SERVER-24572 Add support for collecting information from /proc/stat

6 files changed, 615 insertions, 3 deletions

diff --git a/src/mongo/base/error_codes.err b/src/mongo/base/error_codes.err
index 3979f9bdf59..aa3c0b24803 100644
--- a/src/mongo/base/error_codes.err
+++ b/src/mongo/base/error_codes.err
@@ -172,6 +172,7 @@ error_code("TooManyMatchingDocuments", 170)
 error_code("CannotIndexParallelArrays", 171)
 error_code("TransportSessionNotFound", 172)
 error_code("QueryPlanKilled", 173)
+error_code("FileOpenFailed", 174)
 
 # Non-sequential error codes (for compatibility only)
 error_code("SocketException", 9001)
diff --git a/src/mongo/base/string_data.h b/src/mongo/base/string_data.h
index b1491b919e6..98a4dc6f7f1 100644
--- a/src/mongo/base/string_data.h
+++ b/src/mongo/base/string_data.h
@@ -36,6 +36,7 @@
 #include <stdexcept>
 #include <string>
 
+#include "mongo/stdx/type_traits.h"
 #define MONGO_INCLUDE_INVARIANT_H_WHITELISTED
 #include "mongo/util/invariant.h"
 #undef MONGO_INCLUDE_INVARIANT_H_WHITELISTED
@@ -63,6 +64,9 @@ public:
     // Declared in string_data_comparator_interface.h.
     class ComparatorInterface;
 
+    // Iterator type
+    using const_iterator = const char*;
+
     /** Constructs an empty StringData. */
     constexpr StringData() = default;
 
@@ -98,6 +102,23 @@ public:
     constexpr friend StringData operator"" _sd(const char* c, std::size_t len);
 
     /**
+     * Constructs a StringData with begin and end iterators. begin points to the beginning of the
+     * string. end points to the position past the end of the string. In a null-terminated string,
+     * end points to the null-terminator.
+     *
+     * We template the second parameter to ensure if StringData is called with 0 in the second
+     * parameter, the (ptr,len) constructor is chosen instead.
+     */
+    template <
+        typename InputIt,
+        typename = stdx::enable_if_t<std::is_same<StringData::const_iterator, InputIt>::value>>
+    StringData(InputIt begin, InputIt end) {
+        invariant(begin && end);
+        _data = begin;
+        _size = std::distance(begin, end);
+    }
+
+    /**
      * Returns -1, 0, or 1 if 'this' is less, equal, or greater than 'other' in
      * lexicographical order.
      */
@@ -170,9 +191,6 @@ public:
     //
     // iterators
     //
-
-    typedef const char* const_iterator;
-
     const_iterator begin() const {
         return rawData();
     }
diff --git a/src/mongo/util/SConscript b/src/mongo/util/SConscript
index 31f2d017eda..0a4864eea40 100644
--- a/src/mongo/util/SConscript
+++ b/src/mongo/util/SConscript
@@ -529,3 +529,24 @@ env.CppUnitTest(
         '$BUILD_DIR/mongo/base',
     ]
 )
+
+if env.TargetOSIs('linux'):
+    env.Library(
+        target='procparser',
+        source=[
+            "procparser.cpp",
+        ],
+        LIBDEPS=[
+            '$BUILD_DIR/mongo/base',
+        ],
+    )
+
+    env.CppUnitTest(
+        target='procparser_test',
+        source=[
+            'procparser_test.cpp',
+        ],
+        LIBDEPS=[
+            'procparser',
+        ],
+    )
diff --git a/src/mongo/util/procparser.cpp b/src/mongo/util/procparser.cpp
new file mode 100644
index 00000000000..b0fa73bd122
--- /dev/null
+++ b/src/mongo/util/procparser.cpp
@@ -0,0 +1,283 @@
+/**
+ * Copyright (C) 2016 MongoDB Inc.
+ *
+ * This program is free software: you can redistribute it and/or  modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * As a special exception, the copyright holders give permission to link the
+ * code of portions of this program with the OpenSSL library under certain
+ * conditions as described in each individual source file and distribute
+ * linked combinations including the program with the OpenSSL library. You
+ * must comply with the GNU Affero General Public License in all respects
+ * for all of the code used other than as permitted herein. If you modify
+ * file(s) with this exception, you may extend this exception to your
+ * version of the file(s), but you are not obligated to do so. If you do not
+ * wish to do so, delete this exception statement from your version. If you
+ * delete this exception statement from all source files in the program,
+ * then also delete it in the license file.
