Python

This page contains a reference of all exported Kore functions to Python.

Kore must be compiled with PYTHON=1 for this to work. Python 3.6 or higher should be used.

Pulling in Python files

You can import Python files into your Kore application using the python_import configuration option:

python_import ./src/hello.py

If you would like to add a search path for modules (PYTHONPATH) you can specify this using the python_path configuration option:

python_path /var/site-packages/mymodules/

Intro

Before you write any Python code you must import the kore module:

import kore

Note that the Python code is expected to run inside of the Kore worker process, the kore module being imported is not available outside of this worker process.

Shortcuts

Kore

Constants

The kore module exports some constants that can be used by the Python code.

  • LOG_INFO
  • LOG_NOTICE
  • RESULT_OK
  • RESULT_RETRY
  • RESULT_ERROR
  • MODULE_LOAD
  • MODULE_UNLOAD
  • TIMER_ONESHOT
  • CONN_PROTO_HTTP
  • CONN_PROTO_UNKNOWN
  • CONN_PROTO_WEBSOCKET
  • CONN_STATE_ESTABLISHED

Functions

log

Synopsis

kore.log(priority, string)

Description

Logs the given string to syslog.

Parameter Description
priority Log level priority (kore.LOG_ constants).
string The string to be sent to syslog.

Returns

Nothing

Example

kore.log(kore.LOG_INFO, 'this is a log string from a worker process')

timer

Synopsis

kore.timer(method, delay, flags)

Description

Creates a timer that will run after delay milliseconds and call the method specified when expires.

A timer can be primed to run at intervals or as a one-shot occasion.

For a intervals, flags is 0 while for one-shot flags should be kore.TIMER_ONESHOT

A kore.timer object may be stopped by calling the close method on it.

Parameter Description
method The method to call when the timer fires.
delay The delay in milliseconds before the timer fires.
flags Either 0 for an interval timer or kore.TIMER_ONESHOT for a one-shot timer.

Returns

A kore.timer object.

Example

def callback():
    print("called")

mytimer = kore.timer(callback, 100, kore.TIMER\_ONESHOT)

# Stop the timer.
mytimer.close()

proc

Synopsis

kore.proc(command, optional_timeout)

Description

Spawns a new process with the given command and optional timeout in milliseconds.

If timeout is non-zero Kore will raise TimeoutError if the process has not exited before the timeout expires.

If a TimeoutError exception occurs the process is still active and must be killed by calling the kill method on the process object.

See the asynchronous process section for more.

Parameter Description
command The command to be executed.
timeout Optional timeout in milliseconds.

Returns

A kore.proc object.

Example

async def request(req):
    proc = kore.proc("ls -l /tmp")

    try:
        stdout = proc.recv(8192)
        retcode = proc.reap()
        req.response(200, stdout)
    except TimeoutError:
        proc.kill()
        print("process timed out")
        req.response(500, b'')

fatal

Synopsis

kore.fatal(reason)

Description

Terminates the worker process with the given reason as the error message.

Parameter Description
reason String containing the reason why the worker is terminating.

Returns

Nothing

Example

kore.fatal('worker going dead')

tracer

Synopsis

kore.tracer(method)

Description

Sets the callback Kore will call for any uncaught exceptions.

The callback will get 3 parameters:

  • The exception type
  • The exception value
  • The traceback
Parameter Description
method The method to call for uncaught exceptions.

Returns

Nothing

Example

import traceback

def tracer(etype, value, tb):
    traceback.print_exception(etype, value, tb)

def kore_parent_configure(args):
    kore.tracer(tracer)

task_create

Synopsis

kore.task_create(method)

Description

Creates a new task that will run the given method.

There is no way to obtain the result from a task, it will run until it returns from the parent function.

Parameter Description
method The method to call from the new task.

Returns

Nothing

Example

import kore

def coro(id):
    print("i am coro %d" % id)

def kore_worker_configure():
    kore.task_create(coro(1))
    kore.task_create(coro(2))

gather

Synopsis

kore.gather(coroutines)

Description

Awaits all given coroutines and returns their result in a list.

If a coroutine throws an exception that exception is returned as the result for that coroutine.

Parameter Description
coroutines The coroutines to wait for.

Returns

Nothing

Example

import kore

def coro(id):
    print("i am coro %d" % id)

async def request(req):
    results = kore.gather(coro(1), coro(2))

    for result in results:
        if isinstance(result, Exception):
            raise result
        print("result is %s" % result)

    req.response(200, b'')

websocket_broadcast

Synopsis

kore.websocket_broadcast(src, op, data, scope)

Description

Broadcasts a websocket message to all other connected websocket clients.

Parameter Description
src The source kore.connection object.
op The websocket op type.
data The data to be broadcasted.
scope Whether or not this is broadcasted to all workers or just this one.

Returns

Nothing

Example

def onmessage(c, op, data):
    kore.websocket_broadcast(c, op, data, kore.WEBSOCKET_BROADCAST_GLOBAL)

register_database

Synopsis

kore.register_database(name, connstring)

Description

Associates a pgsql connection string with a shortname for a database that can be used later in pgsql.

