src/ruby/ext/grpc/rb_completion_queue.c

/*
 *
 * Copyright 2015, Google Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#include <ruby/ruby.h>

#include "rb_grpc_imports.generated.h"
#include "rb_completion_queue.h"

#include <ruby/thread.h>

#include <grpc/grpc.h>
#include <grpc/support/time.h>
#include "rb_grpc.h"

/* grpc_rb_cCompletionQueue is the ruby class that proxies
 * grpc_completion_queue. */
static VALUE grpc_rb_cCompletionQueue = Qnil;

/* Used to allow grpc_completion_queue_next call to release the GIL */
typedef struct next_call_stack {
  grpc_completion_queue *cq;
  grpc_event event;
  gpr_timespec timeout;
  void *tag;
  volatile int interrupted;
} next_call_stack;

/* Calls grpc_completion_queue_next without holding the ruby GIL */
static void *grpc_rb_completion_queue_next_no_gil(void *param) {
  next_call_stack *const next_call = (next_call_stack*)param;
  gpr_timespec increment = gpr_time_from_millis(20, GPR_TIMESPAN);
  gpr_timespec deadline;
  do {
    deadline = gpr_time_add(gpr_now(GPR_CLOCK_REALTIME), increment);
    next_call->event = grpc_completion_queue_next(next_call->cq,
                                                  deadline, NULL);
    if (next_call->event.type != GRPC_QUEUE_TIMEOUT ||
        gpr_time_cmp(deadline, next_call->timeout) > 0) {
      break;
    }
  } while (!next_call->interrupted);
  return NULL;
}

/* Calls grpc_completion_queue_pluck without holding the ruby GIL */
static void *grpc_rb_completion_queue_pluck_no_gil(void *param) {
  next_call_stack *const next_call = (next_call_stack*)param;
  gpr_timespec increment = gpr_time_from_millis(20, GPR_TIMESPAN);
  gpr_timespec deadline;
  do {
    deadline = gpr_time_add(gpr_now(GPR_CLOCK_REALTIME), increment);
    next_call->event = grpc_completion_queue_pluck(next_call->cq,
                                                   next_call->tag,
                                                   deadline, NULL);
    if (next_call->event.type != GRPC_QUEUE_TIMEOUT ||
        gpr_time_cmp(deadline, next_call->timeout) > 0) {
      break;
    }
  } while (!next_call->interrupted);
  return NULL;
}

/* Shuts down and drains the completion queue if necessary.
 *
 * This is done when the ruby completion queue object is about to be GCed.
 */
static void grpc_rb_completion_queue_shutdown_drain(grpc_completion_queue *cq) {
  next_call_stack next_call;
  grpc_completion_type type;
  int drained = 0;
  MEMZERO(&next_call, next_call_stack, 1);

  grpc_completion_queue_shutdown(cq);
  next_call.cq = cq;
  next_call.event.type = GRPC_QUEUE_TIMEOUT;
  /* TODO: the timeout should be a module level constant that defaults
   * to gpr_inf_future(GPR_CLOCK_REALTIME).
   *
   * - at the moment this does not work, it stalls.  Using a small timeout like
   *   this one works, and leads to fast test run times; a longer timeout was
   *   causing unnecessary delays in the test runs.
   *
   * - investigate further, this is probably another example of C-level cleanup
   * not working consistently in all cases.
   */
  next_call.timeout = gpr_time_add(gpr_now(GPR_CLOCK_REALTIME),
                                   gpr_time_from_micros(5e3, GPR_TIMESPAN));
  do {
    rb_thread_call_without_gvl(grpc_rb_completion_queue_next_no_gil,
                               (void *)&next_call, NULL, NULL);
    type = next_call.event.type;
    if (type == GRPC_QUEUE_TIMEOUT) break;
    if (type != GRPC_QUEUE_SHUTDOWN) {
      ++drained;
      rb_warning("completion queue shutdown: %d undrained events", drained);
    }
  } while (type != GRPC_QUEUE_SHUTDOWN);
}

