services/horizon: Remove db2/core.

services/horizon/CHANGELOG.md

@@ -6,6 +6,11 @@ file. This project adheres to [Semantic Versioning](http://semver.org/).x
 ## Unreleased
 
 * Add `--parallel-workers` and `--parallel-job-size` to `horizon db reingest range`. `--parallel-workers` will parallelize reingestion using the supplied number of workers.
+* Remove Stellar Core's database dependency for non-ingesting instances of Horizon ((#2759)[https://github.com/stellar/go/pull/2759]).
+  Horizon doesn't require access to a Stellar Core database if it is only serving HTTP request, this allows the separation of front-end and ingesting instances. 
+  The following config parameters were removed:
+  - `core-db-max-open-connections`
+  - `core-db-max-idle-connections`
 
 ## v1.5.0
 

services/horizon/cmd/root.go

@@ -174,7 +174,7 @@ var configOpts = support.ConfigOptions{
 		ConfigKey:   &config.MaxDBConnections,
 		OptType:     types.Int,
 		FlagDefault: 0,
-		Usage:       "when set has a priority over horizon-db-max-open-connections, horizon-db-max-idle-connections, core-db-max-open-connections, core-db-max-idle-connections. max horizon database open connections. may need to be increased when responses are slow but DB CPU is normal",
+		Usage:       "when set has a priority over horizon-db-max-open-connections, horizon-db-max-idle-connections. max horizon database open connections may need to be increased when responses are slow but DB CPU is normal",
 	},
 	&support.ConfigOption{
 		Name:        "horizon-db-max-open-connections",
@@ -190,20 +190,6 @@ var configOpts = support.ConfigOptions{
 		FlagDefault: 20,
 		Usage:       "max horizon database idle connections. may need to be set to the same value as horizon-db-max-open-connections when responses are slow and DB CPU is normal, because it may indicate that a lot of time is spent closing/opening idle connections. This can happen in case of high variance in number of requests. must be equal or lower than max open connections",
 	},
-	&support.ConfigOption{
-		Name:        "core-db-max-open-connections",
-		ConfigKey:   &config.CoreDBMaxOpenConnections,
-		OptType:     types.Int,
-		FlagDefault: 20,
-		Usage:       "max core database open connections. may need to be increased when responses are slow but DB CPU is normal",
-	},
-	&support.ConfigOption{
-		Name:        "core-db-max-idle-connections",
-		ConfigKey:   &config.CoreDBMaxIdleConnections,
-		OptType:     types.Int,
-		FlagDefault: 20,
-		Usage:       "max core database idle connections. may need to be set to the same value as core-db-max-open-connections when responses are slow and DB CPU is normal, because it may indicate that a lot of time is spent closing/opening idle connections. This can happen in case of high variance in number of requests. must be equal or lower than max open connections",
-	},
 	&support.ConfigOption{
 		Name:           "sse-update-frequency",
 		ConfigKey:      &config.SSEUpdateFrequency,
@@ -430,8 +416,6 @@ func initRootConfig() {
 	if config.MaxDBConnections != 0 {
 		config.HorizonDBMaxOpenConnections = config.MaxDBConnections
 		config.HorizonDBMaxIdleConnections = config.MaxDBConnections
-		config.CoreDBMaxOpenConnections = config.MaxDBConnections
-		config.CoreDBMaxIdleConnections = config.MaxDBConnections
 	}
 }
 

services/horizon/internal/app.go

@@ -14,7 +14,6 @@ import (
 	"github.com/stellar/go/clients/stellarcore"
 	proto "github.com/stellar/go/protocols/stellarcore"
 	horizonContext "github.com/stellar/go/services/horizon/internal/context"
-	"github.com/stellar/go/services/horizon/internal/db2/core"
 	"github.com/stellar/go/services/horizon/internal/db2/history"
 	"github.com/stellar/go/services/horizon/internal/expingest"
 	"github.com/stellar/go/services/horizon/internal/ledger"
@@ -61,7 +60,6 @@ type App struct {
 	config          Config
 	web             *web
 	historyQ        *history.Q
-	coreQ           *core.Q
 	ctx             context.Context
 	cancel          func()
 	horizonVersion  string
@@ -79,7 +77,6 @@ type App struct {
 	historyElderLedgerGauge  metrics.Gauge
 	horizonConnGauge         metrics.Gauge
 	coreLatestLedgerGauge    metrics.Gauge
-	coreConnGauge            metrics.Gauge
 	goroutineGauge           metrics.Gauge
 }
 
@@ -181,7 +178,6 @@ func (a *App) Close() {
 // closed" errors.
 func (a *App) CloseDB() {
 	a.historyQ.Session.DB.Close()
-	a.coreQ.Session.DB.Close()
 }
 
 // HistoryQ returns a helper object for performing sql queries against the
@@ -196,18 +192,6 @@ func (a *App) HorizonSession(ctx context.Context) *db.Session {
 	return &db.Session{DB: a.historyQ.Session.DB, Ctx: ctx}
 }
 
-// CoreSession returns a new session that loads data from the stellar core
-// database. The returned session is bound to `ctx`.
-func (a *App) CoreSession(ctx context.Context) *db.Session {
-	return &db.Session{DB: a.coreQ.Session.DB, Ctx: ctx}
-}
-
-// CoreQ returns a helper object for performing sql queries aginst the
-// stellar core database.
-func (a *App) CoreQ() *core.Q {
-	return a.coreQ
-}
-
 // IsHistoryStale returns true if the latest history ledger is more than
 // `StaleThreshold` ledgers behind the latest core ledger
 func (a *App) IsHistoryStale() bool {
@@ -427,7 +411,6 @@ func (a *App) UpdateMetrics() {
 	a.coreLatestLedgerGauge.Update(int64(ls.CoreLatest))
 
 	a.horizonConnGauge.Update(int64(a.historyQ.Session.DB.Stats().OpenConnections))
-	a.coreConnGauge.Update(int64(a.coreQ.Session.DB.Stats().OpenConnections))
 }
 
