Debugging

Checking cache hits/misses¶

• Use varnishlog -g request -q 'ReqURL ~ "^/some/path/"' to filter
• Check Requests for VCL_call with MISS, PASS or HIT
• Normally, an unpaged cache will be either be MISSed or PASSed, the next request should HIT
• If Varnish is clustered, the request may be PASSed to the responsible instance, so control all instances

Useful Prometheus queries¶

Probably only applicable for Varnish Plus

• varnish_msestore_g_alloc_bytes: In-memory cache size
• rate(varnish_mse_n_lru_nuked[5m]): Eviction rate for cached objects in MSE -> Too many (case-by-case defintion) may hint to the MSE cache being too small