equivalent to the packet_sent event. This event is emitted when the HTTP/3 framing actually happens. Note: this is not necessarily the same as when the HTTP/3 data is passed on to the QUIC layer. For that, see the "data_moved" event in [QLOG-QUIC].¶

Definition:¶

HTTPFrameCreated = {
    stream_id: uint64
    ? length: uint64
    frame: HTTPFrame
    ? raw: RawInfo
}

Note: in HTTP/3, DATA frames can have arbitrarily large lengths to reduce frame header overhead. As such, DATA frames can span many QUIC packets and can be created in a streaming fashion. In this case, the frame_created event is emitted once for the frame header, and further streamed data is indicated using the data_moved event.¶

3.1.5. frame_parsed

Importance: Core¶

HTTP equivalent to the packet_received event. This event is emitted when we actually parse the HTTP/3 frame. Note: this is not necessarily the same as when the HTTP/3 data is actually received on the QUIC layer. For that, see the "data_moved" event in [QLOG-QUIC].¶

Definition:¶

HTTPFrameParsed = {
    stream_id: uint64
    ? length: uint64
    frame: HTTPFrame
    ? raw: RawInfo
}

Note: in HTTP/3, DATA frames can have arbitrarily large lengths to reduce frame header overhead. As such, DATA frames can span many QUIC packets and can be processed in a streaming fashion. In this case, the frame_parsed event is emitted once for the frame header, and further streamed data is indicated using the data_moved event.¶

3.1.6. push_resolved

Importance: Extra¶

This event is emitted when a pushed resource is successfully claimed (used) or, conversely, abandoned (rejected) by the application on top of HTTP/3 (e.g., the web browser). This event is added to help debug problems with unexpected PUSH behaviour, which is commonplace with HTTP/2.¶

Definition:¶

HTTPPushResolved = {
    ? push_id: uint64

    ; in case this is logged from a place that does not have access
    ; to the push_id
    ? stream_id: uint64

    decision: HTTPPushDecision
}

HTTPPushDecision = "claimed" / "abandoned"

3.2.1. state_updated

Importance: Base¶

This event is emitted when one or more of the internal QPACK variables changes value. Note that some variables have two variations (one set locally, one requested by the remote peer). This is reflected in the "owner" field. As such, this field MUST be correct for all variables included a single event instance. If you need to log settings from two sides, you MUST emit two separate event instances.¶

Definition:¶

QPACKStateUpdate = {
    owner: Owner
    ? dynamic_table_capacity: uint64

    ; effective current size, sum of all the entries
    ? dynamic_table_size: uint64
    ? known_received_count: uint64
    ? current_insert_count: uint64
}

3.2.2. stream_state_updated

Importance: Core¶

This event is emitted when a stream becomes blocked or unblocked by header decoding requests or QPACK instructions.¶

Note: This event is of "Core" importance, as it might have a large impact on HTTP/3's observed performance.¶

Definition:¶

QPACKStreamStateUpdate = {
    stream_id: uint64
    ; streams are assumed to start "unblocked"
    ; until they become "blocked"
    state: QPACKStreamState
}

QPACKStreamState = "blocked" / "unblocked"

3.2.3. dynamic_table_updated

Importance: Extra¶

This event is emitted when one or more entries are inserted or evicted from QPACK's dynamic table.¶

Definition:¶

QPACKDynamicTableUpdate = {
    ; local = the encoder's dynamic table
    ; remote = the decoder's dynamic table
    owner: Owner

    update_type: QPACKDynamicTableUpdateType
    entries: [+ QPACKDynamicTableEntry]
}

QPACKDynamicTableUpdateType = "inserted" / "evicted"

QPACKDynamicTableEntry = {
    index: uint64
    ? name: text / hexstring
    ? value: text / hexstring
}

3.2.4. headers_encoded

Importance: Base¶

This event is emitted when an uncompressed header block is encoded successfully.¶

Note: this event has overlap with http.frame_created for the HeadersFrame type. When outputting both events, implementers MAY omit the "headers" field in this event.¶

Definition:¶

QPACKHeadersEncoded = {
    ? stream_id: uint64
    ? headers: [+ HTTPField]

    block_prefix: QPACKHeaderBlockPrefix
    header_block: [+ QPACKHeaderBlockRepresentation]

    ? length: uint
    ? raw: hexstring
}

3.2.5. headers_decoded

Importance: Base¶

This event is emitted when a compressed header block is decoded successfully.¶

Note: this event has overlap with http.frame_parsed for the HeadersFrame type. When outputting both events, implementers MAY omit the "headers" field in this event.¶

Definition:¶

QPACKHeadersDecoded = {
    ? stream_id: uint64
    ? headers: [+ HTTPField]

    block_prefix: QPACKHeaderBlockPrefix
    header_block: [+ QPACKHeaderBlockRepresentation]

    ? length: uint32
    ? raw: hexstring
}

3.2.6. instruction_created

Importance: Base¶

This event is emitted when a QPACK instruction (both decoder and encoder) is created and added to the encoder/decoder stream.¶

Definition:¶

QPACKInstructionCreated = {
    ; see definition in appendix
    instruction: QPACKInstruction
    ? length: uint32
    ? raw: hexstring
}

Note: encoder/decoder semantics and stream_id's are implicit in either the instruction types or can be logged via other events (e.g., http.stream_type_set)¶

