On Dec 14, 2011, at 8:57 AM, Jeff Layton wrote:
> Rather than roll our own "storage engine", use sqlite instead. It fits
> the bill nicely as it does:
>
> - durable on-disk storage
> - the ability to constrain record uniqueness
> - a facility for collating and searching the host records
It should also allow multiple processes (possibly on multiple cluster nodes) to access the on-disk data safely and atomically. No need to invent a file locking scheme from scratch.
> ...it does add a build dependency to nfs-utils, but almost all modern
> distros provide those packages.
>
> The current incarnation of this code dynamically links against a
> provided sqlite library, but we could also consider including their
> single-file "amalgamation" to reduce dependencies (though with all
> the caveats that that entails).
>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
> utils/clstated/Makefile.am | 4 +-
> utils/clstated/clstated.c | 16 ++-
> utils/clstated/sqlite.c | 351 ++++++++++++++++++++++++++++++++++++++++++++
> utils/clstated/sqlite.h | 27 ++++
> 4 files changed, 393 insertions(+), 5 deletions(-)
> create mode 100644 utils/clstated/sqlite.c
> create mode 100644 utils/clstated/sqlite.h
>
> diff --git a/utils/clstated/Makefile.am b/utils/clstated/Makefile.am
> index 9937353..d1cef3c 100644
> --- a/utils/clstated/Makefile.am
> +++ b/utils/clstated/Makefile.am
> @@ -6,9 +6,9 @@
> AM_CFLAGS += -D_LARGEFILE64_SOURCE
> sbin_PROGRAMS = clstated
>
> -clstated_SOURCES = clstated.c
> +clstated_SOURCES = clstated.c sqlite.c
>
> -clstated_LDADD = ../../support/nfs/libnfs.a $(LIBEVENT)
> +clstated_LDADD = ../../support/nfs/libnfs.a $(LIBEVENT) $(LIBSQLITE)
>
> MAINTAINERCLEANFILES = Makefile.in
>
> diff --git a/utils/clstated/clstated.c b/utils/clstated/clstated.c
> index aab09a7..95ac696 100644
> --- a/utils/clstated/clstated.c
> +++ b/utils/clstated/clstated.c
> @@ -36,6 +36,7 @@
>
> #include "xlog.h"
> #include "nfslib.h"
> +#include "sqlite.h"
>
> #ifndef PIPEFS_DIR
> #define PIPEFS_DIR NFS_STATEDIR "/rpc_pipefs"
> @@ -118,21 +119,25 @@ clstate_pipe_reopen(struct clstate_client *clnt)
> static void
> clstate_create(struct clstate_client *clnt)
> {
> + int ret;
> ssize_t bsize, wsize;
> struct clstate_msg *cmsg = &clnt->cl_msg;
>
> - xlog(D_GENERAL, "%s: create client record", __func__);
> + xlog(D_GENERAL, "%s: create client record. cm_addr=%s", __func__,
> + cmsg->cm_addr);
>
> - /* FIXME: create client record on storage here */
> + ret = clstate_insert_client(cmsg->cm_addr, cmsg->cm_u.cm_id,
> + cmsg->cm_len);
>
> /* set up reply */
> - cmsg->cm_status = 0;
> + cmsg->cm_status = ret ? -EREMOTEIO : ret;
> cmsg->cm_len = 0;
> memset(cmsg->cm_addr, 0, sizeof(cmsg->cm_addr) +
> sizeof(cmsg->cm_u.cm_id));
>
> bsize = sizeof(*cmsg);
>
> + xlog(D_GENERAL, "Doing downcall with status %d", cmsg->cm_status);
> wsize = atomicio((void *)write, clnt->cl_fd, cmsg, bsize);
> if (wsize != bsize) {
> xlog(L_ERROR, "%s: problem writing to clstate pipe (%ld): %m",
> @@ -231,6 +236,11 @@ main(int argc, char **argv)
> }
>
> /* set up storage db */
> + rc = clstate_maindb_init();
> + if (rc) {
> + xlog(L_ERROR, "Failed to open main database: %d", rc);
> + goto out;
> + }
>
> /* set up event handler */
> fd = clstate_pipe_open(&clnt);
> diff --git a/utils/clstated/sqlite.c b/utils/clstated/sqlite.c
> new file mode 100644
> index 0000000..ae83634
> --- /dev/null
> +++ b/utils/clstated/sqlite.c
> @@ -0,0 +1,351 @@
> +/*
> + * Copyright (C) 2011 Red Hat, Jeff Layton <jlayton@xxxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version 2
> + * of the License, or (at your option) any later version.
