base: reimagine line splitting in logger.cpp
Previously, we would split messages by line and call the logger
function for each line. We would hold a lock during this, to ensure
that multiple threads would not interleave their messages.
There are a few problems with this approach:
1) Using a lock is not efficient and is not fork safe
2) With APEX, there is one lock per instance of libbase, so we must
move the lock to a location where all instances can access it, or
perform the line splitting in a way that does not require the lock.
To solve these issues, we reimagine line splitting.
1) We move the lock out of the LogMessage::~LogMessage() and make it
the logger's responsibility to split lines, giving the logger the
option to lock or not.
2) We do not need any locks at all for StderrLogger.
Instead, we generate a single string that contains all of the lines
with their appropriate log header. A single write() call is used
to output this at once.
3) Logd handles log messages with newlines correctly, however it only
accepts up to a maximum size of log message. Therefore we
separate the incoming log message into chunks, delimited by new
lines, up to that maximum size, and send each of those to logd.
Note that this is the strategy used in
android.util.Log.printlns().
This should solve a majority of use cases, since the maximum size
that logd accepts is nearly 4K, while remaining lock free.
If interleaving messages absolutely must be avoided, a lock can
still be used given 1) above.
Bug: 65062446
Bug: 153824050
Test: logging, particularly multi-line stack traces, show correctly
Test: existing and new unit tests
Change-Id: Id0cb5669bee7f912da1e17f7010f0ee4c93be1e3
diff --git a/logging_splitters_test.cpp b/logging_splitters_test.cpp
new file mode 100644
index 0000000..679d19e
--- /dev/null
+++ b/logging_splitters_test.cpp
@@ -0,0 +1,325 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * 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 "logging_splitters.h"
+
+#include <string>
+#include <vector>
+
+#include <android-base/strings.h>
+#include <gtest/gtest.h>
+
+namespace android {
+namespace base {
+
+void TestNewlineSplitter(const std::string& input,
+ const std::vector<std::string>& expected_output) {
+ std::vector<std::string> output;
+ auto logger_function = [&](const char* msg, int length) {
+ if (length == -1) {
+ output.push_back(msg);
+ } else {
+ output.push_back(std::string(msg, length));
+ }
+ };
+ SplitByLines(input.c_str(), logger_function);
+
+ EXPECT_EQ(expected_output, output);
+}
+
+TEST(logging_splitters, NewlineSplitter_EmptyString) {
+ TestNewlineSplitter("", std::vector<std::string>{""});
+}
+
+TEST(logging_splitters, NewlineSplitter_BasicString) {
+ TestNewlineSplitter("normal string", std::vector<std::string>{"normal string"});
+}
+
+TEST(logging_splitters, NewlineSplitter_ormalBasicStringTrailingNewline) {
+ TestNewlineSplitter("normal string\n", std::vector<std::string>{"normal string", ""});
+}
+
+TEST(logging_splitters, NewlineSplitter_MultilineTrailing) {
+ TestNewlineSplitter("normal string\nsecond string\nthirdstring",
+ std::vector<std::string>{"normal string", "second string", "thirdstring"});
+}
+
+TEST(logging_splitters, NewlineSplitter_MultilineTrailingNewline) {
+ TestNewlineSplitter(
+ "normal string\nsecond string\nthirdstring\n",
+ std::vector<std::string>{"normal string", "second string", "thirdstring", ""});
+}
+
+TEST(logging_splitters, NewlineSplitter_MultilineEmbeddedNewlines) {
