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fixed exponential backoff bug 

svn path=/trunk/boinc/; revision=1279
This commit is contained in:
Karl Chen 2003-06-03 17:39:27 +00:00
parent 83106847f6
commit 7b1e97f765
1 changed files with 24 additions and 5 deletions
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29
client/pers_file_xfer.C
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@ -262,12 +262,31 @@ void PERS_FILE_XFER::handle_xfer_failure() {
}
}
// return a random number in the range [0,1)
static inline double rand_fraction()
{
// rand() / RAND_MAX is not always reliable
static const int MODULUS = 1357;
return double(rand() % MODULUS) / double(MODULUS);
}
// return a random integer in the range [min,max)
static inline double rand_range(int min, int max)
{
return rand_fraction() * (max-min) + min
}
// return a random integer in the range [max(MIN,e^n),min(MAX,e^n))
static inline int calculate_exponential_backoff(MIN, MAX, int n)
{
double e = exp(n);
return rand_range(max(MIN, e), min(MAX, e));
}
// Cycle to the next URL, or if we've hit all URLs in this cycle,
// backoff and try again later
//
void PERS_FILE_XFER::retry_or_backoff() {
double exp_backoff;
int backoff;
struct tm *newtime;
time_t now;
char buf[256];
@ -284,14 +303,14 @@ void PERS_FILE_XFER::retry_or_backoff() {
//
if (fip->current_url == fip->start_url) {
nretry++;
exp_backoff = exp(((double)rand()/(double)RAND_MAX)*nretry);
// Do an exponential backoff of e^nretry seconds,
// keeping within the bounds of PERS_RETRY_DELAY_MIN and
// PERS_RETRY_DELAY_MAX
//
backoff = (int)max(PERS_RETRY_DELAY_MIN, min(PERS_RETRY_DELAY_MAX, exp_backoff));
next_request_time = now + backoff;
next_request_time = now +
calculate_exponential_backoff(
PERS_RETRY_DELAY_MIN, PERS_RETRY_DELAY_MAX, nretry);
}
if (log_flags.file_xfer_debug) {
sprintf(buf,