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  4. vmod_vtc(3)

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VMOD_VTC(3) Library Functions Manual VMOD_VTC(3)

NAME

vmod_vtc - Utility module for varnishtest

SYNOPSIS

import vtc [from "path"] ;
VOID barrier_sync(STRING addr, DURATION timeout)
BACKEND no_backend()
STEVEDORE no_stevedore()
IP no_ip()
VOID panic(STRING)
VOID sleep(DURATION)
VOID workspace_alloc(ENUM, INT size)
BYTES workspace_reserve(ENUM, INT size)
INT workspace_free(ENUM)
VOID workspace_snapshot(ENUM)
VOID workspace_reset(ENUM)
BOOL workspace_overflowed(ENUM)
VOID workspace_overflow(ENUM)
INT typesize(STRING)


DESCRIPTION

The goal for this VMOD is to provide VCL users and VMOD authors means to test corner cases or reach certain conditions with varnishtest.

VOID barrier_sync(STRING addr, DURATION timeout=0)

When writing test cases, the most common pattern is to start a mock server instance, a Varnish instance, and spin up a mock client. Those entities run asynchronously, and others exist like background processes (process) or log readers (logexpect). While you can synchronize with individual entities and wait for their completion, you must use a barrier if you need to synchronize two or more entities, or wait until a certain point instead of completion.

Not only is it possible to synchronize between test entities, with the barrier_sync function you can even synchronize VCL code:

sub vcl_recv {


    # wait for some barrier b1 to complete


    vtc.barrier_sync("${b1_sock}");
}


If the function fails to synchronize with the barrier for some reason, or if it reaches the optional timeout, it fails the VCL transaction.

MISCELLANEOUS

BACKEND no_backend()

Fails at backend selection.

STEVEDORE no_stevedore()

Fails at storage selection.

IP no_ip()

Returns a null IP address, not even a bogo_ip.

VOID panic(STRING)

It can be useful to crash the child process in order to test the robustness of a VMOD.

VOID sleep(DURATION)

Block the current worker thread.

WORKSPACES

It can be useful to put a workspace in a given state when testing corner cases like resource exhaustion for a transaction, especially for VMOD development. All functions available allow to pick which workspace you need to tamper with, available values are client, backend, session and thread.

VOID workspace_alloc(ENUM, INT size)

VOID workspace_alloc(


   ENUM {client, backend, session, thread},


   INT size
)


Allocate and zero out memory from a workspace. A negative size will allocate as much as needed to leave that many bytes free. The actual allocation size may be higher to comply with memory alignment requirements of the CPU architecture. A failed allocation fails the transaction.

BYTES workspace_reserve(ENUM, INT size)

BYTES workspace_reserve(


   ENUM {client, backend, session, thread},


   INT size
)


Attempt to reserve size bytes and release the reservation right away. Return the size of the reservation.

See vtc.workspace_alloc() for semantics of the size argument.

INT workspace_free(ENUM {client, backend, session, thread})

Find how much unallocated space there is left in a workspace.

VOID workspace_snapshot(ENUM)

VOID workspace_snapshot(ENUM {client, backend, session, thread})


Snapshot a workspace. Only one snapshot may be active at a time.

VOID workspace_reset(ENUM)

VOID workspace_reset(ENUM {client, backend, session, thread})


Reset to the previous snapshot of a workspace, it must be the same workspace too.

BOOL workspace_overflowed(ENUM)

BOOL workspace_overflowed(ENUM {client, backend, session, thread})


Find whether the workspace overflow mark is set or not.

VOID workspace_overflow(ENUM)

VOID workspace_overflow(ENUM {client, backend, session, thread})


Mark a workspace as overflowed.

INT typesize(STRING)

Returns the size in bytes of a collection of C-datatypes:

  • 'p': pointer
  • 'i': int
  • 'd': double
  • 'f': float
  • 'l': long
  • 's': short
  • 'z': size_t
  • 'o': off_t
  • 'j': intmax_t

This can be useful for VMOD authors in conjunction with workspace operations.

SEE ALSO


COPYRIGHT

Copyright (c) 2017 Varnish Software AS
All rights reserved.
Author: Dridi Boukelmoune <dridi.boukelmoune@gmail.com>
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright


   notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright


   notice, this list of conditions and the following disclaimer in the


   documentation and/or other materials provided with the distribution.
THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.