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feat: set the remaining semconv server span attributes #39

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36 changes: 32 additions & 4 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -89,11 +89,30 @@ Attributes set on server spans:
| `url.path` | Request URL path (without query) | Always |
| `url.query` | Query string (without `?`) | When query string is present |
| `url.scheme` | `http` or `https` | Always |
| `server.address` | Requested host, without the port | When `Host` header is present |
| `server.address` | Requested host, without the port | When a host source is present |
| `server.port` | Requested port, or its default | When the port is known |
| `client.address` | Client address, behind proxies when known, else the immediate peer | When the client or peer is known |
| `network.peer.address` | Immediate peer address | When the socket exposes it |
| `network.peer.port` | Immediate peer port | When the peer address is set |
| `network.protocol.version` | HTTP version (e.g. `1.1`) | Always |
| `user_agent.original` | Client `User-Agent` header | When the header is present |
| `http.response.status_code` | Response status code | When response finishes |
| `error.type` | HTTP status code as string | On 5xx responses |

The address attributes follow the proxy headers the way OpenTelemetry's
own HTTP instrumentation does, although a client can spoof them.
`server.address` and `server.port` come from the first of the `Forwarded`
header's `host` parameter, the first `X-Forwarded-Host` entry, and the
`Host` header, each parsed for both the host and the port, including
bracketed IPv6. When the chosen value omits the port, the default comes
from the `Forwarded` `proto` parameter, the first `X-Forwarded-Proto`
entry, or, for the `Host` header, the request scheme, in any letter case.
A port that is not a decimal number from 0 to 65535 is omitted. `client.address` comes from the first `Forwarded` `for`
parameter or the first `X-Forwarded-For` entry, and otherwise from the
immediate peer. `network.peer.address` and `network.peer.port` come
from the socket, so behind a proxy they name the proxy. A malformed
`Forwarded` header is treated as absent.

### HTTP/2 server

A span with kind `SERVER` is created for each incoming HTTP/2 request
Expand All @@ -115,11 +134,20 @@ Attributes set on HTTP/2 server spans:
| `url.path` | Request URL path (without query) | Always |
| `url.query` | Query string (without `?`) | When query string is present |
| `url.scheme` | `http` or `https` | Always |
| `server.address` | Requested host, without the port | When `:authority` is present |
| `server.address` | Requested host, without the port | When a host source is present |
| `server.port` | Requested port, or its default | When the port is known |
| `client.address` | Client address, behind proxies when known, else the immediate peer | When the client or peer is known |
| `network.peer.address` | Immediate peer address | When the socket exposes it |
| `network.peer.port` | Immediate peer port | When the peer address is set |
| `network.protocol.version` | `2.0` | Always |
| `user_agent.original` | Client `User-Agent` header | When the header is present |
| `http.response.status_code` | Response status code | When the response is sent |
| `error.type` | HTTP status code as string | On 5xx responses |

The address attributes follow the same rules as for HTTP/1 server
spans. The `:authority` pseudo-header stands in for the `Host` header,
and the peer attributes come from the session's socket.

### HTTP client

A span with kind `CLIENT` is created for each outgoing HTTP request made via
Expand All @@ -143,8 +171,8 @@ Attributes set on client spans:
| `error.type` | Status code or error name | On 4xx/5xx or errors |

The `server.port` value is the decimal port from the Host header, or the scheme
default (`80` for `http:`, `443` for `https:`) when the header omits it; a
port that is not a decimal number is omitted.
default (`80` for `http:`, `443` for `https:`) when the header omits it. A
port that is not a decimal number from 0 to 65535 is omitted.

### Undici/Fetch client

Expand Down
168 changes: 168 additions & 0 deletions lib/forwarded.js
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@@ -0,0 +1,168 @@
'use strict';

// This parses the Forwarded header (RFC 7239). The header is a
// comma-separated list of elements, each a semicolon-separated list of
// name=value parameters, where a value is a token or a quoted string with
// backslash escapes. Parameter names are case-insensitive, so they are
// lowercased, and values keep their case. A malformed header yields null,
// so a caller treats garbage as absent rather than guessing at it.

