test/core/end2end/tests/filter_latency.cc - platform/external/grpc-grpc - Gitiles

 /*
  *
  * Copyright 2016 gRPC authors.
  *
  * Licensed 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 "test/core/end2end/end2end_tests.h"

 #include <limits.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <string.h>

 #include <grpc/byte_buffer.h>
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
 #include <grpc/support/time.h>

 #include "src/core/lib/channel/channel_stack_builder.h"
 #include "src/core/lib/surface/channel_init.h"
 #include "test/core/end2end/cq_verifier.h"

 enum { TIMEOUT = 200000 };

 static bool g_enable_filter = false;
 static gpr_mu g_mu;
 static gpr_timespec g_client_latency;
 static gpr_timespec g_server_latency;

 static void* tag(intptr_t t) { return (void*)t; }

 static grpc_end2end_test_fixture begin_test(grpc_end2end_test_config config,
                                             const char* test_name,
                                             grpc_channel_args* client_args,
                                             grpc_channel_args* server_args) {
   grpc_end2end_test_fixture f;
   gpr_log(GPR_INFO, "Running test: %s/%s", test_name, config.name);
   f = config.create_fixture(client_args, server_args);
   config.init_server(&f, server_args);
   config.init_client(&f, client_args);
   return f;
 }

 static gpr_timespec n_seconds_from_now(int n) {
   return grpc_timeout_seconds_to_deadline(n);
 }

 static gpr_timespec five_seconds_from_now(void) {
   return n_seconds_from_now(5);
 }

 static void drain_cq(grpc_completion_queue* cq) {
   grpc_event ev;
   do {
     ev = grpc_completion_queue_next(cq, five_seconds_from_now(), nullptr);
   } while (ev.type != GRPC_QUEUE_SHUTDOWN);
 }

 static void shutdown_server(grpc_end2end_test_fixture* f) {
   if (!f->server) return;
   grpc_server_shutdown_and_notify(f->server, f->shutdown_cq, tag(1000));
   GPR_ASSERT(grpc_completion_queue_pluck(f->shutdown_cq, tag(1000),
                                          grpc_timeout_seconds_to_deadline(5),
                                          nullptr)
                  .type == GRPC_OP_COMPLETE);
   grpc_server_destroy(f->server);
   f->server = nullptr;
 }

 static void shutdown_client(grpc_end2end_test_fixture* f) {
   if (!f->client) return;
   grpc_channel_destroy(f->client);
   f->client = nullptr;
 }

 static void end_test(grpc_end2end_test_fixture* f) {
   shutdown_server(f);
   shutdown_client(f);

   grpc_completion_queue_shutdown(f->cq);
   drain_cq(f->cq);
   grpc_completion_queue_destroy(f->cq);
   grpc_completion_queue_destroy(f->shutdown_cq);
 }

 // Simple request via a server filter that saves the reported latency value.
 static void test_request(grpc_end2end_test_config config) {
   grpc_call* c;
   grpc_call* s;
   grpc_slice request_payload_slice =
       grpc_slice_from_copied_string("hello world");
   grpc_byte_buffer* request_payload =
       grpc_raw_byte_buffer_create(&request_payload_slice, 1);
   grpc_end2end_test_fixture f =
       begin_test(config, "filter_latency", nullptr, nullptr);
   cq_verifier* cqv = cq_verifier_create(f.cq);
   grpc_op ops[6];
   grpc_op* op;
   grpc_metadata_array initial_metadata_recv;
   grpc_metadata_array trailing_metadata_recv;
   grpc_metadata_array request_metadata_recv;
   grpc_byte_buffer* request_payload_recv = nullptr;
   grpc_call_details call_details;
   grpc_status_code status;
   grpc_call_error error;
   grpc_slice details;
   int was_cancelled = 2;

   gpr_mu_lock(&g_mu);
   g_client_latency = gpr_time_0(GPR_TIMESPAN);
   g_server_latency = gpr_time_0(GPR_TIMESPAN);
   gpr_mu_unlock(&g_mu);
   const gpr_timespec start_time = gpr_now(GPR_CLOCK_MONOTONIC);

   gpr_timespec deadline = five_seconds_from_now();
   c = grpc_channel_create_call(
       f.client, nullptr, GRPC_PROPAGATE_DEFAULTS, f.cq,
       grpc_slice_from_static_string("/foo"),
       get_host_override_slice("foo.test.google.fr", config), deadline, nullptr);
   GPR_ASSERT(c);

