toil.jobStores.utils

Module Contents

Classes

WritablePipe	An object-oriented wrapper for os.pipe. Clients should subclass it, implement
ReadablePipe	An object-oriented wrapper for os.pipe. Clients should subclass it, implement
ReadableTransformingPipe	A pipe which is constructed around a readable stream, and which provides a

Functions

generate_locator(job_store_type[, local_suggestion, ...])

Generate a random locator for a job store of the given type. Raises an

Attributes

log

toil.jobStores.utils.log

class toil.jobStores.utils.WritablePipe(encoding=None, errors=None)

Bases: abc.ABC

An object-oriented wrapper for os.pipe. Clients should subclass it, implement readFrom() to consume the readable end of the pipe, then instantiate the class as a context manager to get the writable end. See the example below.

>>> import sys, shutil
>>> class MyPipe(WritablePipe):
...     def readFrom(self, readable):
...         shutil.copyfileobj(codecs.getreader('utf-8')(readable), sys.stdout)
>>> with MyPipe() as writable:
...     _ = writable.write('Hello, world!\n'.encode('utf-8'))
Hello, world!

Each instance of this class creates a thread and invokes the readFrom method in that thread. The thread will be join()ed upon normal exit from the context manager, i.e. the body of the with statement. If an exception occurs, the thread will not be joined but a well-behaved readFrom() implementation will terminate shortly thereafter due to the pipe having been closed.

Now, exceptions in the reader thread will be reraised in the main thread:

>>> class MyPipe(WritablePipe):
...     def readFrom(self, readable):
...         raise RuntimeError('Hello, world!')
>>> with MyPipe() as writable:
...     pass
Traceback (most recent call last):
...
RuntimeError: Hello, world!

More complicated, less illustrative tests:

Same as above, but proving that handles are closed:

>>> x = os.dup(0); os.close(x)
>>> class MyPipe(WritablePipe):
...     def readFrom(self, readable):
...         raise RuntimeError('Hello, world!')
>>> with MyPipe() as writable:
...     pass
Traceback (most recent call last):
...
RuntimeError: Hello, world!
>>> y = os.dup(0); os.close(y); x == y
True

Exceptions in the body of the with statement aren’t masked, and handles are closed:

>>> x = os.dup(0); os.close(x)
>>> class MyPipe(WritablePipe):
...     def readFrom(self, readable):
...         pass
>>> with MyPipe() as writable:
...     raise RuntimeError('Hello, world!')
Traceback (most recent call last):
...
RuntimeError: Hello, world!
>>> y = os.dup(0); os.close(y); x == y
True

abstract readFrom(readable)

Implement this method to read data from the pipe. This method should support both binary and text mode output.

Parameters:

readable (file) – the file object representing the readable end of the pipe. Do not explicitly invoke the close() method of the object, that will be done automatically.

__enter__()

__exit__(exc_type, exc_val, exc_tb)

class toil.jobStores.utils.ReadablePipe(encoding=None, errors=None)

Bases: abc.ABC

An object-oriented wrapper for os.pipe. Clients should subclass it, implement writeTo() to place data into the writable end of the pipe, then instantiate the class as a context manager to get the writable end. See the example below.

>>> import sys, shutil
>>> class MyPipe(ReadablePipe):
...     def writeTo(self, writable):
...         writable.write('Hello, world!\n'.encode('utf-8'))
>>> with MyPipe() as readable:
...     shutil.copyfileobj(codecs.getreader('utf-8')(readable), sys.stdout)
Hello, world!

Each instance of this class creates a thread and invokes the writeTo() method in that thread. The thread will be join()ed upon normal exit from the context manager, i.e. the body of the with statement. If an exception occurs, the thread will not be joined but a well-behaved writeTo() implementation will terminate shortly thereafter due to the pipe having been closed.

Now, exceptions in the reader thread will be reraised in the main thread:

>>> class MyPipe(ReadablePipe):
...     def writeTo(self, writable):
...         raise RuntimeError('Hello, world!')
>>> with MyPipe() as readable:
...     pass
Traceback (most recent call last):
...
RuntimeError: Hello, world!

More complicated, less illustrative tests:

Same as above, but proving that handles are closed:

>>> x = os.dup(0); os.close(x)
>>> class MyPipe(ReadablePipe):
...     def writeTo(self, writable):
...         raise RuntimeError('Hello, world!')
>>> with MyPipe() as readable:
...     pass
Traceback (most recent call last):
...
RuntimeError: Hello, world!
>>> y = os.dup(0); os.close(y); x == y
True

Exceptions in the body of the with statement aren’t masked, and handles are closed:

>>> x = os.dup(0); os.close(x)
>>> class MyPipe(ReadablePipe):
...     def writeTo(self, writable):
...         pass
>>> with MyPipe() as readable:
...     raise RuntimeError('Hello, world!')
Traceback (most recent call last):
...
RuntimeError: Hello, world!
>>> y = os.dup(0); os.close(y); x == y
True

abstract writeTo(writable)

Implement this method to write data from the pipe. This method should support both binary and text mode input.

Parameters:

writable (file) – the file object representing the writable end of the pipe. Do not explicitly invoke the close() method of the object, that will be done automatically.

__enter__()

__exit__(exc_type, exc_val, exc_tb)

class toil.jobStores.utils.ReadableTransformingPipe(source, encoding=None, errors=None)

Bases: ReadablePipe

A pipe which is constructed around a readable stream, and which provides a context manager that gives a readable stream.

Useful as a base class for pipes which have to transform or otherwise visit bytes that flow through them, instead of just consuming or producing data.

Clients should subclass it and implement transform(), like so:

>>> import sys, shutil
>>> class MyPipe(ReadableTransformingPipe):
...     def transform(self, readable, writable):
...         writable.write(readable.read().decode('utf-8').upper().encode('utf-8'))
>>> class SourcePipe(ReadablePipe):
...     def writeTo(self, writable):
...         writable.write('Hello, world!\n'.encode('utf-8'))
>>> with SourcePipe() as source:
...     with MyPipe(source) as transformed:
...         shutil.copyfileobj(codecs.getreader('utf-8')(transformed), sys.stdout)
HELLO, WORLD!

The transform() method runs in its own thread, and should move data chunk by chunk instead of all at once. It should finish normally if it encounters either an EOF on the readable, or a BrokenPipeError on the writable. This means that it should make sure to actually catch a BrokenPipeError when writing.

See also: toil.lib.misc.WriteWatchingStream.

abstract transform(readable, writable)

Implement this method to ship data through the pipe.

Parameters:

• readable (file) – the input stream file object to transform.

• writable (file) – the file object representing the writable end of the pipe. Do not explicitly invoke the close() method of the object, that will be done automatically.

writeTo(writable)

Implement this method to write data from the pipe. This method should support both binary and text mode input.

Parameters:

writable (file) – the file object representing the writable end of the pipe. Do not explicitly invoke the close() method of the object, that will be done automatically.

exception toil.jobStores.utils.JobStoreUnavailableException

Bases: RuntimeError

Raised when a particular type of job store is requested but can’t be used.

toil.jobStores.utils.generate_locator(job_store_type, local_suggestion=None, decoration=None)

Generate a random locator for a job store of the given type. Raises an JobStoreUnavailableException if that job store cannot be used.

Parameters:

• job_store_type (str) – Registry name of the job store to use.

• local_suggestion (Optional[str]) – Path to a nonexistent local directory suitable for use as a file job store.

• decoration (Optional[str]) – Extra string to add to the job store locator, if convenient.

Return str:

Job store locator for a usable job store.

Return type:

str