+ TestNewlineSplitter(
+ "normal string\n\n\nsecond string\n\nthirdstring\n",
+ std::vector<std::string>{"normal string", "", "", "second string", "", "thirdstring", ""});
+}
+
+void TestLogdChunkSplitter(const std::string& tag, const std::string& file,
+ const std::string& input,
+ const std::vector<std::string>& expected_output) {
+ std::vector<std::string> output;
+ auto logger_function = [&](LogId, LogSeverity, const char*, const char* msg) {
+ output.push_back(msg);
+ };
+
+ SplitByLogdChunks(MAIN, FATAL, tag.c_str(), file.empty() ? nullptr : file.c_str(), 1000,
+ input.c_str(), logger_function);
+
+ auto return_lengths = [&] {
+ std::string sizes;
+ sizes += "expected_output sizes:";
+ for (const auto& string : expected_output) {
+ sizes += " " + std::to_string(string.size());
+ }
+ sizes += "\noutput sizes:";
+ for (const auto& string : output) {
+ sizes += " " + std::to_string(string.size());
+ }
+ return sizes;
+ };
+
+ EXPECT_EQ(expected_output, output) << return_lengths();
+}
+
+TEST(logging_splitters, LogdChunkSplitter_EmptyString) {
+ TestLogdChunkSplitter("tag", "", "", std::vector<std::string>{""});
+}
+
+TEST(logging_splitters, LogdChunkSplitter_BasicString) {
+ TestLogdChunkSplitter("tag", "", "normal string", std::vector<std::string>{"normal string"});
+}
+
+TEST(logging_splitters, LogdChunkSplitter_NormalBasicStringTrailingNewline) {
+ TestLogdChunkSplitter("tag", "", "normal string\n", std::vector<std::string>{"normal string\n"});
+}
+
+TEST(logging_splitters, LogdChunkSplitter_MultilineTrailing) {
+ TestLogdChunkSplitter("tag", "", "normal string\nsecond string\nthirdstring",
+ std::vector<std::string>{"normal string\nsecond string\nthirdstring"});
+}
+
+TEST(logging_splitters, LogdChunkSplitter_MultilineTrailingNewline) {
+ TestLogdChunkSplitter("tag", "", "normal string\nsecond string\nthirdstring\n",
+ std::vector<std::string>{"normal string\nsecond string\nthirdstring\n"});
+}
+
+TEST(logging_splitters, LogdChunkSplitter_MultilineEmbeddedNewlines) {
+ TestLogdChunkSplitter(
+ "tag", "", "normal string\n\n\nsecond string\n\nthirdstring\n",
+ std::vector<std::string>{"normal string\n\n\nsecond string\n\nthirdstring\n"});
+}
+
+// This test should return the same string, the logd logger itself will truncate down to size.
+// This has historically been the behavior both in libbase and liblog.
+TEST(logging_splitters, LogdChunkSplitter_HugeLineNoNewline) {
+ auto long_string = std::string(LOGGER_ENTRY_MAX_PAYLOAD, 'x');
+ ASSERT_EQ(LOGGER_ENTRY_MAX_PAYLOAD, static_cast<int>(long_string.size()));
+
+ TestLogdChunkSplitter("tag", "", long_string, std::vector{long_string});
+}
+
+std::string ReduceToMaxSize(const std::string& tag, const std::string& string) {
+ return string.substr(0, LOGGER_ENTRY_MAX_PAYLOAD - tag.size() - 35);
+}
+
+TEST(logging_splitters, LogdChunkSplitter_MultipleHugeLineNoNewline) {
+ auto long_string_x = std::string(LOGGER_ENTRY_MAX_PAYLOAD, 'x');
+ auto long_string_y = std::string(LOGGER_ENTRY_MAX_PAYLOAD, 'y');
+ auto long_string_z = std::string(LOGGER_ENTRY_MAX_PAYLOAD, 'z');
+
+ auto long_strings = long_string_x + '\n' + long_string_y + '\n' + long_string_z;
+
+ std::string tag = "tag";
+ std::vector expected = {ReduceToMaxSize(tag, long_string_x), ReduceToMaxSize(tag, long_string_y),
+ long_string_z};
+
+ TestLogdChunkSplitter(tag, "", long_strings, expected);
+}
+
+// With a ~4k buffer, we should print 2 long strings per logger call.
