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Merge pull request #1769 from nghttp2/randomize-backend-addresses 

nghttpx: Randomize backend address backend robin order per thread (2nd Ed.)
This commit is contained in:
Tatsuhiro Tsujikawa 2022-08-04 19:03:53 +09:00 committed by GitHub
parent a3be763650 39d9efe4bd
commit 092014d5af
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2 changed files with 24 additions and 0 deletions
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4
src/shrpx_worker.cc
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@ -360,6 +360,10 @@ void Worker::replace_downstream_config(
addr.seq = seq++;
}
util::shuffle(std::begin(shared_addr->addrs),
std::end(shared_addr->addrs), randgen_,
[](auto i, auto j) { std::swap((*i).seq, (*j).seq); });
if (shared_addr->affinity.type == SessionAffinity::NONE) {
std::map<StringRef, WeightGroup *> wgs;
size_t num_wgs = 0;

20
src/util.h
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@ -879,6 +879,26 @@ void random_bytes(OutputIt first, OutputIt last, Generator &gen) {
std::generate(first, last, [&dis, &gen]() { return dis(gen); });
}
// Shuffles the range [|first|, |last|] by calling swap function |fun|
// for each pair. |fun| takes 2 RandomIt iterators. If |fun| is
// noop, no modification is made.
template <typename RandomIt, typename Generator, typename SwapFun>
void shuffle(RandomIt first, RandomIt last, Generator &&gen, SwapFun fun) {
auto len = std::distance(first, last);
if (len < 2) {
return;
}
for (unsigned int i = 0; i < static_cast<unsigned int>(len - 1); ++i) {
auto dis = std::uniform_int_distribution<unsigned int>(i, len - 1);
auto j = dis(gen);
if (i == j) {
continue;
}
fun(first + i, first + j);
}
}
template <typename OutputIterator, typename CharT, size_t N>
OutputIterator copy_lit(OutputIterator it, CharT (&s)[N]) {
return std::copy_n(s, N - 1, it);