HIREDIS-VIP

Hiredis-vip is a C client library for the Redis database.

Hiredis-vip supported redis cluster.

Hiredis-vip fully contained and based on Hiredis .

CLUSTER SUPPORT

FEATURES:

• SUPPORT REDIS CLUSTER:

  • Connect to redis cluster and run commands.

• SUPPORT MULTI-KEY COMMAND:

  • Support MSET, MGET and DEL.

• SUPPORT PIPELING:

  • Support redis pipeline and can contain multi-key command like above.

• SUPPORT Asynchronous API:

  • User can run commands with asynchronous mode.

CLUSTER API:

redisClusterContext *redisClusterConnect(const char *addrs, int flags);
redisClusterContext *redisClusterConnectWithTimeout(const char *addrs, const struct timeval tv, int flags);
redisClusterContext *redisClusterConnectNonBlock(const char *addrs, int flags);
void redisClusterFree(redisClusterContext *cc);
void redisClusterSetMaxRedirect(redisClusterContext *cc, int max_redirect_count);
void *redisClusterFormattedCommand(redisClusterContext *cc, char *cmd, int len);
void *redisClustervCommand(redisClusterContext *cc, const char *format, va_list ap);
void *redisClusterCommand(redisClusterContext *cc, const char *format, ...);
void *redisClusterCommandArgv(redisClusterContext *cc, int argc, const char **argv, const size_t *argvlen);
redisContext *ctx_get_by_node(struct cluster_node *node, const struct timeval *timeout, int flags);
int redisClusterAppendFormattedCommand(redisClusterContext *cc, char *cmd, int len);
int redisClustervAppendCommand(redisClusterContext *cc, const char *format, va_list ap);
int redisClusterAppendCommand(redisClusterContext *cc, const char *format, ...);
int redisClusterAppendCommandArgv(redisClusterContext *cc, int argc, const char **argv, const size_t *argvlen);
int redisClusterGetReply(redisClusterContext *cc, void **reply);
void redisClusterReset(redisClusterContext *cc);

redisClusterAsyncContext *redisClusterAsyncConnect(const char *addrs, int flags);
int redisClusterAsyncSetConnectCallback(redisClusterAsyncContext *acc, redisConnectCallback *fn);
int redisClusterAsyncSetDisconnectCallback(redisClusterAsyncContext *acc, redisDisconnectCallback *fn);
int redisClusterAsyncFormattedCommand(redisClusterAsyncContext *acc, redisClusterCallbackFn *fn, void *privdata, char *cmd, int len);
int redisClustervAsyncCommand(redisClusterAsyncContext *acc, redisClusterCallbackFn *fn, void *privdata, const char *format, va_list ap);
int redisClusterAsyncCommand(redisClusterAsyncContext *acc, redisClusterCallbackFn *fn, void *privdata, const char *format, ...);
int redisClusterAsyncCommandArgv(redisClusterAsyncContext *acc, redisClusterCallbackFn *fn, void *privdata, int argc, const char **argv, const size_t *argvlen);

void redisClusterAsyncDisconnect(redisClusterAsyncContext *acc);
void redisClusterAsyncFree(redisClusterAsyncContext *acc);

Quick usage

If you want used but not read the follow, please reference the examples: https://github.com/vipshop/hiredis-vip/wiki

Cluster synchronous API

To consume the synchronous API, there are only a few function calls that need to be introduced:

redisClusterContext *redisClusterConnect(const char *addrs, int flags);
void redisClusterSetMaxRedirect(redisClusterContext *cc, int max_redirect_count);
void *redisClusterCommand(redisClusterContext *cc, const char *format, ...);
void redisClusterFree(redisClusterContext *cc);

Cluster connecting

The function redisClusterConnect is used to create a so-called redisClusterContext. The context is where Hiredis-vip Cluster holds state for connections. The redisClusterContext struct has an integer err field that is non-zero when the connection is in an error state. The field errstr will contain a string with a description of the error. After trying to connect to Redis using redisClusterContext you should check the err field to see if establishing the connection was successful:

redisClusterContext *cc = redisClusterConnect("127.0.0.1:6379", HIRCLUSTER_FLAG_NULL);
if (cc != NULL && cc->err) {
    printf("Error: %s\n", cc->errstr);
    // handle error
}

Cluster sending commands

The next that will be introduced is redisClusterCommand. This function takes a format similar to printf. In the simplest form, it is used like this:

reply = redisClusterCommand(clustercontext, "SET foo bar");

The specifier %s interpolates a string in the command, and uses strlen to determine the length of the string:

reply = redisClusterCommand(clustercontext, "SET foo %s", value);

Internally, Hiredis-vip splits the command in different arguments and will convert it to the protocol used to communicate with Redis. One or more spaces separates arguments, so you can use the specifiers anywhere in an argument:

reply = redisClusterCommand(clustercontext, "SET key:%s %s", myid, value);

Cluster multi-key commands

Hiredis-vip supports mget/mset/del multi-key commands. Those multi-key commands is highly effective. Millions of keys in one mget command just used several seconds.