+TEST(logging_splitters, LogdChunkSplitter_Multiple2kLines) {
+ std::vector expected = {
+ std::string(2000, 'a') + '\n' + std::string(2000, 'b'),
+ std::string(2000, 'c') + '\n' + std::string(2000, 'd'),
+ std::string(2000, 'e') + '\n' + std::string(2000, 'f'),
+ };
+
+ auto long_strings = Join(expected, '\n');
+
+ TestLogdChunkSplitter("tag", "", long_strings, expected);
+}
+
+TEST(logging_splitters, LogdChunkSplitter_ExactSizedLines) {
+ const char* tag = "tag";
+ ptrdiff_t max_size = LOGGER_ENTRY_MAX_PAYLOAD - strlen(tag) - 35;
+ auto long_string_a = std::string(max_size, 'a');
+ auto long_string_b = std::string(max_size, 'b');
+ auto long_string_c = std::string(max_size, 'c');
+
+ auto long_strings = long_string_a + '\n' + long_string_b + '\n' + long_string_c;
+
+ TestLogdChunkSplitter(tag, "", long_strings,
+ std::vector{long_string_a, long_string_b, long_string_c});
+}
+
+TEST(logging_splitters, LogdChunkSplitter_UnderEqualOver) {
+ std::string tag = "tag";
+ ptrdiff_t max_size = LOGGER_ENTRY_MAX_PAYLOAD - tag.size() - 35;
+
+ auto first_string_size = 1000;
+ auto first_string = std::string(first_string_size, 'a');
+ auto second_string_size = max_size - first_string_size - 1;
+ auto second_string = std::string(second_string_size, 'b');
+
+ auto exact_string = std::string(max_size, 'c');
+
+ auto large_string = std::string(max_size + 50, 'd');
+
+ auto final_string = std::string("final string!\n\nfinal \n \n final \n");
+
+ std::vector expected = {first_string + '\n' + second_string, exact_string,
+ ReduceToMaxSize(tag, large_string), final_string};
+
+ std::vector input_strings = {first_string + '\n' + second_string, exact_string, large_string,
+ final_string};
+ auto long_strings = Join(input_strings, '\n');
+
+ TestLogdChunkSplitter(tag, "", long_strings, expected);
+}
+
+TEST(logging_splitters, LogdChunkSplitter_WithFile) {
+ std::string tag = "tag";
+ std::string file = "/path/to/myfile.cpp";
+ int line = 1000;
+ auto file_header = StringPrintf("%s:%d] ", file.c_str(), line);
+ ptrdiff_t max_size = LOGGER_ENTRY_MAX_PAYLOAD - tag.size() - 35;
+
+ auto first_string_size = 1000;
+ auto first_string = std::string(first_string_size, 'a');
+ auto second_string_size = max_size - first_string_size - 1 - 2 * file_header.size();
+ auto second_string = std::string(second_string_size, 'b');
+
+ auto exact_string = std::string(max_size - file_header.size(), 'c');
+
+ auto large_string = std::string(max_size + 50, 'd');
+
+ auto final_string = std::string("final string!");
+
+ std::vector expected = {
+ file_header + first_string + '\n' + file_header + second_string, file_header + exact_string,
+ file_header + ReduceToMaxSize(file_header + tag, large_string), file_header + final_string};
+
+ std::vector input_strings = {first_string + '\n' + second_string, exact_string, large_string,
+ final_string};
+ auto long_strings = Join(input_strings, '\n');
+
+ TestLogdChunkSplitter(tag, file, long_strings, expected);
+}
+
+// We set max_size based off of tag, so if it's too large, the buffer will be sized wrong.
+// We could recover from this, but it's certainly an error for someone to attempt to use a tag this
+// large, so we abort instead.
+TEST(logging_splitters, LogdChunkSplitter_TooLongTag) {
+ auto long_tag = std::string(5000, 'x');
+ auto logger_function = [](LogId, LogSeverity, const char*, const char*) {};
+ ASSERT_DEATH(
+ SplitByLogdChunks(MAIN, ERROR, long_tag.c_str(), nullptr, 0, "message", logger_function), "");
+}
+
+// We do handle excessively large file names correctly however.
