ModuleFile Grammar

Rule ModuleFile

The ModuleFile rule defines a module in tremor.

A module is a unit of compilation.

rule ModuleFile ::=
    ModuleBody 
  ;

Represents the compiled form of a tremor source file.

Currently this can be troy deployment files, trickle query files, or tremor script files.

This is part of of tremor's compiler and runtime and not user modifiable.

Rule ModuleBody

The ModuleBody rule defines the structure of a valid module in tremor.

Modules begin with optional module comments.

Modules MUST define at least one statement, but may define many.

Statements are ; semi-colon delimited.

rule ModuleBody ::=
    ( ModComment ) ?  ModuleStmts 
  ;

The body of a compiled tremor source file has a module level comment ( lines beginning with 3 hashes ) and the statements that form the logic of that module.

This is part of of tremor's compiler and runtime and not user modifiable.

Rule ModComment

The ModComment rule specifies module comments in tremor.

Documentation comments for modules are optional.

A module documentation comment begins with a ### triple-hash and they are line delimited.

Muliple successive comments are coalesced together to form a complete comment.

The content of a module documentation comment is markdown syntax.

rule ModComment ::=
     '<mod-comment>' 
  | ModComment  '<mod-comment>' 
  ;

Example

Module level comments are used throughout the tremor standard library and used as part of our document generation process.

Here is a modified snippet from the standard library to illustrate

### The tremor language standard library it provides the following modules:
###
### * [array](std/array.md) - functions to deal with arrays (`[]`)
### * [base64](std/base64.md) - functions for base64 en and decoding
### * [binary](std/base64.md) - functions to deal with binary data (`<< 1, 2, 3 >>`)
### * [float](std/float.md) - functions to deal with floating point numbers
### * [integer](std/integer.md) - functions to deal with integer numbers
### * [json](std/json.md) - functions to deal with JSON
...

Rule ModuleStmts

The ModuleStmts rule defines a set of module statements.

Module statements are a ; semi-colon delimited set of ModuleStmt rules

rule ModuleStmts ::=
    ModuleStmt  ';' ModuleStmts 
  | ModuleStmt  ';' ?  
  ;

The set of computed statements in a compiled script.

This is part of of tremor's compiler and runtime and not user modifiable.

Rule DocComment

The DocComment rule specifies documentation comments in tremor.

Documentation comments are optional.

A documentation comment begins with a ## double-hash and they are line delimited.

Muliple successive comments are coalesced together to form a complete comment.

The content of a documentation comment is markdown syntax.

rule DocComment ::=
     '<doc-comment>' 
  | DocComment  '<doc-comment>' 
  ;

Example

Documentation level comments are used throughout the tremor standard library and used as part of our document generation process.

Here is a modified snippet from the standard library to illustrate

## Returns the instance of tremor.
##
## Returns a `string`
intrinsic fn instance() as system::instance;
...

This is a builtin function implemented in rust and used in a script as follows:

use tremor::system;

system::instance()

Rule ModuleStmt

The ModuleStmt rule defines the statement types that are valid in a tremor module.

rule ModuleStmt ::=
    Use 
  | Const 
  | FnDefn 
  | Intrinsic 
  | DefineWindow 
  | DefineOperator 
  | DefineScript 
  | DefinePipeline 
  | DefineConnector 
  | DefineFlow 
  ;

The set of statements that are legal in any tremor supported domain specific language.

This is part of of tremor's compiler and runtime and not user modifiable.

Rule Use

Imports definitions from an external source for use in the current source file.

The contents of a source file form a module.

TREMOR_PATH

The TREMOR_PATH environment path variable is a : delimited set of paths.

Each path is an absolute or relative path to a directory.

When using relative paths - these are relative to the working directory where the tremor executable is executed from.

The tremor standard library MUST be added to the path to be accessible to scripts.

rule Use ::=
     'use' ModularTarget 
  |  'use' ModularTarget  'as' Ident 
  ;

Modules

Modules can be scripts. Scripts can store function and constant definitions.

Scripts are stored in .tremor files.

Modules can be queries. Queries can store window, pipeline, script and operator definitions.

Scripts are stored in .trickle files.

Modules can be deployments. Deployments can store connector, pipeline and flow definitions.

Deployments are stored in .troy files.

Conditioning

Modules in tremor are resolved via the TREMOR_PATH environment variable. The variable can refer to multiple directory paths, each separated by a : colon. The relative directory structure and base file name of the source file form the relative module path.

Constraints

It is not recommended to have overlapping or shared directories across the set of paths provided in the tremor path.

It is not recommended to have multiple definitions mapping to the same identifier.

