Add comments and a check or two to the dockerfile. (#56)

* Add comments and a check or two to the dockerfile.
* Don't distribute dev tools

Author: pboothe

Dockerfile

@@ -1,5 +1,7 @@
-FROM golang:1.13 as build
+# Build the traceroute-caller binary
+FROM golang:1.13 as build_caller
 ADD . /go/src/github.com/m-lab/traceroute-caller
+RUN rm /go/src/github.com/m-lab/traceroute-caller/Dockerfile
 ENV GOARCH amd64
 ENV CGO_ENABLED 0
 ENV GOOS linux
@@ -10,35 +12,68 @@ RUN go get -v \
 RUN chmod -R a+rx /go/bin/traceroute-caller
 
 
-FROM ubuntu:latest
-# Install all the standard packages we need and then remove the apt-get lists.
+# Build the binaries that are called by traceroute-caller
+FROM ubuntu:latest as build_tracers
+# Install all the packages we need and then remove the apt-get lists.
+# iproute2 gives us ss
+# all the other packages are for the build processes.
 RUN apt-get update && \
-    apt-get install -y python python-pip make iproute2 coreutils autoconf libtool git build-essential && \
+    apt-get install -y make coreutils autoconf libtool git build-essential && \
     apt-get clean && \
     rm -rf /var/lib/apt/lists/*
 
+# Build and install scamper
 RUN ls -l
 RUN mkdir /scamper-src
 ADD ./vendor/scamper/ /scamper-src
 RUN chmod +x /scamper-src/scamper-cvs-20190916/configure
 WORKDIR /scamper-src/scamper-cvs-20190916/
-RUN ./configure
+RUN ./configure --prefix=/scamper
 RUN make -j 8
 RUN make install
-RUN ldconfig
 
+# Build and install paris-traceroute
 RUN mkdir /pt-src
 ADD ./vendor/libparistraceroute/ /pt-src
 WORKDIR /pt-src
-RUN mkdir m4
+RUN mkdir -p m4
 RUN ./autogen.sh
-RUN ./configure
+RUN ./configure --prefix=/paris-traceroute
 RUN make -j 8
 RUN make install
+
+# Create an image for the binaries that are called by traceroute-caller without
+# any of the build tools.
+FROM ubuntu:latest
+# Install all the packages we need and then remove the apt-get lists.
+# iproute2 gives us ss
+RUN apt-get update && \
+    apt-get install -y iproute2 && \
+    apt-get clean && \
+    rm -rf /var/lib/apt/lists/*
+
+# Bring the statically-linked traceroute-caller binary from the go build image.
+COPY --from=build_caller /go/bin/traceroute-caller /
+
+# Bring the dynamically-linked traceroute binaries from their build image.
+COPY --from=build_tracers /scamper /scamper
+RUN cp -R /scamper/* /usr/local/.
+RUN rm -Rf /scamper
+
+COPY --from=build_tracers /paris-traceroute /paris-traceroute
+RUN cp -R /paris-traceroute/* /usr/local/.
+RUN rm -Rf /paris-traceroute
+
+# They are dynamically-linked, so make sure to run ldconfig to locate all new
+# libraries.
 RUN ldconfig
 
-COPY --from=build /go/bin/traceroute-caller /
+# Verify that all the binaries we depend on are actually available
+RUN which paris-traceroute
+RUN which scamper
+RUN which sc_attach
+RUN which sc_warts2json
+RUN which ss
 
 WORKDIR /
-
 ENTRYPOINT ["/traceroute-caller"]