Implement proposed k8s-stream-file format

Instead of parsing the contents of the data read from the `stdout` and
`stderr` pipes, this commit adds support for a "stream" format, named
`k8s-stream-file`, which just records what is read from a pipe to disk.

It significantly saves on CPU spend processing the buffer read, uses only
2 I/O vectors, and never touches the memory read from the pipe.

This is an updated implementation of
cri-o/cri-o#1605.

src/ctr_logging.c

@@ -24,9 +24,11 @@ static inline int sd_journal_sendv(G_GNUC_UNUSED const struct iovec *iov, G_GNUC
 /* Different types of container logging */
 static gboolean use_journald_logging = FALSE;
 static gboolean use_k8s_logging = FALSE;
+static gboolean use_k8s_stream_logging = FALSE;
 
 /* Value the user must input for each log driver */
 static const char *const K8S_FILE_STRING = "k8s-file";
+static const char *const K8S_STREAM_FILE_STRING = "k8s-stream-file";
 static const char *const JOURNALD_FILE_STRING = "journald";
 
 /* Max log size for any log file types */
@@ -64,6 +66,7 @@ static void parse_log_path(char *log_config);
 static const char *stdpipe_name(stdpipe_t pipe);
 static int write_journald(int pipe, char *buf, ssize_t num_read);
 static int write_k8s_log(stdpipe_t pipe, const char *buf, ssize_t buflen);
+static int write_k8s_stream_log(stdpipe_t pipe, const char *buf, ssize_t buflen);
 static bool get_line_len(ptrdiff_t *line_len, const char *buf, ssize_t buflen);
 static ssize_t writev_buffer_append_segment(int fd, writev_buffer_t *buf, const void *data, ssize_t len);
 static ssize_t writev_buffer_flush(int fd, writev_buffer_t *buf);
@@ -134,9 +137,10 @@ void configure_log_drivers(gchar **log_drivers, int64_t log_size_max_, char *cuu
  * parse_log_path branches on log driver type the user inputted.
  * log_config will either be a ':' delimited string containing:
  * <DRIVER_NAME>:<PATH_NAME> or <PATH_NAME>
- * in the case of no colon, the driver will be kubernetes-log-file,
+ * in the case the log driver is 'k8s-stream-file', the <PATH_NAME> must be present.
+ * in the case of no colon, the driver will be k8s-file,
  * in the case the log driver is 'journald', the <PATH_NAME> is ignored.
- * exits with error if <DRIVER_NAME> isn't 'journald' or 'kubernetes-log-file'
+ * exits with error if <DRIVER_NAME> isn't 'journald', 'k8s-file', or 'k8s-stream-file'.
  */
 static void parse_log_path(char *log_config)
 {
@@ -165,6 +169,17 @@ static void parse_log_path(char *log_config)
 		return;
 	}
 