+ */
+
+#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kFTDC
+
+#include "mongo/platform/basic.h"
+
+#include "mongo/util/procparser.h"
+
+#include <algorithm>
+#include <array>
+#include <boost/algorithm/string/finder.hpp>
+#include <boost/algorithm/string/split.hpp>
+#include <fcntl.h>
+#include <string>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <type_traits>
+#include <unistd.h>
+
+#include "mongo/base/parse_number.h"
+#include "mongo/base/status.h"
+#include "mongo/base/status_with.h"
+#include "mongo/base/string_data.h"
+#include "mongo/bson/bsonobjbuilder.h"
+#include "mongo/util/log.h"
+#include "mongo/util/mongoutils/str.h"
+#include "mongo/util/scopeguard.h"
+#include "mongo/util/text.h"
+namespace mongo {
+
+namespace {
+
+/**
+ * Get USER_HZ for the machine. See time(7) for an explanation.
+ */
+int64_t getTicksPerSecond() {
+    int64_t ret = sysconf(_SC_CLK_TCK);
+    return ret;
+}
+
+/**
+ * Convert USER_HZ to milliseconds.
+ */
+double convertTicksToMilliSeconds(const int64_t ticks, const int64_t ticksPerSecond) {
+    return static_cast<double>(ticks) / (static_cast<double>(ticksPerSecond) / 1000.0);
+}
+
+const size_t kFileBufferSize = 16384;
+const size_t kFileReadRetryCount = 5;
+
+/**
+ * Read a file from disk as a string with a null-terminating byte using the POSIX file api.
+ *
+ * This function is designed to get all the data it needs from small /proc files in a single read.
+ * The /proc/stat and /proc/diskstats files can vary in size, but 16kb will cover most cases.
+ *
+ * Finally, we return errors instead of throwing to ensure that FTDC can return partial information
+ * on failure instead of no information. Some container filesystems may overlay /proc so we may not
+ * be reading directly from the kernel.
+ */
+StatusWith<std::string> readFileAsString(StringData filename) {
+    int fd = open(filename.toString().c_str(), 0);
+    if (fd == -1) {
+        int err = errno;
+        return Status(ErrorCodes::FileOpenFailed,
+                      str::stream() << "Failed to open file " << filename << " with error: "
+                                    << errnoWithDescription(err));
+    }
+    auto scopedGuard = MakeGuard([fd] { close(fd); });
+
+    BufBuilder builder(kFileBufferSize);
+    std::array<char, kFileBufferSize> buf;
+
+    ssize_t size_read = 0;
+
+    // Read until the end as needed
+    do {
+
+        // Retry if interrupted
+        size_t retry = 0;
+
+        do {
+            size_read = read(fd, buf.data(), kFileBufferSize);
+
+            if (size_read == -1) {
+                int err = errno;
+
+                // Retry if we hit EGAIN or EINTR a few times before giving up
+                if (retry < kFileReadRetryCount && (err == EAGAIN || err == EINTR)) {
+                    ++retry;
+                    continue;
+                }
+
+                return Status(ErrorCodes::FileStreamFailed,
+                              str::stream() << "Failed to read file " << filename << " with error: "
+                                            << errnoWithDescription(err));
+            }
+
+            break;
+        } while (true);
+
+        if (size_read != 0) {
+            builder.appendBuf(buf.data(), size_read);
+        }
+    } while (size_read != 0);
+
+    // Null terminate the buffer since we are about to convert it to a string
+    builder.appendChar(0);
+
+    return std::string(builder.buf(), builder.len());
+}
+
+
+const char* const kAdditionCpuFields[] = {"user_ms",
+                                          "nice_ms",
+                                          "system_ms",
+                                          "idle_ms",
+                                          "iowait_ms",
+                                          "irq_ms",
+                                          "softirq_ms",
+                                          "steal_ms",
+                                          "guest_ms",
+                                          "guest_nice_ms"};
+const size_t kAdditionCpuFieldCount = std::extent<decltype(kAdditionCpuFields)>::value;
+
+}  // namespace
+
+namespace procparser {
+// Here is an example of the type of string it supports.