   grpc_metadata_array_init(&initial_metadata_recv);
   grpc_metadata_array_init(&trailing_metadata_recv);
   grpc_metadata_array_init(&request_metadata_recv);
   grpc_call_details_init(&call_details);

   memset(ops, 0, sizeof(ops));
   op = ops;
   op->op = GRPC_OP_SEND_INITIAL_METADATA;
   op->data.send_initial_metadata.count = 0;
   op->data.send_initial_metadata.metadata = nullptr;
   op->flags = 0;
   op->reserved = nullptr;
   op++;
   op->op = GRPC_OP_SEND_MESSAGE;
   op->data.send_message.send_message = request_payload;
   op->flags = 0;
   op->reserved = nullptr;
   op++;
   op->op = GRPC_OP_SEND_CLOSE_FROM_CLIENT;
   op->flags = 0;
   op->reserved = nullptr;
   op++;
   op->op = GRPC_OP_RECV_INITIAL_METADATA;
   op->data.recv_initial_metadata.recv_initial_metadata = &initial_metadata_recv;
   op->flags = 0;
   op->reserved = nullptr;
   op++;
   op->op = GRPC_OP_RECV_STATUS_ON_CLIENT;
   op->data.recv_status_on_client.trailing_metadata = &trailing_metadata_recv;
   op->data.recv_status_on_client.status = &status;
   op->data.recv_status_on_client.status_details = &details;
   op->flags = 0;
   op->reserved = nullptr;
   op++;
   error = grpc_call_start_batch(c, ops, static_cast<size_t>(op - ops), tag(1),
                                 nullptr);
   GPR_ASSERT(GRPC_CALL_OK == error);

   error =
       grpc_server_request_call(f.server, &s, &call_details,
                                &request_metadata_recv, f.cq, f.cq, tag(101));
   GPR_ASSERT(GRPC_CALL_OK == error);

   CQ_EXPECT_COMPLETION(cqv, tag(101), 1);
   cq_verify(cqv);

   memset(ops, 0, sizeof(ops));
   op = ops;
   op->op = GRPC_OP_SEND_INITIAL_METADATA;
   op->data.send_initial_metadata.count = 0;
   op->flags = 0;
   op->reserved = nullptr;
   op++;
   op->op = GRPC_OP_SEND_STATUS_FROM_SERVER;
   op->data.send_status_from_server.trailing_metadata_count = 0;
   op->data.send_status_from_server.status = GRPC_STATUS_UNIMPLEMENTED;
   grpc_slice status_string = grpc_slice_from_static_string("xyz");
   op->data.send_status_from_server.status_details = &status_string;
   op->flags = 0;
   op->reserved = nullptr;
   op++;
   op->op = GRPC_OP_RECV_CLOSE_ON_SERVER;
   op->data.recv_close_on_server.cancelled = &was_cancelled;
   op->flags = 0;
   op->reserved = nullptr;
   op++;
   error = grpc_call_start_batch(s, ops, static_cast<size_t>(op - ops), tag(102),
                                 nullptr);
   GPR_ASSERT(GRPC_CALL_OK == error);

   CQ_EXPECT_COMPLETION(cqv, tag(102), 1);
   CQ_EXPECT_COMPLETION(cqv, tag(1), 1);
   cq_verify(cqv);

   GPR_ASSERT(status == GRPC_STATUS_UNIMPLEMENTED);
   GPR_ASSERT(0 == grpc_slice_str_cmp(details, "xyz"));

   grpc_slice_unref(details);
   grpc_metadata_array_destroy(&initial_metadata_recv);
   grpc_metadata_array_destroy(&trailing_metadata_recv);
   grpc_metadata_array_destroy(&request_metadata_recv);
   grpc_call_details_destroy(&call_details);

   grpc_call_unref(s);
   grpc_call_unref(c);

   cq_verifier_destroy(cqv);

   grpc_byte_buffer_destroy(request_payload);
   grpc_byte_buffer_destroy(request_payload_recv);

   end_test(&f);
   config.tear_down_data(&f);

   const gpr_timespec end_time = gpr_now(GPR_CLOCK_MONOTONIC);
   const gpr_timespec max_latency = gpr_time_sub(end_time, start_time);

