[Libguestfs] [PATCH libnbd 2/2] interop: Retry TCP connections to qemu-nbd.

The test interop-qemu-nbd-tls-certs frequently fails on slow (32 bit) machines in Fedora Koji. (Is crypto slow on these already overloaded machines?) As we cannot wait for a signal when qemu-nbd is ready start serving, we have to use a sleep. The current sleep is 5 seconds, which is not long enough. Making the sleep longer would work but is inconsiderate for people using faster machines. Therefore replace this with a retry loop with exponential backoff. I tested this with a simple wrapper around qemu-nbd which did: sleep 5; exec /usr/bin/qemu-nbd "$@" --- interop/interop.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/interop/interop.c b/interop/interop.c index 662d871..a3ab39b 100644 --- a/interop/interop.c +++ b/interop/interop.c @@ -28,6 +28,7 @@ #include <fcntl.h> #include <time.h> #include <signal.h> +#include <errno.h> #include <sys/types.h> #include <libnbd.h> @@ -44,6 +45,7 @@ main (int argc, char *argv[]) int port; char port_str[16]; pid_t pid = -1; + int retry; #endif int64_t actual_size; char buf[512]; @@ -114,14 +116,19 @@ main (int argc, char *argv[]) } /* Unfortunately there's no good way to wait for qemu-nbd to start - * serving, so ... + * serving, so we need to retry here. */ - sleep (5); - - if (nbd_connect_tcp (nbd, "localhost", port_str) == -1) { - fprintf (stderr, "%s\n", nbd_get_error ()); - goto out; + for (retry = 0; retry < 5; ++retry) { + sleep (1 << retry); + if (nbd_connect_tcp (nbd, "localhost", port_str) == -1) { + fprintf (stderr, "%s\n", nbd_get_error ()); + if (nbd_get_errno () != ECONNREFUSED) + goto out; + } + else break; } + if (retry == 5) + goto out; #else /* !SERVE_OVER_TCP */ -- 2.23.0