+// Note: intr output has been trimmed
+//
+// The cpu field maps up to 10 individual fields depending on the kernel version. For other views,
+// this code assumes there is only a single value.
+//
+// For more information, see:
+// Documentation/filesystems/proc.txt in the Linux kernel
+// proc(5) man page
+//
+// > cat /proc/stat
+// cpu  41801 9179 32206 831134223 34279 0 947 0 0 0
+// cpu0 2977 450 2475 69253074 1959 0 116 0 0 0
+// cpu1 6213 4261 9400 69177349 845 0 539 0 0 0
+// cpu2 1949 831 3699 69261035 645 0 0 0 0 0
+// cpu3 2222 644 3283 69264801 783 0 0 0 0 0
+// cpu4 16576 607 4757 69232589 8195 0 291 0 0 0
+// cpu5 3742 391 4571 69257332 2322 0 0 0 0 0
+// cpu6 2173 376 743 69284308 400 0 0 0 0 0
+// cpu7 1232 375 704 69285753 218 0 0 0 0 0
+// cpu8 960 127 576 69262851 18107 0 0 0 0 0
+// cpu9 1755 227 744 69283938 362 0 0 0 0 0
+// cpu10 1380 641 678 69285193 219 0 0 0 0 0
+// cpu11 618 244 572 69285995 218 0 0 0 0 0
+// intr 54084718 135 2 ....
+// ctxt 190305514
+// btime 1463584038
+// processes 47438
+// procs_running 1
+// procs_blocked 0
+// softirq 102690251 8 26697410 115481 23345078 816026 0 2296 26068778 0 25645174
+//
+Status parseProcStat(const std::vector<StringData>& keys,
+                     StringData data,
+                     int64_t ticksPerSecond,
+                     BSONObjBuilder* builder) {
+    bool foundKeys = false;
+
+    using string_split_iterator = boost::split_iterator<StringData::const_iterator>;
+
+    // Split the file by lines.
+    // token_compress_on means the iterator skips over consecutive '\n'. This should not be a
+    // problem in normal /proc/stat output.
+    for (string_split_iterator lineIt = string_split_iterator(
+             data.begin(),
+             data.end(),
+             boost::token_finder([](char c) { return c == '\n'; }, boost::token_compress_on));
+         lineIt != string_split_iterator();
+         ++lineIt) {
+
+        StringData line((*lineIt).begin(), (*lineIt).end());
+
+        // Split the line by spaces since that is the only delimiter for stat files.
+        // token_compress_on means the iterator skips over consecutive ' '. This is needed for the
+        // first line which is "cpu  <number>".
+        string_split_iterator partIt = string_split_iterator(
+            line.begin(),
+            line.end(),
+            boost::token_finder([](char c) { return c == ' '; }, boost::token_compress_on));
+
+        // Skip processing this line if we do not have a key.
+        if (partIt == string_split_iterator()) {
+            continue;
+        }
+
+        StringData key((*partIt).begin(), (*partIt).end());
+
+        ++partIt;
+
+        // Skip processing this line if we only have a key, and no number.
+        if (partIt == string_split_iterator()) {
+            continue;
+        }
+
+        // Check if the key is in the list. /proc/stat will have extra keys, and
+        // may not have the keys we want.
+        if (keys.empty() || std::find(keys.begin(), keys.end(), key) != keys.end()) {
+
+            foundKeys = true;
+
+            if (key == "cpu") {
+                // Cpu is 10 fields, we need to chew through all of them.
+                // Some kernels we support lack the last field or two: guest and/or guest_nice.
