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Early Draft Review #1 Specification
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Distributed real-time specification for Java

Profile image of E. Douglas JensenE. Douglas Jensen

2006

https://doi.org/10.1145/1167999.1168002
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7 pages

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Abstract

The Distributed Real-Time Specification for Java (DRTSJ) is under development within Sun's Java Community Process (JCP) as Java Specification Request 50 (JSR-50), lead by the MITRE Corporation. We present the engineering considerations and design decisions settled by the Expert Group, the current and proposed form of the Reference Implementation, and a summary of open issues. In particular, we present an approach to integrating the distributable threads programming model with the Real-Time Specification for Java and discuss the ramifications for composing distributed, real-time systems in Java. The Expert Group plans to release an initial Early Draft Review (EDR) for previewing the distributable threads abstraction in the coming months, which we describe in detail. Along with that EDR, we will make available a demonstration application from Virginia Tech, and a DRTSJ-compatible RTSJ VM from Apogee.

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Related papers

The Distributed Real-Time Specification for Java
E. Douglas Jensen

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The Distributed Real-Time Specification for Java (DRTSJ) is under development within Sun's Java Community Process (JCP) as Java Specification Request 50 (JSR-50), lead by the MITRE Corporation. We present the engineering considerations and design decisions settled by the Expert Group, the current and proposed form of the Reference Implementation, and a summary of open issues. In particular, we present an approach to integrating the distributable threads programming model with the Real-Time Specification for Java and discuss the ramifications for composing distributed, real-time systems in Java. The Expert Group plans to release an initial Early Draft Review (EDR) for previewing the distributable threads abstraction in the coming months, which we describe in detail. Along with that EDR, we will make available a demonstration application from Virginia Tech, and a DRTSJ-compatible RTSJ VM from Apogee.

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E. Douglas Jensen

Work is beginning on the Distributed Real-Time Specification for Java, as part of Sun's Java Co mmunity Process. This paper summarizes some ideas about an initial approach to the specification. The approach is based on providing a natural and minimal mechanistic extension to Remote Method Invocation (RMI) to support the end-to -end timeliness (and other) properties of distributed -in the sense of trans-node -behaviors. These timeliness properties must be preserved for any distributed real-time computing system, regardless of its application programming model -whether RPC, mobile objects, or whatever. The proposed extension also facilitates real-time distributed programming with control flow programming models in particular. A similar facility has proven effective in several other distributed real-time operating system and middleware contexts, and is a primary feature of the unified proposal to OMG for D ynamic Real-Time CORBA.

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Rationale for the direction of the distributed real-time specification for Java panel position paper
E. Douglas Jensen

… on Object-Oriented Real-Time Distributed Computing, 2002.( …

This paper summarizes the rationale for the Distributed Real-Time Specification for Java (DRTSJ), being developed by the JSR-50 Expert Group in Sun's Java Community Process, as of December 2001. The DRTSJ is focused on supporting predictability of end-to-end timeliness for sequentially transnode behaviors (e.g., chains of invocations) in dynamic distributed object systems. The rationale explains how this focus was arrived at, by defining what "real-time," "distributed," and "distributed real-time" mean in the context of the DRTSJ, since those terms are commonly used in widely different ways, especially by practitioners.

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Pablo Basanta Val

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Current trends in real-time systems identify Java as a new alternative to develop both centralized and distributed real-time systems. Many efforts have been devoted to develop the Real-Time Specification for Java (RTSJ), and there is substantial ongoing activity to produce a straightforward and valuable Distributed Real Time Specification for Java (DRTSJ). The current paper provides a contribution to this latter activity defining, from different angles, a synchronous scheduling service aligned with principles of some popular real-time architectures. This service orchestrates the system in such a way that it provides end-toend guarantees in the distributed transactions, guaranteeing their timely execution across the network and nodes. The service is described from two points of view: the system one, characterizing a portable model; and the programmer one, defining a distributed object-oriented implementation of a model based on Real-Time Remote Method Invocation (RTRMI). Finally, it also presents results of an implementation carried out to judge the efficiency of the service, offering a preliminary predictability and performance assessment of a distributed real-time Java technology.

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Related topics

  • Computer Science
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  • Java Modeling Language
  • Real-Time Java

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    On Distributed Real-Time Scheduling in Networked Embedded Systems in the Presence of Crash Failures
    E. Douglas Jensen

    Lecture Notes in Computer Science, 2007

    We consider the problem of scheduling distributable realtime threads in networked embedded systems that operate under runtime uncertainties including those on thread execution times, thread arrivals, and node failure occurrences. We present a distributed scheduling algorithm called CUA. We show that CUA satisfies thread time constraints in the presence of crash failures, is early-deciding, has an efficient message complexity of O(fn) (where f is the number of crashes that actually occur and n is the number of nodes), and is time-optimal with a time lower bound of O(D + fd + nk) (where D is the message delay upper bound, d is the failure detection bound, and k is the maximum number of threads). In crash-free runs, the algorithm constructs schedules within O(D + nk), and yields optimal total utility if nodes are also not overloaded. The algorithm is also "best-effort" in that a high importance thread that may arrive at any time has a very high likelihood for feasible completion (in contrast to classical admission control algorithms which favor feasible completion of admitted threads over admitting new ones, irrespective of thread importance).

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