109 lines
4.7 KiB
Markdown
109 lines
4.7 KiB
Markdown
# Apache Prometheus Exporter
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Exports Prometheus metrics from Apache access logs.
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See the [docker](./docker) folder for an example setup using Docker Compose.
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## 1. Configure Apache Access Log Format
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The following snippet will create a log format named `prometheus` that includes all information the exporter expects. See [Apache documentation](https://httpd.apache.org/docs/2.4/mod/mod_log_config.html#formats) for explanation of the format.
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```apache
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LogFormat "%t %h \"%r\" %>s %O %{ms}T \"%{Referer}i\" \"%{User-Agent}i\"" prometheus
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```
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## 2. Configure Apache Virtual Hosts
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The following snippet is an example of how you could configure Apache to serve 3 domains from different folders using macros.
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Each domain has its own access and error log file. The log files are rotated daily, with a dedicated folder for each day, and a `${APACHE_LOG_DIR}/latest/` folder with hard links to today's log files - this folder will be watched by the exporter.
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```apache
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<Macro Logs $domain>
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ErrorLog "|/usr/bin/rotatelogs -l -f -D -L ${APACHE_LOG_DIR}/latest/$domain.error.log ${APACHE_LOG_DIR}/%Y-%m-%d/$domain.error.log 86400"
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CustomLog "|/usr/bin/rotatelogs -l -f -D -L ${APACHE_LOG_DIR}/latest/$domain.access.log ${APACHE_LOG_DIR}/%Y-%m-%d/$domain.access.log 86400" prometheus
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</Macro>
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<Macro Domain $domain>
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<VirtualHost *:80>
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ServerName $domain
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DocumentRoot /var/www/html/$domain
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Use Logs $domain
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</VirtualHost>
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</Macro>
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Domain first.example.com
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Domain second.example.com
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Domain third.example.com
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UndefMacro Domain
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UndefMacro Logs
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```
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In this example, the `first.example.com` domain will be served from `/var/www/html/first.example.com`, and its logs will be written to:
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- `${APACHE_LOG_DIR}/latest/first.example.com.access.log`
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- `${APACHE_LOG_DIR}/latest/first.example.com.error.log`
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## 3. Configure the Exporter
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The exporter requires the following environment variables:
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### `HTTP_HOST`
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The host that the HTTP server for metrics will listen on. If omitted, defaults to `127.0.0.1`.
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### `ACCESS_LOG_FILE_PATTERN`, `ERROR_LOG_FILE_PATTERN`
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The path to the access/error log files. You may use a single wildcard to match multiple files in a folder, or to match multiple folders in one level of the path. Whatever is matched by the wildcard will become the Prometheus label `file`. If there is no wildcard, the `file` label will be empty.
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#### Example 1 (File Name Wildcard)
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Log files for all domains are in `/var/log/apache2/latest/` and are named `<domain>.access.log` and `<domain>.error.log`. This is the set up from the Apache configuration example above.
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**Pattern:** `/var/log/apache2/latest/*.access.log`
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- Metrics for `/var/log/apache2/latest/first.example.com.access.log` will be labeled: `first.example.com`
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- Metrics for `/var/log/apache2/latest/first.example.com.error.log` will be labeled: `first.example.com`
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- Metrics for `/var/log/apache2/latest/second.example.com.access.log` will be labeled: `second.example.com`
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The wildcard may appear anywhere in the file name.
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#### Example 2 (Folder Wildcard)
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Every domain has its own folder in `/var/log/apache2/latest/` containing log files named `access.log` and `error.log`.
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**Pattern:** `/var/log/apache2/latest/*/access.log`
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- Metrics for `/var/log/apache2/latest/first.example.com/access.log` will be labeled: `first.example.com`
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- Metrics for `/var/log/apache2/latest/first.example.com/error.log` will be labeled: `first.example.com`
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- Metrics for `/var/log/apache2/latest/second.example.com/access.log` will be labeled: `second.example.com`
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The wildcard must not include any prefix or suffix, so `/*/` is accepted, but `/prefix_*/` or `/*_suffix/` is not.
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#### Notes
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> The exporter only searches for files when it starts. If you need the exporter to watch a new file or forget a deleted file, you must restart it.
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## 4. Launch the Exporter
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Start the exporter. The standard output will show which log files have been found, the web server host, and the metrics endpoint URL.
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If no errors are shown, the exporter will begin reading the found log files from the end, and printing each line to the standard output. When a log file is rotated, the exporter will begin reading it from the beginning.
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Press `Ctrl-C` to stop the exporter. Signals other than `SIGINT` are ignored.
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#### Notes
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> The exporter is designed to work and tested with the `rotatelogs` tool in a Linux container. Any other tools or operating systems are unsupported.
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> If an error occurs while reading a file or re-opening a rotated file, the exporter will stop watching it and print the error to standard output.
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## 5. Collect Prometheus Metrics
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Currently, the exporter exposes only these metrics:
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- `apache_requests_total` total number of requests
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- `apache_errors_total` total number of errors
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More detailed metrics will be added in the future.
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