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stream_js module

stream_js module#

The module is used to implement handlers in njs — a subset of the JavaScript language.

The module is built as dynamic and available as a separate package angie-module-njs in our repository.

Example Configuration#

stream {
    js_import stream.js;

    js_set $bar stream.bar;
    js_set $req_line stream.req_line;

    server {
        listen 12345;

        js_preread stream.preread;
        return     $req_line;
    }

    server {
        listen 12346;

        js_access  stream.access;
        proxy_pass 127.0.0.1:8000;
        js_filter  stream.header_inject;
    }
}

http {
    server {
        listen 8000;
        location / {
            return 200 $http_foo\n;
        }
    }
}

The stream.js file:

var line = '';

function bar(s) {
    var v = s.variables;
    s.log("hello from bar() handler!");
    return "bar-var" + v.remote_port + "; pid=" + v.pid;
}

function preread(s) {
    s.on('upload', function (data, flags) {
        var n = data.indexOf('\n');
        if (n != -1) {
            line = data.substr(0, n);
            s.done();
        }
    });
}

function req_line(s) {
    return line;
}

// Read HTTP request line.
// Collect bytes in 'req' until
// request line is read.
// Injects HTTP header into a client's request

var my_header =  'Foo: foo';
function header_inject(s) {
    var req = '';
    s.on('upload', function(data, flags) {
        req += data;
        var n = req.search('\n');
        if (n != -1) {
            var rest = req.substr(n + 1);
            req = req.substr(0, n + 1);
            s.send(req + my_header + '\r\n' + rest, flags);
            s.off('upload');
        }
    });
}

function access(s) {
    if (s.remoteAddress.match('^192.*')) {
        s.deny();
        return;
    }

    s.allow();
}

export default {bar, preread, req_line, header_inject, access};

Directives#

js_access#

Syntax:

js_access function | module.function;

Default:

—

Context:

stream, server

Sets an njs function which will be called at the access phase. Module functions can be referenced.

The function is called once at the moment when the stream session reaches the access phase for the first time. The function is called with the following arguments:

s

the stream session object

At this phase, it is possible to perform initialization or register a callback with the s.on() method for each incoming data chunk until one of the following methods are called: s.done(), s.decline(), s.allow(). As soon as one of these methods is called, the stream session processing switches to the next phase and all current s.on() callbacks are dropped.

js_fetch_buffer_size#

Syntax:

js_fetch_buffer_size size;

Default:

js_fetch_buffer_size 16k;

Context:

stream, server

Sets the size of the buffer used for reading and writing with Fetch API.

js_fetch_ciphers#

Syntax:

js_fetch_ciphers ciphers;

Default:

js_fetch_ciphers HIGH:!aNULL:!MD5;

Context:

stream, server

Specifies the enabled ciphers for HTTPS connections with Fetch API. The ciphers are specified in the format understood by the OpenSSL library.

The full list can be viewed using the “openssl ciphers” command.

js_fetch_max_response_buffer_size#

Syntax:

js_fetch_max_response_buffer_size size;

Default:

js_fetch_max_response_buffer_size 1m;

Context:

stream, server

Sets the maximum size of the response received with Fetch API.

js_fetch_protocols#

Syntax:

js_fetch_protocols [TLSv1] [TLSv1.1] [TLSv1.2] [TLSv1.3];

Default:

js_fetch_protocols TLSv1 TLSv1.1 TLSv1.2;

Context:

stream, server

Enables the specified protocols for HTTPS connections with Fetch API.

js_fetch_timeout#

Syntax:

js_fetch_timeout time;

Default:

js_fetch_timeout 60s;

Context:

stream, server

Defines a timeout for reading and writing for Fetch API. The timeout is set only between two successive read/write operations, not for the whole response. If no data is transmitted within this time, the connection is closed.

js_fetch_trusted_certificate#

Syntax:

js_fetch_trusted_certificate file;

Default:

—

Context:

stream, server

Specifies a file with trusted CA certificates in the PEM format used to verify the HTTPS certificate with Fetch API.

js_fetch_verify#

Syntax:

js_fetch_verify on | off;

Default:

js_fetch_verify on;

Context:

stream, server

Enables or disables verification of the HTTPS server certificate with Fetch API.

js_fetch_verify_depth#

Syntax:

js_fetch_verify_depth number;

Default:

js_fetch_verify_depth 100;

Context:

stream, server

Sets the verification depth in the HTTPS server certificates chain with Fetch API.

js_filter#

Syntax:

js_filter function | module.function;

Default:

—

Context:

stream, server

Sets a data filter. Module functions can be referenced.