Rule Const

The Const rule defines a rule that binds an immutable expression to an identifier.

As the value cannot be changed at runtime.

rule Const ::=
    ( DocComment ) ?   'const' Ident  '=' ComplexExprImut 
  ;

How do I create new immutable constant variable in tremor?

use std::base64;
const snot = "snot";
const badger = "badger";
const snot_badger = { "#{snot}": "#{base64::encode(badger)}" };

Rule FnDefn

The FnDefn rule allows user defined functions to be defined.

This rule allows tremor users to create functions for reuse in one or many tremor applications.

rule FnDefn ::=
    ( DocComment ) ?   'fn' Ident  '('  '.'  '.'  '.'  ')'  'with' InnerExprs  'end' 
  | ( DocComment ) ?   'fn' Ident  '(' FnArgs  ','  '.'  '.'  '.'  ')'  'with' InnerExprs  'end' 
  | ( DocComment ) ?   'fn' Ident  '('  ')'  'with' InnerExprs  'end' 
  | ( DocComment ) ?   'fn' Ident  '(' FnArgs  ')'  'with' InnerExprs  'end' 
  | ( DocComment ) ?   'fn' Ident  '('  ')'  'of' FnCases  'end' 
  | ( DocComment ) ?   'fn' Ident  '(' FnArgs  ')'  'of' FnCases  'end' 
  ;

Pattern match based function arguments

Functions defined with an of keyword in their signature use pattern matching against arguments

fn fib_(a, b, n) of
  case (a, b, n) when n > 0 => recur(b, a + b, n - 1)
  default => a
end;

Ordinary functions

Functions defined with a with keyword in their signature use ordinary arity based matching.

fn fib(n) with
  fib_(0, 1, n)
end;

Function documentation

In modular functions, it is customary to provide user level documentation for the intended users of a function. Here is an example from the tremor standard library

### Trace Identifiers
###
###

use std::type;
use std::binary;
use std::array;
use std::string;

## Is the `trace_id` valid
##
## Checks the `trace_id` argument to see if it is a valid
## trace id. A legal trace id is one of:
##
## * An array of integers in the range of [0..=255] of length 8
## * A binary 16 byte value
## * A 32-byte hex-encoded string
## * An array of 16 int values
## * Regardless of representation, the value must not be all zeroes
##
## Returns a record when the representation is well-formed of the form:
##
## ```tremor
## {
##    "kind": "string"|"binary"|"array", # Depends on input
##    "valid": true|false,               # True if well-formed and valid
##    "value": "<trace_id>"              # Representation depends on `kind`
## }
## ```
##
## Returns an empty record `{}` when the representation not well-formed
##
fn is_valid(trace_id) of
    # String representation
    case(trace_id) when type::is_string(trace_id) =>
      { "kind": "string", "valid": trace_id != "00000000000000000000000000000000" and string::bytes(trace_id) == 32, "value": trace_id }
    # Binary representation
    case(trace_id) when type::is_binary(trace_id) =>
      let arr = binary::into_bytes(trace_id);
      { "kind": "binary", "valid": binary::len(arr) == 16 and trace_id != << 0:64, 0:64 >>, "value": trace_id }
    # Array representation
    case(trace_id) when type::is_array(trace_id) =>
      { "kind": "array", "valid":  array::len(arr) == 16 and trace_id != [ 0, 0, 0, 0, 0, 0, 0, 0], "value": trace_id }
    default =>
      false
end

Rule Intrinsic

The intrinsic rule defines intrinsic function signatures.

This rule allows tremor maintainers to document the builtin functions implemented as native rust code. The facility also allows document generation tools to document builtin intrinsic functions in the same way as user defined functions.

In short, these can be thought of as runtime provided.

For information on how to define user defined functions see the function rule.

rule Intrinsic ::=
    ( DocComment ) ?   'intrinsic'  'fn' Ident  '('  ')'  'as' ModularTarget 
  | ( DocComment ) ?   'intrinsic'  'fn' Ident  '(' FnArgs  ')'  'as' ModularTarget 
  | ( DocComment ) ?   'intrinsic'  'fn' Ident  '(' FnArgs  ','  '.'  '.'  '.'  ')'  'as' ModularTarget 
  | ( DocComment ) ?   'intrinsic'  'fn' Ident  '('  '.'  '.'  '.'  ')'  'as' ModularTarget 
  ;

Example

From our standard library generated documentation, we can see that the base64 encode function is an intrinsic function.

## Encodes a `binary` as a base64 encoded string
##
## Returns a `string`
intrinsic fn encode(input) as base64::encode;

Rule DefineWindow

The DefineWindow rule defines a temporal window specification.

