Skip to content
Fetching contributors…
Cannot retrieve contributors at this time
510 lines (448 sloc) 16.8 KB
/* diskstore.c implements a very simple disk backed key-value store used
* by Redis for the "disk" backend. This implementation uses the filesystem
* to store key/value pairs. Every file represents a given key.
*
* The key path is calculated using the SHA1 of the key name. For instance
* the key "foo" is stored as a file name called:
*
* /0b/ee/0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33
*
* The couples of characters from the hex output of SHA1 are also used
* to locate two two levels of directories to store the file (as most
* filesystems are not able to handle too many files in a single dir).
*
* In the end there are 65536 final directories (256 directories inside
* every 256 top level directories), so that with 1 billion of files every
* directory will contain in the average 15258 entires, that is ok with
* most filesystems implementation.
*
* Note that since Redis supports multiple databases, the actual key name
* is:
*
* /0b/ee/<dbid>_0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33
*
* so for instance if the key is inside DB 0:
*
* /0b/ee/0_0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33
*
* The actaul implementation of this disk store is highly dependant to the
* filesystem implementation itself. This implementation may be replaced by
* a B+TREE implementation in future implementations.
*
* Data ok every key is serialized using the same format used for .rdb
* serialization. Everything is serialized on every entry: key name,
* ttl information in case of keys with an associated expire time, and the
* serialized value itself.
*
* Because the format is the same of the .rdb files it is trivial to create
* an .rdb file starting from this format just by mean of scanning the
* directories and concatenating entries, with the sole addition of an
* .rdb header at the start and the end-of-db opcode at the end.
*
* -------------------------------------------------------------------------
*
* Copyright (c) 2010-2011, Salvatore Sanfilippo <antirez at gmail dot com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Redis nor the names of its contributors may be used
* to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include "redis.h"
#include "sha1.h"
#include <fcntl.h>
#include <sys/stat.h>
#include <dirent.h>
int create256dir(char *prefix) {
char buf[1024];
int j;
for (j = 0; j < 256; j++) {
snprintf(buf,sizeof(buf),"%s%02x",prefix,j);
if (mkdir(buf,0755) == -1) {
redisLog(REDIS_WARNING,"Error creating dir %s for diskstore: %s",
buf,strerror(errno));
return REDIS_ERR;
}
}
return REDIS_OK;
}
int dsOpen(void) {
struct stat sb;
int retval, j;
char *path = server.ds_path;
char buf[1024];
if ((retval = stat(path,&sb) == -1) && errno != ENOENT) {
redisLog(REDIS_WARNING, "Error opening disk store at %s: %s",
path, strerror(errno));
return REDIS_ERR;
}
/* Directory already in place. Assume everything is ok. */
if (retval == 0 && S_ISDIR(sb.st_mode)) {
redisLog(REDIS_NOTICE,"Disk store %s exists", path);
return REDIS_OK;
}
/* File exists but it's not a directory */
if (retval == 0 && !S_ISDIR(sb.st_mode)) {
redisLog(REDIS_WARNING,"Disk store at %s is not a directory", path);
return REDIS_ERR;
}
