Refactor creation of prepared queries

CHANGELOG.md

@@ -5,6 +5,10 @@ project adheres to [Semantic Versioning](http://semver.org/).
 
 ## Unreleased
 
+- Refactor creation of prepared queries (#604, @mjungsbluth)
+
+  When using the opa-envoy-plugin as a Go library, the interface EvalContext contains a breaking change [#604](https://github.com/open-policy-agent/opa-envoy-plugin/pull/604) that allows users of the library to control all three types of options that can be passed during preparation and evaluation of the underlying Rego query.  
+
 ### Fixes
 
 - Support escaped forward-slashes (`\/`) in JSON request bodies (#256, @Dakatan).

envoyauth/evaluation.go

@@ -3,13 +3,11 @@ package envoyauth
 import (
 	"context"
 	"fmt"
-	"sync"
 
 	"github.com/open-policy-agent/opa/ast"
 	"github.com/open-policy-agent/opa/bundle"
 	"github.com/open-policy-agent/opa/config"
 	"github.com/open-policy-agent/opa/logging"
-	"github.com/open-policy-agent/opa/metrics"
 	"github.com/open-policy-agent/opa/rego"
 	"github.com/open-policy-agent/opa/storage"
 	"github.com/open-policy-agent/opa/topdown/builtins"
@@ -25,17 +23,21 @@ type EvalContext interface {
 	Store() storage.Store
 	Compiler() *ast.Compiler
 	Runtime() *ast.Term
-	PreparedQueryDoOnce() *sync.Once
 	InterQueryBuiltinCache() iCache.InterQueryCache
-	PreparedQuery() *rego.PreparedEvalQuery
-	SetPreparedQuery(*rego.PreparedEvalQuery)
 	Logger() logging.Logger
 	Config() *config.Config
 	DistributedTracing() tracing.Options
+	CreatePreparedQueryOnce(opts PrepareQueryOpts) (*rego.PreparedEvalQuery, error)
+}
+
+// PrepareQueryOpts - Options to prepare a Rego query to be passed to the CreatePreparedQueryOnce method
+type PrepareQueryOpts struct {
+	Opts        []func(*rego.Rego)
+	PrepareOpts []rego.PrepareOption
 }
 
 // Eval - Evaluates an input against a provided EvalContext and yields result
-func Eval(ctx context.Context, evalContext EvalContext, input ast.Value, result *EvalResult, opts ...func(*rego.Rego)) error {
+func Eval(ctx context.Context, evalContext EvalContext, input ast.Value, result *EvalResult, evalOpts ...rego.EvalOption) error {
 	var err error
 	logger := evalContext.Logger()
 
@@ -64,7 +66,19 @@ func Eval(ctx context.Context, evalContext EvalContext, input ast.Value, result
 		"txn":   result.TxnID,
 	}).Debug("Executing policy query.")
 
-	err = constructPreparedQuery(evalContext, result.Txn, result.Metrics, opts)
+	pq, err := evalContext.CreatePreparedQueryOnce(
+		PrepareQueryOpts{
+			Opts: []func(*rego.Rego){
+				rego.Metrics(result.Metrics),
+				rego.ParsedQuery(evalContext.ParsedQuery()),
+				rego.Compiler(evalContext.Compiler()),
+				rego.Store(evalContext.Store()),
+				rego.Transaction(result.Txn),
+				rego.Runtime(evalContext.Runtime()),
+				rego.EnablePrintStatements(true),
+				rego.DistributedTracingOpts(evalContext.DistributedTracing()),
+			},
+		})
 	if err != nil {
 		return err
 	}
@@ -76,15 +90,22 @@ func Eval(ctx context.Context, evalContext EvalContext, input ast.Value, result
 		ndbCache = builtins.NDBCache{}
 	}
 
+	evalOpts = append(
+		[]rego.EvalOption{
+			rego.EvalParsedInput(input),
+			rego.EvalTransaction(result.Txn),
+			rego.EvalMetrics(result.Metrics),
+			rego.EvalInterQueryBuiltinCache(evalContext.InterQueryBuiltinCache()),
+			rego.EvalPrintHook(&ph),
+			rego.EvalNDBuiltinCache(ndbCache),
+		},
+		evalOpts...,
+	)
+
 	var rs rego.ResultSet
-	rs, err = evalContext.PreparedQuery().Eval(
+	rs, err = pq.Eval(
 		ctx,
-		rego.EvalParsedInput(input),
-		rego.EvalTransaction(result.Txn),
-		rego.EvalMetrics(result.Metrics),
-		rego.EvalInterQueryBuiltinCache(evalContext.InterQueryBuiltinCache()),
-		rego.EvalPrintHook(&ph),
-		rego.EvalNDBuiltinCache(ndbCache),
+		evalOpts...,
 	)
 
 	switch {
@@ -101,28 +122,6 @@ func Eval(ctx context.Context, evalContext EvalContext, input ast.Value, result
 	return nil
 }
 