+                for (size_t index = 0;
+                     partIt != string_split_iterator() && index < kAdditionCpuFieldCount;
+                     ++partIt, ++index) {
+
+                    StringData stringValue((*partIt).begin(), (*partIt).end() - (*partIt).begin());
+
+                    uint64_t value;
+
+                    if (!parseNumberFromString(stringValue, &value).isOK()) {
+                        value = 0;
+                    }
+
+                    builder->appendNumber(kAdditionCpuFields[index],
+                                          convertTicksToMilliSeconds(value, ticksPerSecond));
+                }
+            } else {
+                StringData stringValue((*partIt).begin(), (*partIt).end() - (*partIt).begin());
+
+                uint64_t value;
+
+                if (!parseNumberFromString(stringValue, &value).isOK()) {
+                    value = 0;
+                }
+
+                builder->appendNumber(key, value);
+            }
+        }
+    }
+
+    return foundKeys ? Status::OK()
+                     : Status(ErrorCodes::NoSuchKey, "Failed to find any keys in stat string");
+}
+
+Status parseProcStatFile(StringData filename,
+                         const std::vector<StringData>& keys,
+                         BSONObjBuilder* builder) {
+    auto swString = readFileAsString(filename);
+    if (!swString.isOK()) {
+        return swString.getStatus();
+    }
+
+    return parseProcStat(keys, swString.getValue(), getTicksPerSecond(), builder);
+}
+
+}  // namespace procparser
+}  // namespace mongo
diff --git a/src/mongo/util/procparser.h b/src/mongo/util/procparser.h
new file mode 100644
index 00000000000..3bbb0ece16e
--- /dev/null
+++ b/src/mongo/util/procparser.h
@@ -0,0 +1,73 @@
+/**
+ * Copyright (C) 2016 MongoDB Inc.
+ *
+ * This program is free software: you can redistribute it and/or  modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * As a special exception, the copyright holders give permission to link the
+ * code of portions of this program with the OpenSSL library under certain
+ * conditions as described in each individual source file and distribute
+ * linked combinations including the program with the OpenSSL library. You
+ * must comply with the GNU Affero General Public License in all respects
+ * for all of the code used other than as permitted herein. If you modify
+ * file(s) with this exception, you may extend this exception to your
+ * version of the file(s), but you are not obligated to do so. If you do not
+ * wish to do so, delete this exception statement from your version. If you
+ * delete this exception statement from all source files in the program,
+ * then also delete it in the license file.
+ */
+
+#pragma once
+
+#include <cstdint>
+#include <string>
+#include <vector>
+
+#include "mongo/base/status.h"
+#include "mongo/base/string_data.h"
+
+namespace mongo {
+
+class BSONObjBuilder;
+
+namespace procparser {
+
+/**
+ * Reads a string matching /proc/stat format, and writes the values of the specified keys into
+ * builder. If fields are not in the "data" parameter, they are omitted. Converts fields
+ * from USER_HZ to milliseconds, and names fields with a "_ms" suffix. If the string is empty,
+ * corrupt, or missing fields, the builder will simply be missing fields.
+ *
+ * keys - sorted vector of field names to include in the output, "cpu" will include the 11 fields
+ *        that make up cpu. If keys is empty, all keys are outputed.
+ * data - string to parsee
+ * ticksPerSecond - USER_HZ value
+ * builder - BSON output
+ */
+Status parseProcStat(const std::vector<StringData>& keys,
+                     StringData data,
+                     int64_t ticksPerSecond,
+                     BSONObjBuilder* builder);
+
+/**
+* Read from file, and write the specified list of keys into builder.
+*
+* See parseProcStat.
+*
+* Returns Status errors on file reading issues.
+*/
+Status parseProcStatFile(StringData filename,
+                         const std::vector<StringData>& keys,
+                         BSONObjBuilder* builder);
+
+}  // namespace procparser
+}  // namespace mongo
diff --git a/src/mongo/util/procparser_test.cpp b/src/mongo/util/procparser_test.cpp
new file mode 100644
index 00000000000..f21c9683025
--- /dev/null
+++ b/src/mongo/util/procparser_test.cpp
@@ -0,0 +1,216 @@
+/**
+ * Copyright (C) 2016 MongoDB Inc.
+ *
+ * This program is free software: you can redistribute it and/or  modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * As a special exception, the copyright holders give permission to link the
+ * code of portions of this program with the OpenSSL library under certain
+ * conditions as described in each individual source file and distribute
+ * linked combinations including the program with the OpenSSL library. You
+ * must comply with the GNU Affero General Public License in all respects
+ * for all of the code used other than as permitted herein. If you modify
+ * file(s) with this exception, you may extend this exception to your
+ * version of the file(s), but you are not obligated to do so. If you do not
+ * wish to do so, delete this exception statement from your version. If you
+ * delete this exception statement from all source files in the program,
+ * then also delete it in the license file.