/* New disk store, create the directory structure now, as creating
* them in a lazy way is not a good idea, after very few insertions
* we'll need most of the 65536 directories anyway. */
redisLog(REDIS_NOTICE,"Disk store %s does not exist: creating", path);
if (mkdir(path,0755) == -1) {
redisLog(REDIS_WARNING,"Disk store init failed creating dir %s: %s",
path, strerror(errno));
return REDIS_ERR;
}
/* Create the top level 256 directories */
snprintf(buf,sizeof(buf),"%s/",path);
if (create256dir(buf) == REDIS_ERR) return REDIS_ERR;
/* For every 256 top level dir, create 256 nested dirs */
for (j = 0; j < 256; j++) {
snprintf(buf,sizeof(buf),"%s/%02x/",path,j);
if (create256dir(buf) == REDIS_ERR) return REDIS_ERR;
}
return REDIS_OK;
}
int dsClose(void) {
return REDIS_OK;
}
/* Convert key into full path for this object. Dirty but hopefully
* is fast enough. Returns the length of the returned path. */
int dsKeyToPath(redisDb *db, char *buf, robj *key) {
SHA1_CTX ctx;
unsigned char hash[20];
char hex[40], digits[] = "0123456789abcdef";
int j, l;
char *origbuf = buf;
SHA1Init(&ctx);
SHA1Update(&ctx,key->ptr,sdslen(key->ptr));
SHA1Final(hash,&ctx);
/* Convert the hash into hex format */
for (j = 0; j < 20; j++) {
hex[j*2] = digits[(hash[j]&0xF0)>>4];
hex[(j*2)+1] = digits[hash[j]&0x0F];
}
/* Create the object path. Start with server.ds_path that's the root dir */
l = sdslen(server.ds_path);
memcpy(buf,server.ds_path,l);
buf += l;
*buf++ = '/';
/* Then add xx/yy/ that is the two level directories */
buf[0] = hex[0];
buf[1] = hex[1];
buf[2] = '/';
buf[3] = hex[2];
buf[4] = hex[3];
buf[5] = '/';
buf += 6;
/* Add the database number followed by _ and finall the SHA1 hex */
l = ll2string(buf,64,db->id);
buf += l;
buf[0] = '_';
memcpy(buf+1,hex,40);
buf[41] = '\0';
return (buf-origbuf)+41;
}
int dsSet(redisDb *db, robj *key, robj *val, time_t expire) {
char buf[1024], buf2[1024];
FILE *fp;
int retval, len;
len = dsKeyToPath(db,buf,key);
memcpy(buf2,buf,len);
snprintf(buf2+len,sizeof(buf2)-len,"-%ld-%ld",(long)time(NULL),(long)val);
while ((fp = fopen(buf2,"w")) == NULL) {
if (errno == ENOSPC) {
redisLog(REDIS_WARNING,"Diskstore: No space left on device. Please make room and wait 30 seconds for Redis to continue.");
sleep(30);
} else {
redisLog(REDIS_WARNING,"diskstore error opening %s: %s",
buf2, strerror(errno));
redisPanic("Unrecoverable diskstore error. Exiting.");
}
}
if ((retval = rdbSaveKeyValuePair(fp,key,val,expire,time(NULL))) == -1)
return REDIS_ERR;
fclose(fp);
if (retval == 0) {
/* Expired key. Unlink failing not critical */
unlink(buf);
unlink(buf2);
} else {
/* Use rename for atomic updadte of value */
if (rename(buf2,buf) == -1) {
redisLog(REDIS_WARNING,"rename(2) returned an error: %s",
strerror(errno));
redisPanic("Unrecoverable diskstore error. Exiting.");
}
}
return REDIS_OK;
}
robj *dsGet(redisDb *db, robj *key, time_t *expire) {
char buf[1024];
int type;
time_t expiretime = -1; /* -1 means: no expire */
robj *dskey; /* Key as loaded from disk. */
robj *val;
FILE *fp;
dsKeyToPath(db,buf,key);
fp = fopen(buf,"r");
if (fp == NULL && errno == ENOENT) return NULL; /* No such key */
if (fp == NULL) {
redisLog(REDIS_WARNING,"Disk store failed opening %s: %s",
buf, strerror(errno));
goto readerr;
}
if ((type = rdbLoadType(fp)) == -1) goto readerr;
if (type == REDIS_EXPIRETIME) {
