view contrib/chg/procutil.c @ 39772:ae531f5e583c

testing: add interface unit tests for file storage

Our strategy for supporting alternate storage backends is to define
interfaces for everything then "code to the interface."

We already have interfaces for various primitives, including file
and manifest storage.

What we don't have is generic unit tests for those interfaces. Up
to this point we've been relying on high-level integration tests
(mainly in the form of existing .t tests) to test alternate storage
backends. And my experience with developing the "simple store" test
extension is that such testing is very tedious: it takes several
minutes to run all tests and when you find a failure, it is often
non-trivial to debug.

This commit starts to change that.

This commit introduces the mercurial.testing.storage module. It
contains testing code for storage. Currently, it defines some
unittest.TestCase classes for testing the file storage interfaces.
It also defines some factory functions that allow a caller to easily
spawn a custom TestCase "bound" to a specific file storage backend
implementation.

A new .py test has been added. It simply defines a callable to produce
filelog and transaction instances on demand and then "registers" the
various test classes so the filelog class can be tested with the
storage interface unit tests.

As part of writing the tests, I identified a couple of apparent
bugs in revlog.py and filelog.py! These are tracked with inline
TODO comments.

Writing the tests makes it more obvious where the storage interface
is lacking. For example, we raise either IndexError or
error.LookupError for missing revisions depending on whether we
use an integer revision or a node. Also, we raise error.RevlogError
in various places when we should be raising a storage-agnostic
error type.

The storage interfaces are currently far from perfect and there is much
work to be done to improve them. But at least with this commit we
finally have the start of unit tests that can be used to "qualify"
the behavior of a storage backend. And when implementing and debugging
new storage backends, we now have an obvious place to define new
tests and have obvious places to insert breakpoints to facilitate
debugging. This should be invaluable when implementing new storage
backends.

I added the mercurial.testing package because these interface
conformance tests are generic and need to be usable by all storage
backends. Having the code live in tests/ would make it difficult for
storage backends implemented in extensions to test their interface
conformance. First, it would require obtaining a copy of Mercurial's
storage test code in order to test. Second, it would make testing
against multiple Mercurial versions difficult, as you would need to
import N copies of the storage testing code in order to achieve test
coverage. By making the test code part of the Mercurial distribution
itself, extensions can `import mercurial.testing.*` to access and run
the test code. The test will run against whatever Mercurial version
is active.

FWIW I've always wanted to move parts of run-tests.py into the
mercurial.* package to make the testing story simpler (e.g. imagine an
`hg debugruntests` command that could invoke the test harness). While I
have no plans to do that in the near future, establishing the
mercurial.testing package does provide a natural home for that code
should someone do this in the future.

Differential Revision: https://phab.mercurial-scm.org/D4650

/*
 * Utilities about process handling - signal and subprocess (ex. pager)
 *
 * Copyright (c) 2011 Yuya Nishihara <[e-mail]>
 *
 * This software may be used and distributed according to the terms of the
 * GNU General Public License version 2 or any later version.
 */

#include <assert.h>
#include <errno.h>
#include <signal.h>
#include <stdio.h>
#include <string.h>
#include <sys/wait.h>
#include <unistd.h>

#include "procutil.h"
#include "util.h"

static pid_t pagerpid = 0;
static pid_t peerpgid = 0;
static pid_t peerpid = 0;

static void forwardsignal(int sig)
{
	assert(peerpid > 0);
	if (kill(peerpid, sig) < 0)
		abortmsgerrno("cannot kill %d", peerpid);
	debugmsg("forward signal %d", sig);
}

static void forwardsignaltogroup(int sig)
{
	/* prefer kill(-pgid, sig), fallback to pid if pgid is invalid */
	pid_t killpid = peerpgid > 1 ? -peerpgid : peerpid;
	if (kill(killpid, sig) < 0)
		abortmsgerrno("cannot kill %d", killpid);
	debugmsg("forward signal %d to %d", sig, killpid);
}

static void handlestopsignal(int sig)
{
	sigset_t unblockset, oldset;
	struct sigaction sa, oldsa;
	if (sigemptyset(&unblockset) < 0)
		goto error;
	if (sigaddset(&unblockset, sig) < 0)
		goto error;
	memset(&sa, 0, sizeof(sa));
	sa.sa_handler = SIG_DFL;
	sa.sa_flags = SA_RESTART;
	if (sigemptyset(&sa.sa_mask) < 0)
		goto error;

	forwardsignal(sig);
	if (raise(sig) < 0) /* resend to self */
		goto error;
	if (sigaction(sig, &sa, &oldsa) < 0)
		goto error;
	if (sigprocmask(SIG_UNBLOCK, &unblockset, &oldset) < 0)
		goto error;
	/* resent signal will be handled before sigprocmask() returns */
	if (sigprocmask(SIG_SETMASK, &oldset, NULL) < 0)
		goto error;
	if (sigaction(sig, &oldsa, NULL) < 0)
		goto error;
	return;

error:
	abortmsgerrno("failed to handle stop signal");
}

static void handlechildsignal(int sig UNUSED_)
{
	if (peerpid == 0 || pagerpid == 0)
		return;
	/* if pager exits, notify the server with SIGPIPE immediately.
	 * otherwise the server won't get SIGPIPE if it does not write
	 * anything. (issue5278) */
	if (waitpid(pagerpid, NULL, WNOHANG) == pagerpid)
		kill(peerpid, SIGPIPE);
}

void setupsignalhandler(pid_t pid, pid_t pgid)
{
	if (pid <= 0)
		return;
	peerpid = pid;
	peerpgid = (pgid <= 1 ? 0 : pgid);

	struct sigaction sa;
	memset(&sa, 0, sizeof(sa));

