Document the new logs endpoint and env variable

**What**
- Document the new logs handler url env variable in the gateway readme
- Document the logs handler in the swagger docs
Signed-off-by: Lucas Roesler <roesler.lucas@gmail.com>

api-docs/swagger.yml

@@ -332,6 +332,41 @@ paths:
           description: Not Found
         '500':
           description: Internal Server Error
+  '/system/logs':
+      get:
+        summary: Get a stream of the logs for a specific function
+        produces:
+          - application/x-ndjson
+      parameters:
+      - in: query
+        name: name
+        description: Function name
+        type: string
+        required: true
+      - in: query
+        name: since
+        description: Only return logs after a specific date (RFC3339)
+        type: string
+        required: false
+      - in: query
+        name: tail
+        description: Sets the maximum number of log messages to return, <=0 means unlimited
+        type: integer
+        required: false
+      - in: query
+        name: follow
+        description: When true, the request will stream logs until the request timeout
+        type: boolean
+        required: false
+      responses:
+        '200':
+          description: Newline delimited stream of log messages
+          schema:
+            $ref: '#/definitions/LogEntry'
+        '404':
+          description: Not Found
+        '500':
+          description: Internal Server Error
   '/system/info':
     get:
       summary: Get info such as provider version number and provider orchestrator
@@ -559,6 +594,22 @@ definitions:
         example: changeme
     required:
     - name
+  LogEntry:
+    type: object
+    property:
+      name:
+        type: string
+        description: the function name
+      instance:
+        type: string
+        description: the name/id of the specific function instance
+      timestamp:
+        type: string
+        format: date-time
+        description: the timestamp of when the log message was recorded
+      text:
+        type: string
+        description: raw log message content
   SecretName:
     type: object
     properties:

gateway/README.md

@@ -45,7 +45,9 @@ See the [openfaas/store](https://github.com/openfaas/store) repo for more.
 
 ## Logs
 
-Logs are available at the function level and can be accessed through Swarm or Kubernetes using native tooling. You can also install a Docker logging driver to aggregate your logs. By default functions will not write the request and response bodies to stdout. You can toggle this behaviour by setting `read_debug` for the request and `write_debug` for the response.
+Logs are available at the function level via the API.
+
+You can also install a Docker logging driver to aggregate your logs. By default functions will not write the request and response bodies to stdout. You can toggle this behaviour by setting `read_debug` for the request and `write_debug` for the response.
 
 ## Tracing
 
@@ -67,6 +69,7 @@ The gateway can be configured through the following environment variables:
 | `write_timeout`        | HTTP timeout for writing a response body from your function (in seconds). Default: `8`  |
 | `read_timeout`         | HTTP timeout for reading the payload from the client caller (in seconds). Default: `8` |
 | `functions_provider_url`             | URL of upstream [functions provider](https://github.com/openfaas/faas-provider/) - i.e. Swarm, Kubernetes, Nomad etc  |
+| `logs_provider_url` | URL of the upstream function logs api provider, optional, when empty the `functions_provider_url` is used |
 | `faas_nats_address`          | Address of NATS service. Required for asynchronous mode |
 | `faas_nats_port`    | Port for NATS service. Requrired for asynchronous mode |
 | `faas_prometheus_host`         | Host to connect to Prometheus. Default: `"prometheus"` |