EGL Multifile Blobcache: Add status file

Add a status file that contains the cache version and
platform build ID.  On future startups, if those values
don't match, clear the cache.

This alleviates a problem on driver updates, which cause
all new queries to miss, creating new entires, filling the
cache.  For apps with many small entries, the start up
time has become a problem.

Test: libEGL_test, EGL_test, ANGLE trace tests, apps
Bug: b/295051628
Bug: b/310535559
Change-Id: I17b91fb6c994237fb5c2a220db4f23050d45742b

4 files changed, 443 insertions, 13 deletions

diff --git a/opengl/libs/EGL/MultifileBlobCache.cpp b/opengl/libs/EGL/MultifileBlobCache.cpp
index 13a5e7baa7..9905210014 100644
--- a/opengl/libs/EGL/MultifileBlobCache.cpp
+++ b/opengl/libs/EGL/MultifileBlobCache.cpp
@@ -18,6 +18,7 @@
 
 #include "MultifileBlobCache.h"
 
+#include <android-base/properties.h>
 #include <dirent.h>
 #include <fcntl.h>
 #include <inttypes.h>
@@ -64,6 +65,7 @@ namespace android {
 MultifileBlobCache::MultifileBlobCache(size_t maxKeySize, size_t maxValueSize, size_t maxTotalSize,
                                        size_t maxTotalEntries, const std::string& baseDir)
       : mInitialized(false),
+        mCacheVersion(0),
         mMaxKeySize(maxKeySize),
         mMaxValueSize(maxValueSize),
         mMaxTotalSize(maxTotalSize),
@@ -78,6 +80,26 @@ MultifileBlobCache::MultifileBlobCache(size_t maxKeySize, size_t maxValueSize, s
         return;
     }
 
+    // Set the cache version, override if debug value set
+    mCacheVersion = kMultifileBlobCacheVersion;
+    int debugCacheVersion = base::GetIntProperty("debug.egl.blobcache.cache_version", -1);
+    if (debugCacheVersion >= 0) {
+        ALOGV("INIT: Using %u as cacheVersion instead of %u", debugCacheVersion, mCacheVersion);
+        mCacheVersion = debugCacheVersion;
+    }
+
+    // Set the platform build ID, override if debug value set
+    mBuildId = base::GetProperty("ro.build.id", "");
+    std::string debugBuildId = base::GetProperty("debug.egl.blobcache.build_id", "");
+    if (!debugBuildId.empty()) {
+        ALOGV("INIT: Using %s as buildId instead of %s", debugBuildId.c_str(), mBuildId.c_str());
+        if (debugBuildId.length() > PROP_VALUE_MAX) {
+            ALOGV("INIT: debugBuildId is too long (%zu), reduce it to %u", debugBuildId.length(),
+                  PROP_VALUE_MAX);
+        }
+        mBuildId = debugBuildId;
+    }
+
     // Establish the name of our multifile directory
     mMultifileDirName = baseDir + ".multifile";
 
@@ -95,14 +117,30 @@ MultifileBlobCache::MultifileBlobCache(size_t maxKeySize, size_t maxValueSize, s
     mTaskThread = std::thread(&MultifileBlobCache::processTasks, this);
 
     // See if the dir exists, and initialize using its contents
+    bool statusGood = false;
+
+    // Check that our cacheVersion and buildId match
     struct stat st;
     if (stat(mMultifileDirName.c_str(), &st) == 0) {
+        if (checkStatus(mMultifileDirName.c_str())) {
+            statusGood = true;
+        } else {
+            ALOGV("INIT: Cache status has changed, clearing the cache");
+            if (!clearCache()) {
+                ALOGE("INIT: Unable to clear cache");
+                return;
+            }
+        }
+    }
+
+    if (statusGood) {
         // Read all the files and gather details, then preload their contents
         DIR* dir;
         struct dirent* entry;
         if ((dir = opendir(mMultifileDirName.c_str())) != nullptr) {
             while ((entry = readdir(dir)) != nullptr) {
-                if (entry->d_name == "."s || entry->d_name == ".."s) {
+                if (entry->d_name == "."s || entry->d_name == ".."s ||
+                    strcmp(entry->d_name, kMultifileBlobCacheStatusFile) == 0) {
                     continue;
                 }
 