   // Perform checks after test tear-down
   // Guards against the case that there's outstanding channel-related work on a
   // call prior to verification
   gpr_mu_lock(&g_mu);
   GPR_ASSERT(gpr_time_cmp(max_latency, g_client_latency) >= 0);
   GPR_ASSERT(gpr_time_cmp(gpr_time_0(GPR_TIMESPAN), g_client_latency) <= 0);
   GPR_ASSERT(gpr_time_cmp(max_latency, g_server_latency) >= 0);
   GPR_ASSERT(gpr_time_cmp(gpr_time_0(GPR_TIMESPAN), g_server_latency) <= 0);
   // Server latency should always be smaller than client latency, however since
   // we only calculate latency at destruction time, and that might mean that we
   // need to wait for outstanding channel-related work, this isn't verifiable
   // right now (the server MAY hold on to the call for longer than the client).
   // GPR_ASSERT(gpr_time_cmp(g_server_latency, g_client_latency) < 0);
   gpr_mu_unlock(&g_mu);
 }

 /*******************************************************************************
  * Test latency filter
  */

 static grpc_error* init_call_elem(grpc_call_element* elem,
                                   const grpc_call_element_args* args) {
   return GRPC_ERROR_NONE;
 }

 static void client_destroy_call_elem(grpc_call_element* elem,
                                      const grpc_call_final_info* final_info,
                                      grpc_closure* ignored) {
   gpr_mu_lock(&g_mu);
   g_client_latency = final_info->stats.latency;
   gpr_mu_unlock(&g_mu);
 }

 static void server_destroy_call_elem(grpc_call_element* elem,
                                      const grpc_call_final_info* final_info,
                                      grpc_closure* ignored) {
   gpr_mu_lock(&g_mu);
   g_server_latency = final_info->stats.latency;
   gpr_mu_unlock(&g_mu);
 }

 static grpc_error* init_channel_elem(grpc_channel_element* elem,
                                      grpc_channel_element_args* args) {
   return GRPC_ERROR_NONE;
 }

 static void destroy_channel_elem(grpc_channel_element* elem) {}

 static const grpc_channel_filter test_client_filter = {
     grpc_call_next_op,
     grpc_channel_next_op,
     0,
     init_call_elem,
     grpc_call_stack_ignore_set_pollset_or_pollset_set,
     client_destroy_call_elem,
     0,
     init_channel_elem,
     destroy_channel_elem,
     grpc_channel_next_get_info,
     "client_filter_latency"};

 static const grpc_channel_filter test_server_filter = {
     grpc_call_next_op,
     grpc_channel_next_op,
     0,
     init_call_elem,
     grpc_call_stack_ignore_set_pollset_or_pollset_set,
     server_destroy_call_elem,
     0,
     init_channel_elem,
     destroy_channel_elem,
     grpc_channel_next_get_info,
     "server_filter_latency"};

 /*******************************************************************************
  * Registration
  */

 static bool maybe_add_filter(grpc_channel_stack_builder* builder, void* arg) {
   grpc_channel_filter* filter = static_cast<grpc_channel_filter*>(arg);
   if (g_enable_filter) {
     // Want to add the filter as close to the end as possible, to make
     // sure that all of the filters work well together.  However, we
     // can't add it at the very end, because the connected channel filter
     // must be the last one.  So we add it right before the last one.
     grpc_channel_stack_builder_iterator* it =
         grpc_channel_stack_builder_create_iterator_at_last(builder);
     GPR_ASSERT(grpc_channel_stack_builder_move_prev(it));
     const bool retval = grpc_channel_stack_builder_add_filter_before(
         it, filter, nullptr, nullptr);
     grpc_channel_stack_builder_iterator_destroy(it);
     return retval;
   } else {
     return true;
   }
 }

 static void init_plugin(void) {
   gpr_mu_init(&g_mu);
   grpc_channel_init_register_stage(GRPC_CLIENT_CHANNEL, INT_MAX,
                                    maybe_add_filter,
                                    (void*)&test_client_filter);
   grpc_channel_init_register_stage(GRPC_CLIENT_DIRECT_CHANNEL, INT_MAX,
                                    maybe_add_filter,
                                    (void*)&test_client_filter);
   grpc_channel_init_register_stage(GRPC_SERVER_CHANNEL, INT_MAX,
                                    maybe_add_filter,
                                    (void*)&test_server_filter);
 }

 static void destroy_plugin(void) { gpr_mu_destroy(&g_mu); }

 void filter_latency(grpc_end2end_test_config config) {
   g_enable_filter = true;
   test_request(config);
   g_enable_filter = false;
 }

 void filter_latency_pre_init(void) {
   grpc_register_plugin(init_plugin, destroy_plugin);
 }
	/*
	*
	* Copyright 2016 gRPC authors.
	*
	* Licensed 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 "test/core/end2end/end2end_tests.h"

