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Code Issues Releases Wiki Activity

ircd::net::dns: Deduplicate requests at resolve() entry.

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This commit is contained in:
Jason Volk 2019-09-11 12:11:01 -07:00
parent 47204888d6
commit 83c58cf42e
1 changed files with 18 additions and 3 deletions
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19
modules/net_dns.cc
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@ -108,20 +108,35 @@ ircd::net::dns::resolve(const hostport &hp,
const opts &opts,
callback cb)
{
assert(ctx::current);
if(unlikely(!opts.qtype))
throw error
{
"A query type is required; not specified; cannot be deduced here."
};
if(opts.cache_check)
// Try to satisfy from the cache first. This requires a ctx.
if(likely(ctx::current && opts.cache_check))
if(cache::get(hp, opts, cb))
return;
// Remote query will be made; register this callback as waiting for reply
if(cb)
cache::waiting.emplace_back(hp, opts, std::move(cb));
// Check if there is already someone else waiting on the same query
const auto count
{
!cb? 1: std::count_if(begin(cache::waiting), end(cache::waiting), []
(const auto &a)
{
const auto &b(cache::waiting.back());
return a.opts.qtype == b.opts.qtype && a.key != b.key;
})
};
// When nobody else is already waiting on this query we have to submit it.
assert(count >= 1);
if(count == 1)
resolver_call(hp, opts);
}