Italian center for Astronomical Archives publishing solution: modular and distributed

The Italian center for Astronomical Archives has, among its goals, to provide astronomical data resources as interoperable services based on IVOA standards. It did so for part of its archives (mainly raw telescope data from LBT, TNG and Italian national telescopes) and continued on with hosted data collections and providing expertise to national and international research projects (like WINGS, VIPERS, VIALACTEA). Its expertise and knowledge of the VO comes from active participation within IVOA and VO at European and international level, with a double-fold goal: learn from the collaboration (acquiring skills and technical knowledge) and provide inputs (implementations and feedback) to the VO community. In this scenario the first solution to build an easy to configure and maintain resource publisher conformant to VO standards proved to be too optimistic, not considering the complexity the IVOA architecture could have reached in a short while. For this reason it has been necessary to re-think the architecture with a modular system. This latter is now partially in place and will gradually replace the previous solution allowing for an easier to extend and rework if major changes will happen at the level of VO standards. The solution chosen for the architecture orbits around the messaging concept, where each modular component speaks to the other interested parties through a system of broker-managed queues (currently using AMQP with RabbitMQ as the broker). The messaging system lets us free to choose the development language for the business logic components, not only for the front-end, web interfacing solutions (needed to expose VO HTTP based protocols), but also on the archives and database access components, the logging systems and any other tool or component that may be needed in the future. The first implementation covered the simplest VO protocol, the Simple Cone Search, were the messaging task architecture connects the parametric HTTP interface to the database backend access module, the logging module, and allows multiple cone search resources to be managed together through a configuration manager module. Even if it has been initially used as a test for the new architecture, it already proved the flexibility required by the overall system when the database backend needed to be changed from a MySQL to a PostgreSQL+PgSphere solution. Another implementation test has been made to leverage task distribution over multiple servers dedicated to computation to allow for a single HTTP interface to serve simultaneously: FITS cubes direct linking, cubes cutout (using an AST and cfitsio engine) and cubes positional merging (using a Montage based solution). The solution proved also to be a quick answer to load distribution (although not really efficient). Alongside these the implementation of the SIA-2.0 standard protocol is ongoing, following the scheme used for the Simple Cone Search, while for the TAP protocol implementation we will be re-using and adapting the already available TAPlib library. Alongside this production, message-driven, publishers, a first administration tool (TASMAN) has been developed to ease the build up and maintenance of the TAP_SCHEMA component of TAP services including also ObsCore maintenance capability. Future work will be devoted at widening the range of VO protocols covered by the set of available modules, improve the configuration management and develop specific purpose modules common to all the service components.