QPID-1148 - from Manuel Tiera

Lock file abstraction in sys/ with implementation portable to Linux and Solaris.

Changes by myself:
 - Makefile.am - must be updated for any new/renamed/removed source files.
 - Exception.h, Daemon.h, LockFile.h: Replaced throwIf() with if (...) throw ErrnoException(...)

The idiom throwIf(call-system-function(), "msg", errno) is incorret
(my fault, not Manuels). It assumes the first argument that makes a
system call call will be evaluated before the last one which fetches
errno. This may not be true on some compilers/platforms.


git-svn-id: https://svn.apache.org/repos/asf/incubator/qpid/trunk/qpid@674865 13f79535-47bb-0310-9956-ffa450edef68

8 files changed, 128 insertions, 88 deletions

diff --git a/cpp/src/Makefile.am b/cpp/src/Makefile.am
index e90e1831fe..fb57a9fe47 100644
--- a/cpp/src/Makefile.am
+++ b/cpp/src/Makefile.am
@@ -86,7 +86,8 @@ posix_plat_hdr = \
   qpid/sys/posix/PrivatePosix.h \
   qpid/sys/posix/Mutex.h \
   qpid/sys/posix/Thread.h \
-  qpid/sys/posix/Fork.h
+  qpid/sys/posix/Fork.h \
+  qpid/sys/posix/LockFile.h
 
 platform_src = $(posix_plat_src)
 platform_hdr = $(posix_plat_hdr)
@@ -553,6 +554,7 @@ nobase_include_HEADERS = \
   qpid/sys/ProtocolFactory.h \
   qpid/sys/Runnable.h \
   qpid/sys/Fork.h \
+  qpid/sys/LockFile.h \
   qpid/sys/ScopedIncrement.h \
   qpid/sys/Semaphore.h \
   qpid/sys/Serializer.h \
diff --git a/cpp/src/qpid/DataDir.cpp b/cpp/src/qpid/DataDir.cpp
index 879f4de202..18b52b9b8f 100644
--- a/cpp/src/qpid/DataDir.cpp
+++ b/cpp/src/qpid/DataDir.cpp
@@ -26,13 +26,13 @@
 #include <sys/file.h>
 #include <fcntl.h>
 #include <cerrno>
+#include <unistd.h>
 
 namespace qpid {
 
 DataDir::DataDir (std::string path) :
     enabled (!path.empty ()),
-    dirPath (path),
-    dirFd(-1)
+    dirPath (path)
 {
     if (!enabled)
     {
@@ -50,24 +50,12 @@ DataDir::DataDir (std::string path) :
         else
             throw Exception ("Data directory not found: " + path);
     }
-    int dirFd = ::open(path.c_str(), 0);
-    if (dirFd == -1)
-        throw Exception(QPID_MSG("Can't open data directory: " << dirPath << ": " << strError(errno)));
-    int result = ::flock(dirFd, LOCK_EX | LOCK_NB);
-    if (result != 0) {
-        if (errno == EWOULDBLOCK)
-            throw Exception(QPID_MSG("Data directory locked by another process: " << path));
-        throw  Exception(QPID_MSG("Cannot lock data directory: " << strError(errno)));
-    }
-    QPID_LOG (info, "Locked data directory: " << dirPath);
+    std::string lockFileName(path);
+    lockFileName += "/lock";
+    lockFile = std::auto_ptr<sys::LockFile>(new sys::LockFile(lockFileName, true));
 }
 
-DataDir::~DataDir () {
-    if (dirFd != -1) {
-        ::close(dirFd);         // Closing the fd unlocks the directory.
-        QPID_LOG (info, "Unlocked data directory: " << dirPath);
-    }
-}
+DataDir::~DataDir () {}
 
 } // namespace qpid
 
diff --git a/cpp/src/qpid/DataDir.h b/cpp/src/qpid/DataDir.h
index 6bd27fcda2..7de5ebf62d 100644
--- a/cpp/src/qpid/DataDir.h
+++ b/cpp/src/qpid/DataDir.h
@@ -22,6 +22,8 @@
  */
 
 #include <string>
+#include <memory>
+#include "qpid/sys/LockFile.h"
 
 namespace qpid {
 
@@ -32,7 +34,7 @@ class DataDir
 {
     const bool        enabled;
     const std::string dirPath;
-    int dirFd;
+    std::auto_ptr<qpid::sys::LockFile> lockFile;
 
   public:
 
diff --git a/cpp/src/qpid/Exception.h b/cpp/src/qpid/Exception.h
index 1be433f17a..4e91f85ddb 100644
--- a/cpp/src/qpid/Exception.h
+++ b/cpp/src/qpid/Exception.h
@@ -28,12 +28,13 @@
 
 #include <memory>
 #include <string>
+#include <errno.h>
 
 namespace qpid
 {
 
 /** Get the error message for a system number err, e.g. errno. */
-std::string strError(int err);
+std::string strError(int err=errno);
 
