Support multiple discovery nodes

src/brpc/policy/discovery_naming_service.cpp

@@ -48,12 +48,32 @@ DEFINE_int32(discovery_reregister_threshold, 3, "The renew error threshold beyon
 static pthread_once_t s_init_discovery_channel_once = PTHREAD_ONCE_INIT;
 static Channel* s_discovery_channel = NULL;
 
-int ParseNodesResult(const butil::IOBuf& buf, std::string* server_addr) {
+static int ListDiscoveryNodes(const char* discovery_api_addr, std::string* servers) {
+    Channel api_channel;
+    ChannelOptions channel_options;
+    channel_options.protocol = PROTOCOL_HTTP;
+    channel_options.timeout_ms = FLAGS_discovery_timeout_ms;
+    channel_options.connect_timeout_ms = FLAGS_discovery_timeout_ms / 3;
+    if (api_channel.Init(discovery_api_addr, "", &channel_options) != 0) {
+        LOG(FATAL) << "Fail to init channel to " << discovery_api_addr;
+        return -1;
+    }
+    Controller cntl;
+    cntl.http_request().uri() = discovery_api_addr;
+    api_channel.CallMethod(NULL, &cntl, NULL, NULL, NULL);
+    if (cntl.Failed()) {
+        LOG(FATAL) << "Fail to access " << cntl.http_request().uri()
+                   << ": " << cntl.ErrorText();
+        return -1;
+    }
+
+    servers->assign("list://");
+
+    const std::string response = cntl.response_attachment().to_string();
     BUTIL_RAPIDJSON_NAMESPACE::Document d;
-    const std::string response = buf.to_string();
     d.Parse(response.c_str());
     if (!d.IsObject()) {
-        LOG(ERROR) << "Fail to parse " << buf << " as json object";
+        LOG(ERROR) << "Fail to parse " << response << " as json object";
         return -1;
     }
     auto itr = d.FindMember("data");
@@ -77,50 +97,39 @@ int ParseNodesResult(const butil::IOBuf& buf, std::string* server_addr) {
                 itr_status->value.GetUint() != 0) {
             continue;
         }
-        server_addr->assign(itr_addr->value.GetString(),
-                            itr_addr->value.GetStringLength());
-        // Currently, we just use the first successful result
-        break;
+        servers->push_back(',');
+        servers->append(itr_addr->value.GetString(),
+                        itr_addr->value.GetStringLength());
     }
     return 0;
 }
 
-static void InitDiscoveryChannel() {
-    Channel api_channel;
+static void NewDiscoveryChannel() {
+    // NOTE: Newly added discovery server is NOT detected until this server
+    // is restarted. The reasons for this design is that NS cluster rarely 
+    // changes. Although we could detect new discovery servers by implmenenting
+    // a NamingService, however which is too heavy for solving such a rare case.
+    std::string discovery_servers;
+    if (ListDiscoveryNodes(FLAGS_discovery_api_addr.c_str(), &discovery_servers) != 0) {
+        LOG(ERROR) << "Fail to get discovery nodes from " << FLAGS_discovery_api_addr;
+        return;
+    }
     ChannelOptions channel_options;
     channel_options.protocol = PROTOCOL_HTTP;
     channel_options.timeout_ms = FLAGS_discovery_timeout_ms;
     channel_options.connect_timeout_ms = FLAGS_discovery_timeout_ms / 3;
-    if (api_channel.Init(FLAGS_discovery_api_addr.c_str(), "", &channel_options) != 0) {
-        LOG(FATAL) << "Fail to init channel to " << FLAGS_discovery_api_addr;
-        return;
-    }
-    Controller cntl;
-    cntl.http_request().uri() = FLAGS_discovery_api_addr;
-    api_channel.CallMethod(NULL, &cntl, NULL, NULL, NULL);
-    if (cntl.Failed()) {
-        LOG(FATAL) << "Fail to access " << cntl.http_request().uri()
-                   << ": " << cntl.ErrorText();
-        return;
-    }
-    std::string discovery_addr;
-    if (ParseNodesResult(cntl.response_attachment(), &discovery_addr) != 0) {
-        LOG(FATAL) << "Fail to parse nodes result from discovery api server";
-        return;
-    }
     s_discovery_channel = new Channel;
-    if (s_discovery_channel->Init(discovery_addr.c_str(), "", &channel_options) != 0) {
-        LOG(FATAL) << "Fail to init channel to " << discovery_addr;
+    if (s_discovery_channel->Init(discovery_servers.c_str(), "rr", &channel_options) != 0) {
+        LOG(ERROR) << "Fail to init channel to " << discovery_servers;
         return;
     }
 }
 
