api: add the role implementation

The role is generally similar in functionality to
`cartridge-metrics-role`. But there is also a difference. The key
difference - the role does not support `health` format.

The role name is `roles.metrics-export` it could be configured in the
Tarantool 3 cluster configuration like this:

```yaml
roles: [roles.metrics-export]
roles_cfg:
  roles.metrics-export:
    http:
    - listen: 8081
      endpoints:
      - path: /metrics/json
        format: json
      - path: /metrics/prometheus/
        format: prometheus
    - listen: '127.0.0.1:8082'
      endpoints:
      - path: /metrics/prometheus
        format: prometheus
      - path: /metrics/json/
        format: json
```

* `http` - is an export type name. The `http` is only supported at
  now. It allows to export metrics via a list of HTTP servers.
  * `listen` - is an address/port to listen via a HTTP server.
  * `endpoints` - is a list of endpoints to share via the HTTP server.
    * `path` - is an endpoint path.
    * `format` - is an export format for the endpoint, at now the role
      supports only `json` and `prometheus`.

Closes #6

.github/workflows/testing.yaml

@@ -85,9 +85,7 @@ jobs:
         id: cache-rocks
         with:
           path: .rocks/
-          key: "cache-rocks-${{ matrix.tarantool }}${{ env.VERSION_POSTFIX }}-\
-            ${{ matrix.cartridge-version }}-\
-            ${{ matrix.metrics-version }}"
+          key: "cache-rocks-${{ matrix.tarantool }}${{ env.VERSION_POSTFIX }}"
 
       - name: Setup tt
         run: |

AUTHORS

@@ -3,7 +3,7 @@ many contributions from the community.
 
 Below follows a list of people, who contributed their code.
 
-Fedor Terekhin
+Fedor Terekhin, Oleg Jukovec
 
 NOTE: If you can commit a change to this list, please do not hesitate
 to add your name to it.

CHANGELOG.md

@@ -9,6 +9,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+- The role implementation (#6).
+
 ### Fixed
 
 ### Changed

Makefile

@@ -4,6 +4,25 @@
 MAKEFILE_PATH := $(abspath $(lastword $(MAKEFILE_LIST)))
 PROJECT_DIR := $(patsubst %/,%,$(dir $(MAKEFILE_PATH)))
 
+# Look for .rocks/bin directories upward starting from the project
+# directory.
+#
+# It is useful for luacheck and luatest.
+#
+# Note: The PROJECT_DIR holds a real path.
+define ENABLE_ROCKS_BIN
+	$(if $(wildcard $1/.rocks/bin),
+		$(eval ROCKS_PATH := $(if $(ROCKS_PATH),$(ROCKS_PATH):,)$1/.rocks/bin)
+	)
+	$(if $1,
+		$(eval $(call ENABLE_ROCKS_BIN,$(patsubst %/,%,$(dir $1))))
+	)
+endef
+$(eval $(call ENABLE_ROCKS_BIN,$(PROJECT_DIR)))
+
+# Add found .rocks/bin to PATH.
+PATH := $(if $(ROCKS_PATH),$(ROCKS_PATH):$(PATH),$(PATH))
+
 SHELL := $(shell which bash)
 SEED ?= $(shell /bin/bash -c "echo $$RANDOM")
 

metrics-export-role-scm-1.rockspec

@@ -1,18 +1,24 @@
 package = "metrics-export-role"
 version = "scm-1"
+
 source = {
     url = "git+https://github.com/tarantool/metrics-export-role",
     branch = "master",
 }
+
 description = {
     summary = "The Tarantool 3 role for metrics export via HTTP",
     homepage = "https://github.com/tarantool/metrics-export-role",
     license = "BSD2",
     maintainer = "Fedor Terekhin <[email protected]>"
 }
+
 dependencies = {
     "lua >= 5.1",
+    "tarantool >= 3.0",
+    "http >= 1.5.0",
 }
+
 build = {
     type = "builtin",
     modules = {