Cluster prototype: handles client-initiated commands (not dequeues)

Details
 - Cluster.cpp: serializes all frames thru cluster (see below)
 - broker/ConnectionManager: Added handler chain in front of Connection::received.
 - sys::Fork and ForkWithMessage - abstractions for forking with posix impl.
 - tests/ForkedBroker.h: test utility to fork a broker process. 
 - broker/SignalHandler: Encapsulated signal handling from qpidd.cpp
 - Various minor logging & error message improvements to aid debugging.

NB: current impl will not scale. It is functional working starting point so we
can start testing & profiling to find the right optimizations.


git-svn-id: https://svn.apache.org/repos/asf/incubator/qpid/trunk/qpid@674107 13f79535-47bb-0310-9956-ffa450edef68

3 files changed, 217 insertions, 4 deletions

diff --git a/cpp/src/qpid/sys/posix/Fork.cpp b/cpp/src/qpid/sys/posix/Fork.cpp
new file mode 100644
index 0000000000..78017a5f91
--- /dev/null
+++ b/cpp/src/qpid/sys/posix/Fork.cpp
@@ -0,0 +1,132 @@
+/*
+ *
+ * Copyright (c) 2006 The Apache Software Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+#include "qpid/sys/Fork.h"
+#include "qpid/log/Statement.h"
+#include "qpid/Exception.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+namespace qpid {
+namespace sys {
+
+using namespace std;
+
+namespace {
+/** Throw an exception containing msg and strerror if condition is true. */
+void throwIf(bool condition, const string& msg) {
+    if (condition) 
+        throw Exception(msg + (errno? ": "+strError(errno) : string()) + ".");
+}
+
+void writeStr(int fd, const std::string& str) {
+    const char* WRITE_ERR = "Error writing to parent process";
+    int size = str.size();
+    throwIf(int(sizeof(size)) > ::write(fd, &size, sizeof(size)), WRITE_ERR);
+    throwIf(size > ::write(fd, str.data(), size), WRITE_ERR);
+}
+
+string readStr(int fd) {
+    string value;
+    const char* READ_ERR = "Error reading from forked process";
+    int size;
+    throwIf(int(sizeof(size)) > ::read(fd, &size, sizeof(size)), READ_ERR);
+    if (size > 0) {          // Read string message
+        value.resize(size);
+        throwIf(size > ::read(fd, const_cast<char*>(value.data()), size), READ_ERR);
+    }
+    return value;
+}
+
+} // namespace
+
+Fork::Fork() {}
+Fork::~Fork() {}
+
+void Fork::fork() {
+    pid_t pid = ::fork();
+    throwIf(pid < 0, "Failed to fork the process");
+    if (pid == 0) child();
+    else parent(pid);
+}
+
+ForkWithMessage::ForkWithMessage() {
+    pipeFds[0] = pipeFds[1] = -1;
+}
+
+struct AutoCloseFd {
+    int fd;
+    AutoCloseFd(int d) : fd(d) {}
+    ~AutoCloseFd() { ::close(fd); }
+};
+
+void ForkWithMessage::fork() {
+    throwIf(::pipe(pipeFds) < 0, "Can't create pipe");
+    pid_t pid = ::fork();
+    throwIf(pid < 0, "Fork fork failed");
+    if (pid == 0) {             // Child
+        AutoCloseFd ac(pipeFds[1]); // Write side.
+        ::close(pipeFds[0]); // Read side
+        try {
+            child();
+        }
+        catch (const std::exception& e) {
+            QPID_LOG(error, "Error in forked child: " << e.what());
+            std::string msg = e.what();
+            if (msg.empty()) msg = " "; // Make sure we send a non-empty error string.
+            writeStr(pipeFds[1], msg);
+        }
+    }
+    else {                      // Parent
+        close(pipeFds[1]);      // Write side.
+        AutoCloseFd ac(pipeFds[0]); // Read side
+        parent(pid);
+    }
+}
+
+string ForkWithMessage::wait(int timeout) { // parent waits for child.
+    errno = 0;                  
+    struct timeval tv;
+    tv.tv_sec = timeout;
+    tv.tv_usec = 0;