Example:

reply = redisClusterCommand(clustercontext, "mget %s %s %s %s", key1, key2, key3, key4);

Cluster cleaning up

To disconnect and free the context the following function can be used:

void redisClusterFree(redisClusterContext *cc);

This function immediately closes the socket and then frees the allocations done in creating the context.

Cluster pipelining

The function redisClusterGetReply is exported as part of the Hiredis API and can be used when a reply is expected on the socket. To pipeline commands, the only things that needs to be done is filling up the output buffer. For this cause, two commands can be used that are identical to the redisClusterCommand family, apart from not returning a reply:

int redisClusterAppendCommand(redisClusterContext *cc, const char *format, ...);
int redisClusterAppendCommandArgv(redisClusterContext *cc, int argc, const char **argv);

After calling either function one or more times, redisClusterGetReply can be used to receive the subsequent replies. The return value for this function is either REDIS_OK or REDIS_ERR, where the latter means an error occurred while reading a reply. Just as with the other commands, the err field in the context can be used to find out what the cause of this error is.

void redisClusterReset(redisClusterContext *cc);

Warning: You must call redisClusterReset function after one pipelining anyway.

The following examples shows a simple cluster pipeline:

redisReply *reply;
redisClusterAppendCommand(clusterContext,"SET foo bar");
redisClusterAppendCommand(clusterContext,"GET foo");
redisClusterGetReply(clusterContext,&reply); // reply for SET
freeReplyObject(reply);
redisClusterGetReply(clusterContext,&reply); // reply for GET
freeReplyObject(reply);
redisClusterReset(clusterContext);

Cluster asynchronous API

Hiredis-vip comes with an cluster asynchronous API that works easily with any event library. Now we just support and test for libevent and redis ae, if you need for other event libraries, please contact with us, and we will support it quickly.

Connecting

The function redisAsyncConnect can be used to establish a non-blocking connection to Redis. It returns a pointer to the newly created redisAsyncContext struct. The err field should be checked after creation to see if there were errors creating the connection. Because the connection that will be created is non-blocking, the kernel is not able to instantly return if the specified host and port is able to accept a connection.

redisClusterAsyncContext *acc = redisClusterAsyncConnect("127.0.0.1:6379", HIRCLUSTER_FLAG_NULL);
if (acc->err) {
    printf("Error: %s\n", acc->errstr);
    // handle error
}

The cluster asynchronous context can hold a disconnect callback function that is called when the connection is disconnected (either because of an error or per user request). This function should have the following prototype:

void(const redisAsyncContext *c, int status);

On a disconnect, the status argument is set to REDIS_OK when disconnection was initiated by the user, or REDIS_ERR when the disconnection was caused by an error. When it is REDIS_ERR, the err field in the context can be accessed to find out the cause of the error.

You not need to reconnect in the disconnect callback, hiredis-vip will reconnect this connection itself when commands come to this redis node.

Setting the disconnect callback can only be done once per context. For subsequent calls it will return REDIS_ERR. The function to set the disconnect callback has the following prototype:

int redisClusterAsyncSetDisconnectCallback(redisClusterAsyncContext *acc, redisDisconnectCallback *fn);

Sending commands and their callbacks

In an cluster asynchronous context, commands are automatically pipelined due to the nature of an event loop. Therefore, unlike the cluster synchronous API, there is only a single way to send commands. Because commands are sent to Redis cluster asynchronously, issuing a command requires a callback function that is called when the reply is received. Reply callbacks should have the following prototype:

void(redisClusterAsyncContext *acc, void *reply, void *privdata);

The privdata argument can be used to curry arbitrary data to the callback from the point where the command is initially queued for execution.

The functions that can be used to issue commands in an asynchronous context are:

int redisClusterAsyncCommand(
  redisClusterAsyncContext *acc, 
  redisClusterCallbackFn *fn, 
  void *privdata, const char *format, ...);

This function work like their blocking counterparts. The return value is REDIS_OK when the command was successfully added to the output buffer and REDIS_ERR otherwise. Example: when the connection is being disconnected per user-request, no new commands may be added to the output buffer and REDIS_ERR is returned on calls to the redisClusterAsyncCommand family.

If the reply for a command with a NULL callback is read, it is immediately freed. When the callback for a command is non-NULL, the memory is freed immediately following the callback: the reply is only valid for the duration of the callback.

All pending callbacks are called with a NULL reply when the context encountered an error.

Disconnecting

An cluster asynchronous connection can be terminated using:

void redisClusterAsyncDisconnect(redisClusterAsyncContext *acc);

When this function is called, the connection is not immediately terminated. Instead, new commands are no longer accepted and the connection is only terminated when all pending commands have been written to the socket, their respective replies have been read and their respective callbacks have been executed. After this, the disconnection callback is executed with the REDIS_OK status and the context object is freed.

Hooking it up to event library X

There are a few hooks that need to be set on the cluster context object after it is created. See the adapters/ directory for bindings to ae and libevent.

AUTHORS

Hiredis-vip was maintained and used at vipshop(https://github.com/vipshop). The redis client library part in hiredis-vip is same as hiredis(https://github.com/redis/hiredis). The redis cluster client library part in hiredis-vip is written by deep(https://github.com/deep011). Hiredis-vip is released under the BSD license.