Add --max_assets_per_path_request flag (#4046)

services/horizon/CHANGELOG.md

@@ -11,6 +11,7 @@ file. This project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Changes
 
+* Add a new horizon flag `--max-assets-per-path-request` (`15` by default) that sets the number of assets to consider for strict-send and strict-recieve ([4046](https://github.com/stellar/go/pull/4046))
 * Add `is_source=true` parameter to transaction endpoints (e.g. `GET /accounts/{account_id}/transactions?is_source=true` ) to
   allow filtering transactions based on their source account. [4044](https://github.com/stellar/go/pull/4044)
 * Add an endpoint that allows querying for which liquidity pools an account is participating in [4043](https://github.com/stellar/go/pull/4043)

services/horizon/internal/app.go

@@ -211,6 +211,10 @@ func (a *App) HorizonSession() db.SessionInterface {
 	return a.historyQ.SessionInterface.Clone()
 }
 
+func (a *App) Config() Config {
+	return a.config
+}
+
 // UpdateCoreLedgerState triggers a refresh of Stellar-Core ledger state.
 // This is done separately from Horizon ledger state update to prevent issues
 // in case Stellar-Core query timeout.
@@ -511,21 +515,22 @@ func (a *App) init() error {
 	initTxSubMetrics(a)
 
 	routerConfig := httpx.RouterConfig{
-		DBSession:             a.historyQ.SessionInterface,
-		TxSubmitter:           a.submitter,
-		RateQuota:             a.config.RateQuota,
-		BehindCloudflare:      a.config.BehindCloudflare,
-		BehindAWSLoadBalancer: a.config.BehindAWSLoadBalancer,
-		SSEUpdateFrequency:    a.config.SSEUpdateFrequency,
-		StaleThreshold:        a.config.StaleThreshold,
-		ConnectionTimeout:     a.config.ConnectionTimeout,
-		NetworkPassphrase:     a.config.NetworkPassphrase,
-		MaxPathLength:         a.config.MaxPathLength,
-		PathFinder:            a.paths,
-		PrometheusRegistry:    a.prometheusRegistry,
-		CoreGetter:            a,
-		HorizonVersion:        a.horizonVersion,
-		FriendbotURL:          a.config.FriendbotURL,
+		DBSession:               a.historyQ.SessionInterface,
+		TxSubmitter:             a.submitter,
+		RateQuota:               a.config.RateQuota,
+		BehindCloudflare:        a.config.BehindCloudflare,
+		BehindAWSLoadBalancer:   a.config.BehindAWSLoadBalancer,
+		SSEUpdateFrequency:      a.config.SSEUpdateFrequency,
+		StaleThreshold:          a.config.StaleThreshold,
+		ConnectionTimeout:       a.config.ConnectionTimeout,
+		NetworkPassphrase:       a.config.NetworkPassphrase,
+		MaxPathLength:           a.config.MaxPathLength,
+		MaxAssetsPerPathRequest: a.config.MaxAssetsPerPathRequest,
+		PathFinder:              a.paths,
+		PrometheusRegistry:      a.prometheusRegistry,
+		CoreGetter:              a,
+		HorizonVersion:          a.horizonVersion,
+		FriendbotURL:            a.config.FriendbotURL,
 		HealthCheck: healthCheck{
 			session: a.historyQ.SessionInterface,
 			ctx:     a.ctx,

services/horizon/internal/config.go

@@ -45,8 +45,10 @@ type Config struct {
 	LogFile            string
 
 	// MaxPathLength is the maximum length of the path returned by `/paths` endpoint.
-	MaxPathLength          uint
-	DisablePoolPathFinding bool
+	MaxPathLength uint
+	// MaxAssetsPerPathRequest is the maximum number of assets considered for `/paths/strict-send` and `/paths/strict-recieve`
+	MaxAssetsPerPathRequest int
+	DisablePoolPathFinding  bool
 
