Ringserver¶

Ringserver is a generic ring buffer. The server is commonly used as a buffer for (near) real-time streaming feeds of time series data. Each individual time series is commonly identified with a stream name (for seismological data these are equivalent to unique channels by convention), but the stream names are completely arbitrary. In general, data clients connect to the server and submit a "subscription" for specific streams and as other data clients submit data into the system they are sent to clients with matching subscriptions. By identifying each buffer packet uniquely and allowing a client to select a starting point in the buffer clients can resume broken connections without data loss.

Communicating with a server is generally done using the DataLink protocol over TCP/IP. A DataLink client can query the server for various server details, submit data, and subscribe to streams. Server details can include stream lists, client lists and server statistics. A library in C that implements the DataLink protocol is available.

The dalitool program can be used to monitor and diagnose a ringserver node. Source code for this program and the ringserver itself is available here:

http://www.iris.edu/pub/programs/ringserver

Server configuration, on-the-fly changes¶

Most common options can be configured using command line arguments to ringserver. All options can be configured via a configuration file. Most options, if specified via the configuration file, can be changed on the fly. The server will monitor the configuration file for changes and apply them as needed, this reduces the amount of down-time and eases the maintenance of a ringserver node.

SeedLink support¶

While the architecture implemented by ringserver is completely generic some additions have been made to support the SeedLink protocol. In particular for packets where the data are 512-byte miniSEED records the server can be configured to serve the streams via SeedLink. This option must be enabled, listening for SeedLink connections is not enabled by default.

Stand-alone SeedLink server¶

The ringserver software may be used to implement a stand-alone SeedLink server. One per-requisite to serving data via SeedLink from ringserver to is have data formatted as 512-byte miniSEED data records. To accomplish this there are two options:

• Users that already have 512-byte miniSEED written to files may configure ringserver to continuously scan directories and files and read any newly arriving data. Read How to configure ringserver as a turkey SeedLink streaming server for more information.

• Users that can write a program that can submit 512-byte miniSEED data to ringserver via DataLink (TCP/IP) simply need to configure the server to listen for SeedLink connections and run their submission client.

Implementation and resource requirements¶

3rd party libraries used¶

The ringserver program uses the following opensource libraries:

• PCRE - Perl Compatible Regular Expressions (www.pcre.org)
• Mini-XML - Lightweight XML Library (www.minixml.org)