Home
Reference
Find details on the SPL language, toolkits, APIs, commands, and more.
Streams Processing Language (SPL)
Streams Processing Language (SPL) is a distributed data flow composition language that is used in Teracloud® Streams. SPL has primitive types, program structures, and definitions that are tailored for streaming data.
Operator config clause
The config clause specifies hints and directives that influence how the compiler builds an operator invocation, or how the runtime system runs it.
Operator placement config clause
placement : host

Welcome
Learn about the core capabilities of Teracloud® Streams, its architecture, and key concepts.
Installing
Use this information to install, upgrade, and uninstall the Teracloud® Streams product.
Configuring
Create a basic or an enterprise domain which is a single point for configuring and managing common resources, security, and instances.
Administering
Administer the product by using the Teracloud® Streams graphical user interface, APIs, or the streamtool command-line interface.
Developing
Develop stream applications with the Streams Processing Language (SPL), Java, and Python.
Troubleshooting
Resolve problems with Teracloud® Streams using the troubleshooting tools provided with the product as well as the resources offered by Teracloud Support.
Reference
Find details on the SPL language, toolkits, APIs, commands, and more.
- APIs
  Application programming interfaces (APIs) provide functions that simplify applications development.
- Job configuration overlays
  You can specify or change configuration parameters when you use the submitjob or updateoperators operations. The settings control submission constraints, host constraints and locations, and operator status. Parameters are captured and updated in the configuration JSON file. When you change the values in the job configuration overlay file, the changes override any previously set values.
- Commands
  Teracloud® Streams provides a number of commands you use to perform tasks.
- Operator model
  An operator model is an XML document that describes the basic properties of a primitive operator.
- Streams Processing Language (SPL)
  Streams Processing Language (SPL) is a distributed data flow composition language that is used in Teracloud® Streams. SPL has primitive types, program structures, and definitions that are tailored for streaming data.
  - Language overview
    SPL contains types, expressions, statements, functions, clauses, and other elements of a programming language.
  - Grammar notation
    This language specification adopts a flavor of Backus-Naur Form (BNF) to describe the syntax of language features.
  - Lexical syntax
    SPL defines a set of rules to determine the syntax of a program.
  - Grammar overview
    Here is the SPL grammar syntax, with references to the sections that contain the semantics.
  - Expression language
    Though SPL is a streaming language, there are many places where it uses expressions that are found in traditional imperative or functional languages.
  - Annotations
    Operators can be annotated. Annotations influence the run time behavior of stream applications.
  - Types
    SPL has several primitive types that are tailored for streaming, and a few composite types that are inspired by scripting languages but statically checked. The following topics describe the types, how to define them, and how to convert values between different types.
  - Operators
    Operators process tuples in an incoming stream and produce an output stream as a result. SPL supports two kinds of operators: primitive operators and composite operators. A primitive operator is written in C++ or Java™. A composite operator is written in SPL and contains a reusable stream subgraph.
  - Program structure
  - Operator config clause
    The config clause specifies hints and directives that influence how the compiler builds an operator invocation, or how the runtime system runs it.
    - Simple config clauses in operators
      The config clause can have subclauses that influence how an operator is compiled or run.
    - Operator placement config clause
- Toolkits
  A toolkit is a set of SPL artifacts, which are organized into a package. Toolkits make SPL or native functions and primitive or composite operators reusable across different applications.
- SPLDOC markup
  You can use SPLDOC markup in the descriptions associated with the SPL artifacts in a toolkit. The spl-make-doc command generates HTML documentation from the marked up artifacts.
Glossary
Use this glossary to find terms and definitions for Teracloud® Streams.

placement : host

type:

rstring with IP address or host name. Each operator instance can have at most one host subconfg.

example:

config placement :
      host("server1.teracloud.com");

description:

Placement of operator instance, specifies on which host it runs. The following table describes the various forms for specifying the host subconfig:

Table 1. Formats for specifying the host subconfig.
Format	Description
`host("10.4.40.83");`	The host is specified as an IP address.
`host("foo.test.teracloud.com");`	The host is specified as a host name.
`host(MyPool[5]);`	The host is specified as a fixed offset in a pool of hosts.
`host(MyPool);`	A host pool is specified and Teracloud® Streams picks a host from the pool at run time.

Note:

A fixed offset can be specified only for sized pools.
If your application has user-defined parallelism, you can use the replicateHostTags element in the parallel annotation to influence the placement of operator instances in host pools.

default:

Place the operator instance on any host in the default pool.