 	NetworkPassphrase string
 	SentryDSN         string

services/horizon/internal/flags.go

@@ -356,6 +356,13 @@ func Flags() (*Config, support.ConfigOptions) {
 			FlagDefault: uint(3),
 			Usage:       "the maximum number of assets on the path in `/paths` endpoint, warning: increasing this value will increase /paths response time",
 		},
+		&support.ConfigOption{
+			Name:        "max-assets-per-path-request",
+			ConfigKey:   &config.MaxAssetsPerPathRequest,
+			OptType:     types.Int,
+			FlagDefault: int(15),
+			Usage:       "the maximum number of assets in '/paths/strict-send' and '/paths/strict-recieve' endpoints",
+		},
 		&support.ConfigOption{
 			Name:        "disable-pool-path-finding",
 			ConfigKey:   &config.DisablePoolPathFinding,

services/horizon/internal/httpx/router.go

@@ -26,27 +26,26 @@ import (
 	"github.com/stellar/go/support/render/problem"
 )
 
-const maxAssetsForPathFinding = 15
-
 type RouterConfig struct {
 	DBSession        db.SessionInterface
 	PrimaryDBSession db.SessionInterface
 	TxSubmitter      *txsub.System
 	RateQuota        *throttled.RateQuota
 
-	BehindCloudflare      bool
-	BehindAWSLoadBalancer bool
-	SSEUpdateFrequency    time.Duration
-	StaleThreshold        uint
-	ConnectionTimeout     time.Duration
-	NetworkPassphrase     string
-	MaxPathLength         uint
-	PathFinder            paths.Finder
-	PrometheusRegistry    *prometheus.Registry
-	CoreGetter            actions.CoreStateGetter
-	HorizonVersion        string
-	FriendbotURL          *url.URL
-	HealthCheck           http.Handler
+	BehindCloudflare        bool
+	BehindAWSLoadBalancer   bool
+	SSEUpdateFrequency      time.Duration
+	StaleThreshold          uint
+	ConnectionTimeout       time.Duration
+	NetworkPassphrase       string
+	MaxPathLength           uint
+	MaxAssetsPerPathRequest int
+	PathFinder              paths.Finder
+	PrometheusRegistry      *prometheus.Registry
+	CoreGetter              actions.CoreStateGetter
+	HorizonVersion          string
+	FriendbotURL            *url.URL
+	HealthCheck             http.Handler
 }
 
 type Router struct {
@@ -189,13 +188,13 @@ func (r *Router) addRoutes(config *RouterConfig, rateLimiter *throttled.HTTPRate
 			StaleThreshold:       config.StaleThreshold,
 			SetLastLedgerHeader:  true,
 			MaxPathLength:        config.MaxPathLength,
-			MaxAssetsParamLength: maxAssetsForPathFinding,
+			MaxAssetsParamLength: config.MaxAssetsPerPathRequest,
 			PathFinder:           config.PathFinder,
 		}}
 		findFixedPaths := ObjectActionHandler{actions.FindFixedPathsHandler{
 			MaxPathLength:        config.MaxPathLength,
 			SetLastLedgerHeader:  true,
-			MaxAssetsParamLength: maxAssetsForPathFinding,
+			MaxAssetsParamLength: config.MaxAssetsPerPathRequest,
 			PathFinder:           config.PathFinder,
 		}}
 		r.With(stateMiddleware.Wrap).Method(http.MethodGet, "/paths", findPaths)

services/horizon/internal/integration/parameters_test.go

@@ -145,6 +145,25 @@ func TestCaptiveCoreConfigFilesystemState(t *testing.T) {
 	})
 }
 
+func TestMaxAssetsForPathRequests(t *testing.T) {
+	t.Run("default", func(t *testing.T) {
+		test := NewParameterTest(t, map[string]string{})
+		err := test.StartHorizon()
+		assert.NoError(t, err)
+		test.WaitForHorizon()
+		assert.Equal(t, test.Horizon().Config().MaxAssetsPerPathRequest, 15)
+		test.Shutdown()
+	})
+	t.Run("set to 2", func(t *testing.T) {
+		test := NewParameterTest(t, map[string]string{"max-assets-per-path-request": "2"})
+		err := test.StartHorizon()
+		assert.NoError(t, err)
+		test.WaitForHorizon()
+		assert.Equal(t, test.Horizon().Config().MaxAssetsPerPathRequest, 2)
+		test.Shutdown()
+	})
+}
+
 // Pattern taken from testify issue:
 // https://github.com/stretchr/testify/issues/858#issuecomment-600491003
 //