Update README.md

README.md

 # ca-tango-db-cache-mgr
 
+## Installation
+
+### Dependencies
+
+#### hiredis
+
+Either install from package manager or
+
+> git clone https://github.com/redis/hiredis.git
+
+> cd hiredis
+
+> mkdir build && cd build
+
+> cmake .. -DCMAKE_INSTALL_PREFIX=/usr/local/hiredis
+
+> make -j9 && sudo make install
+
+#### redis-plus-plus
+
+> git clone https://github.com/sewenew/redis-plus-plus
+
+> cd redis-plus-plus
+
+> mkdir build && cd build
+
+If redis has been manually installed in /usr/local/hiredis, then execute
+
+> cmake .. -DCMAKE_INSTALL_PREFIX=/opt/redis-plus-plus -DCMAKE_PREFIX_PATH=/opt/hiredis -DHIREDIS_HEADER=/opt/redis-plus-plus/include
+
+otherwise the options -DCMAKE_PREFIX_PATH and HIREDIS_HEADER is not necessary.
+We experienced that CMAKE_PREFIX_PATH is not enough to let redis plus plus include hiredis files
+correctly, and we need to add also -DHIREDIS_HEADER. 
+
+> make -j9 
+
+> sudo make install 
+
+### service Installation
+
+Assuming the paths mentioned above were used to install hiredis and redis-plus-plus:
+
+> git clone https://gitlab.elettra.eu/puma/server/ca-tango-db-cache-mgr
+
+Adjust PKG_CONFIG_PATH according to the caserver-lib, hiredis, redis-plus-plus, cumbia-libs
+installation paths. For example:
+
+> export PKG_CONFIG_PATH=/opt/caserver-lib/lib/pkgconfig:/opt/hiredis/lib/pkgconfig:/opt/redis-plus-plus/lib/pkgconfig:$PKG_CONFIG_PATH
+
+*nlohmann-json* dependency is also required. You can place a copy in the *subprojects* directory if the
+package is not installed system-wide
+
+
+
 ### request syntax
 
 > curl -v http://woody.elettra.eu:9296 -d $'{"srcs":[{"src":"test/device/1/double_scalar"}]}'