Prevent zombie processes from accumulating in the Kvrocks container (#…

…7412)

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### Motivation and context
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I saw several hundreds of zombie processes accumulate in the Kvrocks
container in production. This should fix that. See the comment in
`docker-compose.yml` for more explanation.

Note that as far as I'm aware, Kubernetes does not use healthcheck
commands configured in Docker images, so this issue should be irrelevant
for Kubernetes deployments.

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changelog.d/20240130_184639_roman.md

@@ -0,0 +1,4 @@
+### Fixed
+
+- Prevented zombie processes from accumulating in the Kvrocks container
+  (<https://github.com/opencv/cvat/pull/7412>)

docker-compose.yml

@@ -57,6 +57,12 @@ services:
     command: [
       "--dir", "/var/lib/kvrocks/data"
     ]
+    # The kvrocks image a) has a healthcheck command, and b) has a root process
+    # that doesn't reap children, so it's susceptible to the problem described here:
+    # <https://stackoverflow.com/a/77109064>. Kvrocks also uses a tiny timeout for
+    # its healthcheck command (1s), which makes the problem more likely to manifest.
+    # Use a separate init process as a workaround.
+    init: true
     volumes:
       - cvat_cache_db:/var/lib/kvrocks/data
     networks: