[lxc-devel] [PATCH 1/2] API support for container snapshots (v2)
Stéphane Graber
stgraber at ubuntu.com
Tue Sep 10 16:31:04 UTC 2013
On Fri, Sep 06, 2013 at 06:07:47PM -0500, Serge Hallyn wrote:
> The api allows for creating, listing, and restoring of container
> snapshots. Snapshots are created as snapshot clones of the
> original container - i.e. btrfs and lvm will be done as snapshot,
> a directory-backed container will have overlayfs snapshots. A
> restore is a copy-clone, using the same backing store as the
> original container had.
>
> Changelog:
>
> . remove lxcapi_snap_open, which wasn't defined anyway.
> . rename get_comment to get_commentpath
> . if no newname is specified at restore, use c->name (as we meant to)
> rather than segving.
> . when choosing a snapshot index, use the correct path to check for.
>
> Signed-off-by: Serge Hallyn <serge.hallyn at ubuntu.com>
Acked-by: Stéphane Graber <stgraber at ubuntu.com>
> ---
> src/lxc/lxccontainer.c | 278 +++++++++++++++++++++++++++++++++++++++++++++++++
> src/lxc/lxccontainer.h | 50 +++++++++
> src/tests/Makefile.am | 7 +-
> src/tests/snapshot.c | 130 +++++++++++++++++++++++
> 4 files changed, 463 insertions(+), 2 deletions(-)
> create mode 100644 src/tests/snapshot.c
>
> diff --git a/src/lxc/lxccontainer.c b/src/lxc/lxccontainer.c
> index 3c657ca..635c17e 100644
> --- a/src/lxc/lxccontainer.c
> +++ b/src/lxc/lxccontainer.c
> @@ -27,6 +27,7 @@
> #include <errno.h>
> #include <fcntl.h>
> #include <sched.h>
> +#include <dirent.h>
> #include "config.h"
> #include "lxc.h"
> #include "state.h"
> @@ -68,6 +69,13 @@ static bool file_exists(char *f)
> return stat(f, &statbuf) == 0;
> }
>
> +static void remove_trailing_slashes(char *p)
> +{
> + int l = strlen(p);
> + while (--l >= 0 && (p[l] == '/' || p[l] == '\n'))
> + p[l] = '\0';
> +}
> +
> /*
> * A few functions to help detect when a container creation failed.
> * If a container creation was killed partway through, then trying
> @@ -2192,6 +2200,272 @@ static int lxcapi_attach_run_wait(struct lxc_container *c, lxc_attach_options_t
> return lxc_wait_for_pid_status(pid);
> }
>
> +int get_next_index(const char *lxcpath, char *cname)
> +{
> + char *fname;
> + struct stat sb;
> + int i = 0, ret;
> +
> + fname = alloca(strlen(lxcpath) + 20);
> + while (1) {
> + sprintf(fname, "%s/snap%d", lxcpath, i);
> + ret = stat(fname, &sb);
> + if (ret != 0)
> + return i;
> + i++;
> + }
> +}
> +
> +static int lxcapi_snapshot(struct lxc_container *c, char *commentfile)
> +{
> + int i, flags, ret;
> + struct lxc_container *c2;
> + char snappath[MAXPATHLEN], newname[20];
> +
> + // /var/lib/lxc -> /var/lib/lxcsnaps \0
> + ret = snprintf(snappath, MAXPATHLEN, "%ssnaps/%s", c->config_path, c->name);
> + if (ret < 0 || ret >= MAXPATHLEN)
> + return -1;
> + i = get_next_index(snappath, c->name);
> +
> + if (mkdir_p(snappath, 0755) < 0) {
> + ERROR("Failed to create snapshot directory %s", snappath);
> + return -1;
> + }
> +
> + ret = snprintf(newname, 20, "snap%d", i);
> + if (ret < 0 || ret >= 20)
> + return -1;
> +
> + flags = LXC_CLONE_SNAPSHOT | LXC_CLONE_KEEPMACADDR | LXC_CLONE_KEEPNAME;
> + c2 = c->clone(c, newname, snappath, flags, NULL, NULL, 0, NULL);