+	// Driver is k8s-file, k8s-stream-file, or empty
+	if (!strcmp(driver, K8S_STREAM_FILE_STRING)) {
+		if (path == NULL) {
+			nexitf("k8s-stream-file requires a filename");
+		}
+		use_k8s_logging = TRUE;
+		use_k8s_stream_logging = TRUE;
+		k8s_log_path = path;
+		return;
+	}
+
 	// Driver is k8s-file or empty
 	if (!strcmp(driver, K8S_FILE_STRING)) {
 		if (path == NULL) {
@@ -188,9 +203,18 @@ static void parse_log_path(char *log_config)
 /* write container output to all logs the user defined */
 bool write_to_logs(stdpipe_t pipe, char *buf, ssize_t num_read)
 {
-	if (use_k8s_logging && write_k8s_log(pipe, buf, num_read) < 0) {
-		nwarn("write_k8s_log failed");
-		return G_SOURCE_CONTINUE;
+	if (use_k8s_logging) {
+		if (use_k8s_stream_logging) {
+			if (write_k8s_log(pipe, buf, num_read) < 0) {
+				nwarn("write_k8s_log failed");
+				return G_SOURCE_CONTINUE;
+			}
+		} else {
+			if (write_k8s_stream_log(pipe, buf, num_read) < 0) {
+				nwarn("write_k8s_stream_log failed");
+				return G_SOURCE_CONTINUE;
+			}
+		}
 	}
 	if (use_journald_logging && write_journald(pipe, buf, num_read) < 0) {
 		nwarn("write_journald failed");
@@ -540,3 +564,110 @@ void sync_logs(void)
 		if (fsync(k8s_log_fd) < 0)
 			pwarn("Failed to sync log file before exit");
 }
+
+
+/* strlen("1997-03-25T13:20:42.999999999+01:00 stdout 9999999999 999999999 ") + 1 */
+#define TSSTREAMBUFLEN 128
+
+/*
+ * PROPOSED: CRI Stream Format, variable length file format
+ */
+static int set_k8s_stream_timestamp(char *buf, ssize_t bufsiz, ssize_t *tsbuflen, const char *pipename, uint64_t offset, ssize_t buflen,
+				    ssize_t *btbw)
+{
+	char off_sign = '+';
+	int off, len, err = -1;
+
+	struct timespec ts;
+	if (clock_gettime(CLOCK_REALTIME, &ts) < 0) {
+		/* If CLOCK_REALTIME is not supported, we set nano seconds to 0 */
+		if (errno == EINVAL) {
+			ts.tv_nsec = 0;
+		} else {
+			return err;
+		}
+	}
+
+	struct tm current_tm;
+	if (localtime_r(&ts.tv_sec, &current_tm) == NULL)
+		return err;
+
+	off = (int)current_tm.tm_gmtoff;
+	if (current_tm.tm_gmtoff < 0) {
+		off_sign = '-';
+		off = -off;
+	}
+
+	len = snprintf(buf, bufsiz, "%d-%02d-%02dT%02d:%02d:%02d.%09ld%c%02d:%02d %s %lud %ld ", current_tm.tm_year + 1900,
+		       current_tm.tm_mon + 1, current_tm.tm_mday, current_tm.tm_hour, current_tm.tm_min, current_tm.tm_sec, ts.tv_nsec,
+		       off_sign, off / 3600, off % 3600, pipename, offset, buflen);
+
+	if (len < bufsiz)
+		err = 0;
+
+	*tsbuflen = len;
+	*btbw = len + buflen;
+	return err;
+}
+
+
+/*
+ * PROPOSED: CRI Stream Format, variable length file format
+ *
+ * %d-%02d-%02dT%02d:%02d:%02d.%09ld%c%02d:%02d %(stream)s %(offset)lud %(buflen)ld %(buf)s
+ *
+ * The CRI stream fromat requires us to write each buffer read with a
+ * timestamp, stream, length (human readable ascii), and the buffer contents
+ * read (with a space character separating the buffer length string from the
+ * buffer.
+ */
+static int write_k8s_stream_log(stdpipe_t pipe, const char *buf, ssize_t buflen)
+{
+	writev_buffer_t bufv = {0};
+	char tsbuf[TSSTREAMBUFLEN];
+	static ssize_t bytes_written = 0;
+	static uint64_t offset = 0;
+	ssize_t bytes_to_be_written = 0;
+	ssize_t tsbuflen = 0;
+
+	/*
+	 * Use the same timestamp for every line of the log in this buffer.
+	 * There is no practical difference in the output since write(2) is
+	 * fast.
+	 */
+	if (set_k8s_stream_timestamp(tsbuf, sizeof tsbuf, &tsbuflen, stdpipe_name(pipe), buflen, offset, &bytes_to_be_written))
+		/* TODO: We should handle failures much more cleanly than this. */
+		return -1;
+
+	/*
+	 * We re-open the log file if writing out the bytes will exceed the max
+	 * log size. We also reset the state so that the new file is started with
+	 * a timestamp.
+	 */
+	if ((opt_log_size_max > 0) && (bytes_written + bytes_to_be_written) > opt_log_size_max) {
+		bytes_written = 0;
+
+		reopen_k8s_file();
+	}
+
+	/* Output the timestamp, stream, and length */
+	if (writev_buffer_append_segment(k8s_log_fd, &bufv, tsbuf, tsbuflen) < 0) {
+		nwarn("failed to write (timestamp, stream) to log");
+		goto stream_next;
+	}
+
+	/* Output the actual contents. */
+	if (writev_buffer_append_segment(k8s_log_fd, &bufv, buf, buflen) < 0) {
+		nwarn("failed to write buffer to log");
+	}
+
+stream_next:
+	bytes_written += bytes_to_be_written;
+	offset += (uint64_t)bytes_to_be_written;
+
+	if (writev_buffer_flush(k8s_log_fd, &bufv) < 0) {
+		nwarn("failed to flush buffer to log");
+	}
+
+	return 0;
+}