	/* deadly signals meant to be sent to a process group:
	 * - SIGHUP: usually generated by the kernel, when termination of a
	 *   process causes that process group to become orphaned
	 * - SIGINT: usually generated by the terminal */
	sa.sa_handler = forwardsignaltogroup;
	sa.sa_flags = SA_RESTART;
	if (sigemptyset(&sa.sa_mask) < 0)
		goto error;
	if (sigaction(SIGHUP, &sa, NULL) < 0)
		goto error;
	if (sigaction(SIGINT, &sa, NULL) < 0)
		goto error;

	/* terminate frontend by double SIGTERM in case of server freeze */
	sa.sa_handler = forwardsignal;
	sa.sa_flags |= SA_RESETHAND;
	if (sigaction(SIGTERM, &sa, NULL) < 0)
		goto error;

	/* notify the worker about window resize events */
	sa.sa_flags = SA_RESTART;
	if (sigaction(SIGWINCH, &sa, NULL) < 0)
		goto error;
	/* forward user-defined signals */
	if (sigaction(SIGUSR1, &sa, NULL) < 0)
		goto error;
	if (sigaction(SIGUSR2, &sa, NULL) < 0)
		goto error;
	/* propagate job control requests to worker */
	sa.sa_handler = forwardsignal;
	sa.sa_flags = SA_RESTART;
	if (sigaction(SIGCONT, &sa, NULL) < 0)
		goto error;
	sa.sa_handler = handlestopsignal;
	sa.sa_flags = SA_RESTART;
	if (sigaction(SIGTSTP, &sa, NULL) < 0)
		goto error;
	/* get notified when pager exits */
	sa.sa_handler = handlechildsignal;
	sa.sa_flags = SA_RESTART;
	if (sigaction(SIGCHLD, &sa, NULL) < 0)
		goto error;

	return;

error:
	abortmsgerrno("failed to set up signal handlers");
}

void restoresignalhandler(void)
{
	struct sigaction sa;
	memset(&sa, 0, sizeof(sa));
	sa.sa_handler = SIG_DFL;
	sa.sa_flags = SA_RESTART;
	if (sigemptyset(&sa.sa_mask) < 0)
		goto error;

	if (sigaction(SIGHUP, &sa, NULL) < 0)
		goto error;
	if (sigaction(SIGTERM, &sa, NULL) < 0)
		goto error;
	if (sigaction(SIGWINCH, &sa, NULL) < 0)
		goto error;
	if (sigaction(SIGCONT, &sa, NULL) < 0)
		goto error;
	if (sigaction(SIGTSTP, &sa, NULL) < 0)
		goto error;
	if (sigaction(SIGCHLD, &sa, NULL) < 0)
		goto error;

	/* ignore Ctrl+C while shutting down to make pager exits cleanly */
	sa.sa_handler = SIG_IGN;
	if (sigaction(SIGINT, &sa, NULL) < 0)
		goto error;

	peerpid = 0;
	return;

error:
	abortmsgerrno("failed to restore signal handlers");
}

/* This implementation is based on hgext/pager.py (post 369741ef7253)
 * Return 0 if pager is not started, or pid of the pager */
pid_t setuppager(const char *pagercmd, const char *envp[])
{
	assert(pagerpid == 0);
	if (!pagercmd)
		return 0;

	int pipefds[2];
	if (pipe(pipefds) < 0)
		return 0;
	pid_t pid = fork();
	if (pid < 0)
		goto error;
	if (pid > 0) {
		close(pipefds[0]);
		if (dup2(pipefds[1], fileno(stdout)) < 0)
			goto error;
		if (isatty(fileno(stderr))) {
			if (dup2(pipefds[1], fileno(stderr)) < 0)
				goto error;
		}
		close(pipefds[1]);
		pagerpid = pid;
		return pid;
	} else {
		dup2(pipefds[0], fileno(stdin));
		close(pipefds[0]);
		close(pipefds[1]);

		int r =
		    execle("/bin/sh", "/bin/sh", "-c", pagercmd, NULL, envp);
		if (r < 0) {
			abortmsgerrno("cannot start pager '%s'", pagercmd);
		}
		return 0;
	}

error:
	close(pipefds[0]);
	close(pipefds[1]);
	abortmsgerrno("failed to prepare pager");
	return 0;
}

void waitpager(void)
{
	if (pagerpid == 0)
		return;

	/* close output streams to notify the pager its input ends */
	fclose(stdout);
	fclose(stderr);
	while (1) {
		pid_t ret = waitpid(pagerpid, NULL, 0);
		if (ret == -1 && errno == EINTR)
			continue;
		break;
	}
}