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Fixes a case where the NextHop consistent hash ring may not be completely searched. #6303

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Merged
jrushford merged 1 commit into from
Jan 6, 2020
Merged

Fixes a case where the NextHop consistent hash ring may not be completely searched. #6303

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13 changes: 10 additions & 3 deletions proxy/http/remap/NextHopConsistentHash.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -36,7 +36,7 @@ constexpr std::string_view hash_key_cache = "cache_key";

static HostRecord *
chash_lookup(std::shared_ptr<ATSConsistentHash> ring, uint64_t hash_key, ATSConsistentHashIter *iter, bool *wrapped,
ATSHash64Sip24 *hash, bool *hash_init, uint64_t sm_id)
ATSHash64Sip24 *hash, bool *hash_init, bool *mapWrapped, uint64_t sm_id)
{
HostRecord *host_rec = nullptr;

Expand All @@ -46,6 +46,11 @@ chash_lookup(std::shared_ptr<ATSConsistentHash> ring, uint64_t hash_key, ATSCons
} else {
host_rec = static_cast<HostRecord *>(ring->lookup(nullptr, iter, wrapped, hash));
}
bool wrap_around = *wrapped;
*wrapped = (*mapWrapped && *wrapped) ? true : false;
if (!*mapWrapped && wrap_around) {
*mapWrapped = true;
}

return host_rec;
}
Expand Down Expand Up @@ -261,7 +266,8 @@ NextHopConsistentHash::findNextHop(const uint64_t sm_id, ParentResult &result, R

do { // search until we've selected a different parent if !firstcall
std::shared_ptr<ATSConsistentHash> r = rings[cur_ring];
hostRec = chash_lookup(r, hash_key, &result.chashIter[cur_ring], &wrapped, &hash, &result.chash_init[cur_ring], sm_id);
hostRec = chash_lookup(r, hash_key, &result.chashIter[cur_ring], &wrapped, &hash, &result.chash_init[cur_ring],
&result.mapWrapped[cur_ring], sm_id);
wrap_around[cur_ring] = wrapped;
lookups++;
// the 'available' flag is maintained in 'host_groups' and not the hash ring.
Expand Down Expand Up @@ -322,7 +328,8 @@ NextHopConsistentHash::findNextHop(const uint64_t sm_id, ParentResult &result, R
break;
}
std::shared_ptr<ATSConsistentHash> r = rings[cur_ring];
hostRec = chash_lookup(r, hash_key, &result.chashIter[cur_ring], &wrapped, &hash, &result.chash_init[cur_ring], sm_id);
hostRec = chash_lookup(r, hash_key, &result.chashIter[cur_ring], &wrapped, &hash, &result.chash_init[cur_ring],
&result.mapWrapped[cur_ring], sm_id);
wrap_around[cur_ring] = wrapped;
lookups++;
if (hostRec) {
Expand Down
8 changes: 4 additions & 4 deletions proxy/http/remap/unit-tests/test_NextHopConsistentHash.cc
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Expand Up @@ -257,17 +257,17 @@ SCENARIO("Testing NextHopConsistentHash class (all firstcalls), using policy 'co
result.reset();
strategy->findNextHop(20004, result, request, fail_threshold, retry_time);
CHECK(result.result == ParentResultType::PARENT_SPECIFIED);
CHECK(strcmp(result.hostname, "q1.bar.com") == 0);
CHECK(strcmp(result.hostname, "s1.bar.com") == 0);

// mark down q1.bar.com
// mark down s1.bar.com
strategy->markNextHopDown(20004, result, 1, fail_threshold);

// fifth request
br(&request, "rabbit.net/asset1");
result.reset();
strategy->findNextHop(20005, result, request, fail_threshold, retry_time);
CHECK(result.result == ParentResultType::PARENT_DIRECT);
CHECK(result.hostname == nullptr);
CHECK(result.result == ParentResultType::PARENT_SPECIFIED);
CHECK(strcmp(result.hostname, "q1.bar.com") == 0);

// sixth request - wait and p1 should now become available
time_t now = time(nullptr) + 5;
Expand Down