Use thrift config for thrift server

Summary:
SRP Emulation failure due to D28695635 (facebook@f1d2779) deleted the GFlag usage for thrift server.

- Replace the GFlag usage with Open/R thrift config;
- Change the SSL enable logic from
```
if (sslContext_) {
```
to
```
if (config_->isSecureThriftServerEnabled()) {
```

Reviewed By: xiangxu1121

Differential Revision: D28977793

fbshipit-source-id: ee9cbfc1704028065d72db27505188e626b47f5c

openr/Main.cpp

@@ -489,7 +489,7 @@ main(int argc, char** argv) {
     setupThriftServerTls(
         *thriftCtrlServer,
         config->getSSLThriftPolicy(),
-        config->getSSLAcceptablePeers(),
+        config->getSSLSeedPath(),
         sslContext);
   }
 

openr/config/Config.h

@@ -369,7 +369,7 @@ class Config {
   }
 
   const std::string
-  getSSLCertPath() {
+  getSSLCertPath() const {
     auto certPath = getThriftServerConfig().x509_cert_path_ref();
     if ((not certPath) && isSecureThriftServerEnabled()) {
       throw std::invalid_argument(
@@ -379,7 +379,7 @@ class Config {
   }
 
   const std::string
-  getSSLEccCurve() {
+  getSSLEccCurve() const {
     auto eccCurve = getThriftServerConfig().ecc_curve_name_ref();
     if ((not eccCurve) && isSecureThriftServerEnabled()) {
       throw std::invalid_argument(
@@ -389,7 +389,7 @@ class Config {
   }
 
   const std::string
-  getSSLCaPath() {
+  getSSLCaPath() const {
     auto caPath = getThriftServerConfig().x509_ca_path_ref();
     if ((not caPath) && isSecureThriftServerEnabled()) {
       throw std::invalid_argument(
@@ -399,7 +399,7 @@ class Config {
   }
 
   const std::string
-  getSSLKeyPath() {
+  getSSLKeyPath() const {
     std::string keyPath;
     const auto& keyPathConfig = getThriftServerConfig().x509_key_path_ref();
 
@@ -412,6 +412,16 @@ class Config {
     return keyPath;
   }
 
+  const std::string
+  getSSLSeedPath() const {
+    auto seedPath = getThriftServerConfig().ticket_seed_path_ref();
+    if ((not seedPath) && isSecureThriftServerEnabled()) {
+      throw std::invalid_argument(
+          "enable_secure_thrift_server = true, but ticket_seed_path is empty");
+    }
+    return seedPath.value();
+  }
+
   const std::string
   getSSLAcceptablePeers() {
     // If unspecified, will use accept connection from any authenticated peer