	#include <limits.h>
	#include <stdbool.h>
	#include <stdio.h>
	#include <string.h>

	#include <grpc/byte_buffer.h>
	#include <grpc/support/alloc.h>
	#include <grpc/support/log.h>
	#include <grpc/support/time.h>

	#include "src/core/lib/channel/channel_stack_builder.h"
	#include "src/core/lib/surface/channel_init.h"
	#include "test/core/end2end/cq_verifier.h"

	enum { TIMEOUT = 200000 };

	static bool g_enable_filter = false;
	static gpr_mu g_mu;
	static gpr_timespec g_client_latency;
	static gpr_timespec g_server_latency;

	static void* tag(intptr_t t) { return (void*)t; }

	static grpc_end2end_test_fixture begin_test(grpc_end2end_test_config config,
	const char* test_name,
	grpc_channel_args* client_args,
	grpc_channel_args* server_args) {
	grpc_end2end_test_fixture f;
	gpr_log(GPR_INFO, "Running test: %s/%s", test_name, config.name);
	f = config.create_fixture(client_args, server_args);
	config.init_server(&f, server_args);
	config.init_client(&f, client_args);
	return f;
	}

	static gpr_timespec n_seconds_from_now(int n) {
	return grpc_timeout_seconds_to_deadline(n);
	}

	static gpr_timespec five_seconds_from_now(void) {
	return n_seconds_from_now(5);
	}

	static void drain_cq(grpc_completion_queue* cq) {
	grpc_event ev;
	do {
	ev = grpc_completion_queue_next(cq, five_seconds_from_now(), nullptr);
	} while (ev.type != GRPC_QUEUE_SHUTDOWN);
	}

	static void shutdown_server(grpc_end2end_test_fixture* f) {
	if (!f->server) return;
	grpc_server_shutdown_and_notify(f->server, f->shutdown_cq, tag(1000));
	GPR_ASSERT(grpc_completion_queue_pluck(f->shutdown_cq, tag(1000),
	grpc_timeout_seconds_to_deadline(5),
	nullptr)
	.type == GRPC_OP_COMPLETE);
	grpc_server_destroy(f->server);
	f->server = nullptr;
	}

	static void shutdown_client(grpc_end2end_test_fixture* f) {
	if (!f->client) return;
	grpc_channel_destroy(f->client);
	f->client = nullptr;
	}

	static void end_test(grpc_end2end_test_fixture* f) {
	shutdown_server(f);
	shutdown_client(f);

	grpc_completion_queue_shutdown(f->cq);
	drain_cq(f->cq);
	grpc_completion_queue_destroy(f->cq);
	grpc_completion_queue_destroy(f->shutdown_cq);
	}

	// Simple request via a server filter that saves the reported latency value.
	static void test_request(grpc_end2end_test_config config) {
	grpc_call* c;
	grpc_call* s;
	grpc_slice request_payload_slice =
	grpc_slice_from_copied_string("hello world");
	grpc_byte_buffer* request_payload =
	grpc_raw_byte_buffer_create(&request_payload_slice, 1);
	grpc_end2end_test_fixture f =
	begin_test(config, "filter_latency", nullptr, nullptr);
	cq_verifier* cqv = cq_verifier_create(f.cq);
	grpc_op ops[6];
	grpc_op* op;
	grpc_metadata_array initial_metadata_recv;
	grpc_metadata_array trailing_metadata_recv;
	grpc_metadata_array request_metadata_recv;
	grpc_byte_buffer* request_payload_recv = nullptr;
	grpc_call_details call_details;
	grpc_status_code status;
	grpc_call_error error;
	grpc_slice details;
	int was_cancelled = 2;

	gpr_mu_lock(&g_mu);
	g_client_latency = gpr_time_0(GPR_TIMESPAN);
	g_server_latency = gpr_time_0(GPR_TIMESPAN);
	gpr_mu_unlock(&g_mu);
	const gpr_timespec start_time = gpr_now(GPR_CLOCK_MONOTONIC);

	gpr_timespec deadline = five_seconds_from_now();
	c = grpc_channel_create_call(
	f.client, nullptr, GRPC_PROPAGATE_DEFAULTS, f.cq,
	grpc_slice_from_static_string("/foo"),
	get_host_override_slice("foo.test.google.fr", config), deadline, nullptr);
	GPR_ASSERT(c);

