Dynamically manage service states based on user defined conditions

Old event system has been replaced with a more generic condition
concept. The idea is that finit plugins may provide arbitrary
conditions that services may specify as dependencies that they require
to run.

In order to accomodate this, the service management has been
redesigned to use a state machine.

plugins/pidfile.c

@@ -0,0 +1,121 @@
+#include <limits.h>
+#include <paths.h>
+
+#include <sys/inotify.h>
+
+#include "../finit.h"
+#include "../cond.h"
+#include "../helpers.h"
+#include "../plugin.h"
+
+struct context {
+	int fd;
+	int wd;
+};
+
+static void pidfile_callback(void *UNUSED(arg), int fd, int UNUSED(events))
+{
+	static char ev_buf[8 *(sizeof(struct inotify_event) + NAME_MAX + 1)];
+	static char cond[MAX_ARG_LEN];
+
+	struct inotify_event *ev;
+	ssize_t sz, len;
+	char *basename;
+	svc_t *svc;
+
+	sz = read(fd, ev_buf, sizeof(ev_buf));
+	if (sz <= 0) {
+		_pe("invalid inotify event\n");
+		return;
+	}
+
+	for (ev = (void *)ev_buf; sz > sizeof(*ev);
+	     len = sizeof(*ev) + ev->len, ev = (void *)ev + len, sz -= len) {
+	     /* ev = (void *)(ev + 1) + ev->len, sz -= sizeof(*ev) + ev->len) { */
+		if (!ev->mask || !strstr(ev->name, ".pid"))
+			continue;
+
+		basename = strtok(ev->name, ".");
+		svc = svc_find_by_nameid(basename, 1);
+		if (!svc)
+			continue;
+
+		/* TODO FIXME XXX WKZ check that pid is controlled by finit */
+		
+		_d("%s: match %s", basename, svc->cmd);
+		snprintf(cond, sizeof(cond), "svc%s", svc->cmd);
+		if (ev->mask & (IN_CREATE | IN_ATTRIB))
+			cond_set(cond);
+		else if (ev->mask & IN_DELETE)
+			cond_clear(cond);
+	}
+}
+
+static void pidfile_reconf(void *_null)
+{
+	static char name[MAX_ARG_LEN];
+
+	svc_t *svc;
+	(void)(_null);
+
+	for (svc = svc_iterator(1); svc; svc = svc_iterator(0)) {
+		if (svc->state == SVC_RUNNING_STATE && !svc_is_changed(svc)) {
+			snprintf(name, MAX_ARG_LEN, "svc%s", svc->cmd);
+			cond_set_path(cond_path(name), COND_ON);
+		}
+	}
+}
+
+static void pidfile_init (void *arg)
+{
+	struct context *ctx = arg;
+
+	ctx->wd = inotify_add_watch(ctx->fd, _PATH_VARRUN,
+				    IN_CREATE | IN_ATTRIB | IN_DELETE);
+	if (ctx->wd < 0) {
+		_pe("inotify_add_watch()");
+		close(ctx->fd);
+		return;
+	}
+
+	_d("pidfile monitor active");
+}
+
+static struct context pidfile_ctx;
+
+static plugin_t plugin = {
+	.hook[HOOK_BASEFS_UP]  = { .arg = &pidfile_ctx, .cb = pidfile_init },
+	.hook[HOOK_SVC_RECONF] = { .cb = pidfile_reconf },
+	.io = {
+		.cb    = pidfile_callback,
+		.flags = PLUGIN_IO_READ,
+	},
+};
+
+PLUGIN_INIT(plugin_init)
+{
+	pidfile_ctx.fd = inotify_init();
+	if (pidfile_ctx.fd < 0) {
+		_pe("inotify_init()");
+		return;
+	}
+
+	plugin.io.fd = pidfile_ctx.fd;
+	plugin_register(&plugin);
+}
+
+PLUGIN_EXIT(plugin_exit)
+{
+	inotify_rm_watch(pidfile_ctx.fd, pidfile_ctx.wd);
+	close(pidfile_ctx.fd);
+	
+	plugin_unregister(&plugin);
+}
+
+/**
+ * Local Variables:
+ *  version-control: t
+ *  indent-tabs-mode: t
+ *  c-file-style: "linux"
+ * End:
+ */