+ */
+
+#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kFTDC
+
+#include "mongo/platform/basic.h"
+
+#include "mongo/util/procparser.h"
+
+#include <boost/filesystem.hpp>
+#include <map>
+
+#include "mongo/bson/bsonobj.h"
+#include "mongo/bson/bsonobjbuilder.h"
+#include "mongo/unittest/unittest.h"
+#include "mongo/util/log.h"
+
+namespace mongo {
+
+namespace {
+using StringMap = std::map<std::string, uint64_t>;
+
+StringMap toStringMap(BSONObj& obj) {
+    StringMap map;
+
+    for (const auto& e : obj) {
+        map[e.fieldName()] = e.numberLong();
+    }
+
+    return map;
+}
+
+#define ASSERT_KEY(_key) ASSERT_TRUE(stringMap.find(_key) != stringMap.end());
+#define ASSERT_NO_KEY(_key) ASSERT_TRUE(stringMap.find(_key) == stringMap.end());
+#define ASSERT_KEY_AND_VALUE(_key, _value) ASSERT_EQUALS(stringMap.at(_key), _value);
+
+#define ASSERT_PARSE_STAT(_keys, _x)                                 \
+    BSONObjBuilder builder;                                          \
+    ASSERT_OK(procparser::parseProcStat(_keys, _x, 1000, &builder)); \
+    auto obj = builder.obj();                                        \
+    auto stringMap = toStringMap(obj);
+
+TEST(FTDCProcStat, TestStat) {
+
+    std::vector<StringData> keys{"cpu", "ctxt", "processes"};
+
+    // Normal case
+    {
+        ASSERT_PARSE_STAT(
+            keys,
+            "cpu  41801 9179 32206 831134223 34279 0 947 0 0 0\n"
+            "cpu0 2977 450 2475 69253074 1959 0 116 0 0 0\n"
+            "cpu1 6213 4261 9400 69177349 845 0 539 0 0 0\n"
+            "cpu2 1949 831 3699 69261035 645 0 0 0 0 0\n"
+            "cpu3 2222 644 3283 69264801 783 0 0 0 0 0\n"
+            "cpu4 16576 607 4757 69232589 8195 0 291 0 0 0\n"
+            "cpu5 3742 391 4571 69257332 2322 0 0 0 0 0\n"
+            "cpu6 2173 376 743 69284308 400 0 0 0 0 0\n"
+            "cpu7 1232 375 704 69285753 218 0 0 0 0 0\n"
+            "cpu8 960 127 576 69262851 18107 0 0 0 0 0\n"
+            "cpu9 1755 227 744 69283938 362 0 0 0 0 0\n"
+            "cpu10 1380 641 678 69285193 219 0 0 0 0 0\n"
+            "cpu11 618 244 572 69285995 218 0 0 0 0 0\n"
+            "intr 54084718 135 2 ....\n"
+            "ctxt 190305514\n"
+            "btime 1463584038\n"
+            "processes 47438\n"
+            "procs_running 1\n"
+            "procs_blocked 0\n"
+            "softirq 102690251 8 26697410 115481 23345078 816026 0 2296 26068778 0 25645174\n");
+        ASSERT_KEY_AND_VALUE("user_ms", 41801UL);
+        ASSERT_KEY_AND_VALUE("nice_ms", 9179UL);
+        ASSERT_KEY_AND_VALUE("system_ms", 32206UL);
+        ASSERT_KEY_AND_VALUE("idle_ms", 831134223UL);
+        ASSERT_KEY_AND_VALUE("iowait_ms", 34279UL);
+        ASSERT_KEY_AND_VALUE("irq_ms", 0UL);
+        ASSERT_KEY_AND_VALUE("softirq_ms", 947UL);
+        ASSERT_KEY_AND_VALUE("steal_ms", 0UL);
+        ASSERT_KEY_AND_VALUE("guest_ms", 0UL);
+        ASSERT_KEY_AND_VALUE("guest_nice_ms", 0UL);
+        ASSERT_KEY_AND_VALUE("ctxt", 190305514UL);
+        ASSERT_KEY_AND_VALUE("processes", 47438UL);
+    }
+
+    // Missing fields in cpu and others
+    {
+        ASSERT_PARSE_STAT(keys,
+                          "cpu  41801 9179 32206\n"
+                          "ctxt 190305514\n");
