output_thread: fixed wrong pipe io function usage

output_thread patch #1 : pipe creation is platform dependent, in unixes it's
achieved through the pipe syscall but in windows it's a socket pair created
through libevent which means instead of read/write we need to use recv/send
which was already abstracted through flb_pipe_(r/w).

output_thread patch #2 : in windows the SOCKET data type is defined as an
UINT_PTR which means in 64 bit operating systems it's an 8 byte number
instead of 4. libevent abstracts this through the evutil_socket_t data type
which in turn is abstracted using the flb_pipefd_t data type in fluent bit.

The problem comes to play when calling mk_event_channel_create which
receives 2 int pointers to return both pipe endpoints. This means there
are 2 possible bugs (one of which was happening and the other is not
really a concern I think) :

Since mk_event_channel_create was only modifying the low part of the elements
in the ch_parent_events array and the structure was not zeroed when allocated,
the high parts of those 64 bit members contained garbage which caused any
winsock calls to return error 10038 (not a socket). That's the reason why I
added a memset call in line 421.

There is still a possible issue with mk_event_channel_create which we should
fix by moving our platform dependent data type to mk_lib and defining our
flb local data types to those if need be (for consistency).

Signed-off-by: Leonardo Alminana <leonardo@calyptia.com>

src/flb_output_thread.c

@@ -92,7 +92,7 @@ static inline int handle_output_event(struct flb_config *config,
      * Notify the parent event loop the return status, just forward the same
      * 64 bits value.
      */
-    ret = write(ch_parent, &val, sizeof(val));
+    ret = flb_pipe_w(ch_parent, &val, sizeof(val));
     if (ret == -1) {
         flb_errno();
         return -1;
@@ -376,7 +376,9 @@ int flb_output_thread_pool_flush(struct flb_task *task,
 
     flb_plg_debug(out_ins, "task_id=%i assigned to thread #%i",
                   task->id, th->id);
-    n = write(th_ins->ch_parent_events[1], &task, sizeof(struct flb_task *));
+
+    n = flb_pipe_w(th_ins->ch_parent_events[1], &task, sizeof(struct flb_task*));
+
     if (n == -1) {
         flb_errno();
         return -1;
@@ -416,6 +418,8 @@ int flb_output_thread_pool_create(struct flb_config *config,
             flb_errno();
             continue;
         }
+        memset(th_ins, 0, sizeof(struct flb_out_thread_instance));
+
         th_ins->config = config;
         th_ins->ins = ins;
         th_ins->coro_id = 0;
@@ -518,7 +522,7 @@ void flb_output_thread_pool_destroy(struct flb_output_instance *ins)
         }
 
         th_ins = th->params.data;
-        n = write(th_ins->ch_parent_events[1], &stop, sizeof(stop));
+        n = flb_pipe_w(th_ins->ch_parent_events[1], &stop, sizeof(stop));
         if (n < 0) {
             flb_errno();
             flb_plg_error(th_ins->ins, "could not signal worker thread");