@@ -125,7 +163,8 @@ MultifileBlobCache::MultifileBlobCache(size_t maxKeySize, size_t maxValueSize, s
                 if (st.st_size <= 0 || st.st_atime <= 0) {
                     ALOGE("INIT: Entry %u has invalid stats! Removing.", entryHash);
                     if (remove(fullPath.c_str()) != 0) {
-                        ALOGE("Error removing %s: %s", fullPath.c_str(), std::strerror(errno));
+                        ALOGE("INIT: Error removing %s: %s", fullPath.c_str(),
+                              std::strerror(errno));
                     }
                     continue;
                 }
@@ -142,7 +181,7 @@ MultifileBlobCache::MultifileBlobCache(size_t maxKeySize, size_t maxValueSize, s
                 MultifileHeader header;
                 size_t result = read(fd, static_cast<void*>(&header), sizeof(MultifileHeader));
                 if (result != sizeof(MultifileHeader)) {
-                    ALOGE("Error reading MultifileHeader from cache entry (%s): %s",
+                    ALOGE("INIT: Error reading MultifileHeader from cache entry (%s): %s",
                           fullPath.c_str(), std::strerror(errno));
                     close(fd);
                     return;
@@ -152,7 +191,8 @@ MultifileBlobCache::MultifileBlobCache(size_t maxKeySize, size_t maxValueSize, s
                 if (header.magic != kMultifileMagic) {
                     ALOGE("INIT: Entry %u has bad magic (%u)! Removing.", entryHash, header.magic);
                     if (remove(fullPath.c_str()) != 0) {
-                        ALOGE("Error removing %s: %s", fullPath.c_str(), std::strerror(errno));
+                        ALOGE("INIT: Error removing %s: %s", fullPath.c_str(),
+                              std::strerror(errno));
                     }
                     close(fd);
                     continue;
@@ -177,7 +217,7 @@ MultifileBlobCache::MultifileBlobCache(size_t maxKeySize, size_t maxValueSize, s
                 if (header.crc !=
                     crc32c(mappedEntry + sizeof(MultifileHeader),
                            fileSize - sizeof(MultifileHeader))) {
-                    ALOGE("INIT: Entry %u failed CRC check! Removing.", entryHash);
+                    ALOGV("INIT: Entry %u failed CRC check! Removing.", entryHash);
                     if (remove(fullPath.c_str()) != 0) {
                         ALOGE("Error removing %s: %s", fullPath.c_str(), std::strerror(errno));
                     }
@@ -186,11 +226,12 @@ MultifileBlobCache::MultifileBlobCache(size_t maxKeySize, size_t maxValueSize, s
 
                 // If the cache entry is damaged or no good, remove it
                 if (header.keySize <= 0 || header.valueSize <= 0) {
-                    ALOGE("INIT: Entry %u has a bad header keySize (%lu) or valueSize (%lu), "
+                    ALOGV("INIT: Entry %u has a bad header keySize (%lu) or valueSize (%lu), "
                           "removing.",
                           entryHash, header.keySize, header.valueSize);
                     if (remove(fullPath.c_str()) != 0) {
-                        ALOGE("Error removing %s: %s", fullPath.c_str(), std::strerror(errno));
+                        ALOGE("INIT: Error removing %s: %s", fullPath.c_str(),
+                              std::strerror(errno));
                     }
                     continue;
                 }
@@ -228,9 +269,17 @@ MultifileBlobCache::MultifileBlobCache(size_t maxKeySize, size_t maxValueSize, s
         // If the multifile directory does not exist, create it and start from scratch
         if (mkdir(mMultifileDirName.c_str(), 0755) != 0 && (errno != EEXIST)) {
             ALOGE("Unable to create directory (%s), errno (%i)", mMultifileDirName.c_str(), errno);
+            return;
+        }
+
+        // Create new status file
+        if (!createStatus(mMultifileDirName.c_str())) {
+            ALOGE("INIT: Failed to create status file!");
+            return;
         }
     }
 
+    ALOGV("INIT: Multifile BlobCache initialization succeeded");
     mInitialized = true;
 }
 