 /**
  * Base class for Qpid runtime exceptions.
@@ -52,6 +53,11 @@ class Exception : public std::exception
     mutable std::string whatStr;
 };
 
+/** Exception that includes an errno message. */
+struct ErrnoException : public Exception {
+    ErrnoException(const std::string& msg, int err=errno) : Exception(msg+": "+strError(err)) {}
+};
+    
 struct SessionException : public Exception {
     const framing::ReplyCode code;
     SessionException(framing::ReplyCode code_, const std::string& message)
diff --git a/cpp/src/qpid/broker/Daemon.cpp b/cpp/src/qpid/broker/Daemon.cpp
index 10f48d9e0f..89d0e20a2b 100644
--- a/cpp/src/qpid/broker/Daemon.cpp
+++ b/cpp/src/qpid/broker/Daemon.cpp
@@ -18,6 +18,7 @@
 #include "Daemon.h"
 #include "qpid/log/Statement.h"
 #include "qpid/Exception.h"
+#include "qpid/sys/LockFile.h"
 
 #include <errno.h>
 #include <fcntl.h>
@@ -30,46 +31,7 @@ namespace qpid {
 namespace broker {
 
 using namespace std;
-
-namespace {
-/** Throw an exception containing msg and strerror if throwIf is true.
- * Name is supposed to be reminiscent of perror().
- */
-void throwIf(bool condition, const string& msg, int errNo=errno) {
-    if (condition)
-        throw Exception(msg + (errNo? ": "+strError(errNo) : string(".")));
-}
-
-
-/*
- * Rewritten using low-level IO, for compatibility 
- * with earlier Boost versions, i.e. 103200.
- */
-struct LockFile {
-
-    LockFile(const std::string& path_, bool create)
-        : path(path_), fd(-1), created(create)
-    {
-        errno = 0;
-        int flags=create ? O_WRONLY|O_CREAT|O_NOFOLLOW : O_RDWR;
-        fd = ::open(path.c_str(), flags, 0644);
-        throwIf(fd < 0,"Cannot open "+path);
-        throwIf(::lockf(fd, F_TLOCK, 0) < 0, "Cannot lock "+path);
-    }
-
-    ~LockFile() {
-        if (fd >= 0) {
-            ::lockf(fd, F_ULOCK, 0);
-            ::close(fd);
-        }
-    }
-
-    std::string path;
-    int fd;
-    bool created;
-};
-
-} // namespace
+using qpid::sys::LockFile;
 
 Daemon::Daemon(std::string _pidDir) : pidDir(_pidDir) {
     struct stat s;
@@ -98,25 +60,25 @@ string Daemon::pidFile(string pidDir, uint16_t port) {
  */
 void Daemon::fork()
 {
-    throwIf(::pipe(pipeFds) < 0, "Can't create pipe");  
-    throwIf((pid = ::fork()) < 0, "Daemon fork failed");
+    if(::pipe(pipeFds) < 0) throw ErrnoException("Can't create pipe");  
+    if ((pid = ::fork()) < 0) throw ErrnoException("Daemon fork failed");
     if (pid == 0) {             // Child
         try {
             QPID_LOG(debug, "Forked daemon child process");
             
             // File descriptors
-            throwIf(::close(pipeFds[0])<0, "Cannot close read pipe");
-            throwIf(::close(0)<0, "Cannot close stdin");
-            throwIf(::close(1)<0, "Cannot close stdout");
-            throwIf(::close(2)<0, "Cannot close stderr");
+            if(::close(pipeFds[0])<0) throw ErrnoException("Cannot close read pipe");
+            if(::close(0)<0) throw ErrnoException("Cannot close stdin");
+            if(::close(1)<0) throw ErrnoException("Cannot close stdout");
+            if(::close(2)<0) throw ErrnoException("Cannot close stderr");
             int fd=::open("/dev/null",O_RDWR); // stdin
-            throwIf(fd != 0, "Cannot re-open stdin");
-            throwIf(::dup(fd)<0, "Cannot re-open stdout");
-            throwIf(::dup(fd)<0, "Cannot re-open stderror");
+            if(fd != 0) throw ErrnoException("Cannot re-open stdin");
+            if(::dup(fd)<0) throw ErrnoException("Cannot re-open stdout");
+            if(::dup(fd)<0) throw ErrnoException("Cannot re-open stderror");
 
             // Misc
-            throwIf(setsid()<0, "Cannot set session ID");
-            throwIf(chdir(pidDir.c_str()) < 0, "Cannot change directory to "+pidDir);
+            if(setsid()<0) throw ErrnoException("Cannot set session ID");
+            if(chdir(pidDir.c_str()) < 0) throw ErrnoException("Cannot change directory to "+pidDir);
             umask(027);
 
