/* cache.c: cache management
*
- * Copyright (C) 2006 Lars Hjemli
+ * Copyright (C) 2006-2014 cgit Development Team <cgit@lists.zx2c4.com>
*
* Licensed under GNU General Public License v2
* (see COPYING for full license text)
+ *
+ *
+ * The cache is just a directory structure where each file is a cache slot,
+ * and each filename is based on the hash of some key (e.g. the cgit url).
+ * Each file contains the full key followed by the cached content for that
+ * key.
+ *
*/
#include "cgit.h"
+#include "cache.h"
+#include "html.h"
+#ifdef HAVE_LINUX_SENDFILE
+#include <sys/sendfile.h>
+#endif
-const int NOLOCK = -1;
+#define CACHE_BUFSIZE (1024 * 4)
-char *cache_safe_filename(const char *unsafe)
+struct cache_slot {
+ const char *key;
+ size_t keylen;
+ int ttl;
+ cache_fill_fn fn;
+ int cache_fd;
+ int lock_fd;
+ int stdout_fd;
+ const char *cache_name;
+ const char *lock_name;
+ int match;
+ struct stat cache_st;
+ int bufsize;
+ char buf[CACHE_BUFSIZE];
+};
+
+/* Open an existing cache slot and fill the cache buffer with
+ * (part of) the content of the cache file. Return 0 on success
+ * and errno otherwise.
+ */
+static int open_slot(struct cache_slot *slot)
{
- static char buf[PATH_MAX];
- char *s = buf;
- char c;
-
- while(unsafe && (c = *unsafe++) != 0) {
- if (c == '/' || c == ' ' || c == '&' || c == '|' ||
- c == '>' || c == '<' || c == '.')
- c = '_';
- *s++ = c;
- }
- *s = '\0';
- return buf;
+ char *bufz;
+ ssize_t bufkeylen = -1;
+
+ slot->cache_fd = open(slot->cache_name, O_RDONLY);
+ if (slot->cache_fd == -1)
+ return errno;
+
+ if (fstat(slot->cache_fd, &slot->cache_st))
+ return errno;
+
+ slot->bufsize = xread(slot->cache_fd, slot->buf, sizeof(slot->buf));
+ if (slot->bufsize < 0)
+ return errno;
+
+ bufz = memchr(slot->buf, 0, slot->bufsize);
+ if (bufz)
+ bufkeylen = bufz - slot->buf;
+
+ if (slot->key)
+ slot->match = bufkeylen == slot->keylen &&
+ !memcmp(slot->key, slot->buf, bufkeylen + 1);
+
+ return 0;
}
-int cache_exist(struct cacheitem *item)
+/* Close the active cache slot */
+static int close_slot(struct cache_slot *slot)
{
- if (stat(item->name, &item->st)) {
- item->st.st_mtime = 0;
- return 0;
+ int err = 0;
+ if (slot->cache_fd > 0) {
+ if (close(slot->cache_fd))
+ err = errno;
+ else
+ slot->cache_fd = -1;
}
- return 1;
+ return err;
}
-int cache_create_dirs()
+/* Print the content of the active cache slot (but skip the key). */
+static int print_slot(struct cache_slot *slot)
{
- char *path;
+#ifdef HAVE_LINUX_SENDFILE
+ off_t start_off;
+ int ret;
- path = fmt("%s", cgit_cache_root);
- if (mkdir(path, S_IRWXU) && errno!=EEXIST)
- return 0;
+ start_off = slot->keylen + 1;
- if (!cgit_repo)
+ do {
+ ret = sendfile(STDOUT_FILENO, slot->cache_fd, &start_off,
+ slot->cache_st.st_size - start_off);
+ if (ret < 0) {
+ if (errno == EAGAIN || errno == EINTR)
+ continue;
+ return errno;
+ }
return 0;
+ } while (1);
+#else
+ ssize_t i, j;
+
+ i = lseek(slot->cache_fd, slot->keylen + 1, SEEK_SET);
+ if (i != slot->keylen + 1)
+ return errno;
- path = fmt("%s/%s", cgit_cache_root,
- cache_safe_filename(cgit_repo->url));
+ do {
+ i = j = xread(slot->cache_fd, slot->buf, sizeof(slot->buf));
+ if (i > 0)
+ j = xwrite(STDOUT_FILENO, slot->buf, i);
+ } while (i > 0 && j == i);
- if (mkdir(path, S_IRWXU) && errno!=EEXIST)
+ if (i < 0 || j != i)
+ return errno;
+ else
return 0;
+#endif
+}
- if (cgit_query_page) {
- path = fmt("%s/%s/%s", cgit_cache_root,
- cache_safe_filename(cgit_repo->url),
- cgit_query_page);
- if (mkdir(path, S_IRWXU) && errno!=EEXIST)
- return 0;
- }
- return 1;
+/* Check if the slot has expired */
+static int is_expired(struct cache_slot *slot)
+{
+ if (slot->ttl < 0)
+ return 0;
+ else
+ return slot->cache_st.st_mtime + slot->ttl * 60 < time(NULL);
}
-int cache_refill_overdue(const char *lockfile)
+/* Check if the slot has been modified since we opened it.
