dns: coalesce identical concurrent lookup() requests - #62599
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #62599 +/- ##
=======================================
Coverage 90.28% 90.29%
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Files 760 760
Lines 247061 247080 +19
Branches 46592 46580 -12
=======================================
+ Hits 223058 223090 +32
+ Misses 15491 15442 -49
- Partials 8512 8548 +36
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I think this might break async_hooks continuation, could you verify? Adding an AsyncResource on coalescing would be enough.
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Great observation! Should be fixed now. |
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I have a feeling that the failing test on GHA is relevant, can you take a look? |
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It doesn't look related. Similar failures happened here and here. Also, this test calls The test is flaky, since it relies on external systems which may refuse or time out. |
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When multiple callers issue dns.lookup() for the same (hostname, family,
hints, order) concurrently, only one getaddrinfo call is now dispatched
to the libuv threadpool. All callers share the result.
getaddrinfo is a blocking call that runs on the libuv threadpool (capped
at 4 threads by default, with a slow I/O concurrency limit of 2). When
DNS resolution is slow - e.g. ~10-20 s per call due to a misbehaving
resolver - identical requests queue behind each other, causing timeouts
that grow linearly with the number of concurrent callers:
Before: 100 parallel lookup('host') -> 50 batches × 10 s = 500+ s
After: 100 parallel lookup('host') -> 1 getaddrinfo call = ~10 s
This is particularly severe on WSL, where the DNS relay rewrites QNAMEs
in responses (appending the search domain), causing glibc to discard
them as non-matching and wait for a 5s timeout per retry.
The coalescing is keyed on (hostname, family, hints, order) so lookups
with different options still get separate getaddrinfo calls. Each
caller independently post-processes the shared raw result (applying the
'all' flag, constructing address objects, etc.).
Signed-off-by: Orgad Shaneh <orgad.shaneh@audiocodes.com>
PR-URL: nodejs#62599
Fixes: nodejs#62503
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Rebased. |
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ping? |
When multiple callers issue dns.lookup() for the same (hostname, family,
hints, order) concurrently, only one getaddrinfo call is now dispatched
to the libuv threadpool. All callers share the result.
getaddrinfo is a blocking call that runs on the libuv threadpool (capped
at 4 threads by default, with a slow I/O concurrency limit of 2). When
DNS resolution is slow - e.g. ~10-20 s per call due to a misbehaving
resolver - identical requests queue behind each other, causing timeouts
that grow linearly with the number of concurrent callers:
Before: 100 parallel lookup('host') -> 50 batches × 10 s = 500+ s
After: 100 parallel lookup('host') -> 1 getaddrinfo call = ~10 s
This is particularly severe on WSL, where the DNS relay rewrites QNAMEs
in responses (appending the search domain), causing glibc to discard
them as non-matching and wait for a 5s timeout per retry.
The coalescing is keyed on (hostname, family, hints, order) so lookups
with different options still get separate getaddrinfo calls. Each
caller independently post-processes the shared raw result (applying the
'all' flag, constructing address objects, etc.).
Signed-off-by: Orgad Shaneh <orgad.shaneh@audiocodes.com>
PR-URL: nodejs#62599
Fixes: nodejs#62503
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When multiple callers issue dns.lookup() for the same (hostname, family, hints, order) concurrently, only one getaddrinfo call is now dispatched to the libuv threadpool. All callers share the result.
getaddrinfo is a blocking call that runs on the libuv threadpool (capped at 4 threads by default, with a slow I/O concurrency limit of 2). When DNS resolution is slow - e.g. ~10-20 s per call due to a misbehaving resolver - identical requests queue behind each other, causing timeouts that grow linearly with the number of concurrent callers:
Before: 100 parallel lookup('host') -> 50 batches × 10 s = 500+ s
After: 100 parallel lookup('host') -> 1 getaddrinfo call = ~10 s
This is particularly severe on WSL, where the DNS relay rewrites QNAMEs in responses (appending the search domain), causing glibc to discard them as non-matching and wait for a 5s timeout per retry.
The coalescing is keyed on (hostname, family, hints, order) so lookups with different options still get separate getaddrinfo calls. Each caller independently post-processes the shared raw result (applying the 'all' flag, constructing address objects, etc.).
Fixes: #62503