Modularize the project and use golang project style

Introduce a golang based project approach for the prometheus exporter.
Create a seperate cmd with cli parsing by cobra, a server instance with
logging using logrus.

.gitignore

@@ -1 +1,8 @@
-prometheus-kopano-exporter
+/vendor
+/bin
+/golint.txt
+/govet.txt
+/dist
+/test/tests.*
+/3rdparty-LICENSES.md
+/.vscode

.golangci.yaml

@@ -0,0 +1,74 @@
+run:
+  modules-download-mode: vendor
+
+linters-settings:
+  govet:
+    check-shadowing: true
+    settings:
+      printf:
+        funcs:
+          - (github.com/golangci/golangci-lint/pkg/logutils.Log).Infof
+          - (github.com/golangci/golangci-lint/pkg/logutils.Log).Warnf
+          - (github.com/golangci/golangci-lint/pkg/logutils.Log).Errorf
+          - (github.com/golangci/golangci-lint/pkg/logutils.Log).Fatalf
+  golint:
+    min-confidence: 0
+  gocyclo:
+    min-complexity: 10
+  maligned:
+    suggest-new: true
+  dupl:
+    threshold: 100
+  goconst:
+    min-len: 2
+    min-occurrences: 2
+  misspell:
+    locale: US
+  lll:
+    line-length: 140
+  goimports:
+    local-prefixes: stash.kopano.io/kc/kapi
+  gocritic:
+    enabled-tags:
+      - performance
+      - style
+      - experimental
+
+linters:
+  # inverted configuration with `enable-all` and `disable` is not scalable during updates of golangci-lint
+  disable-all: true
+  enable:
+    - bodyclose
+    - deadcode
+    - dupl
+    - errcheck
+    - funlen
+    - gochecknoinits
+    - goconst
+    - gocritic
+    - gocyclo
+    - gofmt
+    - goimports
+    - golint
+    - gosec
+    - gosimple
+    - govet
+    - ineffassign
+    - interfacer
+    - lll
+    - misspell
+    - nakedret
+    - scopelint
+    - staticcheck
+    - structcheck
+    - stylecheck
+    - typecheck
+    - unconvert
+    - unparam
+    - unused
+    - varcheck
+
+  # don't enable:
+  # - depguard - until https://github.com/OpenPeeDeeP/depguard/issues/7 gets fixed
+  # - maligned,prealloc
+  # - gochecknoglobals

.license-ranger.json

@@ -0,0 +1,4 @@
+{
+	"mode": "mod-vendor",
+	"header": "# Kopano Prometheus Exporter 3rd party licenses\n\nCopyright 2020 Kopano and its licensors. See LICENSE.txt for license information. This document contains a list of open source components used in this project.\n\n## Kopano Prometheus Exporter prometheus-kopano-exporter\n"
+}

Dockerfile.build

@@ -0,0 +1,44 @@
+#
+# Copyright 2019 Kopano and its licensors
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License, version 3 or
+# later, as published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+FROM golang:1.14.0-buster
+
+SHELL ["/bin/bash", "-o", "pipefail", "-c"]
+
+ARG GOLANGCI_LINT_TAG=v1.23.8
+RUN curl -sfL \
+	https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | \
+	sh -s -- -b /usr/local/bin ${GOLANGCI_LINT_TAG}
+
+RUN GOBIN=/usr/local/bin go get -v \
+	github.com/tebeka/go2xunit \
+	&& go clean -cache && rm -rf /root/go
+
+ENV DEBIAN_FRONTEND noninteractive
+
+RUN apt-get update \
+	&& apt-get install -y --no-install-recommends \
+		build-essential \
+	&& apt-get clean \
+	&& rm -rf /var/lib/apt/lists/*
+
+WORKDIR /build
+
+ENV GOCACHE=/tmp/go-build
+ENV GOPATH=""
+ENV HOME=/tmp
+
+CMD ["make", "DATE=reproducible"]