-Channel* GetDiscoveryChannel() {
-    pthread_once(&s_init_discovery_channel_once, InitDiscoveryChannel);
+inline Channel* GetOrNewDiscoveryChannel() {
+    pthread_once(&s_init_discovery_channel_once, NewDiscoveryChannel);
     return s_discovery_channel;
 }
 
-
 bool DiscoveryRegisterParam::IsValid() const {
     return !appid.empty() && !hostname.empty() && !addrs.empty() &&
             !env.empty() && !zone.empty() && !version.empty();
@@ -138,7 +147,7 @@ DiscoveryClient::~DiscoveryClient() {
     }
 }
 
-int ParseCommonResult(const butil::IOBuf& buf, std::string* error_text) {
+static int ParseCommonResult(const butil::IOBuf& buf, std::string* error_text) {
     const std::string s = buf.to_string();
     BUTIL_RAPIDJSON_NAMESPACE::Document d;
     d.Parse(s.c_str());
@@ -161,6 +170,17 @@ int ParseCommonResult(const butil::IOBuf& buf, std::string* error_text) {
 }
 
 int DiscoveryClient::DoRenew() const {
+    // May create short connections which are OK.
+    ChannelOptions channel_options;
+    channel_options.protocol = PROTOCOL_HTTP;
+    channel_options.timeout_ms = FLAGS_discovery_timeout_ms;
+    channel_options.connect_timeout_ms = FLAGS_discovery_timeout_ms / 3;
+    Channel chan;
+    if (chan.Init(_current_discovery_server, &channel_options) != 0) {
+        LOG(FATAL) << "Fail to init channel to " << _current_discovery_server;
+        return -1;
+    }
+
     Controller cntl;
     cntl.http_request().set_method(HTTP_METHOD_POST);
     cntl.http_request().uri() = "/discovery/renew";
@@ -172,7 +192,7 @@ int DiscoveryClient::DoRenew() const {
         << "&region=" << _params.region
         << "&zone=" << _params.zone;
     os.move_to(cntl.request_attachment());
-    GetDiscoveryChannel()->CallMethod(NULL, &cntl, NULL, NULL, NULL);
+    chan.CallMethod(NULL, &cntl, NULL, NULL, NULL);
     if (cntl.Failed()) {
         LOG(ERROR) << "Fail to post /discovery/renew: " << cntl.ErrorText();
         return -1;
@@ -219,15 +239,15 @@ void* DiscoveryClient::PeriodicRenew(void* arg) {
     return NULL;
 }
 
-int DiscoveryClient::Register(const DiscoveryRegisterParam& req) {
+int DiscoveryClient::Register(const DiscoveryRegisterParam& params) {
     if (_registered.load(butil::memory_order_relaxed) ||
             _registered.exchange(true, butil::memory_order_release)) {
         return 0;
     }
-    if (!req.IsValid()) {
+    if (!params.IsValid()) {
         return -1;
     }
-    _params = req;
+    _params = params;
 
     if (DoRegister() != 0) {
         return -1;
@@ -239,7 +259,12 @@ int DiscoveryClient::Register(const DiscoveryRegisterParam& req) {
     return 0;
 }
 
-int DiscoveryClient::DoRegister() const {
+int DiscoveryClient::DoRegister() {
+    Channel* chan = GetOrNewDiscoveryChannel();
+    if (NULL == chan) {
+        LOG(ERROR) << "Fail to create discovery channel";
+        return -1;
+    }
     Controller cntl;
     cntl.http_request().set_method(HTTP_METHOD_POST);
     cntl.http_request().uri() = "/discovery/register";
@@ -255,7 +280,7 @@ int DiscoveryClient::DoRegister() const {
         << "&version=" << _params.version
         << "&metadata=" << _params.metadata;
     os.move_to(cntl.request_attachment());
-    GetDiscoveryChannel()->CallMethod(NULL, &cntl, NULL, NULL, NULL);
+    chan->CallMethod(NULL, &cntl, NULL, NULL, NULL);
     if (cntl.Failed()) {
         LOG(ERROR) << "Fail to register " << _params.appid << ": " << cntl.ErrorText();
         return -1;
@@ -266,10 +291,22 @@ int DiscoveryClient::DoRegister() const {
                 << ": " << error_text;
         return -1;
     }
+    _current_discovery_server = cntl.remote_side();
     return 0;
 }
 