// RFC 7230 section 3.2.6 token characters, the alphabet parameter names
// and unquoted values are built from.
function isTokenChar(code) {
return (
code === 0x21 ||
(code >= 0x23 && code <= 0x27) ||
code === 0x2a ||
code === 0x2b ||
code === 0x2d ||
code === 0x2e ||
(code >= 0x30 && code <= 0x39) ||
(code >= 0x41 && code <= 0x5a) ||
(code >= 0x5e && code <= 0x7a) ||
code === 0x7c ||
code === 0x7e
);
}

// These are the delimiters of the same section. An unquoted value ends at
// them, and a quoted one may contain them.
function isDelimiter(code) {
return (
code === 0x22 ||
code === 0x28 ||
code === 0x29 ||
code === 0x2c ||
code === 0x2f ||
(code >= 0x3a && code <= 0x40) ||
(code >= 0x5b && code <= 0x5d) ||
code === 0x7b ||
code === 0x7d
);
}

function isPrint(code) {
return code >= 0x20 && code <= 0x7e;
}

function isExtended(code) {
return code >= 0x80 && code <= 0xff;
}

// Only a quoted value can carry escapes, and only printable ones, so the
// backslashes are dropped once the value is complete.
function unescapeValue(value) {
return value.replace(/\\(.)/g, '$1');
}

function parseForwarded(header) {
const elements = [];
let element = {};
let parameter;
let start = -1;
let end = -1;
let inQuotes = false;
let escaping = false;
let unescape = false;
let code;

for (let i = 0; i < header.length; i++) {
code = header.charCodeAt(i);

if (parameter === undefined) {
// Whitespace between elements is not part of any parameter.
if (i !== 0 && start === -1 && (code === 0x20 || code === 0x09)) continue;
if (isTokenChar(code)) {
if (start === -1) start = i;
} else if (code === 0x3d && start !== -1) {
parameter = header.slice(start, i).toLowerCase();
start = -1;
} else {
return null;
}
continue;
}

if (escaping && (code === 0x09 || isPrint(code) || isExtended(code))) {
escaping = false;
} else if (isTokenChar(code)) {
// A token cannot resume after whitespace ended the value.
if (end !== -1) return null;
if (start === -1) start = i;
} else if (isDelimiter(code) || isExtended(code)) {
if (inQuotes) {
if (code === 0x22) {
inQuotes = false;
end = i;
} else if (code === 0x5c) {
if (start === -1) start = i;
escaping = unescape = true;
} else if (start === -1) {
start = i;
}
} else if (code === 0x22 && header.charCodeAt(i - 1) === 0x3d) {
// A quote opens a value only directly after the equals sign.
inQuotes = true;
} else if (
(code === 0x2c || code === 0x3b) &&
(start !== -1 || end !== -1)
) {
if (start !== -1) {
if (end === -1) end = i;
element[parameter] = unescape
? unescapeValue(header.slice(start, end))
: header.slice(start, end);
} else {
// A closed quoted pair can be empty, but an unquoted value cannot.
element[parameter] = '';
}
if (code === 0x2c) {
elements.push(element);
element = {};
}
parameter = undefined;
start = end = -1;
} else {
return null;
}
} else if (code === 0x20 || code === 0x09) {
if (end !== -1) continue;
if (inQuotes) {
if (start === -1) start = i;
} else if (start !== -1) {
// Trailing whitespace is not part of an unquoted value.
end = i;
} else {
return null;
}
} else {
return null;
}
}

// The header must end inside a complete pair, not right after a
// separator, inside quotes, or on trailing whitespace.
if (
parameter === undefined ||
inQuotes ||
(start === -1 && end === -1) ||
code === 0x20 ||
code === 0x09
)
return null;

if (start !== -1) {
if (end === -1) end = header.length;
element[parameter] = unescape
? unescapeValue(header.slice(start, end))
: header.slice(start, end);
} else {
element[parameter] = '';
}
elements.push(element);
return elements;
}

module.exports = {
parseForwarded,
};
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