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Merged
mattklein123 merged 5 commits into from
Dec 13, 2020
Merged

stats: Suggest new stats macros to avoid hot-path contention. #14312

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74c4bd8
Suggest new stats macros to avoid hot-path contention.
jmarantz Dec 8, 2020
33d6e05
fix path typos
jmarantz Dec 8, 2020
9ce4ea5
link to lines in current version for the stats macros examples, rathe…
jmarantz Dec 8, 2020
f0b9d1d
Merge branch 'master' into stat-macro-doc-update
jmarantz Dec 12, 2020
7b415d9
add 'control-plane' updates as a motivation to use the macros that split
jmarantz Dec 12, 2020
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9 changes: 8 additions & 1 deletion source/docs/stats.md
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Expand Up @@ -184,7 +184,14 @@ showing the memory layout for a few scenarios of constructing and joining symbol

There are several ways to create hot-path contention looking up stats by name,
and there is no bulletproof way to prevent it from occurring.
* The [stats macros](https://github.com/envoyproxy/envoy/blob/master/include/envoy/stats/stats_macros.h) may be used in a data structure which is constructed in response to requests.
* The [stats macros](https://github.com/envoyproxy/envoy/blob/master/include/envoy/stats/stats_macros.h) may be used in a data structure which is constructed in response to requests. In this
scenario, consider factoring out the symbolization phase using MAKE_STAT_NAMES_STRUCT
in a factory or context during startup, and using MAKE_STATS_STRUCT in the hot-path and during
control-plane updates, so that we do not need to take symbol-table locks. As an example, see
[ClusterInfoImpl::generateStats](https://github.com/envoyproxy/envoy/blob/8188e232a9e0b15111d30f4724cbc7bf77d3964a/source/common/upstream/upstream_impl.cc#L641)
and its
[MAKE_STAT_NAMES_STRUCT](https://github.com/envoyproxy/envoy/blob/8188e232a9e0b15111d30f4724cbc7bf77d3964a/include/envoy/upstream/upstream.h#L646).
invocation.
* An explicit symbol-table lookup, via `StatNamePool` or `StatNameSet` can be
made in the hot path.

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