	grpc_metadata_array_init(&initial_metadata_recv);
	grpc_metadata_array_init(&trailing_metadata_recv);
	grpc_metadata_array_init(&request_metadata_recv);
	grpc_call_details_init(&call_details);

	memset(ops, 0, sizeof(ops));
	op = ops;
	op->op = GRPC_OP_SEND_INITIAL_METADATA;
	op->data.send_initial_metadata.count = 0;
	op->data.send_initial_metadata.metadata = nullptr;
	op->flags = 0;
	op->reserved = nullptr;
	op++;
	op->op = GRPC_OP_SEND_MESSAGE;
	op->data.send_message.send_message = request_payload;
	op->flags = 0;
	op->reserved = nullptr;
	op++;
	op->op = GRPC_OP_SEND_CLOSE_FROM_CLIENT;
	op->flags = 0;
	op->reserved = nullptr;
	op++;
	op->op = GRPC_OP_RECV_INITIAL_METADATA;
	op->data.recv_initial_metadata.recv_initial_metadata = &initial_metadata_recv;
	op->flags = 0;
	op->reserved = nullptr;
	op++;
	op->op = GRPC_OP_RECV_STATUS_ON_CLIENT;
	op->data.recv_status_on_client.trailing_metadata = &trailing_metadata_recv;
	op->data.recv_status_on_client.status = &status;
	op->data.recv_status_on_client.status_details = &details;
	op->flags = 0;
	op->reserved = nullptr;
	op++;
	error = grpc_call_start_batch(c, ops, static_cast<size_t>(op - ops), tag(1),
	nullptr);
	GPR_ASSERT(GRPC_CALL_OK == error);

	error =
	grpc_server_request_call(f.server, &s, &call_details,
	&request_metadata_recv, f.cq, f.cq, tag(101));
	GPR_ASSERT(GRPC_CALL_OK == error);

	CQ_EXPECT_COMPLETION(cqv, tag(101), 1);
	cq_verify(cqv);

	memset(ops, 0, sizeof(ops));
	op = ops;
	op->op = GRPC_OP_SEND_INITIAL_METADATA;
	op->data.send_initial_metadata.count = 0;
	op->flags = 0;
	op->reserved = nullptr;
	op++;
	op->op = GRPC_OP_SEND_STATUS_FROM_SERVER;
	op->data.send_status_from_server.trailing_metadata_count = 0;
	op->data.send_status_from_server.status = GRPC_STATUS_UNIMPLEMENTED;
	grpc_slice status_string = grpc_slice_from_static_string("xyz");
	op->data.send_status_from_server.status_details = &status_string;
	op->flags = 0;
	op->reserved = nullptr;
	op++;
	op->op = GRPC_OP_RECV_CLOSE_ON_SERVER;
	op->data.recv_close_on_server.cancelled = &was_cancelled;
	op->flags = 0;
	op->reserved = nullptr;
	op++;
	error = grpc_call_start_batch(s, ops, static_cast<size_t>(op - ops), tag(102),
	nullptr);
	GPR_ASSERT(GRPC_CALL_OK == error);

	CQ_EXPECT_COMPLETION(cqv, tag(102), 1);
	CQ_EXPECT_COMPLETION(cqv, tag(1), 1);
	cq_verify(cqv);

	GPR_ASSERT(status == GRPC_STATUS_UNIMPLEMENTED);
	GPR_ASSERT(0 == grpc_slice_str_cmp(details, "xyz"));

	grpc_slice_unref(details);
	grpc_metadata_array_destroy(&initial_metadata_recv);
	grpc_metadata_array_destroy(&trailing_metadata_recv);
	grpc_metadata_array_destroy(&request_metadata_recv);
	grpc_call_details_destroy(&call_details);

	grpc_call_unref(s);
	grpc_call_unref(c);

	cq_verifier_destroy(cqv);

	grpc_byte_buffer_destroy(request_payload);
	grpc_byte_buffer_destroy(request_payload_recv);

	end_test(&f);
	config.tear_down_data(&f);

	const gpr_timespec end_time = gpr_now(GPR_CLOCK_MONOTONIC);
	const gpr_timespec max_latency = gpr_time_sub(end_time, start_time);