> + if (!c2) {
> + ERROR("clone of %s:%s failed\n", c->config_path, c->name);
> + return -1;
> + }
> +
> + lxc_container_put(c2);
> +
> + // Now write down the creation time
> + time_t timer;
> + char buffer[25];
> + struct tm* tm_info;
> +
> + time(&timer);
> + tm_info = localtime(&timer);
> +
> + strftime(buffer, 25, "%Y:%m:%d %H:%M:%S", tm_info);
> +
> + char *dfnam = alloca(strlen(snappath) + strlen(newname) + 5);
> + sprintf(dfnam, "%s/%s/ts", snappath, newname);
> + FILE *f = fopen(dfnam, "w");
> + if (!f) {
> + ERROR("Failed to open %s\n", dfnam);
> + return -1;
> + }
> + if (fprintf(f, "%s", buffer) < 0) {
> + SYSERROR("Writing timestamp");
> + fclose(f);
> + return -1;
> + }
> + if (fclose(f) != 0) {
> + SYSERROR("Writing timestamp");
> + return -1;
> + }
> +
> + if (commentfile) {
> + // $p / $name / comment \0
> + int len = strlen(snappath) + strlen(newname) + 10;
> + char *path = alloca(len);
> + sprintf(path, "%s/%s/comment", snappath, newname);
> + return copy_file(commentfile, path) < 0 ? -1 : i;
> + }
> +
> + return i;
> +}
> +
> +static void lxcsnap_free(struct lxc_snapshot *s)
> +{
> + if (s->name)
> + free(s->name);
> + if (s->comment_pathname)
> + free(s->comment_pathname);
> + if (s->timestamp)
> + free(s->timestamp);
> + if (s->lxcpath)
> + free(s->lxcpath);
> +}
> +
> +static char *get_snapcomment_path(char* snappath, char *name)
> +{
> + // $snappath/$name/comment
> + int ret, len = strlen(snappath) + strlen(name) + 10;
> + char *s = malloc(len);
> +
> + if (s) {
> + ret = snprintf(s, len, "%s/%s/comment", snappath, name);
> + if (ret < 0 || ret >= len) {
> + free(s);
> + s = NULL;
> + }
> + }
> + return s;
> +}
> +
> +static char *get_timestamp(char* snappath, char *name)
> +{
> + char path[MAXPATHLEN], *s = NULL;
> + int ret, len;
> + FILE *fin;
> +
> + ret = snprintf(path, MAXPATHLEN, "%s/%s/ts", snappath, name);
> + if (ret < 0 || ret >= MAXPATHLEN)
> + return NULL;
> + if ((fin = fopen(path, "r")) == NULL)
> + return NULL;
> + (void) fseek(fin, 0, SEEK_END);
> + len = ftell(fin);
> + (void) fseek(fin, 0, SEEK_SET);
> + if (len > 0) {
> + s = malloc(len+1);
> + if (s) {
> + s[len] = '\0';
> + if (fread(s, 1, len, fin) != len) {
> + SYSERROR("reading timestamp");
> + free(s);
> + s = NULL;
> + }
> + }
> + }
> + fclose(fin);
> + return s;
> +}
> +
> +static int lxcapi_snapshot_list(struct lxc_container *c, struct lxc_snapshot **ret_snaps)
> +{
> + char snappath[MAXPATHLEN], path2[MAXPATHLEN];
> + int dirlen, count = 0, ret;
> + struct dirent dirent, *direntp;
> + struct lxc_snapshot *snaps =NULL, *nsnaps;
> + DIR *dir;
> +
> + if (!c || !lxcapi_is_defined(c))
> + return -1;
> + // snappath is ${lxcpath}snaps/${lxcname}/
> + dirlen = snprintf(snappath, MAXPATHLEN, "%ssnaps/%s", c->config_path, c->name);
> + if (dirlen < 0 || dirlen >= MAXPATHLEN) {
> + ERROR("path name too long");
> + return -1;
> + }
> + if (!(dir = opendir(snappath))) {
> + INFO("failed to open %s - assuming no snapshots", snappath);
> + return 0;
> + }
> +
> + while (!readdir_r(dir, &dirent, &direntp)) {
> + if (!direntp)
> + break;
> +
> + if (!strcmp(direntp->d_name, "."))
> + continue;
> +
> + if (!strcmp(direntp->d_name, ".."))
