feat: Report available system memory under dcc_free_mem

This patch adds a trivial wrapper HTTP server, written in Python, that
intercepts the requests going towards the `--stats-port` of the running
`distccd` server.
It relays the request verbatim at first, and if the response is a valid
statistics message, extends it at the bottom with a line

    dcc_free_mem 16384 MB

where the numeric value is obtained from `free`'s output under
**Available** system memory.

.github/workflows/docker-image.yml

@@ -34,12 +34,20 @@ jobs:
           mv -v   ./shellcheck-v*/shellcheck "./shellcheck"
           rm -rv  ./shellcheck-v*
           ./shellcheck --version
+      - name: "Install PyCodeStyle"
+        run: |
+          sudo apt-get install -y --no-install-recommends \
+            python3-pycodestyle
       - name: "ShellCheck"
         run: |
           ./shellcheck \
             --color=always \
             etc/cron.*/* \
             usr/local/*bin/*
+      - name: "PyCodeStyle"
+        run: |
+          python3 -m pycodestyle \
+            .
 
   build:
     name: "Build ${{ github.event_name == 'workflow_dispatch' && inputs.release && 'and Deploy' || '' }} Docker Image"
@@ -54,16 +62,87 @@ jobs:
         with:
           load: true
           tags: "distcc-docker:${{ env.RUNS_ON }}"
-      - name: "Simple test"
+      - name: "Test starting the container"
+        run: |
+          docker run \
+            --init \
+            --rm \
+            "distcc-docker:${{ env.RUNS_ON }}" \
+              --jobs $(nproc) \
+              -- \
+              bash -c \
+                "set -x; ps fauxw; /usr/bin/ls -alh .; /usr/bin/ls -alh /var/log; cat /var/log/*; exit;"
+      - name: "Test that \"dcc_free_mem\" is reported"
+        run: |
+          set -ex
+
+          docker run \
+            --detach \
+            --init \
+            --name "distcc-1" \
+            --publish "3632:3632/tcp" \
+            --publish "3633:3633/tcp" \
+            --rm \
+            "distcc-docker:${{ env.RUNS_ON }}" \
+              --jobs $(nproc) \
+              -- \
+                bash -c "set -x; sleep 120; exit;"
+
+          sleep 10
+          STAT_RESULT="$(curl "http://localhost:3633" | grep "dcc_free_mem")"
+          if [ -z "$STAT_RESULT" ]; then
+            echo "Server did not report 'dcc_free_mem'!" >&2
+            exit 1
+          fi
+
+          docker kill "distcc-1"
+      - name: "Test compilation in the container"
         run: |
+          set -ex
+
+          sudo apt-get update -y
+          sudo apt-get install distcc g++ --no-install-recommends
+          sudo update-distcc-symlinks
+
           docker run \
+            --detach \
             --init \
+            --name "distcc-1" \
+            --publish "3632:3632/tcp" \
+            --publish "3633:3633/tcp" \
             --rm \
             "distcc-docker:${{ env.RUNS_ON }}" \
-            --jobs $(nproc) \
-            -- \
-            bash -c \
-              "set -x; ps fauxw; /usr/bin/ls -alh .; /usr/bin/ls -alh /var/log; cat /var/log/*; exit;"
+              --jobs $(nproc) \
+              -- \
+                bash -c "set -x; sleep 120; exit;"
+
+          sleep 10
+          curl "http://localhost:3633"
+
+          echo "int main() { return MY_EXIT_CODE; }" >> main.cpp
+
+          DISTCC_HOSTS="127.0.0.1:3632/$(nproc),lzo" \
+            distcc /usr/bin/g++ \
+            -D MY_EXIT_CODE=42 \
+            -c \
+            ./main.cpp \
+            -o main.o
+
+          rm -v main.cpp
+
+          curl "http://localhost:3633"
+
+          docker kill "distcc-1"
+
+          /usr/bin/g++ main.o -o main
+
+          set +e
+
+          ./main
+          if [ "$?" -ne 42 ]; then
+            echo "Unexpected error code obtained!" >&2
+            exit 1
+          fi
       - name: "Log in to GitHub Container Registry (GHCR)"
         if: "github.ref == 'refs/heads/master' && github.event_name == 'workflow_dispatch' && inputs.release"
         uses: "docker/login-action@v3"

