Merge pull request #5007

af82884 Add "warmup mode" for RPC server. (Daniel Kraft)

doc/release-notes.md

@@ -84,3 +84,14 @@ Using wildcards will result in the rule being rejected with the following error
 
     Error: Invalid -rpcallowip subnet specification: *. Valid are a single IP (e.g. 1.2.3.4), a network/netmask (e.g. 1.2.3.4/255.255.255.0) or a network/CIDR (e.g. 1.2.3.4/24).
 
+RPC Server "Warm-Up" Mode
+=========================
+
+The RPC server is started earlier now, before most of the expensive
+intialisations like loading the block index.  It is available now almost
+immediately after starting the process.  However, until all initialisations
+are done, it always returns an immediate error with code -28 to all calls.
+
+This new behaviour can be useful for clients to know that a server is already
+started and will be available soon (for instance, so that they do not
+have to start it themselves).

src/bitcoin-cli.cpp

@@ -46,6 +46,21 @@ std::string HelpMessageCli()
 //
 // Start
 //
+
+//
+// Exception thrown on connection error.  This error is used to determine
+// when to wait if -rpcwait is given.
+//
+class CConnectionFailed : public std::runtime_error
+{
+public:
+
+    explicit inline CConnectionFailed(const std::string& msg) :
+        std::runtime_error(msg)
+    {}
+
+};
+
 static bool AppInitRPC(int argc, char* argv[])
 {
     //
@@ -101,15 +116,9 @@ Object CallRPC(const string& strMethod, const Array& params)
     SSLIOStreamDevice<asio::ip::tcp> d(sslStream, fUseSSL);
     iostreams::stream< SSLIOStreamDevice<asio::ip::tcp> > stream(d);
 
-    bool fWait = GetBoolArg("-rpcwait", false); // -rpcwait means try until server has started
+    const bool fConnected = d.connect(GetArg("-rpcconnect", "127.0.0.1"), GetArg("-rpcport", itostr(BaseParams().RPCPort())));
-    do {
+    if (!fConnected)
-        bool fConnected = d.connect(GetArg("-rpcconnect", "127.0.0.1"), GetArg("-rpcport", itostr(BaseParams().RPCPort())));
+        throw CConnectionFailed("couldn't connect to server");
-        if (fConnected) break;
-        if (fWait)
-            MilliSleep(1000);
-        else
-            throw runtime_error("couldn't connect to server");
-    } while (fWait);
 
     // HTTP basic authentication
     string strUserPass64 = EncodeBase64(mapArgs["-rpcuser"] + ":" + mapArgs["-rpcpassword"]);
@@ -168,27 +177,43 @@ int CommandLineRPC(int argc, char *argv[])
         std::vector<std::string> strParams(&argv[2], &argv[argc]);
         Array params = RPCConvertValues(strMethod, strParams);
 
-        // Execute
+        // Execute and handle connection failures with -rpcwait
-        Object reply = CallRPC(strMethod, params);
+        const bool fWait = GetBoolArg("-rpcwait", false);
+        do {
+            try {
+                const Object reply = CallRPC(strMethod, params);
 
-        // Parse reply
+                // Parse reply
-        const Value& result = find_value(reply, "result");
+                const Value& result = find_value(reply, "result");
-        const Value& error  = find_value(reply, "error");
+                const Value& error  = find_value(reply, "error");
 
-        if (error.type() != null_type) {
+                if (error.type() != null_type) {
-            // Error
+                    // Error
-            strPrint = "error: " + write_string(error, false);
+                    const int code = find_value(error.get_obj(), "code").get_int();
-            int code = find_value(error.get_obj(), "code").get_int();
+                    if (fWait && code == RPC_IN_WARMUP)
-            nRet = abs(code);
+                        throw CConnectionFailed("server in warmup");
-        } else {
+                    strPrint = "error: " + write_string(error, false);
-            // Result
+                    nRet = abs(code);
-            if (result.type() == null_type)
+                } else {
-                strPrint = "";
+                    // Result
-            else if (result.type() == str_type)
+                    if (result.type() == null_type)
-                strPrint = result.get_str();
+                        strPrint = "";
-            else
+                    else if (result.type() == str_type)
-                strPrint = write_string(result, true);
+                        strPrint = result.get_str();
-        }
+                    else
+                        strPrint = write_string(result, true);
+                }
+
+                // Connection succeeded, no need to retry.
+                break;
+            }
+            catch (const CConnectionFailed& e) {
+                if (fWait)
+                    MilliSleep(1000);
+                else
+                    throw;
+            }
+        } while (fWait);
     }
     catch (boost::thread_interrupted) {
         throw;

src/init.cpp

@@ -752,6 +752,17 @@ bool AppInit2(boost::thread_group& threadGroup)
             threadGroup.create_thread(&ThreadScriptCheck);
     }
 
