Moved PollableCondition, PollableQueue and to sys. Fixed cluster shutdown issues.

sys/PollableCondition: is a generic mechansim to poll for non-IO
events in the Poller.

sys/PollableQueue: is a thread-safe queue template that can be
dispatched from the Poller when there are items on the queue. It uses
PollableCondition.


git-svn-id: https://svn.apache.org/repos/asf/incubator/qpid/trunk/qpid@694243 13f79535-47bb-0310-9956-ffa450edef68

3 files changed, 273 insertions, 0 deletions

diff --git a/cpp/src/qpid/sys/PollableCondition.cpp b/cpp/src/qpid/sys/PollableCondition.cpp
new file mode 100644
index 0000000000..5a3bd583cf
--- /dev/null
+++ b/cpp/src/qpid/sys/PollableCondition.cpp
@@ -0,0 +1,100 @@
+#ifndef QPID_SYS_LINUX_POLLABLECONDITION_CPP
+#define QPID_SYS_LINUX_POLLABLECONDITION_CPP
+
+/*
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ *
+ */
+
+// FIXME aconway 2008-08-11: this could be of more general interest,
+// move to common lib.
+// 
+
+#include "qpid/sys/posix/PrivatePosix.h"
+#include "qpid/sys/PollableCondition.h"
+#include "qpid/Exception.h"
+
+#include <unistd.h>
+#include <fcntl.h>
+
+namespace qpid {
+namespace sys {
+
+PollableCondition::PollableCondition() : IOHandle(new sys::IOHandlePrivate) {
+    int fds[2];
+    if (::pipe(fds) == -1)
+        throw ErrnoException(QPID_MSG("Can't create PollableCondition"));
+    impl->fd = fds[0];
+    writeFd = fds[1];
+    if (::fcntl(impl->fd, F_SETFL, O_NONBLOCK) == -1)
+        throw ErrnoException(QPID_MSG("Can't create PollableCondition"));
+    if (::fcntl(writeFd, F_SETFL, O_NONBLOCK) == -1)
+        throw ErrnoException(QPID_MSG("Can't create PollableCondition"));
+}
+
+bool PollableCondition::clear() {
+    char buf[256];
+    ssize_t n;
+    bool wasSet = false;
+    while ((n = ::read(impl->fd, buf, sizeof(buf))) > 0) 
+        wasSet = true;
+    if (n == -1 && errno != EAGAIN) throw ErrnoException(QPID_MSG("Error clearing PollableCondition"));
+    return wasSet;
+}
+
+void PollableCondition::set() {
+    static const char dummy=0;
+    ssize_t n = ::write(writeFd, &dummy, 1);
+    if (n == -1 && errno != EAGAIN) throw ErrnoException("Error setting PollableCondition");
+}
+
+
+#if 0
+// FIXME aconway 2008-08-12: More efficient Linux implementation using
+// eventfd system call.  Move to separate file & do configure.ac test
+// to enable this when ::eventfd() is available.
+
+#include <sys/eventfd.h>
+
+namespace qpid {
+namespace sys {
+
+PollableCondition::PollableCondition() : IOHandle(new sys::IOHandlePrivate) {
+    impl->fd = ::eventfd(0, 0);
+    if (impl->fd < 0) throw ErrnoException("conditionfd() failed");
+}
+
+bool PollableCondition::clear() {
+    char buf[8];
+    ssize_t n = ::read(impl->fd, buf, 8);
+    if (n != 8) throw ErrnoException("read failed on conditionfd");
+    return *reinterpret_cast<uint64_t*>(buf);
+}
+
+void PollableCondition::set() {
+    static const uint64_t value=1;
+    ssize_t n = ::write(impl->fd, reinterpret_cast<const void*>(&value), 8);
+    if (n != 8) throw ErrnoException("write failed on conditionfd");
+}
+    
+#endif
+
+}} // namespace qpid::sys
+
+#endif  /*!QPID_SYS_LINUX_POLLABLECONDITION_CPP*/
diff --git a/cpp/src/qpid/sys/PollableCondition.h b/cpp/src/qpid/sys/PollableCondition.h
new file mode 100644
index 0000000000..6f0e12a474
--- /dev/null
+++ b/cpp/src/qpid/sys/PollableCondition.h
@@ -0,0 +1,60 @@
+#ifndef QPID_SYS_POLLABLECONDITION_H
+#define QPID_SYS_POLLABLECONDITION_H
+
+/*
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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/IOHandle.h"
+
+// FIXME aconway 2008-08-11: this could be of more general interest,
+// move to sys namespace in common lib. 
+// 
+
+namespace qpid {
+namespace sys {
+
+/**
+ * A pollable condition to integrate in-process conditions with IO