 // DeleteUnretainedHistory forwards to the app's reaper.  See
@@ -479,7 +462,6 @@ func (a *App) init() {
 
 	// horizon-db and core-db
 	mustInitHorizonDB(a)
-	mustInitCoreDB(a)
 
 	if a.config.Ingest {
 		// expingester

services/horizon/internal/config.go

@@ -24,8 +24,6 @@ type Config struct {
 	MaxDBConnections            int
 	HorizonDBMaxOpenConnections int
 	HorizonDBMaxIdleConnections int
-	CoreDBMaxOpenConnections    int
-	CoreDBMaxIdleConnections    int
 
 	SSEUpdateFrequency time.Duration
 	ConnectionTimeout  time.Duration

services/horizon/internal/docs/reference/endpoints/metrics.md

@@ -228,10 +228,7 @@ As noted above, Horizon relies on Stellar Core to stay in sync with the Stellar
 ```shell
 "stellar_core.latest_ledger": {
   "value": 19203710
-},
-"stellar_core.open_connections": {
-  "value": 4
-},
+}
 ```
 
 #### Transaction Submission

services/horizon/internal/expingest/database_backend_test.go

@@ -1,11 +1,10 @@
 package expingest
 
 import (
-	"github.com/stellar/go/network"
 	"testing"
 
 	"github.com/stellar/go/exp/ingest/ledgerbackend"
-	"github.com/stellar/go/services/horizon/internal/db2/core"
+	"github.com/stellar/go/network"
 	"github.com/stellar/go/services/horizon/internal/test"
 )
 
@@ -23,12 +22,11 @@ func TestGetLatestLedger(t *testing.T) {
 func TestGetLatestLedgerNotFound(t *testing.T) {
 	tt := test.Start(t).ScenarioWithoutHorizon("base")
 	defer tt.Finish()
-	q := &core.Q{tt.CoreSession()}
 
 	_, err := tt.CoreDB.Exec(`DELETE FROM ledgerheaders`)
 	tt.Assert.NoError(err, "failed to remove ledgerheaders")
 
-	backend, err := ledgerbackend.NewDatabaseBackendFromSession(q.Session, network.TestNetworkPassphrase)
+	backend, err := ledgerbackend.NewDatabaseBackendFromSession(tt.CoreSession(), network.TestNetworkPassphrase)
 	tt.Assert.NoError(err)
 	_, err = backend.GetLatestLedgerSequence()
 	tt.Assert.EqualError(err, "no ledgers exist in ledgerheaders table")

services/horizon/internal/init.go

@@ -8,7 +8,6 @@ import (
 	"github.com/rcrowley/go-metrics"
 
 	"github.com/stellar/go/exp/orderbook"
-	"github.com/stellar/go/services/horizon/internal/db2/core"
 	"github.com/stellar/go/services/horizon/internal/db2/history"
 	"github.com/stellar/go/services/horizon/internal/expingest"
 	"github.com/stellar/go/services/horizon/internal/simplepath"
@@ -51,27 +50,6 @@ func mustInitHorizonDB(app *App) {
 	)}
 }
 
-func mustInitCoreDB(app *App) {
-	maxIdle := app.config.CoreDBMaxIdleConnections
-	maxOpen := app.config.CoreDBMaxOpenConnections
-	if app.config.Ingest {
-		maxIdle -= expingest.MaxDBConnections
-		maxOpen -= expingest.MaxDBConnections
-		if maxIdle <= 0 {
-			log.Fatalf("max idle connections to stellar-core db must be greater than %d", expingest.MaxDBConnections)
-		}
-		if maxOpen <= 0 {
-			log.Fatalf("max open connections to stellar-core db must be greater than %d", expingest.MaxDBConnections)
-		}
-	}
-
-	app.coreQ = &core.Q{mustNewDBSession(
-		app.config.StellarCoreDatabaseURL,
-		maxIdle,
-		maxOpen,
-	)}
-}
-
 func initExpIngester(app *App) {
 	var err error
 	app.expingester, err = expingest.NewSystem(expingest.Config{
@@ -144,14 +122,12 @@ func initDbMetrics(app *App) {
 	app.historyElderLedgerGauge = metrics.NewGauge()
 	app.coreLatestLedgerGauge = metrics.NewGauge()
 	app.horizonConnGauge = metrics.NewGauge()
-	app.coreConnGauge = metrics.NewGauge()
 	app.goroutineGauge = metrics.NewGauge()
 	app.metrics.Register("history.latest_ledger", app.historyLatestLedgerGauge)
 	app.metrics.Register("history.elder_ledger", app.historyElderLedgerGauge)
 	app.metrics.Register("stellar_core.latest_ledger", app.coreLatestLedgerGauge)
 	app.metrics.Register("order_book_stream.latest_ledger", app.orderBookStream.LatestLedgerGauge)
 	app.metrics.Register("history.open_connections", app.horizonConnGauge)
-	app.metrics.Register("stellar_core.open_connections", app.coreConnGauge)
 	app.metrics.Register("goroutines", app.goroutineGauge)
 }