From 09e45e27ab2134469c458ea87fb57e7e241b76f1 Mon Sep 17 00:00:00 2001
From: Alexey Rybalchenko <alexryba@gmail.com>
Date: Fri, 1 Sep 2017 10:36:55 +0200
Subject: [PATCH] Add introspection docs.

---
 fairmq/README.md             |  3 ++-
 fairmq/docs/Configuration.md | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/fairmq/README.md b/fairmq/README.md
index aa5b4424..a0fe52fd 100644
--- a/fairmq/README.md
+++ b/fairmq/README.md
@@ -16,7 +16,8 @@ Standard FairRoot is running all the different analysis tasks within one process
     1. [Device Configuration](docs/Configuration.md#31-device-configuration)
     2. [Communication Channels Configuration](docs/Configuration.md#32-communication-channels-configuration)
         1. [JSON Parser](docs/Configuration.md#321-json-parser)
-        1. [SuboptParser](docs/Configuration.md#322-suboptparser)
+        2. [SuboptParser](docs/Configuration.md#322-suboptparser)
+    3. [Introspection](docs/Configuration.md#33-introspection)
 4. [Development](docs/Development.md#3-development)
    1. [Testing](docs/Development.md#31-testing)
 5. [Examples](docs/Examples.md#4-examples)
diff --git a/fairmq/docs/Configuration.md b/fairmq/docs/Configuration.md
index 153a073c..eca1a0aa 100644
--- a/fairmq/docs/Configuration.md
+++ b/fairmq/docs/Configuration.md
@@ -91,4 +91,23 @@ The option key `--channel-config` can be used with the list of key/value pairs,
 --channel-config name=output,type=push,method=bind,address=tcp://127.0.0.1:5555
 ```
 
+## 3.3 Introspection
+
+A compiled device executable repots its available configuration. Run the device with one of the following options to see the corresponding help:
+
+- `-h [ --help ]`: All available command line options with their descriptions and default values.
+
+- `--print-options`: All available command line options in a machine-readable format: `<option>:<computed-value>:<<type>>:<description>`.
+
+- `--print-channels`: Prints registered channels in a machine-readable format: `<channel name>:<minimum sub-channels>:<maximum sub-channels>`. There are devices where channels names are not known in advance before the configuration takes place (e.g. FairMQMultiplier has configurable channel names at runtime). This options will only print channels that have been registered in the device by implementing the following method:
+
+```C++
+void YourDevice::RegisterChannelEndpoints()
+{
+    // provide channel name, minimum and maximum number of subchannels
+    RegisterChannelEndpoint("channelA", 1, 10000);
+    RegisterChannelEndpoint("channelB", 1, 1);
+}
+```
+
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