+
+    fd_set fds;
+    FD_ZERO(&fds);
+    FD_SET(pipeFds[0], &fds);
+    int n=select(FD_SETSIZE, &fds, 0, 0, &tv);
+    throwIf(n==0, "Timed out waiting for fork");
+    throwIf(n<0, "Error waiting for fork");
+
+    string error = readStr(pipeFds[0]);
+    if (error.empty()) return readStr(pipeFds[0]);
+    else throw Exception("Error in forked process: " + error);
+}
+
+// Write empty error string followed by value string to pipe.
+void ForkWithMessage::ready(const string& value) { // child
+    // Write empty string for error followed by value.
+    writeStr(pipeFds[1], string()); // No error
+    writeStr(pipeFds[1], value); 
+}
+
+
+}} // namespace qpid::sys
diff --git a/cpp/src/qpid/sys/posix/Fork.h b/cpp/src/qpid/sys/posix/Fork.h
new file mode 100644
index 0000000000..d6fe862ee7
--- /dev/null
+++ b/cpp/src/qpid/sys/posix/Fork.h
@@ -0,0 +1,81 @@
+#ifndef QPID_SYS_POSIX_FORK_H
+#define QPID_SYS_POSIX_FORK_H
+
+/*
+ *
+ * Copyright (c) 2006 The Apache Software Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <string>
+
+namespace qpid {
+namespace sys {
+
+/**
+ * Fork the process. Call parent() in parent and child() in child.
+ */
+class Fork {
+  public:
+    Fork();
+    virtual ~Fork();
+
+    /**
+     * Fork the process.
+     * Calls parent() in the parent process, child() in the child.
+     */
+    virtual void fork();
+
+  protected:
+
+    /** Called in parent process.
+     *@child pid of child process
+     */
+    virtual void parent(pid_t child) = 0;
+
+    /** Called in child process */
+    virtual void child() = 0;
+};
+
+/**
+ * Like Fork but also allows the child to send a string message
+ * or throw an exception to the parent.
+ */
+class ForkWithMessage : public Fork {
+  public:
+    ForkWithMessage();
+    void fork();
+
+  protected:
+    /** Call from parent(): wait for child to send a value or throw exception.
+     * @timeout in seconds to wait for response.
+     * @return value passed by child to ready(). 
+     */
+    std::string wait(int timeout);
+
+    /** Call from child(): Send a value to the parent.
+     *@param value returned by parent call to wait(). 
+     */
+    void ready(const std::string& value);
+
+  private:
+    int pipeFds[2];
+};
+
+}} // namespace qpid::sys
+
+
+
+#endif  /*!QPID_SYS_POSIX_FORK_H*/
diff --git a/cpp/src/qpid/sys/posix/Socket.cpp b/cpp/src/qpid/sys/posix/Socket.cpp
index f4320531a9..d4de1741b1 100644
--- a/cpp/src/qpid/sys/posix/Socket.cpp
+++ b/cpp/src/qpid/sys/posix/Socket.cpp
@@ -137,7 +137,7 @@ const char* h_errstr(int e) {
 }
 }
 
-void Socket::connect(const std::string& host, int port) const
+void Socket::connect(const std::string& host, uint16_t port) const
 {
     std::stringstream namestream;
     namestream << host << ":" << port;
@@ -192,7 +192,7 @@ Socket::recv(void* data, size_t size) const
     return received;
 }
 
-int Socket::listen(int port, int backlog) const
+int Socket::listen(uint16_t port, int backlog) const
 {
     const int& socket = impl->fd;
     int yes=1;
@@ -202,9 +202,9 @@ int Socket::listen(int port, int backlog) const
     name.sin_port = htons(port);
     name.sin_addr.s_addr = 0;
     if (::bind(socket, (struct sockaddr*)&name, sizeof(name)) < 0)
-        throw QPID_POSIX_ERROR(errno);
+        throw Exception(QPID_MSG("Can't bind to port " << port << ": " << strError(errno)));
     if (::listen(socket, backlog) < 0)
-        throw QPID_POSIX_ERROR(errno);
+        throw Exception(QPID_MSG("Can't listen on port " << port << ": " << strError(errno)));
     
     socklen_t namelen = sizeof(name);
     if (::getsockname(socket, (struct sockaddr*)&name, &namelen) < 0)