Fix reload errors for NGINX when large num of match conditions are used

internal/mode/static/nginx/config/http/config.go

@@ -16,7 +16,7 @@ type Location struct {
 	ProxySSLVerify  *ProxySSLVerify
 	Path            string
 	ProxyPass       string
-	HTTPMatchVar    string
+	HTTPMatchVar    []string
 	Rewrites        []string
 	ProxySetHeaders []Header
 }

internal/mode/static/nginx/config/servers.go

@@ -1,6 +1,7 @@
 package config
 
 import (
+	"bytes"
 	"encoding/json"
 	"fmt"
 	"strings"
@@ -16,6 +17,7 @@ const (
 	// HeaderMatchSeparator is the separator for constructing header-based match for NJS.
 	HeaderMatchSeparator = ":"
 	rootPath             = "/"
+	matchMaxLength       = 2000 // TODO: account for character escaping when mapped to config
 )
 
 // baseHeaders contains the constant headers set in each server block
@@ -558,17 +560,48 @@ func convertSetHeaders(headers []dataplane.HTTPHeader) []http.Header {
 	return locHeaders
 }
 
-func convertMatchesToString(matches []httpMatch) string {
+func convertMatchesToString(matches []httpMatch) []string {
 	// FIXME(sberman): De-dupe matches and associated locations
 	// so we don't need nginx/njs to perform unnecessary matching.
 	// https://github.com/nginxinc/nginx-gateway-fabric/issues/662
-	b, err := json.Marshal(matches)
-	if err != nil {
-		// panic is safe here because we should never fail to marshal the match unless we constructed it incorrectly.
-		panic(fmt.Errorf("could not marshal http match: %w", err))
+
+	var matchList []string
+
+	var buffer bytes.Buffer
+	for _, match := range matches {
+		matchBytes, err := json.Marshal(match)
+		if err != nil {
+			// panic is safe here because we should never fail to marshal the match unless we constructed it incorrectly.
+			panic(fmt.Errorf("could not marshal http match: %w", err))
+		}
+		matchLen := len(matchBytes)
+		if buffer.Len()+matchLen+4 > matchMaxLength {
+			// Flush buffer if adding current match exceeds the maximum length
+			buffer.WriteString("]")
+			matchList = append(matchList, buffer.String())
+			buffer.Reset()
+			buffer.WriteString("[")
+		} else {
+			if buffer.Len() > 1 {
+				// Add comma if not first match in the buffer
+				buffer.WriteString(",")
+			} else {
+				// Add opening braces if the first match in the buffer
+				buffer.WriteString("[")
+			}
+		}
+		buffer.Write(matchBytes)
+	}
+
+	if buffer.Len() > 0 {
+		buffer.WriteString("]")
+		matchList = append(matchList, buffer.String())
 	}
 
-	return string(b)
+	for _, m := range matchList {
+		fmt.Println("match --> ", m)
+	}
+	return matchList
 }
 
 func exactPath(path string) string {

internal/mode/static/nginx/config/servers_template.go

@@ -41,10 +41,10 @@ server {
         return {{ $l.Return.Code }} "{{ $l.Return.Body }}";
         {{- end }}
 
-        {{- if $l.HTTPMatchVar }}
-        set $http_matches {{ $l.HTTPMatchVar | printf "%q" }};
-        js_content httpmatches.redirect;
+        {{ range $i, $h := $l.HTTPMatchVar }}
+        set $http_matches_{{ $i }} {{ $h | printf "%q" }};
         {{- end }}
+        js_content httpmatches.redirect;
 
         {{- if $l.ProxyPass -}}
             {{ range $h := $l.ProxySetHeaders }}

internal/mode/static/nginx/config/servers_test.go

@@ -508,11 +508,12 @@ func TestCreateServers(t *testing.T) {
 		},
 	}
 
-	expectedMatchString := func(m []httpMatch) string {
+	expectedMatchString := func(m []httpMatch) []string {
 		g := NewWithT(t)
 		b, err := json.Marshal(m)
 		g.Expect(err).ToNot(HaveOccurred())
-		return string(b)
+		str := string(b)
+		return []string{str}
 	}
 
 	slashMatches := []httpMatch{

internal/mode/static/nginx/modules/src/httpmatches.js

@@ -50,22 +50,26 @@ function redirect(r) {
 }
 
 function extractMatchesFromRequest(r) {
-  if (!r.variables[MATCHES_VARIABLE]) {
-    throw Error(
-      `cannot redirect the request; the variable ${MATCHES_VARIABLE} is not defined on the request object`,
-    );
-  }
-
+  let index = 0;
   let matches;
 
-  try {
-    matches = JSON.parse(r.variables[MATCHES_VARIABLE]);
-  } catch (e) {
-    throw Error(
-      `cannot redirect the request; error parsing ${r.variables[MATCHES_VARIABLE]} into a JSON object: ${e}`,
-    );
+  while (true) {
+    const MATCHES_VARIABLE = `http_matches_${index}`;
+    if (!r.variables[MATCHES_VARIABLE]) {
+      break;
+    }
+
+    try {
+      matches = JSON.parse(r.variables[MATCHES_VARIABLE]);
+    } catch (e) {
+      throw Error(
+        `cannot redirect the request; error parsing ${r.variables[MATCHES_VARIABLE]} into a JSON object: ${e}`,
+      );
+    }
   }
 
+  console.log('matches in js', matches);
+
   if (!Array.isArray(matches)) {
     throw Error(`cannot redirect the request; expected a list of matches, got ${matches}`);
   }