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fix(eth-indexer): make /eth/health O(1) #853

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Merged
raymondjacobson merged 1 commit into from
May 22, 2026
Merged

fix(eth-indexer): make /eth/health O(1) #853

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25 changes: 7 additions & 18 deletions eth/indexer/eth_indexer.go
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Original file line number Diff line number Diff line change
Expand Up @@ -501,30 +501,21 @@ type ethHealth struct {
LastBlockSeen uint64 `json:"last_block_seen"`
CheckpointBlock uint64 `json:"checkpoint_block"`
LastEventAt *time.Time `json:"last_event_at"`
TrackedWallets int64 `json:"tracked_wallets"`
CachedWallets int64 `json:"cached_wallets"`
}

// GetHealth returns indexer liveness in O(1) — all values are either in
// memory or come from a single-row PK lookup. Wallet-population counts
// previously lived on this response but were expensive on prod
// (UNION/COUNT across users + associated_wallets ≈ 3M rows, no index, can
// take 30s+) and don't actually answer "is the indexer alive?", which is
// what a health endpoint is for. If you want population stats, query
// eth_wallet_balances directly.
func (e *EthIndexer) GetHealth(ctx context.Context, maxEventLagSecs int64) (*ethHealth, error) {
checkpoint, err := e.loadCheckpoint(ctx)
if err != nil {
return nil, fmt.Errorf("loading checkpoint: %w", err)
}

var tracked, cached int64
err = e.pool.QueryRow(ctx, `
SELECT
(SELECT COUNT(*) FROM (
SELECT LOWER(wallet) FROM users WHERE wallet IS NOT NULL AND wallet <> ''
UNION
SELECT LOWER(wallet) FROM associated_wallets WHERE chain = 'eth' AND is_delete = FALSE
) t) AS tracked,
(SELECT COUNT(*) FROM eth_wallet_balances) AS cached
`).Scan(&tracked, &cached)
if err != nil {
return nil, fmt.Errorf("counting wallets: %w", err)
}

errs := make([]string, 0)
if !e.connected.Load() && e.wsURL != "" {
errs = append(errs, "websocket subscription not connected")
Expand All @@ -545,8 +536,6 @@ func (e *EthIndexer) GetHealth(ctx context.Context, maxEventLagSecs int64) (*eth
LastBlockSeen: e.lastBlockSeen.Load(),
CheckpointBlock: checkpoint,
LastEventAt: e.lastEventAt.Load(),
TrackedWallets: tracked,
CachedWallets: cached,
}, nil
}

Expand Down
11 changes: 10 additions & 1 deletion eth/indexer/server.go
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Original file line number Diff line number Diff line change
Expand Up @@ -5,12 +5,19 @@ import (
"encoding/json"
"net"
"net/http"
"time"

"github.com/gofiber/fiber/v2"
"github.com/mcuadros/go-defaults"
"go.uber.org/zap"
)

// healthHandlerTimeout caps how long /eth/health is willing to wait on
// downstream work (DB, etc.) before returning an error. The endpoint is
// supposed to be O(1); a 2s ceiling is generous and stops a future slow
// query from hanging the handler indefinitely.
const healthHandlerTimeout = 2 * time.Second

type Server struct {
*fiber.App
logger *zap.Logger
Expand Down Expand Up @@ -39,7 +46,9 @@ func NewServer(indexer *EthIndexer) *Server {
}
defaults.SetDefaults(&q)

health, err := indexer.GetHealth(c.Context(), q.MaxEventLagSecs)
ctx, cancel := context.WithTimeout(c.Context(), healthHandlerTimeout)
defer cancel()
health, err := indexer.GetHealth(ctx, q.MaxEventLagSecs)
if err != nil {
return c.Status(fiber.StatusInternalServerError).JSON(fiber.Map{
"error": err.Error(),
Expand Down
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