> + *
> + * 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.
> + */
> +
> +/*
> + * Explanation:
> + *
> + * This file contains the code to manage the sqlite backend database for the
> + * clstated upcall daemon.
> + *
> + * The main database is called main.sqlite and contains the following tables:
> + *
> + * parameters: simple key/value pairs for storing database info
> + *
> + * addresses: list of server-side addresses recorded in the db, along with
> + * the filenames of their respective db files.
> + *
> + * The daemon attaches to each server-address database as needed. Each
> + * server-address database has the following tables:
Why do you keep separate database files? There are ways to store all of this data in a single database using multiple tables. I'm happy to help you with table design if you like.
> + *
> + * clients: one column containing a BLOB with the clstate as sent by the client
> + * and a timestamp (in epoch seconds) of when the record was
> + * established
I'm not yet clear on what's in cm_addr, but it seems to me that if you store each client's data as structured fields instead of a single BLOB, it will be much easier to use a generic tool like the sqlite3 command to debug the database. That gives the observability and transparency of using a flat file with all the advantages of a database.
Plus, you get automatic data conversion; a one-to-one mapping between data on-disk and data in any endian-ness or word length.
> + *
> + * FIXME: should we also record the fsid being accessed?
I'm not exactly sure what additional data might be needed to support NFSv4 migration, for example. However, using a database means it's relatively painless to add new columns in the future without having to provision them now.
> + */
> +
> +#ifdef HAVE_CONFIG_H
> +#include "config.h"
> +#endif /* HAVE_CONFIG_H */
> +
> +#include <errno.h>
> +#include <event.h>
> +#include <stdbool.h>
> +#include <string.h>
> +#include <sys/stat.h>
> +#include <sys/types.h>
> +#include <fcntl.h>
> +#include <unistd.h>
> +#include <sqlite3.h>
> +#include <linux/limits.h>
> +#include <linux/nfsd/clstate.h>
> +
> +#include "xlog.h"
> +
> +#define CLSTATE_SQLITE_SCHEMA_VERSION 1
> +
> +#ifndef CLSTATE_DIR
> +#define CLSTATE_DIR NFS_STATEDIR "/clstate"
> +#endif
> +
> +/* in milliseconds */
> +#define CLSTATE_SQLITE_BUSY_TIMEOUT 10000
> +
> +/* private data structures */
> +
> +/* global variables */
> +
> +/* top level DB directory */
> +static char *clstate_topdir = CLSTATE_DIR;
> +
> +/* reusable pathname and sql command buffer */
> +static char buf[PATH_MAX];
> +
> +/* global database handle */
> +static sqlite3 *dbh;
> +
> +/* forward declarations */
> +
> +/* '.' is not allowed in dbnames -- convert them to '-' */
> +static void
> +addr_to_dbname(const char *src, char *dst)
> +{
> + while(*src) {
> + if (*src == '.')
> + *dst = '-';
> + else
> + *dst = *src;
> + ++src;
> + ++dst;
> + }
> + *dst = '\0';
> +}
> +
> +void
> +clstate_set_topdir(char *topdir)
> +{
> + clstate_topdir = topdir;
> +}
> +
> +/* make a directory, ignoring EEXIST errors unless it's not a directory */
> +static int
> +mkdir_if_not_exist(char *dirname)
> +{
> + int ret;
> + struct stat statbuf;
> +
> + ret = mkdir(dirname, S_IRWXU);
> + if (ret && errno != EEXIST)
> + return -errno;
> +
> + ret = stat(dirname, &statbuf);
> + if (ret)
> + return -errno;
> +
> + if (!S_ISDIR(statbuf.st_mode))
> + ret = -ENOTDIR;
> +
> + return ret;
> +}
> +
> +/*
> + * Open the "main" database, and attempt to initialize it by creating the
> + * parameters table and inserting the schema version into it. Ignore any errors
> + * from that, and then attempt to select the version out of it again. If the
> + * version appears wrong, then assume that the DB is corrupt or has been
> + * upgraded, and return an error.
