Jakub Zych
fbcfaaf05f
An unmatched request logged its path. A token route reached with another method (405) or with a trailing slash (404) is answered by ServeMux before any route handler records the pattern, so the share or invitation token in the path reached the log. The record now carries method, pattern, status and duration only.
71 lines
4.5 KiB
Markdown
71 lines
4.5 KiB
Markdown
---
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title: Logging
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description: Log through log/slog with sunscreen, the redacting handler every generated main installs, and keep tokens, keys and request bodies out of log records.
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section: services
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order: 105
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---
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# Logging
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SummerCMS logs through the standard library's `log/slog`. Where a WinterCMS plugin calls `Log::error` and relies on a Monolog tap to scrub credentials, a SummerCMS plugin logs through a `*slog.Logger`, and [sunscreen](../../modules/sunscreen/README.md) does the scrubbing.
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## The redacting default logger
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Every application `main` that `summer build` generates calls `sunscreen.InstallDefault(os.Stderr)` as the first statement of `run`, before the configuration is loaded and before any plugin is activated. From then on `slog.Default`, the package-level `slog` functions and the standard `log` package all write through a text handler wrapped by `sunscreen.Wrap`.
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The handler rewrites every record before it is written:
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- The value of an attribute whose key is one of `sunscreen.RedactedKeys` becomes `[REDACTED]`, at any group depth and whatever the letter case: `api_key`, `apikey`, `authorization`, `bearer`, `password`, `secret`, `token`, `webhook_secret`, `admin_password` and the `openai_api_key`, `anthropic_api_key` and `perplexity_api_key` variants.
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- The message, string values, error values and the formatted text of other values are passed through `sunscreen.Scrub`, which replaces `Bearer <token>`, `sk-` style API keys and `x-api-key: <value>`.
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- `slog.LogValuer` values are resolved first, and maps such as `http.Header` are redacted key by key.
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```go src=modules/sunscreen/example_test.go#ExampleWrap
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// Drop the time so the output is stable; a real application keeps it.
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plain := slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{
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ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr {
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if len(groups) == 0 && a.Key == slog.TimeKey {
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return slog.Attr{}
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}
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return a
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},
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})
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logger := slog.New(sunscreen.Wrap(plain))
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logger.Info("vendor call failed",
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"api_key", "live-key-123",
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slog.Group("request", slog.String("Authorization", "Bearer abc.def")),
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"err", errors.New("401 for key sk-abcdefghijklmnopqrstuvwx"),
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)
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// Output:
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// level=INFO msg="vendor call failed" api_key=[REDACTED] request.Authorization=[REDACTED] err="401 for key sk-[REDACTED]"
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```
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## Logging from a plugin
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A plugin resolves a `*slog.Logger` from the application with `backpack.Lookup` and falls back to `slog.Default` when none is published, as the framework modules do. Either way the record goes through the redacting handler.
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Redaction is a safety net for mistakes, not a way to log secrets on purpose. Log identifiers and outcomes: the record id, the vendor, the status code, how long it took. Never log request arguments, tokens, credentials or request and response bodies, which can carry personal data the patterns do not recognise.
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## Request log
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The router can log every request. It is off by default; turn it on with the `http.access_log` key (environment `SUMMER_HTTP__ACCESS_LOG=true`):
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```yaml
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# config/http.yaml
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access_log: true
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```
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Each request then writes one Info record with the message `http request` once it has been served:
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| Attribute | Value |
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|-----------|-------|
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| `method` | The request method. |
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| `pattern` | The matched route, method and path pattern, for example `GET /posts/{id}`. Empty when no route matched. |
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| `status` | The response status; a handler that writes without setting one counts as 200. A 5xx written after the client cancelled the request is logged as 499 (client closed request), since the error came from the cancellation and no client received it. |
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| `duration_ms` | Time spent serving the request, in whole milliseconds. |
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The record never carries the URL path, the query string, request or response headers or the client address, because tokens often travel in paths and query strings. That holds for a request that reached no route too: a token route requested with another method gets a 405 from the router, and its trailing-slash variant a 404, before any route handler runs, so the path would carry the token. It goes to the published `*slog.Logger` or `slog.Default`, so the redacting handler still applies. Grep for the empty `pattern` to find requests that reached no route; the client's own log (a browser, a proxy) shows which path it asked for.
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## Panics
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The router recovers a panicking handler and answers with an opaque 500: the JSON groups send `{"error":true,"message":"Internal server error"}` and the raw groups an empty body. The panic value never reaches the client. See [Routing](routing.md).
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