A window is a mechanism that caches, stores or buffers events for processing over a finite temporal range. The time range can be based on the number of events, the wall clock or other defined parameters.

The named window can be instanciated via operations that support windows such as the select operation.

rule DefineWindow ::=
    ( DocComment ) ?   'define'  'window' Ident  'from' WindowKind CreationWith ( EmbeddedScriptImut ) ?   'end' 
  ;

define window four from tumbling
with
  size = 4
end;

Rule DefineOperator

The DefineOperator rule defines an operator.

An operator is a query operation composed using the builtin operators provided by tremor written in the rust programming language.

The named operator can be parameterized and instanciated via the CreateOperator rule

rule DefineOperator ::=
    ( DocComment ) ?   'define'  'operator' Ident  'from' OperatorKind ArgsWithEnd 
  ;

define pipeline subq
pipeline
  define operator counter from generic::counter;
  create operator counter;
  select event from in into counter;
  select event from counter into out;
end;

create pipeline subq;

select event from in into subq;
select event from subq into out;

Uses the builtin counter sequencing operator to numerate a stream.

Rule DefineScript

The DefineScript rule defines a named operator based on a tremor script.

A script operator is a query operation composed using the scripting language DSL rather than the builtin operators provided by tremor written in the rust programming language.

The named script can be parameterized and instanciated via the CreateScript rule

rule DefineScript ::=
    ( DocComment ) ?   'define'  'script' Ident DefinitionArgs EmbeddedScript 
  ;

define operator bucket from grouper::bucket;

define script categorize
script
  let $rate = 1;
  let $dimensions = event.logger_name;
  let $class = "test";
  event
end;

create operator bucket;
create script categorize;

select event from in into categorize;
select event from categorize into bucket;
select event from bucket into out;

Rule DefinePipeline

The DefinePipeline rule creates a named pipeline.

A pipeline is a query operation composed using the query langauge DSL instead of a builtin operation provided by tremor written in the rust programming language.

The named pipeline can be parameterized and instanciated via the CreatePipeline rule

rule DefinePipeline ::=
    ( DocComment ) ?   'define'  'pipeline' Ident (  'from' Ports ) ?  (  'into' Ports ) ?  DefinitionArgs Pipeline 
  ;

define pipeline identity
pipeline
  select event from in into out;
end;

Rule DefineConnector

The DefineConnector rule defines a connector.

A connector is a runtime artefact that allows tremor to connect to the outside world, or for the outside connector to connect to tremor to send and/or receive data.

The named connector can be parameterized and instanciated via the Create rule

rule DefineConnector ::=
    ( DocComment ) ?   'define'  'connector' Ident  'from' ConnectorKind ArgsWithEnd 
  ;

define connector metronome from metronome
  with
    config = {
      "interval": 1
    }
end;

Define user defind connector metronome from the builtin metronome connector using a 1 second periodicity interval.

define connector exit from exit;

Define user dfeind connector exit from the builtin exit connector with no arguments specified.

Rule DefineFlow

The DefineFlow rule defines a flow.

A flow is a runtime artefact that informs tremor how to interconnect and launch instances of pipelines and connectors.

A flow can define or use multiple in scope and already define pipelines and connectors and interconnect their streams together.

rule DefineFlow ::=
    ( DocComment ) ?   'define'  'flow' Ident DefinitionArgs  'flow' FlowStmts  'end' 
  ;

define flow test
flow
  define connector metronome from metronome
  with
    config = {
      "interval": 1
    }
  end;
  define connector exit from exit;
  define pipeline identity
  args
    snot = "badger",
  pipeline
    select args.snot from in into out;
  end;
  create connector metronome;
  create connector exit;
  create pipeline identity;
  connect /connector/metronome to /pipeline/identity;
  connect /pipeline/identity to /connector/exit;
end;

deploy flow test

A flow definition is a runnable or executable streaming program that describes the connectivity, the logic and how they are interconnected. A deploy statement is responsible for the actual deployment.

Rule ConfigDirectives

The ConfigDirectives rule allows line delimited compiler, interpreter or runtime hints to be specified.

rule ConfigDirectives ::=
    ConfigDirective ConfigDirectives 
  | ConfigDirective 
  ;

See ConfigDirective for supported directives.

Rule ConfigDirective

A ConfigDirective is a directive to the tremor runtime.

Directives MUST begin on a new line with the #!config shebang config token.

rule ConfigDirective ::=
     '#!config' WithExpr 
  ;

Providing a metrics internal via a config directive

# Enable metrics with a 10 second interval
#!config metrics_interval_s = 10

Rule WithExpr

The WithExpr rule defines a name value binding.

rule WithExpr ::=
    Ident  '=' ExprImut 
  ;

Form

name = <value>

Where:

• name is an identifier.
• <value> is any valid immutable expression.

