From 7da3618bf3dfbec19c5f93e367fcb3b607f894ae Mon Sep 17 00:00:00 2001
From: Jan-Piet Mens <jpmens@gmail.com>
Date: Sun, 16 Aug 2015 17:28:09 +0200
Subject: [PATCH] describe monitor hook

---
 README.md | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/README.md b/README.md
index 6bd3370..4001a8b 100644
--- a/README.md
+++ b/README.md
@@ -11,3 +11,21 @@ Recorder
 1. Edit `config.h`
 2. Edit `config.mk` and select features
 2. Type `make`
+
+## Monitoring
+
+In order to monitor the _recorder_, whenever an MQTT message is received, the _recorder_ will add an epoch timestamp and the last received topic a Redis key (if configured) or a file otherwise. The Redis key looks like this:
+
+```
+redis 127.0.0.1:6379> hgetall ot-recorder-monitor
+1) "time"
+2) "1439738692"
+3) "topic"
+4) "owntracks/jjolie/ipad"
+```
+
+The `monitor` file is located relative to STORE and contains a single line, the epoch timestamp at the moment of message reception and the topic separated from eachother by a single space:
+
+```
+1439738692 owntracks/jjolie/ipad
+```