@@ -471,6 +520,112 @@ void MultifileBlobCache::finish() {
     }
 }
 
+bool MultifileBlobCache::createStatus(const std::string& baseDir) {
+    // Populate the status struct
+    struct MultifileStatus status;
+    memset(&status, 0, sizeof(status));
+    status.magic = kMultifileMagic;
+    status.cacheVersion = mCacheVersion;
+
+    // Copy the buildId string in, up to our allocated space
+    strncpy(status.buildId, mBuildId.c_str(),
+            mBuildId.length() > PROP_VALUE_MAX ? PROP_VALUE_MAX : mBuildId.length());
+
+    // Finally update the crc, using cacheVersion and everything the follows
+    status.crc =
+            crc32c(reinterpret_cast<uint8_t*>(&status) + offsetof(MultifileStatus, cacheVersion),
+                   sizeof(status) - offsetof(MultifileStatus, cacheVersion));
+
+    // Create the status file
+    std::string cacheStatus = baseDir + "/" + kMultifileBlobCacheStatusFile;
+    int fd = open(cacheStatus.c_str(), O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
+    if (fd == -1) {
+        ALOGE("STATUS(CREATE): Unable to create status file: %s, error: %s", cacheStatus.c_str(),
+              std::strerror(errno));
+        return false;
+    }
+
+    // Write the buffer contents to disk
+    ssize_t result = write(fd, &status, sizeof(status));
+    close(fd);
+    if (result != sizeof(status)) {
+        ALOGE("STATUS(CREATE): Error writing cache status file: %s, error %s", cacheStatus.c_str(),
+              std::strerror(errno));
+        return false;
+    }
+
+    ALOGV("STATUS(CREATE): Created status file: %s", cacheStatus.c_str());
+    return true;
+}
+
+bool MultifileBlobCache::checkStatus(const std::string& baseDir) {
+    std::string cacheStatus = baseDir + "/" + kMultifileBlobCacheStatusFile;
+
+    // Does status exist
+    struct stat st;
+    if (stat(cacheStatus.c_str(), &st) != 0) {
+        ALOGV("STATUS(CHECK): Status file (%s) missing", cacheStatus.c_str());
+        return false;
+    }
+
+    // If the status entry is damaged or no good, remove it
+    if (st.st_size <= 0 || st.st_atime <= 0) {
+        ALOGE("STATUS(CHECK): Cache status has invalid stats!");
+        return false;
+    }
+
+    // Open the file so we can read its header
+    int fd = open(cacheStatus.c_str(), O_RDONLY);
+    if (fd == -1) {
+        ALOGE("STATUS(CHECK): Cache error - failed to open cacheStatus: %s, error: %s",
+              cacheStatus.c_str(), std::strerror(errno));
+        return false;
+    }
+
+    // Read in the status header
+    MultifileStatus status;
+    size_t result = read(fd, static_cast<void*>(&status), sizeof(MultifileStatus));
+    close(fd);
+    if (result != sizeof(MultifileStatus)) {
+        ALOGE("STATUS(CHECK): Error reading cache status (%s): %s", cacheStatus.c_str(),
+              std::strerror(errno));
+        return false;
+    }
+
+    // Verify header magic
+    if (status.magic != kMultifileMagic) {
+        ALOGE("STATUS(CHECK): Cache status has bad magic (%u)!", status.magic);
+        return false;
+    }
+
+    // Ensure we have a good CRC
+    if (status.crc !=
+        crc32c(reinterpret_cast<uint8_t*>(&status) + offsetof(MultifileStatus, cacheVersion),
+               sizeof(status) - offsetof(MultifileStatus, cacheVersion))) {
+        ALOGE("STATUS(CHECK): Cache status failed CRC check!");
+        return false;
+    }
+
+    // Check cacheVersion
+    if (status.cacheVersion != mCacheVersion) {
+        ALOGV("STATUS(CHECK): Cache version has changed! old(%u) new(%u)", status.cacheVersion,
+              mCacheVersion);
+        return false;
+    }
+
+    // Check buildId
+    if (strcmp(status.buildId, mBuildId.c_str()) != 0) {
+        ALOGV("STATUS(CHECK): BuildId has changed! old(%s) new(%s)", status.buildId,
+              mBuildId.c_str());
+        return false;
+    }
+
+    // All checks passed!
+    ALOGV("STATUS(CHECK): Status file is good! cacheVersion(%u), buildId(%s) file(%s)",
+          status.cacheVersion, status.buildId, cacheStatus.c_str());
+    return true;
+}
+
 void MultifileBlobCache::trackEntry(uint32_t entryHash, EGLsizeiANDROID valueSize, size_t fileSize,
                                     time_t accessTime) {
     mEntries.insert(entryHash);
@@ -606,6 +761,40 @@ bool MultifileBlobCache::applyLRU(size_t cacheSizeLimit, size_t cacheEntryLimit)
     return false;
 }
 
