On Fri, Oct 6, 2017 at 8:44 PM, Ben Pfaff <[email protected]> wrote:
> The implementation cycles through the remotes in random order. This allows
> clients to perform some load balancing across alternative implementations
> of a service.
>
> Signed-off-by: Ben Pfaff <[email protected]>
> ---
> lib/jsonrpc.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++-----
> lib/jsonrpc.h | 6 +++++-
> lib/svec.c | 18 ++++++++++++++++++
> lib/svec.h | 1 +
> 4 files changed, 72 insertions(+), 6 deletions(-)
> diff --git a/lib/svec.c b/lib/svec.c
> index 297a60ce14f9..c1b986bab108 100644
> --- a/lib/svec.c
> +++ b/lib/svec.c
> @@ -20,6 +20,7 @@
> #include <stdlib.h>
> #include <string.h>
> #include "openvswitch/dynamic-string.h"
> +#include "random.h"
> #include "util.h"
> #include "openvswitch/vlog.h"
>
> @@ -174,6 +175,23 @@ svec_compact(struct svec *svec)
> svec->n = j;
> }
>
> +static void
> +swap_strings(char **a, char **b)
> +{
> + char *tmp = *a;
> + *a = *b;
> + *b = tmp;
> +}
> +
> +void
> +svec_shuffle(struct svec *svec)
> +{
> + for (size_t i = 0; i < svec->n; i++) {
> + size_t j = i + random_range(svec->n - i);
> + swap_strings(&svec->names[i], &svec->names[j]);
> + }
> +}
> +
I'm not sure this is as random as we'd like.
Even if there are 10 elements, the first element has a 50% chance of
staying there, since it's only considered for a swap when i == 0.
That extends to the general behavior that the closer an element is to
the beginning, the better chance it has of staying near the beginning.
Or am I reading it wrong?
Thanks,
--
Russell Bryant
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