On Wed, 5 Jan 2022 17:42:49 +0000
Soumya Muralidhar <soumya.muralid...@gigamon.com> wrote:
> Hi Stephen,
>
> Thanks for getting back. But I am looking at storing logs with timestamps in
> a file, basically something similar to syslog. Could you help me with that ?
>
> Regards,
> Soumya
>
> On 1/5/22, 8:17 AM, "Stephen Hemminger" <step...@networkplumber.org> wrote:
>
> WARNING: This email originated from outside of Gigamon. Use caution with
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>
>
> Your message is garbaled with lots of bogus URL's. Please avoid HTML mail
> or weird links.
>
> I use this. There was a more general version submitted as a patch to
> DPDK but no one seemed interested. The reason for redirecting stdout
> is that are libraries we use that print to stdout and want to get
> timestamps
> from them if debugging startup issues.
>
>
> /*
> * Sample of redirecting DPDK log stream.
> *
> * If program is run for debugging then stdout will be a console and
> * put messages onto console stream with timestamps. Otherwise, just
> * put message onto stderr which systemd journal handles. No need for
> * syslog because that causes duplicate messages.
> */
>
> static struct timespec log_t0; /* Start program in monotonic time */
>
> /*
> * Write message to standard output with timestamp.
> * Use writev() so that timestamp and message do not get interleaved.
> */
> static ssize_t
> dpdk_log_tty_write(__rte_unused void *ctx, const char *buf, size_t size)
> {
> struct timespec ts;
> struct iovec iov[2];
> char tbuf[64];
>
> /* format up monotonic timestamp */
> clock_gettime(CLOCK_MONOTONIC, &ts);
>
> ts.tv_sec -= log_t0.tv_sec;
> ts.tv_nsec -= log_t0.tv_nsec;
> if (ts.tv_nsec < 0) {
> --ts.tv_sec;
> ts.tv_nsec += NS_PER_S;
> }
>
> iov[0].iov_base = tbuf;
> iov[0].iov_len = snprintf(tbuf, sizeof(tbuf), "[%8lu.%06lu] ",
> ts.tv_sec, ts.tv_nsec / 1000u);
>
> /* extra cast is workaround to remove const qualifier */
> iov[1].iov_base = (void *)(uintptr_t)buf;
> iov[1].iov_len = size;
>
> return writev(STDOUT_FILENO, iov, 2);
> }
>
> static cookie_io_functions_t dpdk_log_tty_func = {
> .write = dpdk_log_tty_write,
> };
>
> /*
> * Print message to stderr with priority format so that
> * Systemd journal can handle it. Alternative would be
> * to use syslog or use sd_journal; but less is more.
> */
> static ssize_t
> dpdk_log_write(__rte_unused void *ctx, const char *buf, size_t size)
> {
> /* Syslog error levels are from 0 to 7, DPDK uses 1 to 8 */
> int priority = rte_log_cur_msg_loglevel() - 1;
>
> fprintf(stderr, "<%i>%.*s\n", priority, (int)size, buf);
> return size;
> }
>
> static cookie_io_functions_t dpdk_log_func = {
> .write = dpdk_log_write,
> };
>
> /*
> * Override default DPDK logging which duplicates messages
> * to both stderr and syslog.
> */
> static void log_init(void)
> {
> backplane_logtype = rte_log_register("backplane");
> if (backplane_logtype >= 0)
> rte_log_set_level(backplane_logtype, RTE_LOG_INFO);
>
> if (isatty(STDOUT_FILENO)) {
> clock_gettime(CLOCK_MONOTONIC, &log_t0);
>
> stdout = fopencookie(NULL, "w+", dpdk_log_tty_func);
> setlinebuf(stdout);
> rte_openlog_stream(stdout);
> } else {
> FILE *jf;
>
> jf = fopencookie(NULL, "w+", dpdk_log_func);
> rte_openlog_stream(jf);
> }
> }
>
> /* Put DPDK log back onto stderr */
> static void log_uninit(void)
> {
> FILE *logf;
>
> logf = rte_log_get_stream();
> if (logf != stderr) {
> rte_openlog_stream(stderr);
> fclose(logf);
> }
> }
>
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Just use my example and make code like dpdk_tty_log_write that does writev to
your file.
