Update readme file

instrumentation/httpd/README.md

@@ -8,19 +8,73 @@
 
 ## Requirements
 
+- httpd (Apache) ver. 2.4.x on Linux (Current release tested only with Ubuntu LTS 18.04 & 20.04)
+
+### Usage
+
+For manual build please check below. Otherwise please use one of the [released versions](/../releases).
+
+### Installation
+
+Mod_otel works as a module which is loaded when Apache starts. It is written in C++ therefore standard library has to be included as well. Below is an example of lines which should be added to your configuration file (usually `/etc/httpd/conf.d` or equivalent):
+
+```
+LoadFile /usr/lib/x86_64-linux-gnu/libstdc++.so.6
+LoadModule otel_module $SCRIPT_DIR/bazel-out/k8-opt/bin/otel.so
+```
+
+Please check that module is loaded correctly with command `apache2ctl configtest`
+
+### Configuration
+
+Below is the list of possible OpenTelemetry directives.
+
+__OpenTelemetryExporter__
+Configures exporter to be used. At the moment only one global exporter is allowed for entire daemon. Possible values for this setting are:
+- `file` - to export to a file
+- `otlp` - to export using the OpenTelemetry Protocol
+
+__OpenTelemetryPath__
+This option specifies file to which to export when `file` exporter is used. If no `OpenTelemetryPath` is specified then spans goes to standard error output which is apache error log.
+
+__OpenTelemetryEndpoint__
+OpenTelemetryEndpoint specifies where to export spans when OTLP is used. Put hostname and then port. Example value: `host.docker.internal:55680`
+
+__OpenTelemetryBatch__
+This directive takes 3 numerical arguments for batch processing:
+- Max Queue Size
+- Delay (in milliseconds, 1000 = 1s)
+- Max Export Batch Size
+- 
+For example `OpenTelemetryBatch 10 5000 5`
+
+__OpenTelemetryPropagators__
+OpenTelemetryPropagators sets which context propagator should be used (defaults to none). Currently supported values are:
+- `trace-context`
+- `b3`
+- `b3-multiheader`
+
+__OpenTelemetryIgnoreInbound__
+ OpenTelemetryIgnoreInbound indicates that we don't trust incoming context. This is a safe default when httpd is an edge server with traffic from Internet. Set it to false only if you run httpd in safe/trusted environment. Possbile values are `on` and `off` (defaults to on).
+
+ __OpenTelemetrySetAttribute__
+Allows to add extra attribute for each span. It takes two text arguments. For example `OpenTelemetrySetAttribute foo bar` 
+
+List of configuration options can be found in [provided configuration file](./opentelemetry.conf)
+
+## Development
+
+### Requirements
+
 - C++11
 - [OpenTelemetry-Cpp](https://github.com/open-telemetry/opentelemetry-cpp)
-- httpd (Apache) ver. 2.4.x on Linux (Current release tested only with Ubuntu LTS 18.04)
 - Bazel 3.7.x
 
-## Build + development
-
+### Build
 Build can be done within docker or alternatively check Development section for Ubuntu below.  Execute: `make build` to start build process.
 
 After build is successful enable module for httpd (Apache) the `httpd_install_otel.sh` (prepared for Docker Image) script can be used for this.
 
-### Development
-
 For development purposes (to get inside docker) execute `make start` and `make devsh` for each extra terminal.
 
 Build is done with Bazel. Execute: `./build.sh` and it should create file `otel.so` inside `bazel-out/k8-opt/bin` directory.
@@ -35,7 +89,7 @@ ln -s /mnt/host src
 
 When local changes are made, you need to restart the `httpd` server to load new version of library, to do that: `apachectl stop; ./build.sh && apachectl start`
 
-### Development (Ubuntu)
+### Prerequisites (Ubuntu)
 
 On Ubuntu you need packages listed here: [setup_environment.sh](./setup_environment.sh) which are prerequisites to compile opentelemetry-cpp and here: [setup-buildtools.sh](./setup-buildtools.sh) for apache development stuff. Then just execute [bulid.sh](./build.sh).
 
@@ -47,23 +101,9 @@ Please make sure that code is well formatted with this command:
 ./tools/check-formatting.sh
 ```
 
+when contributing.
+
 ### Testing
 
 Integration tests exists in `tests` directory. Please run `run-all.sh` to check functionality.
 
-## Configuration
-
-At the moment only one global exporter is allowed for entire daemon. Include it following way:
-
-```
-<IfModule mod_otel.cpp>
-OpenTelemetryExporter file
-OpenTelemetryPath /tmp/spans
-</IfModule>
-```
-
-in a master configuration which usually is in `/etc/apache2` directory.
-
-If no `OpenTelemetryPath` is specified then spans goes to standard error output which is apache error log.
-
-More detailed information about configuration options can be found in [provided configuration file](./opentelemetry.conf)