Parameter Description
name The friendly name for the database.
connstring The pgsql connection string.

Returns

Nothing

Example

kore.register_database("db", "host=/tmp dbname=hello")

HTTP

Like the C API Kore will pass an http_request data structure to your Python page handler. This data structure is of type kore.http_request.

Constants

  • HTTP_METHOD_GET
  • HTTP_METHOD_PUT
  • HTTP_METHOD_HEAD
  • HTTP_METHOD_POST
  • HTTP_METHOD_DELETE
  • HTTP_METHOD_OPTIONS
  • HTTP_METHOD_PATCH

Getters

  • host - The domain as a unicode string.
  • agent - The user agent as a unicode string.
  • path - The requested path as a unicode string.
  • body - The entire incoming HTTP body as a PyBuffer.
  • method - The requested method as a PyLong. (kore.HTTP_METHOD_GET, etc).
  • body_path - The path to the HTTP body on disk (if enabled).
  • connection - The underlying client connection as a kore.connection object.

Functions

pgsql

Synopsis

result = await req.pgsql(db, query)

Description

Performs an asynchronous PostgreSQL query.

Parameter Description
db A previously configured database name.
query The query to be performed.

Returns

The result of the query as a dictionary.

Example

async def myquery(req):
    result = await req.pgsql("db", "SELECT * FROM pg_delay(10)")
    req.response(200, json.dumps(result).encode("utf-8"))

cookie

Synopsis

cookie = req.cookie(name)

Description

Returns the cookie value for a given name.

Parameter Description
name The name of the cookie to lookup.

Returns

Returns the value of the cookie as a unicode string or None if not found.

Example

def handler(req):
    cookie = req.cookie("my_session")
    if cookie != None:
        # use cookie value to do things.

response

Synopsis

req.response(status, body)

Description

Creates an HTTP response for the given HTTP request.

Parameter Description
status The HTTP status code to include in the response.
body The HTTP body to be included in the response, this must be a binary buffer.

Returns

Nothing

Example

def handler(req):
    req.response(200, b'ok')

argument

Synopsis

value = req.argument(name)

Description

Looks up an HTTP parameter that was previously validated via a Kore params block in the configuration.

Parameter Description
name The name of the parameter to lookup.

Returns

The parameter as a unicode string or None if it was not found.

Example

def handler(req):
    id = req.argument("id")
    if id != None:
        # got an id from somewhere

body_read

Synopsis

length, chunk = req.body_read(length)

Description

Reads up to length bytes from the HTTP body and returns the actual bytes read and data in a tuple.

A returned length of 0 bytes indicates the end of the HTTP body.

Parameter Description
length The number of bytes to read.

Returns

The length and data read.

Example

def handler(req):
    if req.method == kore.HTTP_METHOD_POST:
        try
            length, body = req.body_read(1024)
            # do stuff with the body.
        except:
            kore.log(kore.LOG_INFO, "some error occurred")
            req.response(500, b'')

file_lookup

Synopsis

file = req.file_lookup(name)

Description

Lookup an uploaded file (via multipart/form-data).

Parameter Description
name The name of the file that was uploaded.

Returns

A kore.http_file object that can be used to read data from.

Example

def handler(req):
    if req.method == kore.HTTP_METHOD_POST:
        req.populate_multi()
        try
            file = req.file_lookup("myfile")
            length, data = file.read(1024)
            # do stuff with the data .
        except:
            kore.log(kore.LOG_INFO, "some error occurred")
            req.response(500, b'')

populate_get

Synopsis

req.populate_get()

Description

Instructs Kore to go ahead and parse the incoming querystring and validate parameters according to the configured params {} blocks in the configuration.

Returns

Nothing

populate_post

Synopsis

req.populate_post()

Description

Instructs Kore to go ahead and parse the incoming POST data which is of content-type application/x-www-form-urlencoded and validate parameters according to the configured params {} blocks in the configuration.

Returns

Nothing

populate_multipart

Synopsis

req.populate_multipart()

Description

Instructs Kore to go ahead and parse the incoming body as content-type multipart/form-data and validate parameters according to the configured params {} blocks in the configuration.

Returns

Nothing

populate_cookies

Synopsis

req.populate_cookies()

Description

Instructs Kore to go ahead and parse the incoming cookie header (if any).

Returns

Nothing

request_header

Synopsis

value = req.request_header(name)

Description

Finds the incoming request header by name and returns it.

Parameter Description
name The name of the header to lookup.

Returns

The value of the header as a unicode string or None if the header was not present.

Example

def myhandler(req):
    xrequest = req.request_header("x-request")
    if xrequest != None:
        req.response_header("x-response", xrequest)

    req.response(200, b'hello world)

response_header

Synopsis

req.response_header(name, value)

Description

Adds the given header to the response that will be sent by req.response().

Parameter Description
name The name of the header that will be added.
value The value of the header that will be added.

Returns

Nothing

Example

def myhandler(req):
    xrequest = req.request_header("x-request")
    if xrequest != None:
        req.response_header("x-response", xrequest)

    req.response(200, b'hello world)

websocket_handshake

Synopsis

req.websocket_handshake(onconnect, onmsg, ondisconnect)

Description

Adds the given header to the response that will be sent by req.response().