> + */
> +int
> +clstate_maindb_init(void)
> +{
> + int ret;
> + char *err = NULL;
> + sqlite3_stmt *stmt = NULL;
> +
> + ret = mkdir_if_not_exist(clstate_topdir);
> + if (ret)
> + return ret;
> +
> + ret = snprintf(buf, PATH_MAX - 1, "%s/main.sqlite", clstate_topdir);
> + if (ret < 0)
> + return ret;
> +
> + buf[PATH_MAX - 1] = '\0';
> +
> + ret = sqlite3_open(buf, &dbh);
> + if (ret != SQLITE_OK) {
> + xlog(D_GENERAL, "Unable to open main database: %d", ret);
> + return ret;
> + }
> +
> + ret = sqlite3_busy_timeout(dbh, CLSTATE_SQLITE_BUSY_TIMEOUT);
> + if (ret != SQLITE_OK) {
> + xlog(D_GENERAL, "Unable to set sqlite busy timeout: %d", ret);
> + goto out_err;
> + }
> +
> + /* Try to create table */
> + ret = sqlite3_exec(dbh, "CREATE TABLE IF NOT EXISTS parameters "
> + "(key TEXT PRIMARY KEY, value TEXT);",
> + NULL, NULL, &err);
> + if (ret != SQLITE_OK) {
> + xlog(D_GENERAL, "Unable to create parameter table: %d", ret);
> + goto out_err;
> + }
> +
> + /* insert version into table -- ignore error if it fails */
> + ret = snprintf(buf, sizeof(buf),
> + "INSERT OR IGNORE INTO parameters values (\"version\", "
> + "\"%d\");", CLSTATE_SQLITE_SCHEMA_VERSION);
> + if (ret < 0) {
> + goto out_err;
> + } else if ((size_t)ret >= sizeof(buf)) {
> + ret = -EINVAL;
> + goto out_err;
> + }
> +
> + ret = sqlite3_exec(dbh, (const char *)buf, NULL, NULL, &err);
> + if (ret != SQLITE_OK) {
> + xlog(D_GENERAL, "Unable to insert into parameter table: %d",
> + ret);
> + goto out_err;
> + }
> +
> + ret = sqlite3_prepare_v2(dbh,
> + "SELECT value FROM parameters WHERE key == \"version\";",
> + -1, &stmt, NULL);
> + if (ret != SQLITE_OK) {
> + xlog(D_GENERAL, "Unable to prepare select statement: %d", ret);
> + goto out_err;
> + }
> +
> + /* check schema version */
> + ret = sqlite3_step(stmt);
> + if (ret != SQLITE_ROW) {
> + xlog(D_GENERAL, "Select statement execution failed: %s",
> + sqlite3_errmsg(dbh));
> + goto out_err;
> + }
> +
> + /* process SELECT result */
> + ret = sqlite3_column_int(stmt, 0);
> + if (ret != CLSTATE_SQLITE_SCHEMA_VERSION) {
> + xlog(L_ERROR, "Unsupported database schema version! "
> + "Expected %d, got %d.",
> + CLSTATE_SQLITE_SCHEMA_VERSION, ret);
> + ret = -EINVAL;
> + goto out_err;
> + }
> +
> + sqlite3_free(err);
> + sqlite3_finalize(stmt);
> + return 0;
> +
> +out_err:
> + if (err) {
> + xlog(L_ERROR, "sqlite error: %s", err);
> + sqlite3_free(err);
> + }
> + sqlite3_finalize(stmt);
> + sqlite3_close(dbh);
> + return ret;
> +}
> +
> +static int
> +clstate_db_attach(char *dbname)
> +{
> + int ret;
> + char *err;
> +
> + /* convert address string into valid filename */
> + ret = snprintf(buf, sizeof(buf),
> + "ATTACH DATABASE \"%s/%s.sqlite\" as \"%s\";",
> + clstate_topdir, dbname, dbname);
> + if (ret < 0) {
> + return ret;
> + } else if ((size_t)ret >= sizeof(buf)) {
> + ret = -EINVAL;
> + return ret;
> + }
> +
> + /* attach to new DB in filename */
> + ret = sqlite3_exec(dbh, buf, NULL, NULL, &err);
> + if (ret != SQLITE_OK)
> + xlog(L_ERROR, "Unable to attach database %s: %s", dbname, err);
> +
> + xlog(D_GENERAL, "Attached database %s", dbname);
> + return ret;
> +}
> +
> +static int
> +clstate_db_detach(char *dbname)
> +{
> + int ret;
> + char *err;
> +
