improve troubleshooting guide

README.md

@@ -28,7 +28,7 @@ All variables which can be overridden are stored in [defaults/main.yml](defaults
 | `node_exporter_web_listen_address` | "0.0.0.0:9100" | Address on which node exporter will listen |
 | `node_exporter_enabled_collectors` | ```["systemd",{textfile: {directory: "{{node_exporter_textfile_dir}}"}}]``` | List of dicts defining additionally enabled collectors and their configuration. It adds collectors to [those enabled by default](https://github.com/prometheus/node_exporter#enabled-by-default). |
 | `node_exporter_disabled_collectors` | [] | List of disabled collectors. By default node_exporter disables collectors listed [here](https://github.com/prometheus/node_exporter#disabled-by-default). |
-| `node_exporter_textfile_dir` | "/var/lib/node_exporter" | Directory used by the [Textfile Collector](https://github.com/prometheus/node_exporter#textfile-collector). To get permissions to write metrics in this directory, users must be in `node-exp` system group. __Note__: This variable will have no effect if `node_exporter_enabled_collectors` is overridden.
+| `node_exporter_textfile_dir` | "/var/lib/node_exporter" | Directory used by the [Textfile Collector](https://github.com/prometheus/node_exporter#textfile-collector). To get permissions to write metrics in this directory, users must be in `node-exp` system group. __Note__: More information in TROUBLESHOOTING.md guide.
 | `node_exporter_tls_server_config` | {} | Configuration for TLS authentication. Keys and values are the same as in [node_exporter docs](https://github.com/prometheus/node_exporter/blob/master/https/README.md#sample-config). |
 | `node_exporter_http_server_config` | {} | Config for HTTP/2 support. Keys and values are the same as in [node_exporter docs](https://github.com/prometheus/node_exporter/blob/master/https/README.md#sample-config). |
 | `node_exporter_basic_auth_users` | {} | Dictionary of users and password for basic authentication. Passwords are automatically hashed with bcrypt. |

TROUBLESHOOTING.md

@@ -18,3 +18,26 @@ Or:
 $ export NETRC=
 $ ansible-playbook ...
 ```
+
+## node_exporter doesn't report data from textfile collector
+
+There are 3 potential issues why node_exporter doesn't pick up data:
+
+1. Duplicated metrics across multiple files.
+2. File is not readable by node_exporter process.
+3. Textfile collector is not enabled.
+
+Solving first possibility is out of scope of the role as data is created somewhere else. When creating that data ensure
+files are readable by `node-exp` user. To get access to the directory with files your process needs to be in `node-exp`
+group.
+
+Lastly ansible role misconfiguration can also lead to data not being picked up. Check if `node_exporter` textfile
+collector is enabled in `node_exporter_enabled_collectors` as follows:
+
+```yaml
+node_exporter_enabled_collectors:
+  - textfile:
+      directory: "{{ node_exporter_textfile_dir }}"
+```
+
+__note___: `node_exporter_textfile_dir` variable is only responsible for creating a directory not enabling a collector.