Here is a description how to make Ocsigen applications (more) static in order to ease deployment of the application. This is done on Linux (Ubuntu). Not sure if it will work on other platforms.

Background

One of the challenges I have found with Ocsigen application has been that I have ha to copy parts of the development environment to the target nodes.

Ocsigen supports dynamic loading of both library modules and your application. For example, the example code in ocsigen-start demo relies on dynamic linking. This is fine and easy to work with when developing, but gives challenges when the application is to be deployed to other nodes.

In addition, Ocsigen supports static linking, however, I have not managed to get it fully working. In particular I have problems with delaying registration of service when using RPC.

Here is a description how to make Ocsigen application "semi-static". That is, the majority of modules used in the application is statically linked with the server, while the application (and a few modules that I was unable to statically link) are linked dynamically when the server starts.

Example on making "ocsigen-start" demo application "semi-static"

Create and build the demo application as described in the documentation.

Configuration for static linked modules

Make a copy of the configuration file

myproject$ cp local/etc/myproject/myproject-test.conf local/etc/myproject/myproject-static.conf

Change the file so that it initializes the modules that is part of the server binary. An example of a modified version is in local/etc/myproject.

To find the name used for modules, you might serch for Ocsigen_extensions.register is source code. I'm not sure it is a way to list the name of registered extensions.

Static linked server

For each module that used to be linked dynamically, make sure that they are linked into the server.

In server is a project that will build a "ocsigenserver" with most of the modules linked in.

deploying_ocsigen/server$ dune build

Copy the binary to the project folder.

myproject$ mkdir bin
myproject$ cp ../deploying_ocsigen/server/_build/default/bin/ocsigen_semi_static_server.exe bin/

Modules that need to be loaded dynamically

The ocsigen-toolkit.server and ocsigen-start.server modules can not be linked with the binary. The libraries are missing ".a" files.

So we need to put the modules as part of our release, and load those dynamically.

myproject$ l=$(ocamlfind query ocsigen-start.server)  ;\
cp $l/*.cmxs local/lib/myproject/ ;
l=$(ocamlfind query ocsigen-toolkit.server) ;\
cp $l/*.cmxs local/lib/myproject/

The *.cmxs files get loaded trough the

    <host hostfilter="*">
        ...
      <eliommodule module="local/lib/myproject/ocsigen-toolkit.server.cmxs" />
      <eliommodule module="local/lib/myproject/ocsigen-start.server.cmxs" />
      ...

Findlib

For some reason, the server seems to need findlib.conf. Might be a way to disable this, but the quickest solution is joust to create a dummy file for it.

myproject$ mkdir lib
myproject$ touch lib/findlib.conf

Packing the demo application

myproject$ cd ..
$ tar zcfv myproject.tgz myproject/bin/ myproject/lib myproject/local myproject/local_db/

Running application

Copy the tar file to the target node and unpack it.

othernode:myproject$ export OCAMLFIND_CONF=./lib/findlib.conf; \
  ./bin/ocsigen_semi_static_server.exe -c local/etc/myproject/myproject-static.conf

This is how far I got with making static Ocsigen applications. Hopefully it might be useful for other that needs to deploy applications written using Ocsigen. If you have tips on how to improve it and make it more static, please let me know.