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binwiederhier
b2b1fc1f71
A stalled replica piles up connections in use, so reads go to the replica with the fewest connections in use instead of round-robin, and to the primary when every replica's pool is full. ntfy_db_ping_seconds shows how long each database took to answer its health check.
46 lines
1.2 KiB
Go
46 lines
1.2 KiB
Go
package db
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import (
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"database/sql"
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"sync/atomic"
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"time"
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)
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// Beginner is an interface for types that can begin a database transaction.
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// Both *sql.DB and *DB implement this.
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type Beginner interface {
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Begin() (*sql.Tx, error)
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}
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// Querier is an interface for types that can execute SQL queries.
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// *sql.DB, *sql.Tx, and *DB all implement this.
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type Querier interface {
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Query(query string, args ...any) (*sql.Rows, error)
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}
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// Host pairs a *sql.DB with the host:port it was opened against.
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type Host struct {
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Addr string // "host:port"
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DB *sql.DB
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healthy atomic.Bool
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ping atomic.Int64 // Duration of the last health check ping, in nanoseconds
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}
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// Roles of a connection pool, see PoolStats
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const (
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PoolRolePrimary = "primary"
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PoolRoleReplica = "replica"
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)
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// PoolStats is one connection pool's statistics: the primary's or a replica's
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type PoolStats struct {
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Role string // PoolRolePrimary or PoolRoleReplica
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Addr string // "host:port"
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Healthy bool // The last health check (a ping) succeeded
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Stats sql.DBStats
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// PingDuration is how long the last health check ping took, including any wait for a free
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// connection, so a stalled database shows even when its pool is idle; 0 before the first check
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PingDuration time.Duration
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}
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