Cortex example project (#238)

* Cortex: Add example

* Add license and source to cortexConfig

* Run make precommit

* Switch to infinite loop

exporters/metric/cortex/example/README.md

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+# Cortex Exporter Example
+
+This example exports several metrics to a [Cortex](https://cortexmetrics.io/) instance and displays
+them in [Grafana](https://grafana.com/).
+
+## Requirements
+
+- [Docker Compose](https://docs.docker.com/compose/) installed
+
+## Instructions
+
+1. Run the docker container with the following command
+
+```bash
+docker-compose up -d
+```
+
+2. Log in to the Grafana instance running at [http://localhost:3000](http://localhost:3000). The
+   login credentials are admin/admin.
+
+3. Add Cortex as a data source by creating a new Prometheus data source using
+   [http://localhost:9009/api/prom/](http://localhost:9009/api/prom/) as the endpoint.
+
+4. View collected metrics in Grafana.
+
+5. Shut down the services when you're finished with the example
+
+```bash
+docker-compose down
+```

exporters/metric/cortex/example/config.yml

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+# Copyright The OpenTelemetry 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.
+
+url: http://host.docker.internal:9009/api/prom/push
+remote_timeout: 30s
+push_interval: 2s
+name: Test
+headers:
+  X-Scope-OrgID: 5

exporters/metric/cortex/example/cortexConfig.yml

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+# This Cortex Config is copied from the Cortex Project documentation
+# Source: https://github.com/cortexproject/cortex/blob/master/docs/configuration/single-process-config.yaml
+
+# Configuration for running Cortex in single-process mode.
+# This configuration should not be used in production.
+# It is only for getting started and development.
+
+# Disable the requirement that every request to Cortex has a
+# X-Scope-OrgID header. `fake` will be substituted in instead.
+auth_enabled: false
+
+server:
+  http_listen_port: 9009
+
+  # Configure the server to allow messages up to 100MB.
+  grpc_server_max_recv_msg_size: 104857600
+  grpc_server_max_send_msg_size: 104857600
+  grpc_server_max_concurrent_streams: 1000
+
+distributor:
+  shard_by_all_labels: true
+  pool:
+    health_check_ingesters: true
+
+ingester_client:
+  grpc_client_config:
+    # Configure the client to allow messages up to 100MB.
+    max_recv_msg_size: 104857600
+    max_send_msg_size: 104857600
+    use_gzip_compression: true
+
+ingester:
+  # We want our ingesters to flush chunks at the same time to optimise
+  # deduplication opportunities.
+  spread_flushes: true
+  chunk_age_jitter: 0
+
+  walconfig:
+    wal_enabled: true
+    recover_from_wal: true
+    wal_dir: /tmp/cortex/wal
+
+  lifecycler:
+    # The address to advertise for this ingester.  Will be autodiscovered by
+    # looking up address on eth0 or en0; can be specified if this fails.
+    # address: 127.0.0.1
+
+    # We want to start immediately and flush on shutdown.
+    join_after: 0
+    min_ready_duration: 0s
+    final_sleep: 0s
+    num_tokens: 512
+    tokens_file_path: /tmp/cortex/wal/tokens
+
+    # Use an in memory ring store, so we don't need to launch a Consul.
+    ring:
+      kvstore:
+        store: inmemory
+      replication_factor: 1
+
+# Use local storage - BoltDB for the index, and the filesystem
+# for the chunks.
+schema:
+  configs:
+    - from: 2019-07-29
+      store: boltdb
+      object_store: filesystem
+      schema: v10
+      index:
+        prefix: index_
+        period: 1w
+
+storage:
+  boltdb:
+    directory: /tmp/cortex/index
+
+  filesystem:
+    directory: /tmp/cortex/chunks
+
+  delete_store:
+    store: boltdb
+
+purger:
+  object_store_type: filesystem
+
+frontend_worker:
+  # Configure the frontend worker in the querier to match worker count
+  # to max_concurrent on the queriers.
+  match_max_concurrent: true
+
+# Configure the ruler to scan the /tmp/cortex/rules directory for prometheus
+# rules: https://prometheus.io/docs/prometheus/latest/configuration/recording_rules/#recording-rules
+ruler:
+  enable_api: true
+  enable_sharding: false
+  storage:
+    type: local
+    local:
+      directory: /tmp/cortex/rules

exporters/metric/cortex/example/docker-compose.yml

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+# Copyright The OpenTelemetry 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.
+
+version: "3"
+
+services:
+  app:
+    image: golang:1.14-alpine
+    volumes:
+      - .:/app
+    working_dir: /app
+    command: go run main.go
+  cortex:
+    image: quay.io/cortexproject/cortex:v1.3.0-rc.1
+    command:
+      - -config.file=./config/cortexConfig.yml
+    volumes:
+      - ./cortexConfig.yml:/config/cortexConfig.yml:ro
+    ports:
+      - 9009:9009
+  grafana:
+    image: grafana/grafana:latest
+    ports:
+      - 3000:3000

exporters/metric/cortex/example/go.mod

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+module go.opentelemetry.io/contrib/exporters/metric/cortex/example
+
+go 1.14
+
+require (
+	go.opentelemetry.io/contrib/exporters/metric/cortex v0.10.1
+	go.opentelemetry.io/contrib/exporters/metric/cortex/utils v0.10.1
+	go.opentelemetry.io/otel v0.10.0
+	go.opentelemetry.io/otel/sdk v0.10.0
+	gopkg.in/yaml.v2 v2.2.5 // indirect
+)