276 lines
6.5 KiB
Go
276 lines
6.5 KiB
Go
package postgres
|
|
|
|
import (
|
|
"context"
|
|
"crypto/rand"
|
|
"encoding/hex"
|
|
"errors"
|
|
"fmt"
|
|
"time"
|
|
|
|
"github.com/jackc/pgx/v5"
|
|
"github.com/jackc/pgx/v5/pgxpool"
|
|
"golang.org/x/exp/slog"
|
|
)
|
|
|
|
type QueuedMessage struct {
|
|
// ID of the message. Unique.
|
|
ID string
|
|
Topic string
|
|
Payload []byte
|
|
CreatedAt time.Time
|
|
UpdatedAt time.Time
|
|
|
|
// visibleAt utilizes visibility in the queue. This is used
|
|
// if message was not commited for a long time. (Acked or Nacked)
|
|
visibleAt time.Time
|
|
// versionID of the message. For future use to provide consistency.
|
|
// In case message is tried to be acked with different version id,
|
|
// this message will be discarded and error will be returned.
|
|
versionID uint64
|
|
}
|
|
|
|
type DequeueParams struct {
|
|
// Timeout sets visibleAfter value to the future. Used in case
|
|
// retry is needed, if this message should be handled for sure
|
|
// atleast once.
|
|
// If timeout is 0, this message will be deleted from queue.
|
|
Timeout time.Duration
|
|
Topic string
|
|
}
|
|
|
|
type EnqueueParams struct {
|
|
// Topic to which this message belongs to.
|
|
Topic string
|
|
// Payload of the message.
|
|
Payload []byte
|
|
// VisibleTimeout
|
|
VisibleTimeout time.Duration
|
|
}
|
|
|
|
type QueueClient interface {
|
|
// Enqueue a message into message bus.
|
|
Enqueue(context.Context, EnqueueParams) (QueuedMessage, error)
|
|
// Dequeue a message from message bus.
|
|
Dequeue(context.Context, DequeueParams) (QueuedMessage, error)
|
|
|
|
// Ack removes message from queue in case versionID matches.
|
|
Ack(context.Context, QueuedMessage) error
|
|
// Nack sets visibilityAfter to now() and also updates versionID.
|
|
Nack(context.Context, QueuedMessage) error
|
|
}
|
|
|
|
func (c *client) Queue() QueueClient {
|
|
return &queueClient{
|
|
pool: c.pool,
|
|
logger: c.log.WithGroup("queue"),
|
|
}
|
|
}
|
|
|
|
type queueClient struct {
|
|
pool *pgxpool.Pool
|
|
logger *slog.Logger
|
|
}
|
|
|
|
const tableCreateQuery = `
|
|
CREATE TABLE smth.queue (
|
|
id TEXT NOT NULL,
|
|
version_id BIGINT NOT NULL,
|
|
topic TEXT NOT NULL DEFAULT '',
|
|
payload BYTEA NULL,
|
|
created_at TIMESTAMP WITHOUT TIME ZONE NOT NULL,
|
|
updated_at TIMESTAMP WITHOUT TIME ZONE NOT NULL,
|
|
visible_at TIMESTAMP WITHOUT TIME ZONE NOT NULL,
|
|
|
|
CONSTRAINT PRIMARY KEY (id)
|
|
);
|
|
CREATE INDEX queue_visible_at_idx ON smth.queue(visible_at ASC);
|
|
CREATE INDEX queue_topic_idx ON smth.queue(topic);`
|
|
|
|
func (c *queueClient) scanIntoMessage(row pgx.Row) (qm QueuedMessage, err error) {
|
|
err = row.Scan(
|
|
&qm.ID,
|
|
&qm.Topic,
|
|
&qm.Payload,
|
|
&qm.CreatedAt,
|
|
&qm.UpdatedAt,
|
|
&qm.visibleAt,
|
|
&qm.versionID,
|
|
)
|
|
if err != nil {
|
|
if errors.Is(err, pgx.ErrNoRows) {
|
|
return qm, ErrNoMessage
|
|
}
|
|
|
|
return qm, fmt.Errorf("scanning row: %w", err)
|
|
}
|
|
|
|
return qm, nil
|
|
}
|
|
|
|
func (c *queueClient) Enqueue(ctx context.Context, params EnqueueParams) (qm QueuedMessage, err error) {
|
|
const initialVersion = 1
|
|
const query = `INSERT INTO smth.queue
|
|
(id, topic, payload, created_at, updated_at, visible_at, version_id)
|
|
VALUES
|
|
($1, $2, $3, NOW(), NOW(), $4, $5)
|
|
RETURNING
|
|
id, topic, payload, created_at, updated_at, visible_at, version_id`
|
|
|
|
args := []any{
|
|
c.generateID(),
|
|
params.Topic,
|
|
params.Payload,
|
|
time.Now().Add(params.VisibleTimeout).UTC(),
|
|
initialVersion,
|
|
}
|
|
|
|
qt := traceMethod(ctx, c.logger, "Enqueue")
|
|
defer qt.finish(&err)
|
|
|
|
qt.query(query, args...)
|
|
|
|
qm, err = c.scanIntoMessage(c.pool.QueryRow(ctx, query, args...))
