adding the apache server example (#36)

* adding the apache server example

* Apply suggestions from code review

---------

Co-authored-by: प्रथमेश Sonpatki <csonpatki@gmail.com>

Author: karthikeyangs9

otel-collector/apache-server/README.md

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+# Monitoring Apache Server Metrics with OpenTelemetry
+
+A guide for setting up Apache Server monitoring using OpenTelemetry Collector with Last9. It collects host metrics, Apache Server metrics and sends them to Last9.
+
+## Installation
+
+### 1. Apache Server Setup
+
+```bash
+# Install apache
+sudo apt-get update
+sudo apt-get install -y apache2
+sudo systemctl start apache2
+
+# Verify installation
+sudo systemctl status apache2
+```
+
+Configure Apache Server:
+```bash
+sudo nano /etc/apache2/apache2.conf
+```
+
+Add the below configuration in the conf file:
+```ini
+<Location "/server-status">
+    SetHandler server-status
+    Require host localhost
+</Location>
+```
+Note: Replace `localhost` with your domain name.
+
+```bash
+# Restart Apache
+sudo systemctl restart apache2
+```
+
+### 2. Install OpenTelemetry Collector
+
+```bash
+sudo apt-get update
+sudo apt-get -y install wget systemctl
+wget https://github.com/open-telemetry/opentelemetry-collector-releases/releases/download/v0.110.0/otelcol-contrib_0.110.0_linux_amd64.deb
+sudo dpkg -i otelcol-contrib_0.110.0_linux_amd64.deb
+```
+
+Configure collector:
+```bash
+sudo nano /etc/otelcol-contrib/config.yaml
+```
+
+Copy the configuration from [here](./otel-config.yaml) and update in `/etc/otelcol-contrib/config.yaml`.
+
+Start collector:
+```bash
+otelcol-contrib --config /etc/otelcol-contrib/config.yaml
+```
+
+## Verification
+
+1. Test exporter:
+You can access the following link - http://localhost/server-status in your browser to check the metrics of the apache server
+
+```bash
+curl http://localhost/server-status
+```
+
+## Troubleshooting
+
+1. Apache issues:
+```bash
+sudo systemctl status apache2
+sudo journalctl -u apache2
+```
+2. Collector issues:
+```bash
+sudo systemctl status otelcol-contrib
+sudo journalctl -u otelcol-contrib
+```

otel-collector/apache-server/otel-config.yaml

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+receivers:
+  otlp:
+    protocols:
+      grpc:
+        endpoint: 127.0.0.1:4318
+      http:
+        endpoint: 127.0.0.1:4319
+  apache:
+    endpoint: "http://localhost:80/server-status?auto"
+    collection_interval: 30s
+
+processors:
+  batch:
+    timeout: 5s
+    send_batch_size: 10000
+    send_batch_max_size: 10000
+  resourcedetection/ec2:
+    detectors: ["ec2"]
+    ec2:
+      # A list of regex's to match tag keys to add as resource attributes can be specified
+      tags:
+        # This means you have a tag `Name` associated with the EC2 Instance.
+        - ^Name$
+        # This means you have a tag `app` associated with the EC2 Instance.
+        - ^app$
+  transform/ec2:
+    error_mode: ignore
+    log_statements:
+      - context: resource
+        statements:
+          # Set Service name as the `Name` tag associated with the EC2 Instance. The format is `ec2.tag.<tag_name>`.
+          - set(attributes["service.name"], attributes["ec2.tag.Name"])
+  resourcedetection/system:
+    detectors: ["system"]
+    system:
+      hostname_sources: ["os"]
+  transform/hostmetrics:
+    metric_statements:
+      - context: datapoint
+        statements:
+          - set(attributes["host.name"], resource.attributes["host.name"])
+          - set(attributes["cloud.account.id"], resource.attributes["cloud.account.id"])
+          - set(attributes["cloud.availability_zone"], resource.attributes["cloud.availability_zone"])
+          - set(attributes["cloud.platform"], resource.attributes["cloud.platform"])
+          - set(attributes["cloud.provider"], resource.attributes["cloud.provider"])
+          - set(attributes["cloud.region"], resource.attributes["cloud.region"])
+          - set(attributes["host.type"], resource.attributes["host.type"])
+          - set(attributes["host.image.id"], resource.attributes["host.image.id"])
+exporters:
+  otlp/last9:
+    endpoint: "<LAST9_OTEL_ENDPOINT>"
+    headers:
+      "Authorization": "Basic <LAST9_OAUTH_TOKEN>"
+  debug:
+    verbosity: detailed
+
+service:
+  pipelines:
+    metrics:
+      receivers: [apache]
+      processors: [batch, resourcedetection/system, transform/hostmetrics]
+      exporters: [otlp/last9]