> + continue;
> +
> + ret = snprintf(path2, MAXPATHLEN, "%s/%s/config", snappath, direntp->d_name);
> + if (ret < 0 || ret >= MAXPATHLEN) {
> + ERROR("pathname too long");
> + goto out_free;
> + }
> + if (!file_exists(path2))
> + continue;
> + nsnaps = realloc(snaps, (count + 1)*sizeof(*snaps));
> + if (!nsnaps) {
> + SYSERROR("Out of memory");
> + goto out_free;
> + }
> + snaps = nsnaps;
> + snaps[count].free = lxcsnap_free;
> + snaps[count].name = strdup(direntp->d_name);
> + if (!snaps[count].name)
> + goto out_free;
> + snaps[count].lxcpath = strdup(snappath);
> + if (!snaps[count].lxcpath) {
> + free(snaps[count].name);
> + goto out_free;
> + }
> + snaps[count].comment_pathname = get_snapcomment_path(snappath, direntp->d_name);
> + snaps[count].timestamp = get_timestamp(snappath, direntp->d_name);
> + count++;
> + }
> +
> + if (closedir(dir))
> + WARN("failed to close directory");
> +
> + *ret_snaps = snaps;
> + return count;
> +
> +out_free:
> + if (snaps) {
> + int i;
> + for (i=0; i<count; i++)
> + lxcsnap_free(&snaps[i]);
> + free(snaps);
> + }
> + return -1;
> +}
> +
> +static bool lxcapi_snapshot_restore(struct lxc_container *c, char *snapname, char *newname)
> +{
> + char clonelxcpath[MAXPATHLEN];
> + int ret;
> + struct lxc_container *snap, *rest;
> + struct bdev *bdev;
> + bool b = false;
> +
> + if (!c || !c->name || !c->config_path)
> + return false;
> +
> + bdev = bdev_init(c->lxc_conf->rootfs.path, c->lxc_conf->rootfs.mount, NULL);
> + if (!bdev) {
> + ERROR("Failed to find original backing store type");
> + return false;
> + }
> +
> + if (!newname)
> + newname = c->name;
> + if (strcmp(c->name, newname) == 0) {
> + if (!lxcapi_destroy(c)) {
> + ERROR("Could not destroy existing container %s", newname);
> + bdev_put(bdev);
> + return false;
> + }
> + }
> + ret = snprintf(clonelxcpath, MAXPATHLEN, "%ssnaps/%s", c->config_path, c->name);
> + if (ret < 0 || ret >= MAXPATHLEN) {
> + bdev_put(bdev);
> + return false;
> + }
> + // how should we lock this?
> +
> + snap = lxc_container_new(snapname, clonelxcpath);
> + if (!snap || !lxcapi_is_defined(snap)) {
> + ERROR("Could not open snapshot %s", snapname);
> + if (snap) lxc_container_put(snap);
> + bdev_put(bdev);
> + return false;
> + }
> +
> + rest = lxcapi_clone(snap, newname, c->config_path, 0, bdev->type, NULL, 0, NULL);
> + bdev_put(bdev);
> + if (rest && lxcapi_is_defined(rest))
> + b = true;
> + if (rest)
> + lxc_container_put(rest);
> + lxc_container_put(snap);
> + return b;
> +}
> +
> static int lxcapi_attach_run_waitl(struct lxc_container *c, lxc_attach_options_t *options, const char *program, const char *arg, ...)
> {
> va_list ap;
> @@ -2237,6 +2511,7 @@ struct lxc_container *lxc_container_new(const char *name, const char *configpath
> goto err;
> }
>
> + remove_trailing_slashes(c->config_path);
> c->name = malloc(strlen(name)+1);
> if (!c->name) {
> fprintf(stderr, "Error allocating lxc_container name\n");
> @@ -2305,6 +2580,9 @@ struct lxc_container *lxc_container_new(const char *name, const char *configpath
> c->attach = lxcapi_attach;
> c->attach_run_wait = lxcapi_attach_run_wait;
> c->attach_run_waitl = lxcapi_attach_run_waitl;
> + c->snapshot = lxcapi_snapshot;
> + c->snapshot_list = lxcapi_snapshot_list;
> + c->snapshot_restore = lxcapi_snapshot_restore;
>
> /* we'll allow the caller to update these later */
> if (lxc_log_init(NULL, "none", NULL, "lxc_container", 0, c->config_path)) {
> diff --git a/src/lxc/lxccontainer.h b/src/lxc/lxccontainer.h
> index ad6afa1..f9ae43b 100644
> --- a/src/lxc/lxccontainer.h
> +++ b/src/lxc/lxccontainer.h
> @@ -38,6 +38,8 @@
>
> struct bdev_specs;
>
> +struct lxc_snapshot;
> +
> struct lxc_container {
> // private fields
> char *name;
> @@ -177,6 +179,54 @@ struct lxc_container {
> /* run program in container, wait for it to exit */
> int (*attach_run_wait)(struct lxc_container *c, lxc_attach_options_t *options, const char *program, const char * const argv[]);
> int (*attach_run_waitl)(struct lxc_container *c, lxc_attach_options_t *options, const char *program, const char *arg, ...);
> +
> + /*
> + * snapshot:
> + * If you have /var/lib/lxc/c1 and call c->snapshot() the firs time, it
> + * will return 0, and the container will be /var/lib/lxcsnaps/c1/snap0.
