Make snapshotctl logging better.

snapshotctl merge --logcat --log-to-file
- If --logcat, log to logcat
- If --log-to-file, log to /data/misc/snapshotctl_log/
- If both, log to both
- If none, log to stdout

Test: manually test these 4 cases
Bug: 148818798
Change-Id: I44b52936c0d095867acc6ee781c6bec04f6ebd6b

fs_mgr/libsnapshot/snapshotctl.cpp

@@ -19,9 +19,13 @@
 #include <chrono>
 #include <iostream>
 #include <map>
+#include <sstream>
 
+#include <android-base/file.h>
 #include <android-base/logging.h>
+#include <android-base/unique_fd.h>
 #include <libsnapshot/snapshot.h>
+#include "utility.h"
 
 using namespace std::string_literals;
 
@@ -31,9 +35,11 @@ int Usage() {
                  "Actions:\n"
                  "  dump\n"
                  "    Print snapshot states.\n"
-                 "  merge [--logcat]\n"
+                 "  merge [--logcat] [--log-to-file]\n"
                  "    Initialize merge and wait for it to be completed.\n"
-                 "    If --logcat is specified, log to logcat. Otherwise, log to stdout.\n";
+                 "    If --logcat is specified, log to logcat.\n"
+                 "    If --log-to-file is specified, log to /data/misc/snapshotctl_log/.\n"
+                 "    If both specified, log to both. If none specified, log to stdout.\n";
     return EX_USAGE;
 }
 
@@ -45,20 +51,62 @@ bool DumpCmdHandler(int /*argc*/, char** argv) {
     return SnapshotManager::New()->Dump(std::cout);
 }
 
+class FileLogger {
+  public:
+    FileLogger() {
+        static constexpr const char* kLogFilePath = "/data/misc/snapshotctl_log/";
+        std::stringstream ss;
+        ss << kLogFilePath << "snapshotctl." << Now() << ".log";
+        fd_.reset(TEMP_FAILURE_RETRY(
+                open(ss.str().c_str(),
+                     O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC | O_NOFOLLOW | O_SYNC, 0660)));
+    }
+    // Copy-contuctor needed to be converted to std::function.
+    FileLogger(const FileLogger& other) { fd_.reset(dup(other.fd_)); }
+    void operator()(android::base::LogId, android::base::LogSeverity, const char* /*tag*/,
+                    const char* /*file*/, unsigned int /*line*/, const char* message) {
+        if (fd_ == -1) return;
+        std::stringstream ss;
+        ss << Now() << ":" << message << "\n";
+        (void)android::base::WriteStringToFd(ss.str(), fd_);
+    }
+
+  private:
+    android::base::unique_fd fd_;
+};
+
+class MergeCmdLogger {
+  public:
+    MergeCmdLogger(int argc, char** argv) {
+        for (int i = 0; i < argc; ++i) {
+            if (argv[i] == "--logcat"s) {
+                loggers_.push_back(android::base::LogdLogger());
+            }
+            if (argv[i] == "--log-to-file"s) {
+                loggers_.push_back(std::move(FileLogger()));
+            }
+        }
+        if (loggers_.empty()) {
+            loggers_.push_back(&android::base::StdioLogger);
+        }
+    }
+    void operator()(android::base::LogId id, android::base::LogSeverity severity, const char* tag,
+                    const char* file, unsigned int line, const char* message) {
+        for (auto&& logger : loggers_) {
+            logger(id, severity, tag, file, line, message);
+        }
+    }
+
+  private:
+    std::vector<android::base::LogFunction> loggers_;
+};
+
 bool MergeCmdHandler(int argc, char** argv) {
     auto begin = std::chrono::steady_clock::now();
 
-    bool log_to_logcat = false;
-    for (int i = 2; i < argc; ++i) {
-        if (argv[i] == "--logcat"s) {
-            log_to_logcat = true;
-        }
-    }
-    if (log_to_logcat) {
-        android::base::InitLogging(argv);
-    } else {
-        android::base::InitLogging(argv, &android::base::StdioLogger);
-    }
+    // 'snapshotctl merge' is stripped away from arguments to
+    // Logger.
+    android::base::InitLogging(argv, MergeCmdLogger(argc - 2, argv + 2));
 
     auto state = SnapshotManager::New()->InitiateMergeAndWait();
 

fs_mgr/libsnapshot/snapshotctl.rc

@@ -1,2 +1,2 @@
 on property:sys.boot_completed=1
-    exec_background - root root -- /system/bin/snapshotctl merge --logcat
+    exec_background - root root -- /system/bin/snapshotctl merge --logcat --log-to-file

fs_mgr/libsnapshot/utility.cpp

@@ -15,6 +15,10 @@
 #include "utility.h"
 
 #include <errno.h>
+#include <time.h>
+
+#include <iomanip>
+#include <sstream>
 
 #include <android-base/file.h>
 #include <android-base/logging.h>
@@ -155,5 +159,12 @@ bool WriteStringToFileAtomic(const std::string& content, const std::string& path
     return true;
 }
 
+std::ostream& operator<<(std::ostream& os, const Now&) {
+    struct tm now;
+    time_t t = time(nullptr);
+    localtime_r(&t, &now);
+    return os << std::put_time(&now, "%Y%m%d-%H%M%S");
+}
+
 }  // namespace snapshot
 }  // namespace android

fs_mgr/libsnapshot/utility.h

@@ -15,6 +15,7 @@
 #pragma once
 
 #include <functional>
+#include <iostream>
 #include <string>
 
 #include <android-base/macros.h>
@@ -120,5 +121,9 @@ Return InitializeCow(const std::string& device);
 // is an open fd to |path|, because that fd has an old view of the file.
 bool WriteStringToFileAtomic(const std::string& content, const std::string& path);
 
+// Writes current time to a given stream.
+struct Now {};
+std::ostream& operator<<(std::ostream& os, const Now&);
+
 }  // namespace snapshot
 }  // namespace android

rootdir/init.rc

@@ -600,6 +600,7 @@ on post-fs-data
     mkdir /data/misc/installd 0700 root root
     mkdir /data/misc/apexdata 0711 root root
     mkdir /data/misc/apexrollback 0700 root root
+    mkdir /data/misc/snapshotctl_log 0770 root root
 
     mkdir /data/preloads 0775 system system encryption=None