             // Child behavior
@@ -159,8 +121,8 @@ uint16_t Daemon::wait(int timeout) {            // parent waits for child.
     FD_ZERO(&fds);
     FD_SET(pipeFds[0], &fds);
     int n=select(FD_SETSIZE, &fds, 0, 0, &tv);
-    throwIf(n==0, "Timed out waiting for daemon");
-    throwIf(n<0, "Error waiting for daemon");
+    if(n==0) throw ErrnoException("Timed out waiting for daemon");
+    if(n<0) throw ErrnoException("Error waiting for daemon");
     uint16_t port = 0;
     /*
      * Read the child's port number from the pipe.
diff --git a/cpp/src/qpid/sys/LockFile.h b/cpp/src/qpid/sys/LockFile.h
new file mode 100644
index 0000000000..f06cd6a47d
--- /dev/null
+++ b/cpp/src/qpid/sys/LockFile.h
@@ -0,0 +1,27 @@
+#ifndef _sys_LockFile_h
+#define _sys_LockFile_h
+
+/*
+ *
+ * Copyright (c) 2008 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 "posix/LockFile.h"
+
+#endif /*!_sys_LockFile_h*/
+
+
+       
diff --git a/cpp/src/qpid/sys/posix/Fork.cpp b/cpp/src/qpid/sys/posix/Fork.cpp
index 78017a5f91..ec3af620ef 100644
--- a/cpp/src/qpid/sys/posix/Fork.cpp
+++ b/cpp/src/qpid/sys/posix/Fork.cpp
@@ -32,27 +32,22 @@ 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);
+    if (int(sizeof(size)) > ::write(fd, &size, sizeof(size))) throw ErrnoException(WRITE_ERR);
+    if (size > ::write(fd, str.data(), size)) throw ErrnoException(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 (int(sizeof(size)) > ::read(fd, &size, sizeof(size))) throw ErrnoException(READ_ERR);
     if (size > 0) {          // Read string message
         value.resize(size);
-        throwIf(size > ::read(fd, const_cast<char*>(value.data()), size), READ_ERR);
+        if (size > ::read(fd, const_cast<char*>(value.data()), size)) throw ErrnoException(READ_ERR);
     }
     return value;
 }
@@ -64,7 +59,7 @@ Fork::~Fork() {}
 
 void Fork::fork() {
     pid_t pid = ::fork();
-    throwIf(pid < 0, "Failed to fork the process");
+    if (pid < 0) throw ErrnoException("Failed to fork the process");
     if (pid == 0) child();
     else parent(pid);
 }
@@ -80,9 +75,9 @@ struct AutoCloseFd {
 };
 
 void ForkWithMessage::fork() {
-    throwIf(::pipe(pipeFds) < 0, "Can't create pipe");
+    if(::pipe(pipeFds) < 0) throw ErrnoException("Can't create pipe");
     pid_t pid = ::fork();
-    throwIf(pid < 0, "Fork fork failed");
+    if(pid < 0) throw ErrnoException("Fork fork failed");
     if (pid == 0) {             // Child
         AutoCloseFd ac(pipeFds[1]); // Write side.
         ::close(pipeFds[0]); // Read side
@@ -113,8 +108,8 @@ string ForkWithMessage::wait(int timeout) { // parent waits for child.
     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");
+    if(n<0) throw ErrnoException("Error waiting for fork");
+    if (n==0) throw Exception("Timed out waiting for fork");
 
     string error = readStr(pipeFds[0]);
     if (error.empty()) return readStr(pipeFds[0]);
diff --git a/cpp/src/qpid/sys/posix/LockFile.h b/cpp/src/qpid/sys/posix/LockFile.h
new file mode 100644
index 0000000000..a8fbb678b8
--- /dev/null
+++ b/cpp/src/qpid/sys/posix/LockFile.h
@@ -0,0 +1,58 @@
+#ifndef _sys_posix_LockFile_h
+#define _sys_posix_LockFile_h
+
+#include "check.h"
+
+#include <boost/noncopyable.hpp>
+#include <string>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+/*
+ *
+ * Copyright (c) 2008 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.
+ *
+ */
+namespace qpid {
+namespace sys {
+    
+class LockFile : private boost::noncopyable {
+public:
+    LockFile(const std::string& path_, bool create):
+        path(path_), fd(-1), created(create) {
+        errno = 0;
+        int flags=create ? O_WRONLY|O_CREAT|O_NOFOLLOW : O_RDWR;
+        fd = ::open(path.c_str(), flags, 0644);
+        if (fd < 0) throw ErrnoException("Cannot open " + path, errno);
+        if (::lockf(fd, F_TLOCK, 0) < 0) throw ErrnoException("Cannot lock " + path, errno);
+    }
+
+    ~LockFile() {
+        if (fd >= 0) {
+            ::lockf(fd, F_ULOCK, 0);
+            ::close(fd);
+        }
+    }
+
+    std::string path;
+    int fd;
+    bool created;
+};
+ 
+}
+}
+#endif /*!_sys_posix_LockFile_h*/