3.2.7. instruction_parsed

Importance: Base¶

This event is emitted when a QPACK instruction (both decoder and encoder) is read from the encoder/decoder stream.¶

Definition:¶

QPACKInstructionParsed = {
    ; see QPACKInstruction definition in appendix
    instruction: QPACKInstruction

    ? length: uint32
    ? raw: hexstring
}

Note: encoder/decoder semantics and stream_id's are implicit in either the instruction types or can be logged via other events (e.g., http.stream_type_set)¶

A.3.1. DataFrame

HTTPDataFrame = {
    frame_type: "data"
    ? raw: hexstring
}

A.3.2. HeadersFrame

This represents an uncompressed, plaintext HTTP Headers frame (e.g., no QPACK compression is applied).¶

For example:¶

headers: [
  {
    "name": ":path",
    "value": "/"
  },
  {
    "name": ":method",
    "value": "GET"
  },
  {
    "name": ":authority",
    "value": "127.0.0.1:4433"
  },
  {
    "name": ":scheme",
    "value": "https"
  }
]

HTTPHeadersFrame = {
    frame_type: "headers"
    headers: [* HTTPField]
}

HTTPField = {
    name: text
    value: text
}

A.3.3. CancelPushFrame

HTTPCancelPushFrame = {
    frame_type: "cancel_push"
    push_id: uint64
}

A.3.4. SettingsFrame

HTTPSettingsFrame = {
    frame_type: "settings"
    settings: [* HTTPSetting]
}

HTTPSetting = {
    name: text
    value: uint64
}

A.3.5. PushPromiseFrame

HTTPPushPromiseFrame = {
    frame_type: "push_promise"
    push_id: uint64
    headers: [* HTTPField]
}

A.3.6. GoAwayFrame

HTTPGoawayFrame = {
    frame_type: "goaway"

    ; Either stream_id or push_id.
    ; This is implicit from the sender of the frame
    id: uint64
}

A.3.7. MaxPushIDFrame

HTTPMaxPushIDFrame = {
    frame_type: "max_push_id"
    push_id: uint64
}

A.3.8. ReservedFrame

HTTPReservedFrame = {
    frame_type: "reserved"

    ? length: uint64
}

A.3.9. UnknownFrame

HTTP/3 qlog re-uses QUIC's UnknownFrame definition, since their values and usage overlaps. See [QLOG-QUIC].¶

B.2.1. SetDynamicTableCapacityInstruction

SetDynamicTableCapacityInstruction = {
    instruction_type: "set_dynamic_table_capacity"
    capacity: uint32
}

B.2.2. InsertWithNameReferenceInstruction

InsertWithNameReferenceInstruction = {
    instruction_type: "insert_with_name_reference"
    table_type: QPACKTableType
    name_index: uint32
    huffman_encoded_value: bool
    ? value_length: uint32
    ? value: text
}

B.2.3. InsertWithoutNameReferenceInstruction

InsertWithoutNameReferenceInstruction = {
    instruction_type: "insert_without_name_reference"
    huffman_encoded_name: bool
    ? name_length: uint32
    ? name: text
    huffman_encoded_value: bool
    ? value_length: uint32
    ? value: text
}

B.2.4. DuplicateInstruction

DuplicateInstruction = {
    instruction_type: "duplicate"
    index: uint32
}

B.2.5. SectionAcknowledgementInstruction

SectionAcknowledgementInstruction = {
    instruction_type: "section_acknowledgement"
    stream_id: uint64
}

B.2.6. StreamCancellationInstruction

StreamCancellationInstruction = {
    instruction_type: "stream_cancellation"
    stream_id: uint64
}

B.2.7. InsertCountIncrementInstruction

InsertCountIncrementInstruction = {
    instruction_type: "insert_count_increment"
    increment: uint32
}

B.3.1. IndexedHeaderField

Note: also used for "indexed header field with post-base index"¶

IndexedHeaderField = {
    header_field_type: "indexed_header"

    ; MUST be "dynamic" if is_post_base is true
    table_type: QPACKTableType
    index: uint32

    ; to represent the "indexed header field with post-base index"
    ; header field type
    is_post_base: bool .default false
}

B.3.2. LiteralHeaderFieldWithName

Note: also used for "Literal header field with post-base name reference"¶

LiteralHeaderFieldWithName = {
    header_field_type: "literal_with_name"

    ; the 3rd "N" bit
    preserve_literal: bool

    ; MUST be "dynamic" if is_post_base is true
    table_type: QPACKTableType
    name_index: uint32
    huffman_encoded_value: bool
    ? value_length: uint32
    ? value: text

    ; to represent the "indexed header field with post-base index"
    ; header field type
    is_post_base: bool .default false
}

B.3.3. LiteralHeaderFieldWithoutName

LiteralHeaderFieldWithoutName = {
    header_field_type: "literal_without_name"

    ; the 3rd "N" bit
    preserve_literal: bool
    huffman_encoded_name: bool
    ? name_length: uint32
    ? name: text

    huffman_encoded_value: bool
    ? value_length: uint32
    ? value: text
}

B.3.4. QPACKHeaderBlockPrefix

QPACKHeaderBlockPrefix = {
    required_insert_count: uint32
    sign_bit: bool
    delta_base: uint32
}

B.3.5. QPACKTableType

QPACKTableType = "static" / "dynamic"