Reliable Messaging for Grids and Web Services Geoffrey Fox, Shrideep Pallickara, Damodar Yemme, Hasan Bulut and Sima Patel (gcf, spallick, dyemme, hbulut and Community Grids Lab Indiana University

Message-Based Reliability Web Services exchange messages and interact with resources that produce and absorb messages Action and state (if exists) of a service defined by messages Our approach to Reliability is based on a building a messaging infrastructure that is intrinsically reliable and high performance  WS-RM and WS-Reliability for web services  Naradabrokering message-oriented middleware

Database SS SSSSSSSSS FS FSFS Portal FSFS OSOS OSOS OSOS OSOS OSOS OSOS OSOS OSOS OSOS OSOS OSOS OSOS MD MetaData Filter Service Sensor Service Other Service Another Grid Raw Data  Data  Information  Knowledge  Wisdom Decisions S S Another Service S Another Grid S SS FS SOAP Messages

Applications of our Technology 1) Point-to-point generic linkage of services using WSRM with messages saved in databases as required in specification 2) Scalable Management Architecture to support dynamic robust collections of entities  Applied first to the brokers used in distributed messaging of NaradaBrokering 3) Management of the streams of data from sensors and web-cams  Allow real-time replay and annotation based on real- time saving of messages forming streams

WSRM and WS-Reliability WSRM describes a protocol that facilitates the reliable delivery of messages between two web service endpoints in the presence of component, system or network failures. WSRM facilitates the reliable delivery of messages from the source (or originator) of messages to the sink (or destination) of messages. The delivery (and ordering) guarantees are valid over a group of messages, which is referred to as a sequence.

Publishing Messages in WSRM Every message from the source contains two pieces of information ─  The Sequence that this message is a part of and  A monotonically increasing Message Number within this Sequence. These Message Numbers enable the tracking of problems, if any, in the intended message delivery at a sink.  Message Numbers enable the determination of out of order receipt of messages as well as message losses. Protocol has acknowledgements and negative acknowledges defined

Typical Processing Acknowledgments Upon receipt of acknowledgements a source can determine which messages might have been lost in transit and proceed to retransmit the missed messages. Thus if a sink has acknowledged the receipt of messages 1 ─ 10 and 13 ─ 18.  The source can conclude that messages with Message Numbers 11 and 12 were lost en route to the sink and proceed to retransmit these messages.

Notification of Errors WSRM provides for notification of errors in processing between the endpoints involved in reliable delivery.  These are routed back as SOAP Faults. The range of errors can vary from an inability to decipher a message’s content to complex errors pertaining to violations in implied agreements between the interacting source and sink. All errors are reported as faults with the appropriate wsa:Action attribute, and encapsulated in WSRM fault elements.

Comments on WSRM Implementation We are delivering this to the UK Open Middleware Infrastructure Institute We built WS-Eventing that is available in OMII in FINS Project WS-RM is currently being tested in OMII container (FIRMS Project) and is expected to be finished in a month and released by OMII in approximately June 2006 WS-RM and WS-Eventing use SOAP handlers that are not well supported in current Axis used by OMII; we should hope Axis 2 will be soon mature enough to use

Operation MeanStand Dev Stand Error Min Val Max Val Memory Use (Bytes) Create an XMLBeans based Envelope Document Create an Axis based SOAPMessage Convert an EnvelopeDocument to a SOAPMessage Convert SOAPMessage to EnvelopeDocument Create a WS-Addressing EPR (Contains just a URL address) Create a WS-Addressing EPR (Contains WSA ReferenceProperties) Create an Envelope targeted to a specific WSA EPR Create an Envelope targeted to a specific WSA EPR with most WSA message information headers Parse an EnvelopeDocument to retrieve Wsa Message Info Headers Times are Microseconds

Operation MeanStand Dev Stand Error Min Val Max Val Memory Util (Bytes) CreateWsrmSequenceRequest CreateWsrmSequenceResponse CreateWsrmSequenceDocument Add a WsrmSequenceDocument to an existing envelope. (Contains sequence identifier and message number) Create a WSRM SequenceAcknowledgement based on a set of message numbers CreateTerminateSequence CreateWsrmFault Times are Microseconds

NaradaBrokering Management Framework

Management of services We prefer to build Grids (collections of web services) that use distributed publish-subscribe message-oriented middleware to transport all messages.  Our publish-subscribe software is called NaradaBrokering (NB) and one can bind SOAP to NB transport (very different from WS- Notification/Eventing) building a handler for this NB will guarantee message delivery and its distributed nature has implicit reliability  However we need to maximize reliability of this infrastructure including attention to network QoS, firewalls etc.