Jenkinsfile

@@ -0,0 +1,51 @@
+#!/usr/bin/env groovy
+
+pipeline {
+	agent {
+		dockerfile {
+			filename 'Dockerfile.build'
+		 }
+	}
+	stages {
+		stage('Bootstrap') {
+			steps {
+				echo 'Bootstrapping..'
+				sh 'go version'
+			}
+		}
+		stage('Lint') {
+			steps {
+				echo 'Linting..'
+				sh 'make lint-checkstyle'
+				checkstyle pattern: 'test/tests.lint.xml', canComputeNew: false, unstableTotalHigh: '100'
+			}
+		}
+		stage('Vendor') {
+			steps {
+				echo 'Fetching vendor dependencies..'
+				sh 'make vendor'
+			}
+		}
+		stage('Build') {
+			steps {
+				echo 'Building..'
+				sh 'make DATE=reproducible'
+				sh './bin/promtheus-kopano-exporter version && sha256sum ./bin/prometheus-kopano-exporter'
+			}
+		}
+		stage('Dist') {
+			steps {
+				echo 'Dist..'
+				sh 'test -z "$(git diff --shortstat 2>/dev/null |tail -n1)" && echo "Clean check passed."'
+				sh 'make check'
+				sh 'make dist'
+			}
+		}
+	}
+	post {
+		always {
+			archiveArtifacts 'dist/*.tar.gz'
+			cleanWs()
+		}
+	}
+}

LICENSE.txt

@@ -0,0 +1,13 @@
+Copyright 2020 Kopano and its licensors
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU Affero General Public License, version 3,
+as published by the Free Software Foundation.
+
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
+details.
+
+You should have received a copy of the GNU Affero General Public License
+along with this program. If not, see http://www.gnu.org/licenses/.

