perf(limit-count): use evalsha with NOSCRIPT fallback for Redis script execution#13363
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Pull request overview
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Optimizes the limit-count plugin’s Redis Lua execution by switching from EVAL to EVALSHA with a NOSCRIPT fallback, reducing per-request bandwidth and Redis script parsing overhead.
Changes:
- Use
evalshawithNOSCRIPTfallback in the standalone Redis backend. - Use
evalshawithNOSCRIPTfallback in the Redis Cluster backend. - Add a test that flushes Redis script cache and verifies fallback recovery.
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.
| File | Description |
|---|---|
apisix/plugins/limit-count/limit-count-redis.lua |
Introduces script SHA computation and evalsha + NOSCRIPT fallback for standalone Redis. |
apisix/plugins/limit-count/limit-count-redis-cluster.lua |
Introduces script SHA computation and evalsha + NOSCRIPT fallback for Redis Cluster. |
t/plugin/limit-count-redis.t |
Adds coverage for NOSCRIPT fallback after flushing Redis script cache. |
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…t execution Replace plain red:eval() with red:evalsha() + NOSCRIPT fallback in limit-count Redis and Redis Cluster backends. This reduces per-request network payload from ~200-500 bytes (full script text) to ~40 bytes (SHA1 digest + arguments) and eliminates Redis-side script parsing after the first call. The script SHA1 is computed client-side at module load time using ngx.sha1_bin(), which works correctly for both standalone Redis and Redis Cluster topologies. On NOSCRIPT (after Redis restart or when hitting a new cluster shard), the fallback to eval() implicitly caches the script for subsequent evalsha calls.
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AlinsRan
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May 13, 2026
shreemaan-abhishek
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May 13, 2026
membphis
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May 14, 2026
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The limit-count plugin ships the full Lua script text on every Redis call via
red:eval(). At high RPS this wastes both network bandwidth (~200-500 bytes per call) and Redis CPU (script parsing on every call).This PR replaces
evalwithevalsha+ NOSCRIPT fallback in both the standalone Redis and Redis Cluster backends of the limit-count plugin. The script SHA1 is computed client-side at module load time, avoiding the need forSCRIPT LOAD(which doesn't route correctly in Redis Cluster). On NOSCRIPT (after Redis restart or hitting a new cluster shard), the code falls back toevalwhich implicitly caches the script for subsequent calls.This mirrors the pattern already used by the
limit-connplugin, but improves on it by supporting Redis Cluster mode (limit-conn currently disables evalsha for cluster).Changes:
apisix/plugins/limit-count/limit-count-redis.lua: evalsha + NOSCRIPT fallbackapisix/plugins/limit-count/limit-count-redis-cluster.lua: evalsha + NOSCRIPT fallbackt/plugin/limit-count-redis.t: add test for NOSCRIPT fallback recovery