Refactor the complete code

README.md

@@ -34,18 +34,24 @@ $ cat example/data.json
             "count": 3,
             "some_boolean": false,
             "state": "ACTIVE"
-        },
-    ]
+        }
+    ],
+    "location": "mars"
 }
 
-$ cat example/config.yml
+$ cat examples/config.yml
+---
+metrics:
 - name: example_global_value
   path: $.counter
+  help: Example of a top-level global value scrape in the json
   labels:
     environment: beta # static label
+    location: $.location          # dynamic label
 
 - name: example_value
   type: object
+  help: Example of sub-level value scrapes from a json
   path: $.values[*]?(@.state == "ACTIVE")
   labels:
     environment: beta # static label
@@ -55,35 +61,35 @@ $ cat example/config.yml
     count: $.count # dynamic value
     boolean: $.some_boolean
 
+headers:
+  X-Dummy: my-test-header
+
 $ python -m SimpleHTTPServer 8000 &
 Serving HTTP on 0.0.0.0 port 8000 ...
 
-$ ./json_exporter http://localhost:8000/example/data.json example/config.yml &
-INFO[2016-02-08T22:44:38+09:00] metric registered;name:<example_global_value>
-INFO[2016-02-08T22:44:38+09:00] metric registered;name:<example_value_boolean>
-INFO[2016-02-08T22:44:38+09:00] metric registered;name:<example_value_active>
-INFO[2016-02-08T22:44:38+09:00] metric registered;name:<example_value_count>
-127.0.0.1 - - [08/Feb/2016 22:44:38] "GET /example/data.json HTTP/1.1" 200 -
+$ ./json_exporter --config.file examples/config.yml &
 
-
-$ curl http://localhost:7979/metrics | grep ^example
-example_global_value{environment="beta"} 1234
+$ curl "http://localhost:7979/probe?target=http://localhost:8000/examples/data.json" | grep ^example
+example_global_value{environment="beta",location="mars"} 1234
 example_value_active{environment="beta",id="id-A"} 1
 example_value_active{environment="beta",id="id-C"} 1
 example_value_boolean{environment="beta",id="id-A"} 1
 example_value_boolean{environment="beta",id="id-C"} 0
 example_value_count{environment="beta",id="id-A"} 1
 example_value_count{environment="beta",id="id-C"} 3
+
+# To test through prometheus:
+$ docker run --rm -it -p 9090:9090 -v $PWD/examples/prometheus.yml:/etc/prometheus/prometheus.yml --network host prom/prometheus
 ```
+Then head over to http://localhost:9090/graph?g0.range_input=1h&g0.expr=example_value_active&g0.tab=1 or http://localhost:9090/targets to check the scraped metrics or the targets.
 
 # Docker
 
 ```console
 docker run \
-  -v config.yml:/config.yml
+  -v $PWD/examples/config.yml:/config.yml
   quay.io/prometheuscommunity/json-exporter \
-    http://example.com/target.json \
-    /config.yml
+    --config.file /config.yml
 ```
 
 # See Also

cmd/main.go

@@ -0,0 +1,112 @@
+// Copyright 2020 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cmd
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"os"
+
+	"github.com/go-kit/kit/log"
+	"github.com/go-kit/kit/log/level"
+	"github.com/prometheus-community/json_exporter/config"
+	"github.com/prometheus-community/json_exporter/exporter"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"github.com/prometheus/common/promlog"
+	"github.com/prometheus/common/promlog/flag"
+	"github.com/prometheus/common/version"
+	"gopkg.in/alecthomas/kingpin.v2"
+)
+
+var (
+	configFile    = kingpin.Flag("config.file", "JSON exporter configuration file.").Default("config.yml").ExistingFile()
+	listenAddress = kingpin.Flag("web.listen-address", "The address to listen on for HTTP requests.").Default(":7979").String()
+	configCheck   = kingpin.Flag("config.check", "If true validate the config file and then exit.").Default("false").Bool()
+)
+
+func Run() {
+
+	promlogConfig := &promlog.Config{}
+
+	flag.AddFlags(kingpin.CommandLine, promlogConfig)
+	kingpin.Version(version.Print("json_exporter"))
+	kingpin.HelpFlag.Short('h')
+	kingpin.Parse()
+	logger := promlog.New(promlogConfig)
+
+	level.Info(logger).Log("msg", "Starting json_exporter", "version", version.Info()) //nolint:errcheck
+	level.Info(logger).Log("msg", "Build context", "build", version.BuildContext())    //nolint:errcheck
+
+	level.Info(logger).Log("msg", "Loading config file", "file", *configFile) //nolint:errcheck
+	config, err := config.LoadConfig(*configFile)
+	if err != nil {
+		level.Error(logger).Log("msg", "Error loading config", "err", err) //nolint:errcheck
+		os.Exit(1)
+	}
+	configJson, err := json.Marshal(config)
+	if err != nil {
+		level.Error(logger).Log("msg", "Failed to marshal config to JSON", "err", err) //nolint:errcheck
+	}
+	level.Info(logger).Log("msg", "Loaded config file", "config", string(configJson)) //nolint:errcheck
+
+	if *configCheck {
+		os.Exit(0)
+	}
+
+	http.Handle("/metrics", promhttp.Handler())
+	http.HandleFunc("/probe", func(w http.ResponseWriter, req *http.Request) {
+		probeHandler(w, req, logger, config)
+	})
+	if err := http.ListenAndServe(*listenAddress, nil); err != nil {
+		level.Error(logger).Log("msg", "Failed to start the server", "err", err) //nolint:errcheck
+	}
+}
+
+func probeHandler(w http.ResponseWriter, r *http.Request, logger log.Logger, config config.Config) {
+
+	ctx, cancel := context.WithCancel(r.Context())
+	defer cancel()
+	r = r.WithContext(ctx)
+
+	registry := prometheus.NewPedanticRegistry()
+
+	metrics, err := exporter.CreateMetricsList(config)
+	if err != nil {
+		level.Error(logger).Log("msg", "Failed to create metrics list from config", "err", err) //nolint:errcheck
+	}
+
+	jsonMetricCollector := exporter.JsonMetricCollector{JsonMetrics: metrics}
+	jsonMetricCollector.Logger = logger
+
+	target := r.URL.Query().Get("target")
+	if target == "" {
+		http.Error(w, "Target parameter is missing", http.StatusBadRequest)
+		return
+	}
+
+	data, err := exporter.FetchJson(ctx, logger, target, config)
+	if err != nil {
+		http.Error(w, "Failed to fetch JSON response. TARGET: "+target+", ERROR: "+err.Error(), http.StatusServiceUnavailable)
+		return
+	}
+
+	jsonMetricCollector.Data = data
+
+	registry.MustRegister(jsonMetricCollector)
+	h := promhttp.HandlerFor(registry, promhttp.HandlerOpts{})
+	h.ServeHTTP(w, r)
+
+}