+        ASSERT_KEY_AND_VALUE("user_ms", 41801UL);
+        ASSERT_KEY_AND_VALUE("nice_ms", 9179UL);
+        ASSERT_KEY_AND_VALUE("system_ms", 32206UL);
+        ASSERT_NO_KEY("idle_ms");
+        ASSERT_KEY_AND_VALUE("ctxt", 190305514UL);
+        ASSERT_NO_KEY("processes");
+    }
+
+    // Missing fields in cpu and others
+    {
+        ASSERT_PARSE_STAT(keys,
+                          "cpu  41801\n"
+                          "ctxt 190305514\n");
+        ASSERT_KEY_AND_VALUE("user_ms", 41801UL);
+        ASSERT_NO_KEY("nice_ms");
+        ASSERT_KEY_AND_VALUE("ctxt", 190305514UL);
+        ASSERT_NO_KEY("processes");
+    }
+
+    // Missing fields in cpu
+    {
+        ASSERT_PARSE_STAT(keys,
+                          "cpu  \n"
+                          "ctxt 190305514\n");
+        ASSERT_KEY_AND_VALUE("ctxt", 190305514UL);
+        ASSERT_NO_KEY("processes");
+    }
+
+    // Single string with only cpu and numbers
+    {
+        ASSERT_PARSE_STAT(keys, "cpu 41801 9179 32206");
+        ASSERT_KEY_AND_VALUE("user_ms", 41801UL);
+        ASSERT_KEY_AND_VALUE("nice_ms", 9179UL);
+        ASSERT_KEY_AND_VALUE("system_ms", 32206UL);
+        ASSERT_NO_KEY("idle_ms");
+    }
+
+    // Single string with only cpu
+    {
+        BSONObjBuilder builder;
+        ASSERT_NOT_OK(procparser::parseProcStat(keys, "cpu", 1000, &builder));
+    }
+
+    // Single string with only cpu and a number, and empty ctxt
+    {
+        ASSERT_PARSE_STAT(keys,
+                          "cpu  123\n"
+                          "ctxt");
+        ASSERT_KEY_AND_VALUE("user_ms", 123UL);
+    }
+
+    // Empty String
+    {
+        BSONObjBuilder builder;
+        ASSERT_NOT_OK(procparser::parseProcStat(keys, "", 1000, &builder));
+    }
+}
+
+// Test we can parse the /proc/stat on this machine. Also assert we have the expected fields
+// This tests is designed to exercise our parsing code on various Linuxes and fail
+// Normally when run in the FTDC loop we return a non-fatal error so we may not notice the failure
+// otherwise.
+TEST(FTDCProcStat, TestLocalStat) {
+    std::vector<StringData> keys{
+        "btime", "cpu", "ctxt", "processes", "procs_blocked", "procs_running",
+    };
+
+    BSONObjBuilder builder;
+
+    ASSERT_OK(procparser::parseProcStatFile("/proc/stat", keys, &builder));
+
+    BSONObj obj = builder.obj();
+    auto stringMap = toStringMap(obj);
+    log() << "OBJ:" << obj;
+    ASSERT_KEY("user_ms");
+    ASSERT_KEY("nice_ms");
+    ASSERT_KEY("idle_ms");
+    ASSERT_KEY("system_ms");
+    ASSERT_KEY("iowait_ms");
+    ASSERT_KEY("irq_ms");
+    ASSERT_KEY("softirq_ms");
+    ASSERT_KEY("steal_ms");
+    // Needs 2.6.24 - ASSERT_KEY("guest_ms");
+    // Needs 2.6.33 - ASSERT_KEY("guest_nice_ms");
+    ASSERT_KEY("ctxt");
+    ASSERT_KEY("btime");
+    ASSERT_KEY("processes");
+    ASSERT_KEY("procs_running");
+    ASSERT_KEY("procs_blocked");
+}
+
+TEST(FTDCProcStat, TestLocalNonExistentStat) {
+    std::vector<StringData> keys{
+        "btime", "cpu", "ctxt", "processes", "procs_blocked", "procs_running",
+    };
+    BSONObjBuilder builder;
+
+    ASSERT_NOT_OK(procparser::parseProcStatFile("/proc/does_not_exist", keys, &builder));
+}
+
+}  // namespace
+}  // namespace mongo