+TEST(logging_splitters, LogdChunkSplitter_TooLongFile) {
+ auto long_file = std::string(5000, 'x');
+ std::string tag = "tag";
+
+ std::vector expected = {ReduceToMaxSize(tag, long_file), ReduceToMaxSize(tag, long_file)};
+
+ TestLogdChunkSplitter(tag, long_file, "can't see me\nor me", expected);
+}
+
+void TestStderrOutputGenerator(const char* tag, const char* file, int line, const char* message,
+ const std::string& expected) {
+ // All log messages will show "01-01 00:00:00"
+ struct tm now = {
+ .tm_sec = 0,
+ .tm_min = 0,
+ .tm_hour = 0,
+ .tm_mday = 1,
+ .tm_mon = 0,
+ .tm_year = 1970,
+ };
+
+ int pid = 1234; // All log messages will have 1234 for their PID.
+ uint64_t tid = 4321; // All log messages will have 4321 for their TID.
+
+ auto result = StderrOutputGenerator(now, pid, tid, ERROR, tag, file, line, message);
+ EXPECT_EQ(expected, result);
+}
+
+TEST(logging_splitters, StderrOutputGenerator_Basic) {
+ TestStderrOutputGenerator(nullptr, nullptr, 0, "simple message",
+ "nullptr E 01-01 00:00:00 1234 4321 simple message\n");
+ TestStderrOutputGenerator("tag", nullptr, 0, "simple message",
+ "tag E 01-01 00:00:00 1234 4321 simple message\n");
+ TestStderrOutputGenerator(
+ "tag", "/path/to/some/file", 0, "simple message",
+ "tag E 01-01 00:00:00 1234 4321 /path/to/some/file:0] simple message\n");
+}
+
+TEST(logging_splitters, StderrOutputGenerator_NewlineTagAndFile) {
+ TestStderrOutputGenerator("tag\n\n", nullptr, 0, "simple message",
+ "tag\n\n E 01-01 00:00:00 1234 4321 simple message\n");
+ TestStderrOutputGenerator(
+ "tag", "/path/to/some/file\n\n", 0, "simple message",
+ "tag E 01-01 00:00:00 1234 4321 /path/to/some/file\n\n:0] simple message\n");
+}
+
+TEST(logging_splitters, StderrOutputGenerator_TrailingNewLine) {
+ TestStderrOutputGenerator(
+ "tag", nullptr, 0, "simple message\n",
+ "tag E 01-01 00:00:00 1234 4321 simple message\ntag E 01-01 00:00:00 1234 4321 \n");
+}
+
+TEST(logging_splitters, StderrOutputGenerator_MultiLine) {
+ const char* expected_result =
+ "tag E 01-01 00:00:00 1234 4321 simple message\n"
+ "tag E 01-01 00:00:00 1234 4321 \n"
+ "tag E 01-01 00:00:00 1234 4321 \n"
+ "tag E 01-01 00:00:00 1234 4321 another message \n"
+ "tag E 01-01 00:00:00 1234 4321 \n"
+ "tag E 01-01 00:00:00 1234 4321 final message \n"
+ "tag E 01-01 00:00:00 1234 4321 \n"
+ "tag E 01-01 00:00:00 1234 4321 \n"
+ "tag E 01-01 00:00:00 1234 4321 \n";
+
+ TestStderrOutputGenerator("tag", nullptr, 0,
+ "simple message\n\n\nanother message \n\n final message \n\n\n",
+ expected_result);
+}
+
+TEST(logging_splitters, StderrOutputGenerator_MultiLineLong) {
+ auto long_string_a = std::string(4000, 'a');
+ auto long_string_b = std::string(4000, 'b');
+
+ auto message = long_string_a + '\n' + long_string_b;
+ auto expected_result = "tag E 01-01 00:00:00 1234 4321 " + long_string_a + '\n' +
+ "tag E 01-01 00:00:00 1234 4321 " + long_string_b + '\n';
+ TestStderrOutputGenerator("tag", nullptr, 0, message.c_str(), expected_result);
+}
+
+} // namespace base
+} // namespace android