NaradaBrokering Stream NB supports messages and streams NB role for Grid is Similar to MPI role for MPP Queues

NaradaBrokering Messaging infrastructure for collaboration, peer-to-peer and Grids Implements JMS and native high-performance protocols (message transit time of 1 to 2 ms per hop) Order-preserving message transport with QoS and security profiles Support for different underlying transport such as TCP, UDP, Multicast, RTP SOAP message support and WS-Eventing, WS-RM and WS-Reliability. WS-Notification when specification agreed Active replay support: Pause and Replay live streams. Stream Linkage: can link permanently multiple streams – using in annotation of real-time video streams Replicated storage support for fault tolerance and resiliency to storage failures. Management: HPSearch Scripting Interface to streams and brokers (uses WS-Management) Broker Topics and Message Discovery: Locate appropriate Integration with Axis2 Web Service Container (?) High Performance Transport supporting SOAP Infoset

Management Architecture Multiple Distributed Manager Instances Multiple Distributed Managee Instances With web service proxy WS-Management

Features of the Managee Service The distributed managers use NaradaBrokering itself for robust messaging with the “Managees” (Web Service adaptors or proxies to each broker in NaradaBroker networker)

Features of the Manager Service WS-Management used for communicating between Managers and Managees Managers implement policy and user instructions but this very primitive

Generic Recording and Replay Framework

e - Annotation Player Archived stream player Annotation / WB player Archieved stream list Real time stream list e - Annotation Whiteboard Real time stream player Archived Real Time Real Time Stream List Stream List Player e-Annotation Archived Stream Annotated e-Annotation Player Player Stream Player Whiteboard

Generic Recording and Replay Framework A generic framework for recording and replay of any type of streaming event or data. Active replay of streams: Real-time (live) streams can be replayed, paused and rewound while streams are being recorded.  Fast forward is available for the duration of the recorded stream. Note streams are collections of events and events are essentially messages Rewind is same as undo (as in Office)  Go back N messages in stream Replay is same as redo i.e. re-apply sequence of messages to a Web service ports Good replay implies robust message recording

Generic Recording and Replay Framework Stream linkage: Multiple streams are linked together to construct a session.  A collaboration session can be recorded and replayed within this framework. Examples; Anabas – Uses JMS events to transport data such as whiteboard, shared display, audio, etc. GlobalMMCS – Uses NaradaBrokering RTP Events to transport audio and video data. Streams can be added/removed to/from session dynamically while the session is being recorded. Maintains metadata information for recorded sessions and their streams.  Dynamic metadata stored in high performance light weight WS-Context service

Uniform Event Type For Generic Framework Received events are wrapped inside NaradaBrokering native events (NBEvent) with additional event specific information.  Received event is placed to the payload of the NBEvent to preserve original data and related information.  NBEvent also contains timestamp information to timespace original events during replay and event type to initiate appropriate player for that event type. Events and related metadata are stored in database tables.

Session Recorders Session recorder includes topic recorders that subscribe to each topic defined in that session. Topic recorders are like subscribing clients receiving the streaming events. Topic recorders are specialized for event types. i.e. JMS events need JMS topic recorder to receive those type of events. Event types for those streams are already known from the initiated record request.

Time Differential Service (TDS) Replay of events rely on one critical service: Time differential service. Each replay session has one dedicated TDS to achieve replay, pause, rewinding and fast forwarding of the streams in the session in one operation. Achieves synchronization of multiple streams in the same session by maintaining a shared buffer for those streams. Maintains the timespace between the replay events equal to the timespace between the original received events. Resolution of this timespacing is one millisecond; events can be timespaced with one millisecond accuracy. TDS can be maintained on robust node (NaradaBrokering node that provides stable storage) or on client side. Replication of robust nodes supported for better fault tolerance

Session Players The primary purpose of session player is to simulate clients in the original session. To achieve this;  Each recorded topic (or stream) is mapped to a new topic and events of the same original topic are released to the mapped topic.  While releasing the events, timespacing between events are preserved.  Utilizes Time Differential Service to timespace events Recording of live streams are available for replay as soon as they are stored to the reliable storage. Session players support replay, pause, rewind and fast forward operations. When one of those operations is requested, it is applied to all of the topics (streams) in that session.

Session Players II Figure on the left depicts a scenario for playing a session with multiple streams (NB RTPEvent or JMS event based streams)