The filter function is called once at the moment when the stream session reaches the content phase. The filter function is called with the following arguments:

s

the stream session object

At this phase, it is possible to perform initialization or register a callback with the s.on() method for each incoming data chunk. The s.off() method may be used to unregister a callback and stop filtering.

Note

As the js_filter handler returns its result immediately, it supports only synchronous operations. Thus, asynchronous operations such as ngx.fetch() or setTimeout() are not supported.

js_import#

Syntax:

js_import module.js | export_name from module.js;

Default:

—

Context:

stream, server

Imports a module that implements location and variable handlers in njs. The export_name is used as a namespace to access module functions. If the export_name is not specified, the module name will be used as a namespace.

js_import stream.js;

Here, the module name stream is used as

Several js_import directives can be specified.

js_path#

Syntax:

js_path path;

Default:

—

Context:

stream, server

Sets an additional path for njs modules.

js_preload_object#

Syntax:

js_preload_object name.json | name from file.json;

Default:

—

Context:

stream, server

Preloads an immutable object at configure time. The name is used as a name of the global variable though which the object is available in njs code. If the name is not specified, the file name will be used instead.

js_preload_object map.json;

Here, the map is used as a name while accessing the preloaded object.

Several js_preload_object directives can be specified.

js_preread#

Syntax:

js_preread function | module.function;

Default:

—

Context:

stream, server

Sets an njs function which will be called at the preread phase. Module functions can be referenced.

The function is called once at the moment when the stream session reaches the preread phase for the first time. The function is called with the following arguments:

s

the stream session object

At this phase, it is possible to perform initialization or register a callback with the s.on() method for each incoming data chunk until one of the following methods are called: s.done(), s.decline(), s.allow(). When one of these methods is called, the stream session switches to the next phase and all current s.on() callbacks are dropped.

Note

As the js_preread handler returns its result immediately, it supports only synchronous callbacks. Thus, asynchronous callbacks such as ngx.fetch() or setTimeout() are not supported. Nevertheless, asynchronous operations are supported in s.on() callbacks in the preread phase.

js_set#

Syntax:

js_set $variable function | module.function;

Default:

—

Context:

stream, server

Sets an njs function for the specified variable. Module functions can be referenced.

The function is called when the variable is referenced for the first time for a given request. The exact moment depends on a phase at which the variable is referenced. This can be used to perform some logic not related to variable evaluation. For example, if the variable is referenced only in the log_format directive, its handler will not be executed until the log phase. This handler can be used to do some cleanup right before the request is freed.

Note

As the js_set handler returns its result immediately, it supports only synchronous callbacks. Thus, asynchronous callbacks such as ngx.fetch() or setTimeout() are not supported.

js_shared_dict_zone#

Syntax:

js_shared_dict_zone zone=name:size [timeout=time] [type=string | number] [evict];

Default:

—

Context:

stream

Sets the name and size of the shared memory zone that keeps the key-value dictionary shared between worker processes.

type

the optional parameter, allows redefining the value type to number,
by default the shared dictionary uses a string as a key and a value

timeout

the optional parameter, sets the time after which all shared dictionary entries are removed from the zone

evict

the optional parameter, removes the oldest key-value pair when the zone storage is exhausted

Examples:

example.conf:
    # Creates a 1Mb dictionary with string values,
    # removes key-value pairs after 60 seconds of inactivity:
    js_shared_dict_zone zone=foo:1M timeout=60s;

    # Creates a 512Kb dictionary with string values,
    # forcibly removes oldest key-value pairs when the zone is exhausted:
    js_shared_dict_zone zone=bar:512K timeout=30s evict;

    # Creates a 32Kb permanent dictionary with number values:
    js_shared_dict_zone zone=num:32k type=number;

example.js:
    function get(r) {
        r.return(200, ngx.shared.foo.get(r.args.key));
    }

    function set(r) {
        r.return(200, ngx.shared.foo.set(r.args.key, r.args.value));
    }

    function delete(r) {
        r.return(200, ngx.shared.bar.delete(r.args.key));
    }

    function increment(r) {
        r.return(200, ngx.shared.num.incr(r.args.key, 2));
    }

js_var#

Syntax:

js_var $variable [value];

Default:

—

Context:

stream, server

Declares a writable variable. The value can contain text, variables, and their combination.

Session Object Properties#

Each stream njs handler receives one argument, a stream-session object.

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