	// Perform checks after test tear-down
	// Guards against the case that there's outstanding channel-related work on a
	// call prior to verification
	gpr_mu_lock(&g_mu);
	GPR_ASSERT(gpr_time_cmp(max_latency, g_client_latency) >= 0);
	GPR_ASSERT(gpr_time_cmp(gpr_time_0(GPR_TIMESPAN), g_client_latency) <= 0);
	GPR_ASSERT(gpr_time_cmp(max_latency, g_server_latency) >= 0);
	GPR_ASSERT(gpr_time_cmp(gpr_time_0(GPR_TIMESPAN), g_server_latency) <= 0);
	// Server latency should always be smaller than client latency, however since
	// we only calculate latency at destruction time, and that might mean that we
	// need to wait for outstanding channel-related work, this isn't verifiable
	// right now (the server MAY hold on to the call for longer than the client).
	// GPR_ASSERT(gpr_time_cmp(g_server_latency, g_client_latency) < 0);
	gpr_mu_unlock(&g_mu);
	}

	/*******************************************************************************
	* Test latency filter
	*/

	static grpc_error* init_call_elem(grpc_call_element* elem,
	const grpc_call_element_args* args) {
	return GRPC_ERROR_NONE;
	}

	static void client_destroy_call_elem(grpc_call_element* elem,
	const grpc_call_final_info* final_info,
	grpc_closure* ignored) {
	gpr_mu_lock(&g_mu);
	g_client_latency = final_info->stats.latency;
	gpr_mu_unlock(&g_mu);
	}

	static void server_destroy_call_elem(grpc_call_element* elem,
	const grpc_call_final_info* final_info,
	grpc_closure* ignored) {
	gpr_mu_lock(&g_mu);
	g_server_latency = final_info->stats.latency;
	gpr_mu_unlock(&g_mu);
	}

	static grpc_error* init_channel_elem(grpc_channel_element* elem,
	grpc_channel_element_args* args) {
	return GRPC_ERROR_NONE;
	}

	static void destroy_channel_elem(grpc_channel_element* elem) {}

	static const grpc_channel_filter test_client_filter = {
	grpc_call_next_op,
	grpc_channel_next_op,
	0,
	init_call_elem,
	grpc_call_stack_ignore_set_pollset_or_pollset_set,
	client_destroy_call_elem,
	0,
	init_channel_elem,
	destroy_channel_elem,
	grpc_channel_next_get_info,
	"client_filter_latency"};

	static const grpc_channel_filter test_server_filter = {
	grpc_call_next_op,
	grpc_channel_next_op,
	0,
	init_call_elem,
	grpc_call_stack_ignore_set_pollset_or_pollset_set,
	server_destroy_call_elem,
	0,
	init_channel_elem,
	destroy_channel_elem,
	grpc_channel_next_get_info,
	"server_filter_latency"};

	/*******************************************************************************
	* Registration
	*/

	static bool maybe_add_filter(grpc_channel_stack_builder* builder, void* arg) {
	grpc_channel_filter* filter = static_cast<grpc_channel_filter*>(arg);
	if (g_enable_filter) {
	// Want to add the filter as close to the end as possible, to make
	// sure that all of the filters work well together. However, we
	// can't add it at the very end, because the connected channel filter
	// must be the last one. So we add it right before the last one.
	grpc_channel_stack_builder_iterator* it =
	grpc_channel_stack_builder_create_iterator_at_last(builder);
	GPR_ASSERT(grpc_channel_stack_builder_move_prev(it));
	const bool retval = grpc_channel_stack_builder_add_filter_before(
	it, filter, nullptr, nullptr);
	grpc_channel_stack_builder_iterator_destroy(it);
	return retval;
	} else {
	return true;
	}
	}

	static void init_plugin(void) {
	gpr_mu_init(&g_mu);
	grpc_channel_init_register_stage(GRPC_CLIENT_CHANNEL, INT_MAX,
	maybe_add_filter,
	(void*)&test_client_filter);
	grpc_channel_init_register_stage(GRPC_CLIENT_DIRECT_CHANNEL, INT_MAX,
	maybe_add_filter,
	(void*)&test_client_filter);
	grpc_channel_init_register_stage(GRPC_SERVER_CHANNEL, INT_MAX,
	maybe_add_filter,
	(void*)&test_server_filter);
	}

	static void destroy_plugin(void) { gpr_mu_destroy(&g_mu); }

	void filter_latency(grpc_end2end_test_config config) {
	g_enable_filter = true;
	test_request(config);
	g_enable_filter = false;
	}

	void filter_latency_pre_init(void) {
	grpc_register_plugin(init_plugin, destroy_plugin);
	}