-func constructPreparedQuery(evalContext EvalContext, txn storage.Transaction, m metrics.Metrics, opts []func(*rego.Rego)) error {
-	var err error
-	var pq rego.PreparedEvalQuery
-	evalContext.PreparedQueryDoOnce().Do(func() {
-		opts = append(opts,
-			rego.Metrics(m),
-			rego.ParsedQuery(evalContext.ParsedQuery()),
-			rego.Compiler(evalContext.Compiler()),
-			rego.Store(evalContext.Store()),
-			rego.Transaction(txn),
-			rego.Runtime(evalContext.Runtime()),
-			rego.EnablePrintStatements(true),
-			rego.DistributedTracingOpts(evalContext.DistributedTracing()),
-		)
-
-		pq, err = rego.New(opts...).PrepareForEval(context.Background())
-		evalContext.SetPreparedQuery(&pq)
-	})
-
-	return err
-}
-
 func getRevision(ctx context.Context, store storage.Store, txn storage.Transaction, result *EvalResult) error {
 	revisions := map[string]string{}
 

envoyauth/evaluation_test.go

@@ -21,6 +21,7 @@ import (
 	"github.com/open-policy-agent/opa/storage"
 	"github.com/open-policy-agent/opa/storage/inmem"
 	iCache "github.com/open-policy-agent/opa/topdown/cache"
+	"github.com/open-policy-agent/opa/topdown/print"
 )
 
 func TestGetRevisionLegacy(t *testing.T) {
@@ -116,6 +117,15 @@ func TestGetRevisionMulti(t *testing.T) {
 
 }
 
+type testPrintHook struct {
+	printed string
+}
+
+func (h *testPrintHook) Print(pctx print.Context, msg string) error {
+	h.printed = msg
+	return nil
+}
+
 func TestEval(t *testing.T) {
 	ctx := context.Background()
 
@@ -180,6 +190,17 @@ func TestEval(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
+
+	hook := testPrintHook{}
+
+	erp, _, _ := NewEvalResult()
+	if err := Eval(ctx, server, inputValue, erp, rego.EvalPrintHook(&hook)); err != nil {
+		t.Fatal(err)
+	}
+
+	if exp, act := "{\"firstname\": \"foo\", \"lastname\": \"bar\"}", hook.printed; exp != act {
+		t.Errorf("expected last printed message to be %q, got %q", exp, act)
+	}
 }
 
 func testAuthzServer(logger logging.Logger) (*mockExtAuthzGrpcServer, error) {
@@ -254,6 +275,7 @@ type mockExtAuthzGrpcServer struct {
 	manager                *plugins.Manager
 	preparedQuery          *rego.PreparedEvalQuery
 	preparedQueryDoOnce    *sync.Once
+	preparedQueryErr       error
 	distributedTracingOpts tracing.Options
 }
 
@@ -301,6 +323,17 @@ func (m *mockExtAuthzGrpcServer) DistributedTracing() tracing.Options {
 	return m.distributedTracingOpts
 }
 
+func (m *mockExtAuthzGrpcServer) CreatePreparedQueryOnce(opts PrepareQueryOpts) (*rego.PreparedEvalQuery, error) {
+	m.preparedQueryDoOnce.Do(func() {
+		pq, err := rego.New(opts.Opts...).PrepareForEval(context.Background())
+
+		m.preparedQuery = &pq
+		m.preparedQueryErr = err
+	})
+
+	return m.preparedQuery, m.preparedQueryErr
+}
+
 type testPlugin struct {
 	events []logs.EventV1
 }

internal/internal.go

@@ -225,6 +225,7 @@ type envoyExtAuthzGrpcServer struct {
 	manager                *plugins.Manager
 	preparedQuery          *rego.PreparedEvalQuery
 	preparedQueryDoOnce    *sync.Once
+	preparedQueryErr       error
 	interQueryBuiltinCache iCache.InterQueryCache
 	distributedTracingOpts tracing.Options
 	metricAuthzDuration    prometheus.HistogramVec
@@ -279,6 +280,17 @@ func (p *envoyExtAuthzGrpcServer) DistributedTracing() tracing.Options {
 	return p.distributedTracingOpts
 }
 
+func (p *envoyExtAuthzGrpcServer) CreatePreparedQueryOnce(opts envoyauth.PrepareQueryOpts) (*rego.PreparedEvalQuery, error) {
+	p.preparedQueryDoOnce.Do(func() {
+		pq, err := rego.New(opts.Opts...).PrepareForEval(context.Background())
+
+		p.preparedQuery = &pq
+		p.preparedQueryErr = err
+	})
+
+	return p.preparedQuery, p.preparedQueryErr
+}
+
 func (p *envoyExtAuthzGrpcServer) Start(ctx context.Context) error {
 	p.manager.UpdatePluginStatus(PluginName, &plugins.Status{State: plugins.StateNotReady})
 	go p.listen()