Re: Add timestamp to dpdk.log

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed, 5 Jan 2022 17:42:49 +0000
Soumya Muralidhar <soumya.muralidhar@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" <stephen@networkplumber.org> wrote:
> 
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> 
> 
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>     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.