+ * NB: If stat() fails, we pretend the file is modified.
+ */
+static int is_modified(struct cache_slot *slot)
{
struct stat st;
- if (stat(lockfile, &st))
- return 0;
+ if (stat(slot->cache_name, &st))
+ return 1;
+ return (st.st_ino != slot->cache_st.st_ino ||
+ st.st_mtime != slot->cache_st.st_mtime ||
+ st.st_size != slot->cache_st.st_size);
+}
+
+/* Close an open lockfile */
+static int close_lock(struct cache_slot *slot)
+{
+ int err = 0;
+ if (slot->lock_fd > 0) {
+ if (close(slot->lock_fd))
+ err = errno;
+ else
+ slot->lock_fd = -1;
+ }
+ return err;
+}
+
+/* Create a lockfile used to store the generated content for a cache
+ * slot, and write the slot key + \0 into it.
+ * Returns 0 on success and errno otherwise.
+ */
+static int lock_slot(struct cache_slot *slot)
+{
+ struct flock lock = {
+ .l_type = F_WRLCK,
+ .l_whence = SEEK_SET,
+ .l_start = 0,
+ .l_len = 0,
+ };
+
+ slot->lock_fd = open(slot->lock_name, O_RDWR | O_CREAT,
+ S_IRUSR | S_IWUSR);
+ if (slot->lock_fd == -1)
+ return errno;
+ if (fcntl(slot->lock_fd, F_SETLK, &lock) < 0) {
+ int saved_errno = errno;
+ close(slot->lock_fd);
+ slot->lock_fd = -1;
+ return saved_errno;
+ }
+ if (xwrite(slot->lock_fd, slot->key, slot->keylen + 1) < 0)
+ return errno;
+ return 0;
+}
+
+/* Release the current lockfile. If `replace_old_slot` is set the
+ * lockfile replaces the old cache slot, otherwise the lockfile is
+ * just deleted.
+ */
+static int unlock_slot(struct cache_slot *slot, int replace_old_slot)
+{
+ int err;
+
+ if (replace_old_slot)
+ err = rename(slot->lock_name, slot->cache_name);
else
- return (time(NULL) - st.st_mtime > cgit_cache_max_create_time);
+ err = unlink(slot->lock_name);
+
+ /* Restore stdout and close the temporary FD. */
+ if (slot->stdout_fd >= 0) {
+ dup2(slot->stdout_fd, STDOUT_FILENO);
+ close(slot->stdout_fd);
+ slot->stdout_fd = -1;
+ }
+
+ if (err)
+ return errno;
+
+ return 0;
}
-int cache_lock(struct cacheitem *item)
+/* Generate the content for the current cache slot by redirecting
+ * stdout to the lock-fd and invoking the callback function
+ */
+static int fill_slot(struct cache_slot *slot)
{
- int i = 0;
- char *lockfile = xstrdup(fmt("%s.lock", item->name));
+ /* Preserve stdout */
+ slot->stdout_fd = dup(STDOUT_FILENO);
+ if (slot->stdout_fd == -1)
+ return errno;
- top:
- if (++i > cgit_max_lock_attempts)
- die("cache_lock: unable to lock %s: %s",
- item->name, strerror(errno));
+ /* Redirect stdout to lockfile */
+ if (dup2(slot->lock_fd, STDOUT_FILENO) == -1)
+ return errno;
- item->fd = open(lockfile, O_WRONLY|O_CREAT|O_EXCL, S_IRUSR|S_IWUSR);
+ /* Generate cache content */
+ slot->fn();
- if (item->fd == NOLOCK && errno == ENOENT && cache_create_dirs())
- goto top;
+ /* Make sure any buffered data is flushed to the file */
+ if (fflush(stdout))
+ return errno;
- if (item->fd == NOLOCK && errno == EEXIST &&
- cache_refill_overdue(lockfile) && !unlink(lockfile))
- goto top;
+ /* update stat info */
+ if (fstat(slot->lock_fd, &slot->cache_st))
+ return errno;
- free(lockfile);
- return (item->fd > 0);
+ return 0;
}
-int cache_unlock(struct cacheitem *item)
+/* Crude implementation of 32-bit FNV-1 hash algorithm,
+ * see http://www.isthe.com/chongo/tech/comp/fnv/ for details
+ * about the magic numbers.
