Re: [libvirt] [PATCH v2 01/13] util: add APIs for reading/writing from/to rotating files

Add virRotatingFileReader and virRotatingFileWriter objects which allow reading & writing from/to files with automation rotation to N backup files when a size limit is reached. This is useful for guest logging when a guaranteed finite size limit is required. Use of external tools like logrotate is inadequate since it leaves the possibility for guest to DOS the host in between invokations of logrotate. Signed-off-by: Daniel P. Berrange <berrange(a)redhat.com&gt; --- po/POTFILES.in | 1 + src/Makefile.am | 1 + src/libvirt_private.syms | 13 + src/util/virrotatingfile.c | 608 ++++++++++++++++++++++++++++++++++++++ src/util/virrotatingfile.h | 62 ++++ tests/Makefile.am | 6 + tests/virrotatingfiletest.c | 698 ++++++++++++++++++++++++++++++++++++++++++++ 7 files changed, 1389 insertions(+) create mode 100644 src/util/virrotatingfile.c create mode 100644 src/util/virrotatingfile.h create mode 100644 tests/virrotatingfiletest.c

--- /dev/null +++ b/src/util/virrotatingfile.c @@ -0,0 +1,608 @@

+/* + * virrotatingfile.c: file I/O with size rotation + * + * Copyright (C) 2015 Red Hat, Inc. + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library 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 + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library. If not, see + * <http://www.gnu.org/licenses/>;. + * + */ +

+ + +static virRotatingFileReaderEntryPtr +virRotatingFileReaderEntryNew(const char *path) +{ + virRotatingFileReaderEntryPtr entry; + struct stat sb; + + VIR_DEBUG("Opening %s", path); + + if (VIR_ALLOC(entry) < 0) + return NULL; + + if (VIR_STRDUP(entry->path, path) < 0) + goto error;

+ + if ((entry->fd = open(path, O_RDONLY)) < 0) { + if (errno != ENOENT) { + virReportSystemError(errno, + _("Unable to open file: %s"), path); + goto error; + } + } + + if (entry->fd != -1) { + if (fstat(entry->fd, &sb) < 0) { + virReportSystemError(errno, + _("Unable to determine current file inode: %s"), + path); + goto error; + } + + entry->inode = sb.st_ino; + } + + return entry; + + error: + virRotatingFileReaderEntryFree(entry); + return NULL; +} +

+/** + * virRotatingFileWriterNew + * @path: the base path for files + * @maxlen: the maximum number of bytes to write before rollover + * @maxbackup: number of backup files to keep when rolloing over

+ * @truncate: whether to truncate the current files when opening + * @mode: the file mode to use for creating new files + * + * Create a new object for writing data to a file with + * automatic rollover. If @maxbackup is zero, no backup + * files will be created. The primary file will just get + * truncated and reopened. + * + * The files will never exceed @maxlen bytes in size, + * but may be rolled over before they reach this size + * in order to avoid splitting lines + */ +virRotatingFileWriterPtr virRotatingFileWriterNew(const char *path, + off_t maxlen, + size_t maxbackup, + bool truncate, + mode_t mode) +{ + virRotatingFileWriterPtr file; + + if (VIR_ALLOC(file) < 0) + goto error; + + if (VIR_STRDUP(file->basepath, path) < 0) + goto error; + + file->mode = mode; + file->maxbackup = maxbackup; + file->maxlen = maxlen; + + if (truncate && + virRotatingFileWriterDelete(file) < 0) + goto error; + + if (!(file->entry = virRotatingFileWriterEntryNew(file->basepath, + mode))) + goto error; + + return file; + + error: + virRotatingFileWriterFree(file); + return NULL; +} + +