|
|
if err != nil {
|
|
return qm, fmt.Errorf("scanning row: %w", err)
|
|
}
|
|
|
|
return qm, nil
|
|
}
|
|
|
|
func (c *queueClient) Dequeue(ctx context.Context, params DequeueParams) (qm QueuedMessage, err error) {
|
|
const queryDeletePrefix = `DELETE FROM smth.queue`
|
|
const queryUpdatePrefix = `UPDATE smth.queue SET updated_at = NOW(), version_id = version_id + 1, visible_at = $2`
|
|
const querySuffix = ` WHERE id = (
|
|
SELECT id
|
|
FROM smth.queue
|
|
WHERE
|
|
topic = $1
|
|
and visible_at < NOW()
|
|
ORDER BY visible_at ASC
|
|
LIMIT 1
|
|
FOR UPDATE SKIP LOCKED
|
|
) RETURNING id, topic, payload, created_at, updated_at, visible_at, version_id`
|
|
|
|
var query string
|
|
args := append(
|
|
make([]any, 0, 2),
|
|
params.Topic,
|
|
)
|
|
if params.Timeout == 0 {
|
|
query = queryDeletePrefix + querySuffix
|
|
} else {
|
|
query = queryUpdatePrefix + querySuffix
|
|
args = append(args, time.Now().UTC().Add(params.Timeout))
|
|
}
|
|
|
|
qt := traceMethod(ctx, c.logger, "Dequeue")
|
|
defer qt.finish(&err)
|
|
|
|
qt.query(query, args...)
|
|
|
|
qm, err = c.scanIntoMessage(c.pool.QueryRow(ctx, query, args...))
|
|
if err != nil {
|
|
return qm, fmt.Errorf("querying: %w", err)
|
|
}
|
|
|
|
return qm, nil
|
|
}
|
|
|
|
func (c *queueClient) Ack(ctx context.Context, qm QueuedMessage) (err error) {
|
|
const query = `DELETE FROM smth.queue` +
|
|
` WHERE id = $1` +
|
|
` AND version_id = $2`
|
|
|
|
return c.modifyByMessage(ctx, qm, "Ack", query)
|
|
}
|
|
|
|
func (c *queueClient) Nack(ctx context.Context, qm QueuedMessage) error {
|
|
const query = `UPDATE smth.queue SET` +
|
|
` visible_at = TO_TIMESTMAP(0)` +
|
|
`, updated_at = NOW()` +
|
|
` WHERE id = $1 AND version_id = $2`
|
|
|
|
return c.modifyByMessage(ctx, qm, "Nack", query)
|
|
}
|
|
|
|
func (c *queueClient) modifyByMessage(ctx context.Context, qm QueuedMessage, method, query string) (err error) {
|
|
if qm.versionID == 0 {
|
|
panic("queued message was not fetched")
|
|
}
|
|
|
|
args := []any{
|
|
&qm.ID,
|
|
&qm.versionID,
|
|
}
|
|
|
|
qt := traceMethod(ctx, c.logger, method)
|
|
defer qt.finish(&err)
|
|
|
|
qt.query(query, args...)
|
|
|
|
tag, err := c.pool.Exec(ctx, query, args...)
|
|
if err != nil {
|
|
return fmt.Errorf("executing query: %w", err)
|
|
}
|
|
|
|
affected := tag.RowsAffected()
|
|
qt.setResultCount(affected)
|
|
|
|
if affected == 0 {
|
|
return ErrVersionIDMismatch
|
|
}
|
|
|
|
return nil
|
|
}
|
|
|
|
func (c *queueClient) generateID() string {
|
|
var idByte [8]byte
|
|
_, _ = rand.Read(idByte[:])
|
|
return hex.EncodeToString(idByte[:])
|
|
}
|
|
|
|
type queryTracer struct {
|
|
ctx context.Context
|
|
logger *slog.Logger
|
|
start time.Time
|
|
count int64
|
|
}
|
|
|
|
func (qt *queryTracer) query(query string, args ...any) {
|
|
qt.logger.DebugContext(qt.ctx, "executing query", slog.String("query", query), slog.Any("args", args))
|
|
}
|
|
|
|
func (qt *queryTracer) setResultCount(count int64) {
|
|
qt.count = count
|
|
}
|
|
|
|
func (qt *queryTracer) finish(errptr *error) {
|
|
var err error
|
|
if errptr != nil {
|
|
err = *errptr
|
|
}
|
|
|
|
var level slog.Level
|
|
if err == nil {
|
|
level = slog.LevelDebug
|
|
} else {
|
|
level = slog.LevelDebug
|
|
}
|
|
|
|
qt.logger.Log(qt.ctx, level,
|
|
"query finished",
|
|
slog.Bool("success", err == nil),
|
|
slog.Duration("elapsed", time.Since(qt.start)),
|
|
slog.Int64("rows_count", qt.count),
|
|
)
|
|
}
|
|
|
|
func traceMethod(ctx context.Context, log *slog.Logger, method string) *queryTracer {
|
|
return &queryTracer{
|
|
ctx: ctx,
|
|
logger: log.With(slog.String("method", method)),
|
|
start: time.Now(),
|
|
}
|
|
}
|