+// Clear the cache by removing all entries and deleting the directory
+bool MultifileBlobCache::clearCache() {
+    DIR* dir;
+    struct dirent* entry;
+    dir = opendir(mMultifileDirName.c_str());
+    if (dir == nullptr) {
+        ALOGE("CLEAR: Unable to open multifile dir: %s", mMultifileDirName.c_str());
+        return false;
+    }
+
+    // Delete all entries and the status file
+    while ((entry = readdir(dir)) != nullptr) {
+        if (entry->d_name == "."s || entry->d_name == ".."s) {
+            continue;
+        }
+
+        std::string entryName = entry->d_name;
+        std::string fullPath = mMultifileDirName + "/" + entryName;
+        if (remove(fullPath.c_str()) != 0) {
+            ALOGE("CLEAR: Error removing %s: %s", fullPath.c_str(), std::strerror(errno));
+            return false;
+        }
+    }
+
+    // Delete the directory
+    if (remove(mMultifileDirName.c_str()) != 0) {
+        ALOGE("CLEAR: Error removing %s: %s", mMultifileDirName.c_str(), std::strerror(errno));
+        return false;
+    }
+
+    ALOGV("CLEAR: Cleared the multifile blobcache");
+    return true;
+}
+
 // When removing files, what fraction of the overall limit should be reached when removing files
 // A divisor of two will decrease the cache to 50%, four to 25% and so on
 // We use the same limit to manage size and entry count
diff --git a/opengl/libs/EGL/MultifileBlobCache.h b/opengl/libs/EGL/MultifileBlobCache.h
index 9a396f01c3..18566c2892 100644
--- a/opengl/libs/EGL/MultifileBlobCache.h
+++ b/opengl/libs/EGL/MultifileBlobCache.h
@@ -21,6 +21,7 @@
 #include <EGL/eglext.h>
 
 #include <android-base/thread_annotations.h>
+#include <cutils/properties.h>
 #include <future>
 #include <map>
 #include <queue>
@@ -33,6 +34,9 @@
 
 namespace android {
 
+constexpr uint32_t kMultifileBlobCacheVersion = 1;
+constexpr char kMultifileBlobCacheStatusFile[] = "cache.status";
+
 struct MultifileHeader {
     uint32_t magic;
     uint32_t crc;
@@ -46,6 +50,13 @@ struct MultifileEntryStats {
     time_t accessTime;
 };
 
+struct MultifileStatus {
+    uint32_t magic;
+    uint32_t crc;
+    uint32_t cacheVersion;
+    char buildId[PROP_VALUE_MAX];
+};
+
 struct MultifileHotCache {
     int entryFd;
     uint8_t* entryBuffer;
@@ -105,6 +116,12 @@ public:
     size_t getTotalSize() const { return mTotalCacheSize; }
     size_t getTotalEntries() const { return mTotalCacheEntries; }
 
+    const std::string& getCurrentBuildId() const { return mBuildId; }
+    void setCurrentBuildId(const std::string& buildId) { mBuildId = buildId; }
+
+    uint32_t getCurrentCacheVersion() const { return mCacheVersion; }
+    void setCurrentCacheVersion(uint32_t cacheVersion) { mCacheVersion = cacheVersion; }
+
 private:
     void trackEntry(uint32_t entryHash, EGLsizeiANDROID valueSize, size_t fileSize,
                     time_t accessTime);
@@ -112,6 +129,9 @@ private:
     bool removeEntry(uint32_t entryHash);
     MultifileEntryStats getEntryStats(uint32_t entryHash);
 
+    bool createStatus(const std::string& baseDir);
+    bool checkStatus(const std::string& baseDir);
+
     size_t getFileSize(uint32_t entryHash);
     size_t getValueSize(uint32_t entryHash);
 
@@ -121,12 +141,16 @@ private:
     bool addToHotCache(uint32_t entryHash, int fd, uint8_t* entryBufer, size_t entrySize);
     bool removeFromHotCache(uint32_t entryHash);
 