Makefile

@@ -0,0 +1,119 @@
+PACKAGE  = stash.kopano.io/kgol/prometheus-kopano-exporter
+PACKAGE_NAME = prometheus-kopano-exporter
+
+# Tools
+
+GO      ?= go
+GOFMT   ?= gofmt
+GOLINT  ?= golangci-lint
+
+# Cgo
+
+CGO_ENABLED ?= 0
+
+# Go modules
+
+GO111MODULE ?= on
+
+# Variables
+
+export CGO_ENABLED GO111MODULE
+unexport GOPATH
+
+ARGS    ?=
+PWD     := $(shell dirname $(realpath $(lastword $(MAKEFILE_LIST))))
+DATE    ?= $(shell date -u +"%Y-%m-%dT%H:%M:%SZ")
+VERSION ?= $(shell git describe --tags --always --dirty --match=v* 2>/dev/null | sed 's/^v//' || \
+			cat $(CURDIR)/.version 2> /dev/null || echo 0.0.0-unreleased)
+PKGS     = $(or $(PKG),$(shell $(GO) list -mod=readonly ./... | grep -v "^$(PACKAGE)/vendor/"))
+TESTPKGS = $(shell $(GO) list -mod=readonly -f '{{ if or .TestGoFiles .XTestGoFiles }}{{ .ImportPath }}{{ end }}' $(PKGS) 2>/dev/null)
+CMDS     = $(or $(CMD),$(addprefix cmd/,$(notdir $(shell find "$(PWD)/cmd/" -type d))))
+TIMEOUT  = 30
+
+# Build
+
+.PHONY: all
+all: fmt | $(CMDS) $(PLUGINS)
+
+plugins: fmt | $(PLUGINS)
+
+.PHONY: $(CMDS)
+$(CMDS): vendor ; $(info building $@ ...) @
+	CGO_ENABLED=$(CGO_ENABLED) $(GO) build \
+		-mod=vendor \
+		-trimpath \
+		-tags release \
+		-buildmode=exe \
+		-ldflags '-s -w -buildid=reproducible/$(VERSION) -X $(PACKAGE)/version.Version=$(VERSION) -X $(PACKAGE)/version.BuildDate=$(DATE) -extldflags -static' \
+		-o bin/$(notdir $@) ./$@
+
+# Helpers
+
+.PHONY: lint
+lint: vendor ; $(info running $(GOLINT) ...)	@
+	$(GOLINT) run
+
+.PHONY: lint-checkstyle
+lint-checkstyle: vendor ; $(info running $(GOLINT) checkstyle ...)     @
+	@mkdir -p test
+	$(GOLINT) run --out-format checkstyle --issues-exit-code 0 > test/tests.lint.xml
+
+.PHONY: fmt
+fmt: ; $(info running gofmt ...)	@
+	@ret=0 && for d in $$($(GO) list -mod=readonly -f '{{.Dir}}' ./... | grep -v /vendor/); do \
+		$(GOFMT) -l -w $$d/*.go || ret=$$? ; \
+	done ; exit $$ret
+
+.PHONY: check
+check: ; $(info checking dependencies ...) @
+	@$(GO) mod verify && echo OK
+
+# Mod
+
+go.sum: go.mod ; $(info updating dependencies ...)
+	@$(GO) mod tidy -v
+	@touch $@
+
+.PHONY: vendor
+vendor: go.sum ; $(info retrieving dependencies ...)
+	@$(GO) mod vendor -v
+	@touch $@
+
+# Dist
+
+.PHONY: licenses
+licenses: vendor ; $(info building licenses files ...)
+	$(CURDIR)/scripts/go-license-ranger.py > $(CURDIR)/3rdparty-LICENSES.md
+
+3rdparty-LICENSES.md: licenses
+
+.PHONY: dist
+dist: 3rdparty-LICENSES.md ; $(info building dist tarball ...)
+	@rm -rf "dist/${PACKAGE_NAME}-${VERSION}"
+	@mkdir -p "dist/${PACKAGE_NAME}-${VERSION}"
+	@mkdir -p "dist/${PACKAGE_NAME}-${VERSION}/scripts"
+	@cd dist && \
+	cp -avf ../LICENSE.txt "${PACKAGE_NAME}-${VERSION}" && \
+	cp -avf ../README.md "${PACKAGE_NAME}-${VERSION}" && \
+	cp -avf ../3rdparty-LICENSES.md "${PACKAGE_NAME}-${VERSION}" && \
+	cp -avf ../bin/* "${PACKAGE_NAME}-${VERSION}" && \
+	cp -avf ../scripts/prometheus-kopano-exporter.binscript "${PACKAGE_NAME}-${VERSION}/scripts" && \
+	cp -avf ../scripts/prometheus-kopano-exporter.service "${PACKAGE_NAME}-${VERSION}/scripts" && \
+	cp -avf ../scripts/prometheus-kopano-exporter.cfg "${PACKAGE_NAME}-${VERSION}/scripts" && \
+	tar --owner=0 --group=0 -czvf ${PACKAGE_NAME}-${VERSION}.tar.gz "${PACKAGE_NAME}-${VERSION}" && \
+	cd ..
+
+.PHONE: changelog
+changelog: ; $(info updating changelog ...)
+	$(CHGLOG) --output CHANGELOG.md $(ARGS)
+
+# Rest
+
+.PHONY: clean
+clean: ; $(info cleaning ...)	@
+	@rm -rf bin
+	@rm -rf test/test.*
+
+.PHONY: version
+version:
+	@echo $(VERSION)

cmd/prometheus-kopano-exporter/log.go

@@ -0,0 +1,27 @@
+/*
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ * Copyright 2020 Kopano and its licensors
+ */
+
+package main
+
+import (
+	"os"
+
+	"github.com/sirupsen/logrus"
+)
+
+func newLogger(disableTimestamp bool, logLevelString string) (logrus.FieldLogger, error) {
+	logLevel, err := logrus.ParseLevel(logLevelString)
+	if err != nil {
+		return nil, err
+	}
+
+	return &logrus.Logger{
+		Out: os.Stderr,
+		Formatter: &logrus.TextFormatter{
+			DisableTimestamp: disableTimestamp,
+		},
+		Level: logLevel,
+	}, nil
+}

main.go → cmd/prometheus-kopano-exporter/main.go

@@ -1,6 +1,6 @@
 /*
  * SPDX-License-Identifier: AGPL-3.0-or-later
- * Copyright 2019 Kopano and its licensors
+ * Copyright 2020 Kopano and its licensors
  */
 
 package main
@@ -10,5 +10,6 @@ import (
 )
 
 func main() {
-  cmd.Execute()
+	cmd.RootCmd.AddCommand(commandServe())
+	cmd.RootCmd.Execute()
 }