Parsing windows IIS logs
Prabhat Sharma
March 10, 2024
6 min read
Don’t forget to share!
Introduction
Internet Information Services (IIS) is a flexible, secure and manageable Web server for hosting anything on the Web. Monitoring and analyzing IIS logs can provide valuable insights into the performance and health of your web applications. In this blog, we will walk through the process of capturing IIS logs using the OpenTelemetry Collector (otel-collector) and parsing them using VRL functions in OpenObserve for analysis. You could use fluentbit or vector as well to capture the logs and send them to OpenObserve.
Step 1: Setting Up the otel-collector
The OpenTelemetry Collector offers a vendor-agnostic implementation on how to receive, process, and export telemetry data. In our case, we want to capture IIS logs and send them for analysis. Here's how you can set it up:
- Install the otel-collector: You can install the otel-collector on your server to capture the IIS logs using the one liner command available from your OpenObserve
Ingestionpage.
This will install the otel-collector as a Windows service with the binary and the configuration file in c:\otel-collector
- Configure the filelog receiver: The otel-collector configuration file should include a
filelogreceiver. This receiver will watch for log files in the specified directory and read new log entries as they are written.
Open the configuration file c:\otel-collector\otel-config.yaml and add the following configuration snippet:
receivers:
filelog/iis:
include: ['c:\\inetpub\\logs\\LogFiles\\**\\*']
start_at: beginning
- Configure the OpenTelemetry exporter: The otel-collector configuration file should also include an OpenTelemetry exporter to send the captured logs to OpenObserve.
exporters:
otlphttp/openobserve_iis:
endpoint: http://localhost:5080/api/default/
headers:
stream-name: iis
Authorization: "Basic cm9vdEBleGFtcGxlLmNvbTpXbTNtdTFaS2Vma3pCa1p1"
- Wire them together: Ensure that the service pipelines are correctly wired to use the
filelog/iisreceiver and the appropriate exporter.
Example configuration snippet for the service:
service:
pipelines:
logs/iis:
receivers: [filelog/iis]
processors: [resourcedetection/system, memory_limiter, batch]
exporters: [otlphttp/openobserve_iis]
At this point, the otel-collector is set up to capture IIS logs and send them to OpenObserve for analysis. For the changes to take effect, restart the otel-collector service.
Once the otel-collector is running, it will start capturing IIS logs and sending them to OpenObserve. You should see a new stream iis under streams/logs menu
Step 2: Parsing IIS Logs with VRL
After setting up the otel-collector to capture the IIS logs, the next step is to parse these logs into a structured format that can be easily analyzed. VRL functions can be created in OpenObserve to parse the logs.
The IIS logs are typically written in a space-separated format.
Here is a sample log entry from an IIS log file:
{
"_timestamp": 1710067224558454,
"body": "2024-03-10 10:39:35 ::1 GET / - 80 - ::1 Mozilla/5.0+(Windows+NT+10.0;+Win64;+x64)+AppleWebKit/537.36+(KHTML,+like+Gecko)+Chrome/121.0.0.0+Safari/537.36+Edg/121.0.0.0 - 304 0 0 0",
"dropped_attributes_count": 0,
"host_name": "EC2AMAZ-FI57MQI",
"log_file_name": "u_ex240310.log",
"os_type": "windows",
"severity": ""
}
The body contains detailed information about a single HTTP request in a common log format. Let's break down the components:
2024-03-10 10:39:35: The date and time when the request was received.::1: The source IP address of the request, which in this case is the loopback address (IPv6 format), indicating the request was made locally on the server.GET: The HTTP method used for the request./: The path of the requested resource, which in this case is the root directory.80: The port number on which the request was received.-: This dash often represents the referrer URL, which is missing here, indicating the request was not made through a link on another page.::1: Again, the source IP address, also indicating a local request.Mozilla/5.0 ... Edg/121.0.0.0: The user agent string, which provides information about the client making the request, including the operating system, browser version, and rendering engine.304: The HTTP status code sent in response, indicating that the resource was not modified and the client can use the cached version.0: Substatus code (specific to the server software) which sometimes provides more detail on the response.0: Win32 status code, which can provide information about the status of the request at the operating system level.0: The time taken to serve the request, in milliseconds.
This structured logging is useful for automated processing and analysis, allowing systems and administrators to filter, search, and analyze log data efficiently.
Here's an example of how you can parse the logs using VRL:
pattern = r'^(?P<timestamp>[^\s]+ [^\s]+) (?P<client_ip>[^\s]+) (?P<http_method>[^\s]+) (?P<requested_path>[^\s]+) (?P<placeholder1>[^\s]+) (?P<server_port>[^\s]+) (?P<placeholder2>[^\s]+) (?P<referrer_ip>[^\s]+) (?P<user_agent>.*?) (?P<referrer_url>.*?) (?P<http_status>[^\s]+) (?P<other_codes>[^\s]+ [^\s]+) (?P<response_time>[^\s]+)(?: (?P<forwarded_ips>.*))?$'
.body = parse_regex!(.body, pattern)
Step 3: Viewing Parsed Logs in OpenObserve
Once the logs are parsed, they should look like below:
{
"_timestamp": 1710067224558454,
"body_client_ip": "::1",
"body_forwarded_ips": null,
"body_http_method": "GET",
"body_http_status": "304",
"body_other_codes": "0 0",
"body_placeholder1": "-",
"body_placeholder2": "-",
"body_referrer_ip": "::1",
"body_referrer_url": "-",
"body_requested_path": "/",
"body_response_time": "0",
"body_server_port": "80",
"body_timestamp": "2024-03-10 10:39:34",
"body_user_agent": "Mozilla/5.0+(Windows+NT+10.0;+Win64;+x64)+AppleWebKit/537.36+(KHTML,+like+Gecko)+Chrome/121.0.0.0+Safari/537.36+Edg/121.0.0.0",
"dropped_attributes_count": 0,
"host_name": "EC2AMAZ-FI57MQI",
"log_file_name": "u_ex240310.log",
"os_type": "windows",
"severity": ""
}
Step 4: Save the function and associate it to the stream
You should save the VRL function and associate it to the stream. This will ensure that the logs are parsed and structured as they are ingested into OpenObserve.
Once you have associated the function with the stream, the logs will be parsed and structured as they are ingested into OpenObserve.
Step 5: Analyzing the Data in OpenObserve
With the logs now in OpenObserve, you can use dashboards and alerts to:
- Monitor access patterns and potential security breaches.
- Analyze the performance of your web applications.
- Set up alerts for specific log patterns that might indicate errors or other issues.
Conclusion
By leveraging the power of otel-collector and VRL, you can efficiently capture and send IIS logs to OpenObserve and parse them for comprehensive analysis. This approach allows you to gain deeper insights into your web applications, helping you to maintain performance and reliability. Remember to check the OpenTelemetry and Vector documentation for the most up-to-date instructions and configurations.