+    bool clearCache();
     void trimCache();
     bool applyLRU(size_t cacheSizeLimit, size_t cacheEntryLimit);
 
     bool mInitialized;
     std::string mMultifileDirName;
 
+    std::string mBuildId;
+    uint32_t mCacheVersion;
+
     std::unordered_set<uint32_t> mEntries;
     std::unordered_map<uint32_t, MultifileEntryStats> mEntryStats;
     std::unordered_map<uint32_t, MultifileHotCache> mHotCache;
diff --git a/opengl/libs/EGL/MultifileBlobCache_test.cpp b/opengl/libs/EGL/MultifileBlobCache_test.cpp
index 8e27f5a738..90a0f1ee06 100644
--- a/opengl/libs/EGL/MultifileBlobCache_test.cpp
+++ b/opengl/libs/EGL/MultifileBlobCache_test.cpp
@@ -16,13 +16,17 @@
 
 #include "MultifileBlobCache.h"
 
+#include <android-base/properties.h>
 #include <android-base/test_utils.h>
 #include <fcntl.h>
 #include <gtest/gtest.h>
 #include <stdio.h>
 
+#include <fstream>
 #include <memory>
 
+using namespace std::literals;
+
 namespace android {
 
 template <typename T>
@@ -36,19 +40,35 @@ constexpr size_t kMaxTotalEntries = 64;
 class MultifileBlobCacheTest : public ::testing::Test {
 protected:
     virtual void SetUp() {
+        clearProperties();
         mTempFile.reset(new TemporaryFile());
         mMBC.reset(new MultifileBlobCache(kMaxKeySize, kMaxValueSize, kMaxTotalSize,
                                           kMaxTotalEntries, &mTempFile->path[0]));
     }
 
-    virtual void TearDown() { mMBC.reset(); }
+    virtual void TearDown() {
+        clearProperties();
+        mMBC.reset();
+    }
 
     int getFileDescriptorCount();
+    std::vector<std::string> getCacheEntries();
+
+    void clearProperties();
 
     std::unique_ptr<TemporaryFile> mTempFile;
     std::unique_ptr<MultifileBlobCache> mMBC;
 };
 
+void MultifileBlobCacheTest::clearProperties() {
+    // Clear any debug properties used in the tests
+    base::SetProperty("debug.egl.blobcache.cache_version", "");
+    base::WaitForProperty("debug.egl.blobcache.cache_version", "");
+
+    base::SetProperty("debug.egl.blobcache.build_id", "");
+    base::WaitForProperty("debug.egl.blobcache.build_id", "");
+}
+
 TEST_F(MultifileBlobCacheTest, CacheSingleValueSucceeds) {
     unsigned char buf[4] = {0xee, 0xee, 0xee, 0xee};
     mMBC->set("abcd", 4, "efgh", 4);
@@ -287,4 +307,200 @@ TEST_F(MultifileBlobCacheTest, EnsureFileDescriptorsClosed) {
     ASSERT_LT(getFileDescriptorCount(), kMaxTotalEntries / 2);
 }
 
