src/core/lib/debug/trace.cc

/*
 *
 * Copyright 2015 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 <grpc/support/port_platform.h>

#include "src/core/lib/debug/trace.h"

#include <string.h>

#include <type_traits>

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

GPR_GLOBAL_CONFIG_DEFINE_STRING(
    grpc_trace, "",
    "A comma separated list of tracers that provide additional insight into "
    "how gRPC C core is processing requests via debug logs.");

int grpc_tracer_set_enabled(const char* name, int enabled);

namespace grpc_core {

TraceFlag* TraceFlagList::root_tracer_ = nullptr;

bool TraceFlagList::Set(const char* name, bool enabled) {
  TraceFlag* t;
  if (0 == strcmp(name, "all")) {
    for (t = root_tracer_; t; t = t->next_tracer_) {
      t->set_enabled(enabled);
    }
  } else if (0 == strcmp(name, "list_tracers")) {
    LogAllTracers();
  } else if (0 == strcmp(name, "refcount")) {
    for (t = root_tracer_; t; t = t->next_tracer_) {
      if (strstr(t->name_, "refcount") != nullptr) {
        t->set_enabled(enabled);
      }
    }
  } else {
    bool found = false;
    for (t = root_tracer_; t; t = t->next_tracer_) {
      if (0 == strcmp(name, t->name_)) {
        t->set_enabled(enabled);
        found = true;
      }
    }
    // check for unknowns, but ignore "", to allow to GRPC_TRACE=
    if (!found && 0 != strcmp(name, "")) {
      gpr_log(GPR_ERROR, "Unknown trace var: '%s'", name);
      return false; /* early return */
    }
  }
  return true;
}

void TraceFlagList::Add(TraceFlag* flag) {
  flag->next_tracer_ = root_tracer_;
  root_tracer_ = flag;
}

void TraceFlagList::LogAllTracers() {
  gpr_log(GPR_DEBUG, "available tracers:");
  TraceFlag* t;
  for (t = root_tracer_; t != nullptr; t = t->next_tracer_) {
    gpr_log(GPR_DEBUG, "\t%s", t->name_);
  }
}

// Flags register themselves on the list during construction
TraceFlag::TraceFlag(bool default_enabled, const char* name) : name_(name) {
  static_assert(std::is_trivially_destructible<TraceFlag>::value,
                "TraceFlag needs to be trivially destructible.");
  set_enabled(default_enabled);
  TraceFlagList::Add(this);
}

}  // namespace grpc_core

static void add(const char* beg, const char* end, char*** ss, size_t* ns) {
  size_t n = *ns;
  size_t np = n + 1;
  char* s;
  size_t len;
  GPR_ASSERT(end >= beg);
  len = static_cast<size_t>(end - beg);
  s = static_cast<char*>(gpr_malloc(len + 1));
  memcpy(s, beg, len);
  s[len] = 0;
  *ss = static_cast<char**>(gpr_realloc(*ss, sizeof(char**) * np));
  (*ss)[n] = s;
  *ns = np;
}

static void split(const char* s, char*** ss, size_t* ns) {
  const char* c = strchr(s, ',');
  if (c == nullptr) {
    add(s, s + strlen(s), ss, ns);
  } else {
    add(s, c, ss, ns);
    split(c + 1, ss, ns);
  }
}

static void parse(const char* s) {
  char** strings = nullptr;
  size_t nstrings = 0;
  size_t i;
  split(s, &strings, &nstrings);

  for (i = 0; i < nstrings; i++) {
    if (strings[i][0] == '-') {
      grpc_core::TraceFlagList::Set(strings[i] + 1, false);
    } else {
      grpc_core::TraceFlagList::Set(strings[i], true);
    }
  }

  for (i = 0; i < nstrings; i++) {
    gpr_free(strings[i]);
  }
  gpr_free(strings);
}

void grpc_tracer_init(const char* env_var_name) {
  (void)env_var_name;  // suppress unused variable error
  grpc_tracer_init();
}

void grpc_tracer_init() {
  grpc_core::UniquePtr<char> value = GPR_GLOBAL_CONFIG_GET(grpc_trace);
  parse(value.get());
}

void grpc_tracer_shutdown(void) {}

int grpc_tracer_set_enabled(const char* name, int enabled) {
  return grpc_core::TraceFlagList::Set(name, enabled != 0);
}