/* Helper function to free a completion queue. */
static void grpc_rb_completion_queue_destroy(void *p) {
  grpc_completion_queue *cq = NULL;
  if (p == NULL) {
    return;
  }
  cq = (grpc_completion_queue *)p;
  grpc_rb_completion_queue_shutdown_drain(cq);
  grpc_completion_queue_destroy(cq);
}

static rb_data_type_t grpc_rb_completion_queue_data_type = {
    "grpc_completion_queue",
    {GRPC_RB_GC_NOT_MARKED, grpc_rb_completion_queue_destroy,
     GRPC_RB_MEMSIZE_UNAVAILABLE, {NULL, NULL}},
    NULL, NULL,
#ifdef RUBY_TYPED_FREE_IMMEDIATELY
    /* cannot immediately free because grpc_rb_completion_queue_shutdown_drain
     * calls rb_thread_call_without_gvl. */
    0,
#endif
};

/* Releases the c-level resources associated with a completion queue */
static VALUE grpc_rb_completion_queue_close(VALUE self) {
  grpc_completion_queue* cq = grpc_rb_get_wrapped_completion_queue(self);
  grpc_rb_completion_queue_destroy(cq);
  RTYPEDDATA_DATA(self) = NULL;
  return Qnil;
}

/* Allocates a completion queue. */
static VALUE grpc_rb_completion_queue_alloc(VALUE cls) {
  grpc_completion_queue *cq = grpc_completion_queue_create(NULL);
  if (cq == NULL) {
    rb_raise(rb_eArgError, "could not create a completion queue: not sure why");
  }
  return TypedData_Wrap_Struct(cls, &grpc_rb_completion_queue_data_type, cq);
}

static void unblock_func(void *param) {
  next_call_stack *const next_call = (next_call_stack*)param;
  next_call->interrupted = 1;
}

/* Blocks until the next event for given tag is available, and returns the
 * event. */
grpc_event grpc_rb_completion_queue_pluck_event(VALUE self, VALUE tag,
                                                VALUE timeout) {
  next_call_stack next_call;
  MEMZERO(&next_call, next_call_stack, 1);
  TypedData_Get_Struct(self, grpc_completion_queue,
                       &grpc_rb_completion_queue_data_type, next_call.cq);
  if (TYPE(timeout) == T_NIL) {
    next_call.timeout = gpr_inf_future(GPR_CLOCK_REALTIME);
  } else {
    next_call.timeout = grpc_rb_time_timeval(timeout, /* absolute time*/ 0);
  }
  if (TYPE(tag) == T_NIL) {
    next_call.tag = NULL;
  } else {
    next_call.tag = ROBJECT(tag);
  }
  next_call.event.type = GRPC_QUEUE_TIMEOUT;
  /* Loop until we finish a pluck without an interruption. The internal
     pluck function runs either until it is interrupted or it gets an
     event, or time runs out.

     The basic reason we need this relatively complicated construction is that
     we need to re-acquire the GVL when an interrupt comes in, so that the ruby
     interpreter can do what it needs to do with the interrupt. But we also need
     to get back to plucking when the interrupt has been handled. */
  do {
    next_call.interrupted = 0;
    rb_thread_call_without_gvl(grpc_rb_completion_queue_pluck_no_gil,
                               (void *)&next_call, unblock_func,
                               (void *)&next_call);
    /* If an interrupt prevented pluck from returning useful information, then
       any plucks that did complete must have timed out */
  } while (next_call.interrupted &&
           next_call.event.type == GRPC_QUEUE_TIMEOUT);
  return next_call.event;
}

void Init_grpc_completion_queue() {
  grpc_rb_cCompletionQueue =
      rb_define_class_under(grpc_rb_mGrpcCore, "CompletionQueue", rb_cObject);

  /* constructor: uses an alloc func without an initializer. Using a simple
     alloc func works here as the grpc header does not specify any args for
     this func, so no separate initialization step is necessary. */
  rb_define_alloc_func(grpc_rb_cCompletionQueue,
                       grpc_rb_completion_queue_alloc);

  /* close: Provides a way to close the underlying file descriptor without
     waiting for ruby garbage collection. */
  rb_define_method(grpc_rb_cCompletionQueue, "close",
                   grpc_rb_completion_queue_close, 0);
}

/* Gets the wrapped completion queue from the ruby wrapper */
grpc_completion_queue *grpc_rb_get_wrapped_completion_queue(VALUE v) {
  grpc_completion_queue *cq = NULL;
  TypedData_Get_Struct(v, grpc_completion_queue,
                       &grpc_rb_completion_queue_data_type, cq);
  return cq;
}