Failed to call mallctl with metrics and jemalloc (version 1) enabled

[matrixbot]

This issue has been migrated from #10731.

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Description

My logs are full of the following warnings

2021-08-31 22:02:23,539 - synapse.metrics.jemalloc - 176 - WARNING - sentinel - Failed to read jemalloc stats.resident: Failed to call mallctl
2021-08-31 22:02:23,539 - synapse.metrics.jemalloc - 176 - WARNING - sentinel - Failed to read jemalloc stats.metadata: Failed to call mallctl

Steps to reproduce

• enable jemalloc by setting the environment variable e.g. LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libjemalloc.so.1
• enable metrics collection

The server and metrics appear to still be working properly so I'm not sure what the impact of this warning is.

Version information

• Homeserver: Other

If not matrix.org:

• Version: 1.41.1

• Install method: matrix.org Debian package repository

• Platform:

OS: Ubuntu 18.04.5 LTS
Virtualized: Yes