> + * The second call will return 1, and the snapshot will be
> + * /var/lib/lxcsnaps/c1/snap1.
> + *
> + * On error, returns -1.
> + */
> + int (*snapshot)(struct lxc_container *c, char *commentfile);
> +
> + /*
> + * snapshot_list() will return a description of all snapshots of c in
> + * a simple array. See src/tests/snapshot.c for the proper way to
> + * free the allocated results.
> + *
> + * Returns the number of snapshots.
> + */
> + int (*snapshot_list)(struct lxc_container *, struct lxc_snapshot **);
> +
> + /*
> + * snapshot_restore() will create a new container based on a snapshot.
> + * c is the container whose snapshot we look for, and snapname is the
> + * specific snapshot name (i.e. "snap0"). newname is the name to be
> + * used for the restored container. If newname is the same as
> + * c->name, then c will first be destroyed. That will fail if the
> + * snapshot is overlayfs-based, since the snapshots will pin the
> + * original container.
> + *
> + * The restored container will be a copy (not snapshot) of the snapshot,
> + * and restored in the lxcpath of the original container.
> + *
> + * As an example, c might be /var/lib/lxc/c1, snapname might be 'snap0'
> + * which stands for /var/lib/lxcsnaps/c1/snap0. If newname is c2,
> + * then snap0 will be copied to /var/lib/lxc/c2.
> + *
> + * Returns true on success, false on failure.
> + */
> + bool (*snapshot_restore)(struct lxc_container *c, char *snapname, char *newname);
> +};
> +
> +struct lxc_snapshot {
> + char *name;
> + char *comment_pathname;
> + char *timestamp;
> + char *lxcpath;
> + void (*free)(struct lxc_snapshot *);
> };
>
> struct lxc_container *lxc_container_new(const char *name, const char *configpath);
> diff --git a/src/tests/Makefile.am b/src/tests/Makefile.am
> index 76b38f9..a6dacab 100644
> --- a/src/tests/Makefile.am
> +++ b/src/tests/Makefile.am
> @@ -17,6 +17,7 @@ lxc_test_clonetest_SOURCES = clonetest.c
> lxc_test_console_SOURCES = console.c
> lxc_usernic_test_SOURCES = ../lxc/lxc_user_nic.c ../lxc/nl.c
> lxc_usernic_test_CFLAGS = -DISTEST
> +lxc_test_snapshot_SOURCES = snapshot.c
>
> AM_CFLAGS=-I$(top_srcdir)/src \
> -DLXCROOTFSMOUNT=\"$(LXCROOTFSMOUNT)\" \
> @@ -28,7 +29,8 @@ AM_CFLAGS=-I$(top_srcdir)/src \
> bin_PROGRAMS = lxc-test-containertests lxc-test-locktests lxc-test-startone \
> lxc-test-destroytest lxc-test-saveconfig lxc-test-createtest \
> lxc-test-shutdowntest lxc-test-get_item lxc-test-getkeys lxc-test-lxcpath \
> - lxc-test-cgpath lxc-test-clonetest lxc-test-console lxc-usernic-test
> + lxc-test-cgpath lxc-test-clonetest lxc-test-console lxc-usernic-test \
> + lxc-test-snapshot
>
> bin_SCRIPTS = lxc-test-usernic
>
> @@ -48,4 +50,5 @@ EXTRA_DIST = \
> clonetest.c \
> startone.c \
> console.c \
> - lxc-test-usernic
> + lxc-test-usernic \
> + snapshot.c
> diff --git a/src/tests/snapshot.c b/src/tests/snapshot.c
> new file mode 100644
> index 0000000..7298e53
> --- /dev/null
> +++ b/src/tests/snapshot.c
> @@ -0,0 +1,130 @@
> +/* liblxcapi
> + *
> + * Copyright © 2013 Serge Hallyn <serge.hallyn at ubuntu.com>.
