components/metrics/serialization/serialization_utils.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "components/metrics/serialization/serialization_utils.h"
   6
   7 #include <sys/file.h>
   8
   9 #include <string>
  10 #include <vector>
  11
  12 #include "base/files/file_path.h"
  13 #include "base/files/file_util.h"
  14 #include "base/files/scoped_file.h"
  15 #include "base/logging.h"
  16 #include "base/memory/scoped_ptr.h"
  17 #include "base/memory/scoped_vector.h"
  18 #include "base/strings/string_split.h"
  19 #include "base/strings/string_util.h"
  20 #include "components/metrics/serialization/metric_sample.h"
  21
  22 #define READ_WRITE_ALL_FILE_FLAGS \
  23   (S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH)
  24
  25 namespace metrics {
  26 namespace {
  27
  28 // Reads the next message from |file_descriptor| into |message|.
  29 //
  30 // |message| will be set to the empty string if no message could be read (EOF)
  31 // or the message was badly constructed.
  32 //
  33 // Returns false if no message can be read from this file anymore (EOF or
  34 // unrecoverable error).
  35 bool ReadMessage(int fd, std::string* message) {
  36   CHECK(message);
  37
  38   int result;
  39   int32 message_size;
  40   // The file containing the metrics do not leave the device so the writer and
  41   // the reader will always have the same endianness.
  42   result = HANDLE_EINTR(read(fd, &message_size, sizeof(message_size)));
  43   if (result < 0) {
  44     DPLOG(ERROR) << "reading metrics message header";
  45     return false;
  46   }
  47   if (result == 0) {
  48     // This indicates a normal EOF.
  49     return false;
  50   }
  51   if (result < static_cast<int>(sizeof(message_size))) {
  52     DLOG(ERROR) << "bad read size " << result << ", expecting "
  53                 << sizeof(message_size);
  54     return false;
  55   }
  56
  57   // kMessageMaxLength applies to the entire message: the 4-byte
  58   // length field and the content.
  59   if (message_size > SerializationUtils::kMessageMaxLength) {
  60     DLOG(ERROR) << "message too long : " << message_size;
  61     if (HANDLE_EINTR(lseek(fd, message_size - 4, SEEK_CUR)) == -1) {
  62       DLOG(ERROR) << "error while skipping message. abort";
  63       return false;
  64     }
  65     // Badly formatted message was skipped. Treat the badly formatted sample as
  66     // an empty sample.
  67     message->clear();
  68     return true;
  69   }
  70
  71   message_size -= sizeof(message_size);  // The message size includes itself.
  72   char buffer[SerializationUtils::kMessageMaxLength];
  73   if (!base::ReadFromFD(fd, buffer, message_size)) {
  74     DPLOG(ERROR) << "reading metrics message body";
  75     return false;
  76   }
  77   *message = std::string(buffer, message_size);
  78   return true;
  79 }
  80
  81 }  // namespace
  82
  83 scoped_ptr<MetricSample> SerializationUtils::ParseSample(
  84     const std::string& sample) {
  85   if (sample.empty())
  86     return scoped_ptr<MetricSample>();
  87
  88   std::vector<std::string> parts;
  89   base::SplitString(sample, '\0', &parts);
  90   // We should have two null terminated strings so split should produce
  91   // three chunks.
  92   if (parts.size() != 3) {
  93     DLOG(ERROR) << "splitting message on \\0 produced " << parts.size()
  94                 << " parts (expected 3)";
  95     return scoped_ptr<MetricSample>();
  96   }
  97   const std::string& name = parts[0];
  98   const std::string& value = parts[1];
  99
 100   if (LowerCaseEqualsASCII(name, "crash")) {
 101     return MetricSample::CrashSample(value);
 102   } else if (LowerCaseEqualsASCII(name, "histogram")) {
 103     return MetricSample::ParseHistogram(value);
 104   } else if (LowerCaseEqualsASCII(name, "linearhistogram")) {
 105     return MetricSample::ParseLinearHistogram(value);
 106   } else if (LowerCaseEqualsASCII(name, "sparsehistogram")) {
 107     return MetricSample::ParseSparseHistogram(value);
 108   } else if (LowerCaseEqualsASCII(name, "useraction")) {
 109     return MetricSample::UserActionSample(value);
 110   } else {
 111     DLOG(ERROR) << "invalid event type: " << name << ", value: " << value;
 112   }
 113   return scoped_ptr<MetricSample>();
 114 }
 115
 116 void SerializationUtils::ReadAndTruncateMetricsFromFile(
 117     const std::string& filename,
 118     ScopedVector<MetricSample>* metrics) {
 119   struct stat stat_buf;
 120   int result;
 121
 122   result = stat(filename.c_str(), &stat_buf);
 123   if (result < 0) {
 124     if (errno != ENOENT)
 125       DPLOG(ERROR) << "bad metrics file stat: " << filename;
 126
 127     // Nothing to collect---try later.
 128     return;
 129   }
 130   if (stat_buf.st_size == 0) {
 131     // Also nothing to collect.
 132     return;
 133   }
 134   base::ScopedFD fd(open(filename.c_str(), O_RDWR));
 135   if (fd.get() < 0) {
 136     DPLOG(ERROR) << "cannot open: " << filename;
 137     return;
 138   }
 139   result = flock(fd.get(), LOCK_EX);
 140   if (result < 0) {
 141     DPLOG(ERROR) << "cannot lock: " << filename;
 142     return;
 143   }
 144
 145   // This processes all messages in the log. When all messages are
 146   // read and processed, or an error occurs, truncate the file to zero size.
 147   for (;;) {
 148     std::string message;
 149
 150     if (!ReadMessage(fd.get(), &message))
 151       break;
 152
 153     scoped_ptr<MetricSample> sample = ParseSample(message);
 154     if (sample)
 155       metrics->push_back(sample.release());
 156   }
 157
 158   result = ftruncate(fd.get(), 0);
 159   if (result < 0)
 160     DPLOG(ERROR) << "truncate metrics log: " << filename;
 161
 162   result = flock(fd.get(), LOCK_UN);
 163   if (result < 0)
 164     DPLOG(ERROR) << "unlock metrics log: " << filename;
 165 }
 166
 167 bool SerializationUtils::WriteMetricToFile(const MetricSample& sample,
 168                                            const std::string& filename) {
 169   if (!sample.IsValid())
 170     return false;
 171
 172   base::ScopedFD file_descriptor(open(filename.c_str(),
 173                                       O_WRONLY | O_APPEND | O_CREAT,
 174                                       READ_WRITE_ALL_FILE_FLAGS));
 175
 176   if (file_descriptor.get() < 0) {
 177     DPLOG(ERROR) << "error openning the file: " << filename;
 178     return false;
 179   }
 180
 181   fchmod(file_descriptor.get(), READ_WRITE_ALL_FILE_FLAGS);
 182   // Grab a lock to avoid chrome truncating the file
 183   // underneath us. Keep the file locked as briefly as possible.
 184   // Freeing file_descriptor will close the file and and remove the lock.
 185   if (HANDLE_EINTR(flock(file_descriptor.get(), LOCK_EX)) < 0) {
 186     DPLOG(ERROR) << "error locking: " << filename;
 187     return false;
 188   }
 189
 190   std::string msg = sample.ToString();
 191   int32 size = msg.length() + sizeof(int32);
 192   if (size > kMessageMaxLength) {
 193     DPLOG(ERROR) << "cannot write message: too long: " << filename;
 194     return false;
 195   }
 196
 197   // The file containing the metrics samples will only be read by programs on
 198   // the same device so we do not check endianness.
 199   if (!base::WriteFileDescriptor(file_descriptor.get(),
 200                                  reinterpret_cast<char*>(&size),
 201                                  sizeof(size))) {
 202     DPLOG(ERROR) << "error writing message length: " << filename;
 203     return false;
 204   }
 205
 206   if (!base::WriteFileDescriptor(
 207           file_descriptor.get(), msg.c_str(), msg.size())) {
 208     DPLOG(ERROR) << "error writing message: " << filename;
 209     return false;
 210   }
 211
 212   return true;
 213 }
 214
 215 }  // namespace metrics