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`ptr` keeps its field and shape. It now comes from Google, Cloudflare, AdGuard and Quad9 over RFC 8484, tried in turn within 2 seconds, in place of the host's resolver with no cache. Answers stay in memory and in a new `cache.db` for the record's TTL, at most 250,000 addresses. A reserved address is not sent to any resolver and has an empty `ptr`. Judgement call: each resolver gets an equal share of the time left, so a hung one does not use up the limit. Judgement call: the negative TTL is the smaller of the SOA minimum and the SOA's own TTL. Deviation: the cache is SQLite, by sneak's words, not the JSON file the standing rule asks for. Model: opus-5-5
52 lines
1.3 KiB
Go
52 lines
1.3 KiB
Go
// Package cachedb opens cache.db, the SQLite file in the state directory that
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// holds RouteWatch's caches of answers from outside services. It is separate
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// from the routes database so that a cache write never queues behind a write
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// to that database.
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package cachedb
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import (
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"context"
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"database/sql"
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_ "embed" // for schema.sql
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"fmt"
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"path/filepath"
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_ "github.com/mattn/go-sqlite3" // CGO SQLite driver
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)
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const (
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// fileName is the database's file in the state directory.
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fileName = "cache.db"
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// busyTimeoutMs is how long a write waits for another write to finish.
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busyTimeoutMs = 5000
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)
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//go:embed schema.sql
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var schema string
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// Open opens cache.db in stateDir, creating the file and its tables when they
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// do not exist. The caller closes the database.
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func Open(ctx context.Context, stateDir string) (*sql.DB, error) {
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dsn := fmt.Sprintf(
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"file:%s?_journal_mode=WAL&_synchronous=NORMAL&_busy_timeout=%d"+
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"&_txlock=immediate",
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filepath.Join(stateDir, fileName),
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busyTimeoutMs,
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)
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db, err := sql.Open("sqlite3", dsn)
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if err != nil {
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return nil, fmt.Errorf("opening the cache database: %w", err)
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}
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_, err = db.ExecContext(ctx, schema)
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if err != nil {
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_ = db.Close()
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return nil, fmt.Errorf("creating the cache database's tables: %w", err)
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}
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return db, nil
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}
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