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authorMartin Sustrik <sustrik@fastmq.commkdir>2010-01-13 19:21:23 +0100
committerMartin Sustrik <sustrik@fastmq.commkdir>2010-01-13 19:21:23 +0100
commit067ba3b9f77a253d4ce58e05ef1fa7702c32b2a3 (patch)
treef7e5b694a2e65059ac6c041b0640101229a0d9df
parent06105d164230800e8ea42ddd513e2f7fb27e6f2f (diff)
ZMQII-34: ensure that poll won't return POLLIN event when the message will be filtered out anyway (POSIX)
-rw-r--r--src/socket_base.cpp4
-rw-r--r--src/sub.cpp92
-rw-r--r--src/sub.hpp10
-rw-r--r--src/zmq.cpp50
4 files changed, 110 insertions, 46 deletions
diff --git a/src/socket_base.cpp b/src/socket_base.cpp
index 3e6488d..ad68fdb 100644
--- a/src/socket_base.cpp
+++ b/src/socket_base.cpp
@@ -331,9 +331,7 @@ int zmq::socket_base_t::recv (::zmq_msg_t *msg_, int flags_)
}
else {
while (rc != 0) {
- if (errno == EINPROGRESS)
- app_thread->process_commands (false, true);
- else if (errno == EAGAIN)
+ if (errno == EAGAIN)
app_thread->process_commands (true, false);
else
return -1;
diff --git a/src/sub.cpp b/src/sub.cpp
index bdc27da..b8e3990 100644
--- a/src/sub.cpp
+++ b/src/sub.cpp
@@ -26,14 +26,17 @@
zmq::sub_t::sub_t (class app_thread_t *parent_) :
socket_base_t (parent_),
- all_count (0)
+ all_count (0),
+ has_message (false)
{
options.requires_in = true;
options.requires_out = false;
+ zmq_msg_init (&message);
}
zmq::sub_t::~sub_t ()
{
+ zmq_msg_close (&message);
}
void zmq::sub_t::xattach_pipes (class reader_t *inpipe_,
@@ -115,16 +118,72 @@ int zmq::sub_t::xflush ()
int zmq::sub_t::xrecv (zmq_msg_t *msg_, int flags_)
{
- // Get a message using fair queueing algorithm.
- int rc = fq.recv (msg_, flags_);
+ // If there's already a message prepared by a previous call to zmq_poll,
+ // return it straight ahead.
+ if (has_message) {
+ zmq_msg_move (msg_, &message);
+ has_message = false;
+ return 0;
+ }
+
+ // TODO: This can result in infinite loop in the case of continuous
+ // stream of non-matching messages which breaks the non-blocking recv
+ // semantics.
+ while (true) {
- // If there's no message available, return immediately.
- if (rc != 0 && errno == EAGAIN)
- return -1;
+ // Get a message using fair queueing algorithm.
+ int rc = fq.recv (msg_, flags_);
+ // If there's no message available, return immediately.
+ // The same when error occurs.
+ if (rc != 0)
+ return -1;
+
+ // Check whether the message matches at least one subscription.
+ if (match (msg_))
+ return 0;
+ }
+}
+
+bool zmq::sub_t::xhas_in ()
+{
+ // If there's already a message prepared by a previous call to zmq_poll,
+ // return straight ahead.
+ if (has_message)
+ return true;
+
+ // TODO: This can result in infinite loop in the case of continuous
+ // stream of non-matching messages.
+ while (true) {
+
+ // Get a message using fair queueing algorithm.
+ int rc = fq.recv (&message, ZMQ_NOBLOCK);
+
+ // If there's no message available, return immediately.
+ // The same when error occurs.
+ if (rc != 0) {
+ zmq_assert (errno == EAGAIN);
+ return false;
+ }
+
+ // Check whether the message matches at least one subscription.
+ if (match (&message)) {
+ has_message = true;
+ return true;
+ }
+ }
+}
+
+bool zmq::sub_t::xhas_out ()
+{
+ return false;
+}
+
+bool zmq::sub_t::match (zmq_msg_t *msg_)
+{
// If there is at least one * subscription, the message matches.
if (all_count)
- return 0;
+ return true;
// Check whether the message matches at least one prefix subscription.