 int DiscoveryClient::DoCancel() const {
+    // May create short connections which are OK.
+    ChannelOptions channel_options;
+    channel_options.protocol = PROTOCOL_HTTP;
+    channel_options.timeout_ms = FLAGS_discovery_timeout_ms;
+    channel_options.connect_timeout_ms = FLAGS_discovery_timeout_ms / 3;
+    Channel chan;
+    if (chan.Init(_current_discovery_server, &channel_options) != 0) {
+        LOG(FATAL) << "Fail to init channel to " << _current_discovery_server;
+        return -1;
+    }
+
     Controller cntl;
     cntl.http_request().set_method(HTTP_METHOD_POST);
     cntl.http_request().uri() = "/discovery/cancel";
@@ -281,7 +318,7 @@ int DiscoveryClient::DoCancel() const {
         << "&region=" << _params.region
         << "&zone=" << _params.zone;
     os.move_to(cntl.request_attachment());
-    GetDiscoveryChannel()->CallMethod(NULL, &cntl, NULL, NULL, NULL);
+    chan.CallMethod(NULL, &cntl, NULL, NULL, NULL);
     if (cntl.Failed()) {
         LOG(ERROR) << "Fail to post /discovery/cancel: " << cntl.ErrorText();
         return -1;
@@ -305,12 +342,16 @@ int DiscoveryNamingService::GetServers(const char* service_name,
         LOG_ONCE(ERROR) << "Invalid parameters";
         return -1;
     }
+    Channel* chan = GetOrNewDiscoveryChannel();
+    if (NULL == chan) {
+        LOG(ERROR) << "Fail to create discovery channel";
+    }
     servers->clear();
     Controller cntl;
     cntl.http_request().uri() = butil::string_printf(
             "/discovery/fetchs?appid=%s&env=%s&status=%s", service_name,
             FLAGS_discovery_env.c_str(), FLAGS_discovery_status.c_str());
-    GetDiscoveryChannel()->CallMethod(NULL, &cntl, NULL, NULL, NULL);
+    chan->CallMethod(NULL, &cntl, NULL, NULL, NULL);
     if (cntl.Failed()) {
         LOG(ERROR) << "Fail to get /discovery/fetchs: " << cntl.ErrorText();
         return -1;

src/brpc/policy/discovery_naming_service.h

@@ -44,24 +44,28 @@ struct DiscoveryRegisterParam {
 // ONE DiscoveryClient corresponds to ONE service instance.
 // If your program has multiple service instances to register,
 // you need multiple DiscoveryClient.
-// Note: Unregister is automatically called in dtor.
+// Note: Cancel to the server is automatically called in dtor.
 class DiscoveryClient {
 public:
     DiscoveryClient();
     ~DiscoveryClient();
 
+    // Initialize this client.
+    // Returns 0 on success.
+    // NOTE: Calling more than once does nothing and returns 0.
     int Register(const DiscoveryRegisterParam& req);
 
 private:
     static void* PeriodicRenew(void* arg);
     int DoCancel() const;
-    int DoRegister() const;
+    int DoRegister();
     int DoRenew() const;
 
 private:
     bthread_t _th;
     butil::atomic<bool> _registered;
     DiscoveryRegisterParam _params;
+    butil::EndPoint _current_discovery_server;
 };
 
 class DiscoveryNamingService : public PeriodicNamingService {

test/brpc_naming_service_unittest.cpp

@@ -46,9 +46,6 @@ DECLARE_string(discovery_api_addr);
 DECLARE_string(discovery_env);
 DECLARE_int32(discovery_renew_interval_s);
 
-// Defined in discovery_naming_service.cpp
-int ParseNodesResult(const butil::IOBuf& buf, std::string* server_addr);
-
 } // policy
 } // brpc