if ((expiretime = rdbLoadTime(fp)) == -1) goto readerr;
/* We read the time so we need to read the object type again */
if ((type = rdbLoadType(fp)) == -1) goto readerr;
}
/* Read key */
if ((dskey = rdbLoadStringObject(fp)) == NULL) goto readerr;
/* Read value */
if ((val = rdbLoadObject(type,fp)) == NULL) goto readerr;
fclose(fp);
/* The key we asked, and the key returned, must be the same */
redisAssert(equalStringObjects(key,dskey));
/* Check if the key already expired */
decrRefCount(dskey);
if (expiretime != -1 && expiretime < time(NULL)) {
decrRefCount(val);
unlink(buf); /* This failing is non critical here */
return NULL;
}
/* Everything ok... */
*expire = expiretime;
return val;
readerr:
redisLog(REDIS_WARNING,"Read error reading reading %s. Corrupted key?",
buf);
redisPanic("Unrecoverable error reading from disk store");
return NULL; /* unreached */
}
int dsDel(redisDb *db, robj *key) {
char buf[1024];
dsKeyToPath(db,buf,key);
if (unlink(buf) == -1) {
if (errno == ENOENT) {
return REDIS_ERR;
} else {
redisLog(REDIS_WARNING,"Disk store can't remove %s: %s",
buf, strerror(errno));
redisPanic("Unrecoverable Disk store errore. Existing.");
return REDIS_ERR; /* unreached */
}
} else {
return REDIS_OK;
}
}
int dsExists(redisDb *db, robj *key) {
char buf[1024];
dsKeyToPath(db,buf,key);
return access(buf,R_OK) == 0;
}
int dsGetDbidFromFilename(char *path) {
char id[64];
char *p = strchr(path,'_');
int len = (p - path);
redisAssert(p != NULL && len < 64);
memcpy(id,path,len);
id[len] = '\0';
return atoi(id);
}
void dsFlushOneDir(char *path, int dbid) {
DIR *dir;
struct dirent *dp, de;
dir = opendir(path);
if (dir == NULL) {
redisLog(REDIS_WARNING,"Disk store can't open dir %s: %s",
path, strerror(errno));
redisPanic("Unrecoverable Disk store errore. Existing.");
}
while(1) {
char buf[1024];
readdir_r(dir,&de,&dp);
if (dp == NULL) break;
if (dp->d_name[0] == '.') continue;
/* Check if we need to remove this entry accordingly to the
* DB number. */
if (dbid != -1 && dsGetDbidFromFilename(dp->d_name)) continue;
/* Finally unlink the file */
snprintf(buf,1024,"%s/%s",path,dp->d_name);
if (unlink(buf) == -1) {
redisLog(REDIS_WARNING,
"Can't unlink %s: %s", buf, strerror(errno));
redisPanic("Unrecoverable Disk store errore. Existing.");
}
}
closedir(dir);
}
void dsFlushDb(int dbid) {
char buf[1024];
int j, i;
redisLog(REDIS_NOTICE,"Flushing diskstore DB (%d)",dbid);
for (j = 0; j < 256; j++) {
for (i = 0; i < 256; i++) {
snprintf(buf,1024,"%s/%02x/%02x",server.ds_path,j,i);
dsFlushOneDir(buf,dbid);
}
}
}
void dsRdbSaveSetState(int state) {
pthread_mutex_lock(&server.bgsavethread_mutex);
server.bgsavethread_state = state;
pthread_mutex_unlock(&server.bgsavethread_mutex);
}
void *dsRdbSave_thread(void *arg) {
char tmpfile[256], *filename = (char*)arg;
struct dirent *dp, de;
int j, i, last_dbid = -1;
FILE *fp;
/* Change state to ACTIVE, to signal there is a saving thead working. */
redisLog(REDIS_NOTICE,"Diskstore BGSAVE thread started");
dsRdbSaveSetState(REDIS_BGSAVE_THREAD_ACTIVE);
snprintf(tmpfile,256,"temp-%d.rdb", (int) getpid());
fp = fopen(tmpfile,"w");
if (!fp) {
redisLog(REDIS_WARNING, "Failed opening .rdb for saving: %s",
strerror(errno));
dsRdbSaveSetState(REDIS_BGSAVE_THREAD_DONE_ERR);
return NULL;
}
if (fwrite("REDIS0001",9,1,fp) == 0) goto werr;
sleep(5);