+std::vector<std::string> MultifileBlobCacheTest::getCacheEntries() {
+    std::string cachePath = &mTempFile->path[0];
+    std::string multifileDirName = cachePath + ".multifile";
+    std::vector<std::string> cacheEntries;
+
+    struct stat info;
+    if (stat(multifileDirName.c_str(), &info) == 0) {
+        // We have a multifile dir. Skip the status file and return the only entry.
+        DIR* dir;
+        struct dirent* entry;
+        if ((dir = opendir(multifileDirName.c_str())) != nullptr) {
+            while ((entry = readdir(dir)) != nullptr) {
+                if (entry->d_name == "."s || entry->d_name == ".."s) {
+                    continue;
+                }
+                if (strcmp(entry->d_name, kMultifileBlobCacheStatusFile) == 0) {
+                    continue;
+                }
+                cacheEntries.push_back(multifileDirName + "/" + entry->d_name);
+            }
+        } else {
+            printf("Unable to open %s, error: %s\n", multifileDirName.c_str(),
+                   std::strerror(errno));
+        }
+    } else {
+        printf("Unable to stat %s, error: %s\n", multifileDirName.c_str(), std::strerror(errno));
+    }
+
+    return cacheEntries;
+}
+
+TEST_F(MultifileBlobCacheTest, CacheContainsStatus) {
+    struct stat info;
+    std::stringstream statusFile;
+    statusFile << &mTempFile->path[0] << ".multifile/" << kMultifileBlobCacheStatusFile;
+
+    // After INIT, cache should have a status
+    ASSERT_TRUE(stat(statusFile.str().c_str(), &info) == 0);
+
+    // Set one entry
+    mMBC->set("abcd", 4, "efgh", 4);
+
+    // Close the cache so everything writes out
+    mMBC->finish();
+    mMBC.reset();
+
+    // Ensure status lives after closing the cache
+    ASSERT_TRUE(stat(statusFile.str().c_str(), &info) == 0);
+
+    // Open the cache again
+    mMBC.reset(new MultifileBlobCache(kMaxKeySize, kMaxValueSize, kMaxTotalSize, kMaxTotalEntries,
+                                      &mTempFile->path[0]));
+
+    // Ensure we still have a status
+    ASSERT_TRUE(stat(statusFile.str().c_str(), &info) == 0);
+}
+
+// Verify missing cache status file causes cache the be cleared
+TEST_F(MultifileBlobCacheTest, MissingCacheStatusClears) {
+    // Set one entry
+    mMBC->set("abcd", 4, "efgh", 4);
+
+    // Close the cache so everything writes out
+    mMBC->finish();
+    mMBC.reset();
+
+    // Ensure there is one cache entry
+    ASSERT_EQ(getCacheEntries().size(), 1);
+
+    // Delete the status file
+    std::stringstream statusFile;
+    statusFile << &mTempFile->path[0] << ".multifile/" << kMultifileBlobCacheStatusFile;
+    remove(statusFile.str().c_str());
+
+    // Open the cache again and ensure no cache hits
+    mMBC.reset(new MultifileBlobCache(kMaxKeySize, kMaxValueSize, kMaxTotalSize, kMaxTotalEntries,
+                                      &mTempFile->path[0]));
+
+    // Ensure we have no entries
+    ASSERT_EQ(getCacheEntries().size(), 0);
+}
+
+// Verify modified cache status file BEGIN causes cache to be cleared
+TEST_F(MultifileBlobCacheTest, ModifiedCacheStatusBeginClears) {
+    // Set one entry
+    mMBC->set("abcd", 4, "efgh", 4);
+
+    // Close the cache so everything writes out
+    mMBC->finish();
+    mMBC.reset();
+
+    // Ensure there is one cache entry
+    ASSERT_EQ(getCacheEntries().size(), 1);
+
+    // Modify the status file
+    std::stringstream statusFile;
+    statusFile << &mTempFile->path[0] << ".multifile/" << kMultifileBlobCacheStatusFile;
+
+    // Stomp on the beginning of the cache file
+    const char* stomp = "BADF00D";
+    std::fstream fs(statusFile.str());
+    fs.seekp(0, std::ios_base::beg);
+    fs.write(stomp, strlen(stomp));
+    fs.flush();
+    fs.close();
+
+    // Open the cache again and ensure no cache hits
+    mMBC.reset(new MultifileBlobCache(kMaxKeySize, kMaxValueSize, kMaxTotalSize, kMaxTotalEntries,
+                                      &mTempFile->path[0]));
+
+    // Ensure we have no entries
+    ASSERT_EQ(getCacheEntries().size(), 0);
+}
+
+// Verify modified cache status file END causes cache to be cleared
+TEST_F(MultifileBlobCacheTest, ModifiedCacheStatusEndClears) {
+    // Set one entry
+    mMBC->set("abcd", 4, "efgh", 4);
+
+    // Close the cache so everything writes out
+    mMBC->finish();
