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lws_retry: use base ms number and set jitter percentage

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This commit is contained in:
Andy Green 2019-08-20 04:49:30 +01:00
parent 0fa5563d18
commit 61b5a37a3a
2 changed files with 20 additions and 24 deletions
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23
include/libwebsockets/lws-retry.h
View file

@ -22,28 +22,18 @@
* IN THE SOFTWARE.
*/
/*
* Specifies backoff ranges using a pair of uint32_t in ms for the min, max.
*
* The actual backoff timing is picked randomly within the range.
*/
typedef struct lws_retry_range {
uint32_t min_ms;
uint32_t max_ms;
} lws_retry_range_t;
typedef struct lws_retry_bo {
const lws_retry_range_t *retry_ms_table; /* backoff range pair */
uint16_t retry_ms_table_count; /* ranges in table */
const uint32_t *retry_ms_table; /* base delay in ms */
uint16_t retry_ms_table_count; /* entries in table */
uint16_t conceal_count; /* max retries to conceal */
uint8_t jitter_percent; /* % additional random jitter */
} lws_retry_bo_t;
/**
* lws_retry_get_delay_ms() - get next delay from backoff table
*
* \param lws_context: the lws context (used for getting random)
* \param retry: the retry backoff table we are using
* \param retry: the retry backoff table we are using, or NULL for default
* \param ctry: pointer to the try counter
* \param conceal: pointer to flag set to nonzero if the try should be concealed
* in terms of creating an error
@ -53,9 +43,12 @@ typedef struct lws_retry_bo {
* set if the number of tries is less than the backoff table conceal_count, or
* is zero if it exceeded it. This lets you conceal a certain number of retries
* before alerting the caller there is a problem.
*
* If \p retry is NULL, a default of 3s + (0..300ms jitter) is used. If it's
* non-NULL but jitter_percent is 0, the default of 30% jitter is retained.
*/
LWS_VISIBLE LWS_EXTERN unsigned int
lws_retry_get_delay_ms(struct lws_context *context, const lws_retry_bo_t *retry,
uint16_t *ctry, char *conceal);
uint16_t *ctry, char *conceal);

21
lib/core-net/network.c
View file

@ -383,14 +383,12 @@ lws_socket_bind(struct lws_vhost *vhost, lws_sockfd_type sockfd, int port,
return port;
}
static const lws_retry_range_t default_bo = { 3000, 7000 };
unsigned int
lws_retry_get_delay_ms(struct lws_context *context,
const lws_retry_bo_t *retry, uint16_t *ctry, char *conceal)
const lws_retry_bo_t *retry, uint16_t *ctry,
char *conceal)
{
const lws_retry_range_t *r = &default_bo;
unsigned int ms;
uint64_t ms = 3000, pc = 30; /* sane-ish defaults if no retry table */
uint16_t ra;
if (conceal)
@ -398,15 +396,20 @@ lws_retry_get_delay_ms(struct lws_context *context,
if (retry) {
if (*ctry < retry->retry_ms_table_count)
r = &retry->retry_ms_table[*ctry];
ms = retry->retry_ms_table[*ctry];
else
r = &retry->retry_ms_table[
ms = retry->retry_ms_table[
retry->retry_ms_table_count - 1];
/* if no percent given, use the default 30% */
if (retry->jitter_percent)
pc = retry->jitter_percent;
}
ms = r->min_ms;
if (lws_get_random(context, &ra, sizeof(ra)) == sizeof(ra))
ms += ((r->max_ms - ms) * ra) / 65535;
ms += ((ms * pc * ra) >> 16) / 100;
else
assert(0);
if (*ctry < 0xffff)
(*ctry)++;