Support --socket-dir command line argument

[tjhorner]

The dispatcher server accepts a --socket-dir command line argument to let the user customize the location of the unix domain sockets that are created. The dispatcher client already listens to OVERPASS_SOCKET_DIR, so it would be great if dispatcher_start.sh added the appropriate --socket-dir parameter if OVERPASS_SOCKET_DIR is set. I think some additional work would need to be done for the dispatcher_areas supervisord job and here in the entrypoint.

By default, Overpass stores the domain sockets in the database directory, but this can cause problems if the directory is a network share or otherwise does not support unix domain sockets, so specifying a separate directory for those is required.

Thank you for this Docker image!

[BrendenKingTLG]

I attempted to use a volume mount for the database and store the socket file on the container. Everything seems to be functioning.

https://github.com/BrendenKingTLG/overpass-api-k8

[tjhorner]

@BrendenKingTLG If you are using a normal volume mount on your local filesystem then it will work fine. I ran into issues when I mounted a directory over NFS and used that as my volume mount, but sockets don't work with NFS (understandably)

[BrendenKingTLG]

I use a similar setup with AWS EFS. To avoid issues with socket files being shared across instances, I moved the socket file from the DB volume to a path inside the container.

Step 1: Set OVERPASS_SOCKET_DIR

Define an environment variable to set the socket directory. This can be any path within the container. I use /app/socket:

# Dockerfile (line 45)
ENV OVERPASS_RULES_LOAD=1 \
    OVERPASS_USE_AREAS=true \
    OVERPASS_ALLOW_DUPLICATE_QUERIES=no \
    OVERPASS_SOCKET_DIR=/app/socket

Step 2: Start Dispatcher with --socket-dir

Update your startup script to pass the --socket-dir flag when starting the dispatcher. This argument is supported even though it isn’t shown in the help output:

/app/bin/dispatcher --osm-base --socket-dir=/app/socket --meta --db-dir=/app/db &

Reference: dispatcher_server.cc#L264

Step 3: Mount Only the DB Files

Make sure you mount just the DB directory and not the socket path:

volumeMounts:
  - name: db-volume
    mountPath: /app/db
  - name: data-volume
    mountPath: /data

volumes:
  - name: db-volume
    hostPath:
      path: {{ .Values.volumes.dbHostPath }}
      type: Directory

This way, /app/db includes only the database files, while the sockets remain local to the container. I run multiple API instances sharing the same database without socket conflicts. Hope this helps!