+ */
+#define FNV_OFFSET 0x811c9dc5
+#define FNV_PRIME 0x01000193
+
+unsigned long hash_str(const char *str)
{
- close(item->fd);
- return (rename(fmt("%s.lock", item->name), item->name) == 0);
+ unsigned long h = FNV_OFFSET;
+ unsigned char *s = (unsigned char *)str;
+
+ if (!s)
+ return h;
+
+ while (*s) {
+ h *= FNV_PRIME;
+ h ^= *s++;
+ }
+ return h;
}
-int cache_cancel_lock(struct cacheitem *item)
+static int process_slot(struct cache_slot *slot)
{
- return (unlink(fmt("%s.lock", item->name)) == 0);
+ int err;
+
+ err = open_slot(slot);
+ if (!err && slot->match) {
+ if (is_expired(slot)) {
+ if (!lock_slot(slot)) {
+ /* If the cachefile has been replaced between
+ * `open_slot` and `lock_slot`, we'll just
+ * serve the stale content from the original
+ * cachefile. This way we avoid pruning the
+ * newly generated slot. The same code-path
+ * is chosen if fill_slot() fails for some
+ * reason.
+ *
+ * TODO? check if the new slot contains the
+ * same key as the old one, since we would
+ * prefer to serve the newest content.
+ * This will require us to open yet another
+ * file-descriptor and read and compare the
+ * key from the new file, so for now we're
+ * lazy and just ignore the new file.
+ */
+ if (is_modified(slot) || fill_slot(slot)) {
+ unlock_slot(slot, 0);
+ close_lock(slot);
+ } else {
+ close_slot(slot);
+ unlock_slot(slot, 1);
+ slot->cache_fd = slot->lock_fd;
+ }
+ }
+ }
+ if ((err = print_slot(slot)) != 0) {
+ cache_log("[cgit] error printing cache %s: %s (%d)\n",
+ slot->cache_name,
+ strerror(err),
+ err);
+ }
+ close_slot(slot);
+ return err;
+ }
+
+ /* If the cache slot does not exist (or its key doesn't match the
+ * current key), lets try to create a new cache slot for this
+ * request. If this fails (for whatever reason), lets just generate
+ * the content without caching it and fool the caller to believe
+ * everything worked out (but print a warning on stdout).
+ */
+
+ close_slot(slot);
+ if ((err = lock_slot(slot)) != 0) {
+ cache_log("[cgit] Unable to lock slot %s: %s (%d)\n",
+ slot->lock_name, strerror(err), err);
+ slot->fn();
+ return 0;
+ }
+
+ if ((err = fill_slot(slot)) != 0) {
+ cache_log("[cgit] Unable to fill slot %s: %s (%d)\n",
+ slot->lock_name, strerror(err), err);
+ unlock_slot(slot, 0);
+ close_lock(slot);
+ slot->fn();
+ return 0;
+ }
+ // We've got a valid cache slot in the lock file, which
+ // is about to replace the old cache slot. But if we
+ // release the lockfile and then try to open the new cache
+ // slot, we might get a race condition with a concurrent
+ // writer for the same cache slot (with a different key).
+ // Lets avoid such a race by just printing the content of
+ // the lock file.
