Background thread names (#2784)

* Add ZMQ_THREAD_NAME_PREFIX ctx option

include/zmq.h

@@ -613,6 +613,7 @@ ZMQ_EXPORT void zmq_threadclose (void* thread);
 #define ZMQ_MSG_T_SIZE 6
 #define ZMQ_THREAD_AFFINITY 7
 #define ZMQ_THREAD_AFFINITY_DFLT -1
+#define ZMQ_THREAD_NAME_PREFIX 8
 
 /*  DRAFT Socket methods.                                                     */
 ZMQ_EXPORT int zmq_join (void *s, const char *group);

src/ctx.cpp

@@ -36,6 +36,7 @@
 #include <limits>
 #include <climits>
 #include <new>
+#include <sstream>
 #include <string.h>
 
 #include "ctx.hpp"
@@ -256,6 +257,13 @@ int zmq::ctx_t::set (int option_, int optval_)
         thread_affinity = optval_;
     }
     else
+    if (option_ == ZMQ_THREAD_NAME_PREFIX && optval_ >= 0) {
+        std::ostringstream s;
+        s << optval_;
+        scoped_lock_t locker(opt_sync);
+        thread_name_prefix = s.str();
+    }
+    else
     if (option_ == ZMQ_BLOCKY && optval_ >= 0) {
         scoped_lock_t locker(opt_sync);
         blocky = (optval_ != 0);
@@ -401,11 +409,16 @@ zmq::object_t *zmq::ctx_t::get_reaper ()
 
 void zmq::ctx_t::start_thread (thread_t &thread_, thread_fn *tfn_, void *arg_) const
 {
+    static unsigned int nthreads_started = 0;
+
     thread_.setSchedulingParameters(thread_priority, thread_sched_policy, thread_affinity);
     thread_.start(tfn_, arg_);
 #ifndef ZMQ_HAVE_ANDROID
-    thread_.setThreadName ("ZMQ background");
+    std::ostringstream s;
+    s << thread_name_prefix << "/ZMQbg/" << nthreads_started;
+    thread_.setThreadName (s.str().c_str());
 #endif
+    nthreads_started++;
 }
 
 void zmq::ctx_t::send_command (uint32_t tid_, const command_t &command_)

src/ctx.hpp

@@ -211,10 +211,11 @@ namespace zmq
         //  Is IPv6 enabled on this context?
         bool ipv6;
 
-        //  Thread scheduling parameters.
+        //  Thread parameters.
         int thread_priority;
         int thread_sched_policy;
         int thread_affinity;
+        std::string thread_name_prefix;
 
         //  Synchronisation of access to context options.
         mutex_t opt_sync;

src/zmq_draft.h

@@ -93,6 +93,7 @@
 #define ZMQ_MSG_T_SIZE 6
 #define ZMQ_THREAD_AFFINITY 7
 #define ZMQ_THREAD_AFFINITY_DFLT -1
+#define ZMQ_THREAD_NAME_PREFIX 8
 
 /*  DRAFT Socket methods.                                                     */
 int zmq_join (void *s, const char *group);

tests/test_ctx_options.cpp

@@ -124,6 +124,14 @@ void test_ctx_thread_opts(void* ctx)
     rc = zmq_ctx_set(ctx, ZMQ_THREAD_AFFINITY, cpu_affinity_test);
     assert (rc == 0);
 #endif
+
+
+#ifdef ZMQ_THREAD_NAME_PREFIX
+    // test thread name prefix:
+
+    rc = zmq_ctx_set(ctx, ZMQ_THREAD_NAME_PREFIX, 1234);
+    assert (rc == 0);
+#endif
 }