+ * conditions in a polling loop.
+ *
+ * Setting the condition makes it readable for a poller.
+ * 
+ * Writable/disconnected conditions are undefined and should not be
+ * polled for.
+ */
+class PollableCondition : public sys::IOHandle {
+  public:
+    PollableCondition();
+
+    /** Set the condition, triggers readable in a poller. */ 
+    void set();
+
+    /** Get the current state of the condition, then clear it.
+     *@return The state of the condition before it was cleared.
+     */
+    bool clear();
+
+  private:
+    int writeFd;
+};
+}} // namespace qpid::sys
+
+#endif  /*!QPID_SYS_POLLABLECONDITION_H*/
diff --git a/cpp/src/qpid/sys/PollableQueue.h b/cpp/src/qpid/sys/PollableQueue.h
new file mode 100644
index 0000000000..2e5d3a0d3d
--- /dev/null
+++ b/cpp/src/qpid/sys/PollableQueue.h
@@ -0,0 +1,113 @@
+#ifndef QPID_SYS_POLLABLEQUEUE_H
+#define QPID_SYS_POLLABLEQUEUE_H
+
+/*
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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/PollableCondition.h"
+#include "qpid/sys/Dispatcher.h"
+#include "qpid/sys/Mutex.h"
+#include <boost/function.hpp>
+#include <boost/bind.hpp>
+#include <algorithm>
+#include <deque>
+
+namespace qpid {
+
+namespace sys { class Poller; }
+
+namespace sys {
+
+// FIXME aconway 2008-08-11: this could be of more general interest,
+// move to common lib.
+
+/**
+ * A queue that can be polled by sys::Poller.  Any thread can push to
+ * the queue, on wakeup the poller thread processes all items on the
+ * queue by passing them to a callback in a batch.
+ */
+template <class T>
+class PollableQueue {
+    typedef std::deque<T> Queue;
+
+  public:
+    typedef typename Queue::iterator iterator;
+    
+    /** Callback to process a range of items. */
+    typedef boost::function<void (const iterator&, const iterator&)> Callback;
+
+    /** Functor tempalate to create a Callback from a functor that handles a single item. */
+    template <class F> struct ForEach {
+        F handleOne;
+        ForEach(const F& f) : handleOne(f) {}
+        void operator()(const iterator& i, const iterator& j) const { std::for_each(i, j, handleOne); }
+    };
+    /** Function to create ForEach instances */
+    template <class F> static ForEach<F> forEach(const F& f) { return ForEach<F>(f); }
+    
+    /** When the queue is selected by the poller, values are passed to callback cb. */
+    explicit PollableQueue(const Callback& cb);
+
+    /** Push a value onto the queue. Thread safe */
+    void push(const T& t) { ScopedLock l(lock); queue.push_back(t); condition.set(); }
+
+    /** Start polling. */ 
+    void start(const boost::shared_ptr<sys::Poller>& poller) { handle.startWatch(poller); }
+
+    /** Stop polling. */
+    void stop() { handle.stopWatch(); }
+    
+  private:
+    typedef sys::Mutex::ScopedLock ScopedLock;
+    typedef sys::Mutex::ScopedUnlock ScopedUnlock;
+
+    void dispatch(sys::DispatchHandle&);
+    
+    sys::Mutex lock;
+    Callback callback;
+    PollableCondition condition;
+    sys::DispatchHandle handle;
+    Queue queue;
+    Queue batch;
+};
+
+template <class T> PollableQueue<T>::PollableQueue(const Callback& cb) // FIXME aconway 2008-08-12: 
+    : callback(cb),
+      handle(condition, boost::bind(&PollableQueue<T>::dispatch, this, _1), 0, 0)
+{}
+
+template <class T> void PollableQueue<T>::dispatch(sys::DispatchHandle& h) {
+    ScopedLock l(lock);         // Lock for concurrent push() 
+    batch.clear();
+    batch.swap(queue);
+    condition.clear();
+    {
+        // Process outside the lock to allow concurrent push.
+        ScopedUnlock u(lock);
+        callback(batch.begin(), batch.end()); 
+        h.rewatch();
+    }
+    batch.clear();
+}
+
+}} // namespace qpid::sys
+
+#endif  /*!QPID_SYS_POLLABLEQUEUE_H*/