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Support for read-only slaves. Semantical fixes.

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This commit introduces support for read only slaves via redis.conf and CONFIG GET/SET commands. Also various semantical fixes are implemented here:

1) MULTI/EXEC with only read commands now work where the server is into a state where writes (or commands increasing memory usage) are not allowed. Before this patch everything inside a transaction would fail in this conditions.

2) Scripts just calling read-only commands will work against read only
slaves, when the server is out of memory, or when persistence is into an
error condition. Before the patch EVAL always failed in this condition.
This commit is contained in:
antirez
2012-03-20 17:32:48 +01:00
parent 7a0c72f345
commit f3fd419fc9
6 changed files with 85 additions and 17 deletions
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26
src/redis.c
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@ -211,7 +211,7 @@ struct redisCommand redisCommandTable[] = {
{"lastsave",lastsaveCommand,1,"r",0,NULL,0,0,0,0,0},
{"type",typeCommand,2,"r",0,NULL,1,1,1,0,0},
{"multi",multiCommand,1,"rs",0,NULL,0,0,0,0,0},
{"exec",execCommand,1,"wms",0,NULL,0,0,0,0,0},
{"exec",execCommand,1,"s",0,NULL,0,0,0,0,0},
{"discard",discardCommand,1,"rs",0,NULL,0,0,0,0,0},
{"sync",syncCommand,1,"ars",0,NULL,0,0,0,0,0},
{"flushdb",flushdbCommand,1,"w",0,NULL,0,0,0,0,0},
@ -239,8 +239,8 @@ struct redisCommand redisCommandTable[] = {
{"dump",dumpCommand,2,"ar",0,NULL,1,1,1,0,0},
{"object",objectCommand,-2,"r",0,NULL,2,2,2,0,0},
{"client",clientCommand,-2,"ar",0,NULL,0,0,0,0,0},
{"eval",evalCommand,-3,"wms",0,zunionInterGetKeys,0,0,0,0,0},
{"evalsha",evalShaCommand,-3,"wms",0,zunionInterGetKeys,0,0,0,0,0},
{"eval",evalCommand,-3,"s",0,zunionInterGetKeys,0,0,0,0,0},
{"evalsha",evalShaCommand,-3,"s",0,zunionInterGetKeys,0,0,0,0,0},
{"slowlog",slowlogCommand,-2,"r",0,NULL,0,0,0,0,0},
{"script",scriptCommand,-2,"ras",0,NULL,0,0,0,0,0},
{"time",timeCommand,1,"rR",0,NULL,0,0,0,0,0}
@ -939,7 +939,11 @@ void createSharedObjects(void) {
shared.slowscripterr = createObject(REDIS_STRING,sdsnew(
"-BUSY Redis is busy running a script. You can only call SCRIPT KILL or SHUTDOWN NOSAVE.\r\n"));
shared.bgsaveerr = createObject(REDIS_STRING,sdsnew(
"-MISCONF Redis is configured to save RDB snapshots, but is currently not able to persist on disk. Write commands are disabled. Please check Redis logs for details about the error.\r\n"));
"-MISCONF Redis is configured to save RDB snapshots, but is currently not able to persist on disk. Commands that may modify the data set are disabled. Please check Redis logs for details about the error.\r\n"));
shared.roslaveerr = createObject(REDIS_STRING,sdsnew(
"-READONLY You can't write against a read only slave.\r\n"));
shared.oomerr = createObject(REDIS_STRING,
"-OOM command not allowed when used memory > 'maxmemory'.\r\n");
shared.space = createObject(REDIS_STRING,sdsnew(" "));
shared.colon = createObject(REDIS_STRING,sdsnew(":"));
shared.plus = createObject(REDIS_STRING,sdsnew("+"));
@ -1048,6 +1052,7 @@ void initServerConfig() {
server.repl_state = REDIS_REPL_NONE;
server.repl_syncio_timeout = REDIS_REPL_SYNCIO_TIMEOUT;
server.repl_serve_stale_data = 1;
server.repl_slave_ro = 1;
server.repl_down_since = -1;
/* Client output buffer limits */
@ -1483,8 +1488,7 @@ int processCommand(redisClient *c) {
if (server.maxmemory) {
int retval = freeMemoryIfNeeded();
if ((c->cmd->flags & REDIS_CMD_DENYOOM) && retval == REDIS_ERR) {
addReplyError(c,
"command not allowed when used memory > 'maxmemory'");
addReply(c, shared.oomerr);
return REDIS_OK;
}
}
@ -1499,6 +1503,16 @@ int processCommand(redisClient *c) {
return REDIS_OK;
}
/* Don't accept wirte commands if this is a read only slave. But
* accept write commands if this is our master. */
if (server.masterhost && server.repl_slave_ro &&
!(c->flags & REDIS_MASTER) &&
c->cmd->flags & REDIS_CMD_WRITE)
{
addReply(c, shared.roslaveerr);
return REDIS_OK;
}
/* Only allow SUBSCRIBE and UNSUBSCRIBE in the context of Pub/Sub */
if ((dictSize(c->pubsub_channels) > 0 || listLength(c->pubsub_patterns) > 0)
&&