> + * Copyright © 2013 Canonical Ltd.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2, as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License along
> + * with this program; if not, write to the Free Software Foundation, Inc.,
> + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
> + */
> +#include "../lxc/lxccontainer.h"
> +
> +#include <errno.h>
> +#include <stdlib.h>
> +#include "../lxc/lxc.h"
> +
> +#define MYNAME "snapxxx1"
> +#define RESTNAME "snapxxx2"
> +
> +void try_to_remove()
> +{
> + struct lxc_container *c;
> + char snappath[1024];
> + c = lxc_container_new(RESTNAME, NULL);
> + if (c) {
> + if (c->is_defined(c))
> + c->destroy(c);
> + lxc_container_put(c);
> + }
> + snprintf(snappath, 1024, "%ssnaps/%s", lxc_get_default_config_path(), MYNAME);
> + c = lxc_container_new("snap0", snappath);
> + if (c) {
> + if (c->is_defined(c))
> + c->destroy(c);
> + lxc_container_put(c);
> + }
> + c = lxc_container_new(MYNAME, NULL);
> + if (c) {
> + if (c->is_defined(c))
> + c->destroy(c);
> + lxc_container_put(c);
> + }
> +}
> +
> +int main(int argc, char *argv[])
> +{
> + struct lxc_container *c;
> + char *template = "busybox";
> +
> + if (argc > 1)
> + template = argv[1];
> +
> + try_to_remove();
> + c = lxc_container_new(MYNAME, NULL);
> + if (!c) {
> + fprintf(stderr, "%s: %d: failed to load first container\n", __FILE__, __LINE__);
> + exit(1);
> + }
> +
> + if (c->is_defined(c)) {
> + fprintf(stderr, "%d: %s thought it was defined\n", __LINE__, MYNAME);
> + (void) c->destroy(c);
> + }
> + if (!c->set_config_item(c, "lxc.network.type", "empty")) {
> + fprintf(stderr, "%s: %d: failed to set network type\n", __FILE__, __LINE__);
> + goto err;
> + }
> + c->save_config(c, NULL);
> + if (!c->createl(c, template, NULL, NULL, 0, NULL)) {
> + fprintf(stderr, "%s: %d: failed to create %s container\n", __FILE__, __LINE__, template);
> + goto err;
> + }
> + c->load_config(c, NULL);
> +
> + if (c->snapshot(c, NULL) != 0) {
> + fprintf(stderr, "%s: %d: failed to create snapsot\n", __FILE__, __LINE__);
> + goto err;
> + }
> +
> + // rootfs should be ${lxcpath}snaps/${lxcname}/snap0/rootfs
> + struct stat sb;
> + int ret;
> + char path[1024];
> + snprintf(path, 1024, "%ssnaps/%s/snap0/rootfs", lxc_get_default_config_path(), MYNAME);
> + ret = stat(path, &sb);
> + if (ret != 0) {
> + fprintf(stderr, "%s: %d: snapshot was not actually created\n", __FILE__, __LINE__);
> + goto err;
> + }
> +
> + struct lxc_snapshot *s;
> + int i, n;
> +
> + n = c->snapshot_list(c, &s);
> + if (n < 1) {
> + fprintf(stderr, "%s: %d: failed listing containers\n", __FILE__, __LINE__);
> + goto err;
> + }
> + if (strcmp(s->name, "snap0") != 0) {
> + fprintf(stderr, "%s: %d: snapshot had bad name\n", __FILE__, __LINE__);
> + goto err;
> + }
> + for (i=0; i<n; i++) {
> + s[i].free(&s[i]);
> + }
> + free(s);
> +
> + if (!c->snapshot_restore(c, "snap0", RESTNAME)) {
> + fprintf(stderr, "%s: %d: failed to restore snapshot\n", __FILE__, __LINE__);
> + goto err;
> + }
> +
> + printf("All tests passed\n");
> + lxc_container_put(c);
> + exit(0);
> +
> +err:
> + lxc_container_put(c);
> + fprintf(stderr, "Exiting on error\n");
> + try_to_remove();
> + exit(1);
> +}
> --
> 1.8.1.2
>
>
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--
Stéphane Graber
Ubuntu developer
http://www.ubuntu.com
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