Example

snot = "badger"

Rule ModularTarget

A ModularTarget indexes into tremor's module path.

In tremor a module is a file on the file system.

A module is also a unit of compilation.

A ModularTarget is a :: double-colon delimited set of identifiers.

Leading :: are not supported in a modular target..

Trailing :: are not supported in a modular target.

rule ModularTarget ::=
    Ident 
  | ModPath  '::' Ident 
  ;

Examples

Loading and using a builtin function

# Load the base64 utilities
use std::base64;

# Base64 encode the current `event`.
base64::encode(event)

Loading and using a builtin function with an alias

# Load the base64 utilities
use std::base64 as snot;

# Base64 encode the current `event`.
snot::encode(event)

Rule Ident

An Ident is an identifier - a user defined name for a tremor value.

rule Ident ::=
     '<ident>' 
  ;

Examples of identifiers

let snot = { "snot": "badger" };

Keyword escaping

Surrounding an identifier with a tick '`' allows keywords in tremor's DSLs to be escaped

let `let` = 1234.5;

Emoji

You can even use emoji as identifiers via the escaping mechanism.

let `🚀` = "rocket";

But we cannot think of any good reason to do so!

Rule ArgsWithEnd

The ArgsWithEnd rule defines an arguments block with an end block.

rule ArgsWithEnd ::=
    ArgsClause ?  WithEndClause 
  | 
  ;

An internal rule that defines an optional args block with and optional end token.

This rule is used and shared in other rules as part of their definitions.

Rule ArgsClause

The ArgsClause rule marks the beginning of an arguments block.

A valid clause has one or many argument expressions delimited by a ',' comma.

rule ArgsClause ::=
     'args' ArgsExprs 
  ;

args
  x = y

Rule WithEndClause

The WithEndClause rule defines a with clause with an end terminal token.

rule WithEndClause ::=
    WithClause  'end' 
  ;

with x = y end

Rule DefinitionArgs

The DefinitionArgs rule defines an arguments block without an end block.

rule DefinitionArgs ::=
    ArgsClause ?  
  ;

An optional argument block

args arg1, arg 2

This is a shared internal rule used in other rules as part of their definition.

Rule ArgsExprs

The ArgsExpr rule is a macro rule invocation based on the Sep separator macro rule.

An args expression is a comma delimited set of argument expressions.

rule ArgsExprs ::=
    Sep!(ArgsExprs, ArgsExpr, ",") 
  ;

Rule ArgsExpr

The ArgExpr rule specifies argument lists.

An argument can be an Ident or an assignment of the form <Ident> = <Expr>

rule ArgsExpr ::=
    Ident  '=' ExprImut 
  | Ident 
  ;

As used in deployment rules to set or override arguments specifications. Arguments specifications define interface parameters that must be set by default ( or overridden ) for something to be well defined.

The tremor runtime checks for ommissions and produces an error for attempted instanciations that omit to provide a value for specified arguments.

Rule ExprImut

The ExprImut is the root of immutable expressions in tremor.

rule ExprImut ::=
    OrExprImut 
  ;

The effective root of the subset of the expression langauge applicable in most immutable processing context in tremor is captured by this rule.

Rule CreationWithEnd

The CreationWithEnd rule defines a with block of expressions with a terminal end keyword.

rule CreationWithEnd ::=
    WithEndClause 
  | 
  ;

with x = y end

Rule CreationWith

The CreationWith rule defines an optional with block of expressions without a terminal end keyword.

rule CreationWith ::=
    WithClause 
  | 
  ;

Rule WithClause

The WithClause rule defines a with block with a , comma delimited set of WithExpr rules.

rule WithClause ::=
     'with' WithExprs 
  ;

with x = y

Rule WithExprs

The WithExprs rule defines a , comma delimited set of WithExpr rules.

rule WithExprs ::=
    Sep!(WithExprs, WithExpr, ",") 
  ;

Rule ModPath

The ModPath rule defines a modular path.

A modular path is a sequence of Idents separated by a :: double-colon.

rule ModPath ::=
    ModPath  '::' Ident 
  | Ident 
  ;

How do i reference something from the standard library?

The standard library contains reusable constants, functions and other definitions that can be used in scripts via the Use and ModPath rules.

For example, if you have a file called foo.tremor in a src folder you can append this to your TREMOR_PATH environment variable

export TREMOR_PATH=/path/to/src

Assuming foo.tremor contains the following code:

fn meaning_of_life() of
  42
end;

We can use this in another script as follows:

use foo;

let meaning = foo::meaning_of_life();