+ slot->cache_fd = slot->lock_fd;
+ unlock_slot(slot, 1);
+ if ((err = print_slot(slot)) != 0) {
+ cache_log("[cgit] error printing cache %s: %s (%d)\n",
+ slot->cache_name,
+ strerror(err),
+ err);
+ }
+ close_slot(slot);
+ return err;
}
-int cache_expired(struct cacheitem *item)
+/* Print cached content to stdout, generate the content if necessary. */
+int cache_process(int size, const char *path, const char *key, int ttl,
+ cache_fill_fn fn)
{
- if (item->ttl < 0)
+ unsigned long hash;
+ int i;
+ struct strbuf filename = STRBUF_INIT;
+ struct strbuf lockname = STRBUF_INIT;
+ struct cache_slot slot;
+ int result;
+
+ /* If the cache is disabled, just generate the content */
+ if (size <= 0 || ttl == 0) {
+ fn();
+ return 0;
+ }
+
+ /* Verify input, calculate filenames */
+ if (!path) {
+ cache_log("[cgit] Cache path not specified, caching is disabled\n");
+ fn();
return 0;
- return item->st.st_mtime + item->ttl * 60 < time(NULL);
+ }
+ if (!key)
+ key = "";
+ hash = hash_str(key) % size;
+ strbuf_addstr(&filename, path);
+ strbuf_ensure_end(&filename, '/');
+ for (i = 0; i < 8; i++) {
+ strbuf_addf(&filename, "%x", (unsigned char)(hash & 0xf));
+ hash >>= 4;
+ }
+ strbuf_addbuf(&lockname, &filename);
+ strbuf_addstr(&lockname, ".lock");
+ slot.fn = fn;
+ slot.ttl = ttl;
+ slot.stdout_fd = -1;
+ slot.cache_name = filename.buf;
+ slot.lock_name = lockname.buf;
+ slot.key = key;
+ slot.keylen = strlen(key);
+ result = process_slot(&slot);
+
+ strbuf_release(&filename);
+ strbuf_release(&lockname);
+ return result;
+}
+
+/* Return a strftime formatted date/time
+ * NB: the result from this function is to shared memory
+ */
+static char *sprintftime(const char *format, time_t time)
+{
+ static char buf[64];
+ struct tm *tm;
+
+ if (!time)
+ return NULL;
+ tm = gmtime(&time);
+ strftime(buf, sizeof(buf)-1, format, tm);
+ return buf;
+}
+
+int cache_ls(const char *path)
+{
+ DIR *dir;
+ struct dirent *ent;
+ int err = 0;
+ struct cache_slot slot = { NULL };
+ struct strbuf fullname = STRBUF_INIT;
+ size_t prefixlen;
+
+ if (!path) {
+ cache_log("[cgit] cache path not specified\n");
+ return -1;
+ }
+ dir = opendir(path);
+ if (!dir) {
+ err = errno;
+ cache_log("[cgit] unable to open path %s: %s (%d)\n",
+ path, strerror(err), err);
+ return err;
+ }
+ strbuf_addstr(&fullname, path);
+ strbuf_ensure_end(&fullname, '/');
+ prefixlen = fullname.len;
+ while ((ent = readdir(dir)) != NULL) {
+ if (strlen(ent->d_name) != 8)
+ continue;
+ strbuf_setlen(&fullname, prefixlen);
+ strbuf_addstr(&fullname, ent->d_name);
+ slot.cache_name = fullname.buf;
+ if ((err = open_slot(&slot)) != 0) {
+ cache_log("[cgit] unable to open path %s: %s (%d)\n",
+ fullname.buf, strerror(err), err);
+ continue;
+ }
+ htmlf("%s %s %10"PRIuMAX" %s\n",
+ fullname.buf,
+ sprintftime("%Y-%m-%d %H:%M:%S",
+ slot.cache_st.st_mtime),
+ (uintmax_t)slot.cache_st.st_size,
+ slot.buf);
+ close_slot(&slot);
+ }
+ closedir(dir);
+ strbuf_release(&fullname);
+ return 0;
}
+
+/* Print a message to stdout */
+void cache_log(const char *format, ...)
+{
+ va_list args;
+ va_start(args, format);
+ vfprintf(stderr, format, args);
+ va_end(args);
+}
+
git.ckatri.com / cgit.git / blobdiff