Dockerfile

@@ -4,7 +4,8 @@ FROM ubuntu:20.04
 MAINTAINER Whisperity <whisperity-packages@protonmail.com>
 
 
-RUN export DEBIAN_FRONTEND=noninteractive && \
+RUN \
+  export DEBIAN_FRONTEND=noninteractive && \
   set -x && \
   apt-get update -y && \
   apt-get install -y --no-install-recommends \
@@ -15,6 +16,7 @@ RUN export DEBIAN_FRONTEND=noninteractive && \
     lsb-release \
     locales \
     logrotate \
+    python3 \
     wget \
   && \
   apt-get purge -y --auto-remove && \
@@ -24,7 +26,8 @@ RUN export DEBIAN_FRONTEND=noninteractive && \
   mkdir -pv "/var/log/"
 
 
-RUN export DEBIAN_FRONTEND=noninteractive; \
+RUN \
+  export DEBIAN_FRONTEND=noninteractive; \
   sed -i -e "s/# en_US.UTF-8 UTF-8/en_US.UTF-8 UTF-8/" "/etc/locale.gen" && \
   dpkg-reconfigure --frontend=noninteractive locales && \
   update-locale LANG="en_US.UTF-8"
@@ -34,11 +37,11 @@ ENV \
   LC_ALL="en_US.UTF-8"
 
 
+COPY usr/local/sbin/install-compilers.sh /usr/local/sbin/install-compilers.sh
+
 # Set to non-zero if the compilers should only be installed into the container,
 # and not immediately baked into the image itself.
 ARG LAZY_COMPILERS=0
-
-COPY usr/local/sbin/install-compilers.sh /usr/local/sbin/install-compilers.sh
 RUN \
   if [ "x$LAZY_COMPILERS" = "x0" ]; \
   then \
@@ -52,25 +55,26 @@ RUN \
   fi
 
 
+COPY etc/ /etc/
+COPY usr/ /usr/
+
+
 ARG USERNAME="distcc"
-RUN echo "Creating service user: $USERNAME ..." >&2 && \
-  mkdir -pv "/var/lib/distcc/" && \
-  chmod -Rv 755 "/var/lib/distcc" && \
+RUN \
+  cp -av "/etc/skel/." "/root/" && \
+  echo "Creating service user: $USERNAME ..." >&2 && \
   useradd "$USERNAME" \
-    --system \
+    --create-home \
     --comment "DistCC service" \
+    --home-dir "/var/lib/distcc/" \
     --shell "/bin/bash" \
-    --home-dir "/var/lib/distcc/" && \
-  cp -v "/root/.bashrc" "/root/.profile" "/var/lib/distcc/" && \
+    --system \
+    && \
   chown -Rv "$USERNAME":"$USERNAME" "/var/lib/distcc" && \
   echo "$USERNAME" > "/var/lib/distcc/distcc.user" && \
   chmod -v 444 "/var/lib/distcc/distcc.user"
 
 
-COPY etc/ /etc/
-COPY usr/ /usr/
-
-
 # Expose the DistCC server's normal job and statistics subservice port.
 # Custom ports to be used on the host machine should be managed via Docker.
 EXPOSE \

etc/logrotate.d/cron

@@ -1,6 +1,6 @@
 /var/log/cron.log {
   daily
-  rotate 30
+  rotate 7
 
   compress
   copytruncate

etc/logrotate.d/distcc

@@ -1,6 +1,6 @@
 /var/log/distccd.log {
   daily
-  rotate 30
+  rotate 7
 
   compress
   copytruncate

etc/logrotate.d/http

@@ -0,0 +1,12 @@
+/var/log/access.log
+/var/log/error.log
+{
+  daily
+  rotate 7
+
+  compress
+  copytruncate
+  delaycompress
+  missingok
+  notifempty
+}

etc/skel/.config/htop/htoprc

@@ -0,0 +1,7 @@
+hide_kernel_threads=1
+hide_userland_threads=1
+highlight_base_name=1
+highlight_megabytes=1
+shadow_other_users=0
+show_program_path=0
+tree_view=1