add promtool to tools image (#209)

Author: gabreal

dockerfiles/tools/Dockerfile

@@ -4,18 +4,27 @@ ARG VCS_REF=master
 ARG BUILD_DATE=""
 ARG REGISTRY_PATH=paritytech
 
+ENV PROM_VERSION=2.19.0
+
 # metadata
 LABEL io.parity.image.authors="[email protected]" \
 	io.parity.image.vendor="Parity Technologies" \
 	io.parity.image.title="${REGISTRY_PATH}/tools" \
-	io.parity.image.description="curl git jq rsync make gettext gnupg bash" \
+	io.parity.image.description="curl git jq rsync make gettext gnupg bash promtool" \
 	io.parity.image.source="https://github.com/paritytech/scripts/blob/${VCS_REF}/\
 dockerfiles/tools/Dockerfile" \
 	io.parity.image.documentation="https://github.com/paritytech/scripts/blob/${VCS_REF}/\
 dockerfiles/tools/README.md" \
 	io.parity.image.revision="${VCS_REF}" \
 	io.parity.image.created="${BUILD_DATE}"
 
+
 RUN apk add --no-cache curl git jq rsync make gettext gnupg bash
 
+RUN curl -sS -L https://github.com/prometheus/prometheus/releases/download/v${PROM_VERSION}/prometheus-${PROM_VERSION}.linux-amd64.tar.gz \
+  --output prometheus.tar.gz && \
+	tar -xzf prometheus.tar.gz prometheus-${PROM_VERSION}.linux-amd64/promtool && \
+	mv prometheus-${PROM_VERSION}.linux-amd64/promtool /usr/local/bin && \
+	rm -rf prometheus.tar.gz prometheus-${PROM_VERSION}.linux-amd64
+
 CMD /bin/sh