+    mMBC.reset();
+
+    // Ensure there is one cache entry
+    ASSERT_EQ(getCacheEntries().size(), 1);
+
+    // Modify the status file
+    std::stringstream statusFile;
+    statusFile << &mTempFile->path[0] << ".multifile/" << kMultifileBlobCacheStatusFile;
+
+    // Stomp on the END of the cache status file, modifying its contents
+    const char* stomp = "BADF00D";
+    std::fstream fs(statusFile.str());
+    fs.seekp(-strlen(stomp), std::ios_base::end);
+    fs.write(stomp, strlen(stomp));
+    fs.flush();
+    fs.close();
+
+    // Open the cache again and ensure no cache hits
+    mMBC.reset(new MultifileBlobCache(kMaxKeySize, kMaxValueSize, kMaxTotalSize, kMaxTotalEntries,
+                                      &mTempFile->path[0]));
+
+    // Ensure we have no entries
+    ASSERT_EQ(getCacheEntries().size(), 0);
+}
+
+// Verify mismatched cacheVersion causes cache to be cleared
+TEST_F(MultifileBlobCacheTest, MismatchedCacheVersionClears) {
+    // Set one entry
+    mMBC->set("abcd", 4, "efgh", 4);
+
+    // Close the cache so everything writes out
+    mMBC->finish();
+    mMBC.reset();
+
+    // Ensure there is one cache entry
+    ASSERT_EQ(getCacheEntries().size(), 1);
+
+    // Set a debug cacheVersion
+    std::string newCacheVersion = std::to_string(kMultifileBlobCacheVersion + 1);
+    ASSERT_TRUE(base::SetProperty("debug.egl.blobcache.cache_version", newCacheVersion.c_str()));
+    ASSERT_TRUE(
+            base::WaitForProperty("debug.egl.blobcache.cache_version", newCacheVersion.c_str()));
+
+    // Open the cache again and ensure no cache hits
+    mMBC.reset(new MultifileBlobCache(kMaxKeySize, kMaxValueSize, kMaxTotalSize, kMaxTotalEntries,
+                                      &mTempFile->path[0]));
+
+    // Ensure we have no entries
+    ASSERT_EQ(getCacheEntries().size(), 0);
+}
+
+// Verify mismatched buildId causes cache to be cleared
+TEST_F(MultifileBlobCacheTest, MismatchedBuildIdClears) {
+    // Set one entry
+    mMBC->set("abcd", 4, "efgh", 4);
+
+    // Close the cache so everything writes out
+    mMBC->finish();
+    mMBC.reset();
+
+    // Ensure there is one cache entry
+    ASSERT_EQ(getCacheEntries().size(), 1);
+
+    // Set a debug buildId
+    base::SetProperty("debug.egl.blobcache.build_id", "foo");
+    base::WaitForProperty("debug.egl.blobcache.build_id", "foo");
+
+    // Open the cache again and ensure no cache hits
+    mMBC.reset(new MultifileBlobCache(kMaxKeySize, kMaxValueSize, kMaxTotalSize, kMaxTotalEntries,
+                                      &mTempFile->path[0]));
+
+    // Ensure we have no entries
+    ASSERT_EQ(getCacheEntries().size(), 0);
+}
+
 } // namespace android
diff --git a/opengl/tests/EGLTest/egl_cache_test.cpp b/opengl/tests/EGLTest/egl_cache_test.cpp
index f81c68f66e..ce5818229a 100644
--- a/opengl/tests/EGLTest/egl_cache_test.cpp
+++ b/opengl/tests/EGLTest/egl_cache_test.cpp
@@ -114,25 +114,26 @@ std::string EGLCacheTest::getCachefileName() {
     struct stat info;
     if (stat(multifileDirName.c_str(), &info) == 0) {
         // Ensure we only have one file to manage
-        int realFileCount = 0;
+        int entryFileCount = 0;
 
-        // We have a multifile dir. Return the only real file in it.
+        // We have a multifile dir. Return the only entry file in it.
         DIR* dir;
         struct dirent* entry;
         if ((dir = opendir(multifileDirName.c_str())) != nullptr) {
             while ((entry = readdir(dir)) != nullptr) {
-                if (entry->d_name == "."s || entry->d_name == ".."s) {
+                if (entry->d_name == "."s || entry->d_name == ".."s ||
+                    strcmp(entry->d_name, kMultifileBlobCacheStatusFile) == 0) {
                     continue;
                 }
                 cachefileName = multifileDirName + "/" + entry->d_name;
-                realFileCount++;
+                entryFileCount++;
             }
         } else {
             printf("Unable to open %s, error: %s\n",
                    multifileDirName.c_str(), std::strerror(errno));
         }
 
-        if (realFileCount != 1) {
+        if (entryFileCount != 1) {
             // If there was more than one real file in the directory, this
             // violates test assumptions
             cachefileName = "";