Parameter Description
onconnect The name of the function to be called when a new websocket client is connected.
onmsg The name of the function to be called when a websocket message arrives.
ondisconnect The name of the function to be called when a new websocket client is removed.

Returns

Nothing

Example

def onconnect(c):
    kore.log(kore.LOG_INFO, "%s: connected" % c)

def onmessage(c, op, data):
    # data from c arrived
    # op is the websocket op, WEBSOCKET_OP_TEXT, WEBSOCKET_OP_BINARY
    # data is the data that arrived

def ondisconnect(c):
    kore.log(kore.LOG_INFO, "%s: disconnected" % c)

def ws_connect(req):
    req.websocket_handshake("onconnect", "onmsg", "ondisconnect")

Async/await

Kore exposes several functions that can be awaited upon allowing you to write concurrent page handlers without any callbacks.

Kore currently supports:

For example code covering all asynchronous features, please see the python-async example.

You may choose to create new coroutines using task_create or await several coroutines using gather.

Asynchronous sockets

You can use an existing Python socket object and wrap it inside of a Kore socket. When you have a wrapped socket you can connect/accept, send or recv asynchronously.

Example:

import kore
import socket

async def page(req):
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM |
                                         socket.SOCK_NONBLOCK)

    # Wrap the socket in a Kore object.
    ksock = kore.socket_wrap(sock)

    # Connect and send some data.
    await ksock.connect("127.0.0.1", 3332)
    await ksock.send("hello world")

    # Read a response.
    response = await ksock.recv(1024)

    ksock.close()
    sock.close()

sock.recv

Synopsis

data = await sock.recv(1024)

Description

Reads up to maxlen bytes from the socket.

Parameter Description
maxlen Maximum number of bytes to be read.

Returns

The bytes read as a byte object or None on EOF.

Example

bytes = await sock.recv(1024)
if bytes is None:
    printf("eof!")
else:
    print("received %s" % bytes)

sock.send

Synopsis

await sock.send(data)

Description

Sends the given data over the socket.

Parameter Description
data The data to be sent (as bytes).

Returns

Nothing. In case the peer closes the socket before all data is written a RuntimeException is thrown.

Example

# Will return when all bytes are sent.
await sock.send("Hello world")

sock.accept

Synopsis

await sock.accept()

Description

Accepts a new connection on the socket.

Returns

A kore.socket data object that can be used to send/recv data on.

Example

conn = await sock.accept()
await conn.send("welcome")
conn.close()

sock.connect

Synopsis

await sock.connect()

Description

Connects to a peer.

Returns

Nothing.

Example

# AF_INET socket.
await sock.connect("127.0.0.1", 8888)
data = await sock.recv(1024)
sock.close()

# AF_UNIX socket.
await sock.connect("/var/run/socket.sock")
data = await sock.recv(1024)
sock.close()

sock.close

Synopsis

sock.close()

Description

Closes the underlying socket. If the socket was created from an underlying Python socket, it is not closed.

Returns

Nothing.

Locks

Kore provides a locking mechanism where multiple coroutines can wait upon a lock in a non-blocking way. This allows synchronization between coroutines in a straight forward way.

A lock is created by calling kore.lock().

An coroutine can use the lock with the Python "async with" syntax.

Example:

# Create the lock
lock = kore.lock()

async def request(req):
    # Only allow one request at a time to this handler.
    async with lock:
        # do things
        req.response(200, b'ok')

Queues

Kore provides a queue system that allows objects to be sent back and forth between coroutines in a non-blocking fashion.

The queue is a FIFO queue.

queue.push

Synopsis

queue.push(object)

Description

Pushes the given object onto the queue. The coroutine that waited first on the queue using pop will be woken up.

Parameter Description
object The object to be pushed onto the queue.

Returns

Nothing.

Example

queue = kore.queue()

d = {
    "foo": "bar"
}

queue.push(d)

queue.pop

Synopsis

object = await queue.pop()

Description

Waits for an object to be pushed onto the queue and will return that object.

Returns

The object that was received.

Example

d = await queue.pop()

Asynchronous processes

For a more detailed example, see this source file.

Or see the kore.proc description.

proc.kill

Synopsis

proc.kill()

Description

Sends an immediate SIGKILL to the process.

Returns

Nothing

proc.reap

Synopsis

retcode = proc.reap()

Description

Reaps the process and captures its exit code as the return value.

Returns

The process exit code.

proc.recv

Synopsis

data = await proc.recv(1024)

Description

Reads up to maxlen bytes from the stdout pipe of the process.

Parameter Description
maxlen Maximum number of bytes to be read.

Returns

The bytes read as a byte object or None on EOF.

proc.send

Synopsis

await proc.send(data)

Description

Sends the given data to the process its stdin.

Parameter Description
data The data to be sent (as bytes).

Returns

Nothing. In case the process closes its stdin before all data is written a RuntimeException is thrown.

proc.close_stdin

Synopsis

proc.close_stdin()

Description

Closes the write pipe to the process, making the process see EOF on stdin.

Returns

Nothing.

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