+    /* Start the RPC server already.  It will be started in "warmup" mode
+     * and not really process calls already (but it will signify connections
+     * that the server is there and will be ready later).  Warmup mode will
+     * be disabled when initialisation is finished.
+     */
+    if (fServer)
+    {
+        uiInterface.InitMessage.connect(SetRPCWarmupStatus);
+        StartRPCThreads();
+    }
+
     int64_t nStart;
 
     // ********************************************************* Step 5: verify wallet database integrity
@@ -1248,8 +1259,6 @@ bool AppInit2(boost::thread_group& threadGroup)
 #endif
 
     StartNode(threadGroup);
-    if (fServer)
-        StartRPCThreads();
 
 #ifdef ENABLE_WALLET
     // Generate coins in the background
@@ -1259,6 +1268,7 @@ bool AppInit2(boost::thread_group& threadGroup)
 
     // ********************************************************* Step 11: finished
 
+    SetRPCWarmupFinished();
     uiInterface.InitMessage(_("Done loading"));
 
 #ifdef ENABLE_WALLET

src/rpcprotocol.h

@@ -52,6 +52,7 @@ enum RPCErrorCode
     RPC_VERIFY_ERROR                = -25, // General error during transaction or block submission
     RPC_VERIFY_REJECTED             = -26, // Transaction or block was rejected by network rules
     RPC_VERIFY_ALREADY_IN_CHAIN     = -27, // Transaction already in chain
+    RPC_IN_WARMUP                   = -28, // Client still warming up
 
     // Aliases for backward compatibility
     RPC_TRANSACTION_ERROR           = RPC_VERIFY_ERROR,

src/rpcserver.cpp

@@ -34,6 +34,10 @@ using namespace std;
 static std::string strRPCUserColonPass;
 
 static bool fRPCRunning = false;
+static bool fRPCInWarmup = true;
+static std::string rpcWarmupStatus("RPC server started");
+static CCriticalSection cs_rpcWarmup;
+
 //! These are created by StartRPCThreads, destroyed in StopRPCThreads
 static asio::io_service* rpc_io_service = NULL;
 static map<string, boost::shared_ptr<deadline_timer> > deadlineTimers;
@@ -744,6 +748,19 @@ bool IsRPCRunning()
     return fRPCRunning;
 }
 
+void SetRPCWarmupStatus(const std::string& newStatus)
+{
+    LOCK(cs_rpcWarmup);
+    rpcWarmupStatus = newStatus;
+}
+
+void SetRPCWarmupFinished()
+{
+    LOCK(cs_rpcWarmup);
+    assert(fRPCInWarmup);
+    fRPCInWarmup = false;
+}
+
 void RPCRunHandler(const boost::system::error_code& err, boost::function<void(void)> func)
 {
     if (!err)
@@ -870,6 +887,13 @@ static bool HTTPReq_JSONRPC(AcceptedConnection *conn,
         if (!read_string(strRequest, valRequest))
             throw JSONRPCError(RPC_PARSE_ERROR, "Parse error");
 
+        // Return immediately if in warmup
+        {
+            LOCK(cs_rpcWarmup);
+            if (fRPCInWarmup)
+                throw JSONRPCError(RPC_IN_WARMUP, rpcWarmupStatus);
+        }
+
         string strReply;
 
         // singleton request

src/rpcserver.h

@@ -45,6 +45,13 @@ void StopRPCThreads();
 /* Query whether RPC is running */
 bool IsRPCRunning();
 
+/* Set the RPC warmup status.  When this is done, all RPC calls will error out
+ * immediately with RPC_IN_WARMUP.
+ */
+void SetRPCWarmupStatus(const std::string& newStatus);
+/* Mark warmup as done.  RPC calls will be processed from now on.  */
+void SetRPCWarmupFinished();
+
 /**
  * Type-check arguments; throws JSONRPCError if wrong type given. Does not check that
  * the right number of arguments are passed, just that any passed are the correct type.