Gateway(nginx): Defaulte env variable values with entrypoint scripts

[qclaogui]

Related issues: nginx/docker-nginx#592 , It looked like this feature might not be implemented, so I found another solution: nginx/docker-nginx#687 (comment)

❯ cat 10-default-lgtmp.envsh
#!/usr/bin/env sh
set -eu

# As of version 1.19, the official Nginx Docker image supports templates with
# variable substitution. But that uses `envsubst`, which does not allow for
# defaults for missing variables. Here, first use the regular command shell
# to set the defaults:

# Default value is Mimir in monolithic mode
export MIMIR_DISTRIBUTOR_HOST=${MIMIR_DISTRIBUTOR_HOST:-mimir}
export MIMIR_QUERY_FRONTEND_HOST=${MIMIR_QUERY_FRONTEND_HOST:-mimir}
export MIMIR_ALERT_MANAGER_HOST=${MIMIR_ALERT_MANAGER_HOST:-mimir}
export MIMIR_RULER_HOST=${MIMIR_RULER_HOST:-mimir}
export MIMIR_COMPACTOR_HOST=${MIMIR_COMPACTOR_HOST:-mimir}

# Default value is Loki in monolithic mode
export LOKI_DISTRIBUTOR_HOST=${LOKI_DISTRIBUTOR_HOST:-loki}
export LOKI_INGESTER_HOST=${LOKI_INGESTER_HOST:-loki}
export LOKI_RULER_HOST=${LOKI_RULER_HOST:-loki}
export LOKI_COMPACTOR_HOST=${LOKI_COMPACTOR_HOST:-loki}
export LOKI_QUERIER_HOST=${LOKI_QUERIER_HOST:-loki}
export LOKI_QUERY_FRONTEND_HOST=${LOKI_QUERY_FRONTEND_HOST:-loki}

# Default value is pyroscope in monolithic mode
export PYROSCOPE_DISTRIBUTOR_HOST=${PYROSCOPE_DISTRIBUTOR_HOST:-pyroscope}
export PYROSCOPE_QUERY_FRONTEND_HOST=${PYROSCOPE_QUERY_FRONTEND_HOST:-pyroscope}

export NGINX_ENVSUBST_OUTPUT_DIR=${NGINX_ENVSUBST_OUTPUT_DIR:-/etc/nginx}

moved 10-default-lgtmp.envsh in /docker-entrypoint.d