/* Scan all diskstore dirs looking for keys */
for (j = 0; j < 256; j++) {
for (i = 0; i < 256; i++) {
DIR *dir;
char buf[1024];
/* For every directory, collect all the keys */
snprintf(buf,sizeof(buf),"%s/%02x/%02x",server.ds_path,j,i);
if ((dir = opendir(buf)) == NULL) {
redisLog(REDIS_WARNING,"Disk store can't open dir %s: %s",
buf, strerror(errno));
goto werr;
}
while(1) {
char buf[1024];
int dbid;
FILE *entryfp;
readdir_r(dir,&de,&dp);
if (dp == NULL) break;
if (dp->d_name[0] == '.') continue;
/* If there is a '-' char in the file name, it's a temp file */
if (strchr(dp->d_name,'-') != NULL) continue;
/* Emit the SELECT DB opcode if needed. */
dbid = dsGetDbidFromFilename(dp->d_name);
if (dbid != last_dbid) {
last_dbid = dbid;
if (rdbSaveType(fp,REDIS_SELECTDB) == -1) goto werr;
if (rdbSaveLen(fp,dbid) == -1) goto werr;
}
/* Let's copy this file into the target .rdb */
snprintf(buf,sizeof(buf),"%s/%02x/%02x/%s",
server.ds_path,j,i,dp->d_name);
if ((entryfp = fopen(buf,"r")) == NULL) {
redisLog(REDIS_WARNING,"Can't open %s: %s",
buf,strerror(errno));
closedir(dir);
goto werr;
}
while(1) {
int nread = fread(buf,1,sizeof(buf),entryfp);
if (nread == 0) {
if (ferror(entryfp)) {
redisLog(REDIS_WARNING,"Error reading from file entry while performing BGSAVE for diskstore: %s", strerror(errno));
closedir(dir);
goto werr;
} else {
break;
}
}
if (fwrite(buf,1,nread,fp) != (unsigned)nread) {
closedir(dir);
goto werr;
}
}
fclose(entryfp);
}
closedir(dir);
}
}
/* Output the end of file opcode */
if (rdbSaveType(fp,REDIS_EOF) == -1) goto werr;
/* Make sure data will not remain on the OS's output buffers */
fflush(fp);
fsync(fileno(fp));
fclose(fp);
zfree(filename);
/* Use RENAME to make sure the DB file is changed atomically only
* if the generate DB file is ok. */
if (rename(tmpfile,filename) == -1) {
redisLog(REDIS_WARNING,"Error moving temp DB file on the final destination: %s (diskstore)", strerror(errno));
unlink(tmpfile);
dsRdbSaveSetState(REDIS_BGSAVE_THREAD_DONE_ERR);
return NULL;
}
redisLog(REDIS_NOTICE,"DB saved on disk by diskstore thread");
dsRdbSaveSetState(REDIS_BGSAVE_THREAD_DONE_OK);
return NULL;
werr:
zfree(filename);
fclose(fp);
unlink(tmpfile);
dsRdbSaveSetState(REDIS_BGSAVE_THREAD_DONE_ERR);
redisLog(REDIS_WARNING,"Write error saving DB on disk: %s", strerror(errno));
return NULL;
}
int dsRdbSaveBackground(char *filename) {
pthread_t thread;
if (pthread_create(&thread,NULL,dsRdbSave_thread,zstrdup(filename)) != 0) {
redisLog(REDIS_WARNING,"Can't create diskstore BGSAVE thread: %s",
strerror(errno));
return REDIS_ERR;
} else {
server.bgsavethread = thread;
return REDIS_OK;
}
}
int dsRdbSave(char *filename) {
/* A blocking save is actually a non blocking save... just we wait
* for it to terminate in a non-busy loop. */
redisLog(REDIS_NOTICE,"Starting a blocking SAVE (BGSAVE + blocking wait)");
server.dirty_before_bgsave = server.dirty;
if (dsRdbSaveBackground(filename) == REDIS_ERR) return REDIS_ERR;
while(1) {
usleep(1000);
int state;
pthread_mutex_lock(&server.bgsavethread_mutex);
state = server.bgsavethread_state;
pthread_mutex_unlock(&server.bgsavethread_mutex);
if (state == REDIS_BGSAVE_THREAD_DONE_OK ||
state == REDIS_BGSAVE_THREAD_DONE_ERR) break;
}
return REDIS_OK;
}
Jump to Line
Something went wrong with that request. Please try again.