// TODO: Make this efficient - O(log(n)) where n is number of characters in
@@ -135,25 +194,8 @@ int zmq::sub_t::xrecv (zmq_msg_t *msg_, int flags_)
size_t sub_size = it->size ();
if (sub_size <= msg_size &&
memcmp (zmq_msg_data (msg_), it->data (), sub_size) == 0)
- return 0;
+ return true;
}
- // The message did not pass the filter. Trim it.
- // Note that we are returning a different error code so that the caller
- // knows there are more messages available. We cannot loop here as
- // a stream of non-matching messages would create a DoS situation.
- zmq_msg_close (msg_);
- zmq_msg_init (msg_);
- errno = EINPROGRESS;
- return -1;
-}
-
-bool zmq::sub_t::xhas_in ()
-{
- return fq.has_in ();
-}
-
-bool zmq::sub_t::xhas_out ()
-{
return false;
}
diff --git a/src/sub.hpp b/src/sub.hpp
index df7d369..2044442 100644
--- a/src/sub.hpp
+++ b/src/sub.hpp
@@ -23,6 +23,8 @@
#include <set>
#include <string>
+#include "../bindings/c/zmq.h"
+
#include "socket_base.hpp"
#include "fq.hpp"
@@ -53,6 +55,9 @@ namespace zmq
private:
+ // Check whether the message matches at least one subscription.
+ bool match (zmq_msg_t *msg_);
+
// Fair queueing object for inbound pipes.
fq_t fq;
@@ -62,6 +67,11 @@ namespace zmq
typedef std::multiset <std::string> subscriptions_t;
subscriptions_t subscriptions;
+ // If true, 'message' contains a matching message to return on the
+ // next recv call.
+ bool has_message;
+ zmq_msg_t message;
+
sub_t (const sub_t&);
void operator = (const sub_t&);
};
diff --git a/src/zmq.cpp b/src/zmq.cpp
index 03064bc..1ed96df 100644
--- a/src/zmq.cpp
+++ b/src/zmq.cpp
@@ -324,27 +324,20 @@ int zmq_poll (zmq_pollitem_t *items_, int nitems_, long timeout_)
npollfds++;
}
+ // First iteration just check for events, don't block. Waiting would
+ // prevent exiting on any events that may already been signaled on
+ // 0MQ sockets.
+ int rc = poll (pollfds, npollfds, 0);
+ if (rc == -1 && errno == EINTR) {
+ free (pollfds);
+ return 0;
+ }
+ errno_assert (rc >= 0);
+
int timeout = timeout_ > 0 ? timeout_ / 1000 : -1;
int nevents = 0;
- bool initial = true;
- while (!nevents) {
-
- // Wait for activity. In the first iteration just check for events,
- // don't wait. Waiting would prevent exiting on any events that may
- // already be signaled on 0MQ sockets.
- int rc = poll (pollfds, npollfds, initial ? 0 : timeout);
- if (rc == -1 && errno == EINTR)
- break;
- errno_assert (rc >= 0);
-
- // If timeout was hit with no events signaled, return zero.
- if (!initial && rc == 0) {
- free (pollfds);
- return 0;
- }
- // From now on, perform blocking polling.
- initial = false;
+ while (true) {
// Process 0MQ commands if needed.
if (nsockets && pollfds [npollfds -1].revents & POLLIN)
@@ -376,6 +369,27 @@ int zmq_poll (zmq_pollitem_t *items_, int nitems_, long timeout_)
if (items_ [i].revents)
nevents++;
}
+
+ // If there's at least one event, or if we are asked not to block,
+ // return immediately.
+ if (nevents || !timeout)
+ break;
+
+ // Wait for events.
+ rc = poll (pollfds, npollfds, timeout);
+ if (rc == -1 && errno == EINTR)
+ break;
+ errno_assert (rc >= 0);
+
+ // If timeout was hit with no events signaled, return zero.
+ if (rc == 0)
+ break;
+
+ // If timeout was already applied, we don't want to poll anymore.
+ // Setting timeout to zero will cause termination of the function
+ // once the events we've got are processed.
+ if (timeout > 0)
+ timeout = 0;
}
free (pollfds);