> + /* convert address string into valid filename */
> + ret = snprintf(buf, PATH_MAX - 1, "DETACH DATABASE \"%s\";", dbname);
> + if (ret < 0) {
> + return ret;
> + } else if ((size_t)ret >= sizeof(buf)) {
> + ret = -EINVAL;
> + return ret;
> + }
> +
> + /* attach to new DB in filename */
> + ret = sqlite3_exec(dbh, buf, NULL, NULL, &err);
> + if (ret != SQLITE_OK)
> + xlog(L_ERROR, "Unable to detach database %s: %s", dbname, err);
> +
> + xlog(D_GENERAL, "Detached database %s", dbname);
> + return ret;
> +}
> +
> +/*
> + * Create a client record
> + */
> +int
> +clstate_insert_client(const unsigned char *addr, const unsigned char *clname,
> + const size_t namelen)
> +{
> + int ret;
> + char *err = NULL;
> + char dbname[CLSTATE_MAX_ADDRESS_LEN];
> + sqlite3_stmt *stmt = NULL;
> +
> + addr_to_dbname((const char *)addr, dbname);
> +
> + ret = clstate_db_attach(dbname);
> + if (ret != SQLITE_OK)
> + return ret;
> +
> + snprintf(buf, sizeof(buf), "CREATE TABLE IF NOT EXISTS '%s'.clients "
> + "(id BLOB PRIMARY KEY, time INTEGER);",
> + dbname);
> + if (ret < 0) {
> + goto out_detach;
> + } else if ((size_t)ret >= sizeof(buf)) {
> + ret = -EINVAL;
> + goto out_detach;
> + }
> +
> + ret = sqlite3_exec(dbh, buf, NULL, NULL, &err);
> + if (ret != SQLITE_OK) {
> + xlog(L_ERROR, "Unable to create table: %s", err);
> + goto out_detach;
> + }
> +
> + ret = snprintf(buf, sizeof(buf),
> + "INSERT OR REPLACE INTO '%s'.clients VALUES (?, "
> + "strftime('%%s', 'now'));", dbname);
> + if (ret < 0) {
> + goto out_detach;
> + } else if ((size_t)ret >= sizeof(buf)) {
> + ret = -EINVAL;
> + goto out_detach;
> + }
> +
> + ret = sqlite3_prepare_v2(dbh, buf, ret + 1, &stmt, NULL);
> + if (ret != SQLITE_OK) {
> + xlog(D_GENERAL, "Statement prepare failed: %d", ret);
> + goto out_err;
> + }
> +
> + ret = sqlite3_bind_blob(stmt, 1, (const void *)clname, namelen,
> + SQLITE_STATIC);
> + if (ret != SQLITE_OK) {
> + xlog(D_GENERAL, "Bind blob failed: %d", ret);
> + goto out_err;
> + }
> +
> + ret = sqlite3_step(stmt);
> + if (ret == SQLITE_DONE)
> + ret = SQLITE_OK;
> + else
> + xlog(D_GENERAL, "Unexpected return code from insert: %s",
> + sqlite3_errmsg(dbh));
> +
> +out_err:
> + xlog(D_GENERAL, "%s returning %d", __func__, ret);
> + sqlite3_finalize(stmt);
> + sqlite3_free(err);
> +out_detach:
> + clstate_db_detach(dbname);
> + return ret;
> +}
> diff --git a/utils/clstated/sqlite.h b/utils/clstated/sqlite.h
> new file mode 100644
> index 0000000..4f81745
> --- /dev/null
> +++ b/utils/clstated/sqlite.h
> @@ -0,0 +1,27 @@
> +/*
> + * Copyright (C) 2011 Red Hat, Jeff Layton <jlayton@xxxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version 2
> + * of the License, or (at your option) any later version.
> + *
> + * 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.
> + */
> +
> +#ifndef _SQLITE_H_
> +#define _SQLITE_H_
> +
> +void clstate_set_topdir(char *topdir);
> +int clstate_maindb_init(void);
> +int clstate_insert_client(const unsigned char *addr, const unsigned char *clname, const size_t namelen);
> +
> +#endif /* _SQLITE_H */
> --
> 1.7.1
>
> --
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--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com
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