cluster.h

#ifndef __CLUSTER_H
#define __CLUSTER_H

/*-----------------------------------------------------------------------------
 * Redis cluster data structures, defines, exported API.
 *----------------------------------------------------------------------------*/

#define CLUSTER_SLOTS 16384
#define CLUSTER_OK 0            /* Everything looks ok */
#define CLUSTER_FAIL 1          /* The cluster can't work */
#define CLUSTER_NAMELEN 40      /* sha1 hex length */
#define CLUSTER_PORT_INCR 10000 /* Cluster port = baseport + PORT_INCR */

/* The following defines are amount of time, sometimes expressed as
 * multiplicators of the node timeout value (when ending with MULT). */
#define CLUSTER_FAIL_REPORT_VALIDITY_MULT 2 /* Fail report validity. */
#define CLUSTER_FAIL_UNDO_TIME_MULT 2 /* Undo fail if master is back. */
#define CLUSTER_MF_TIMEOUT 5000 /* Milliseconds to do a manual failover. */
#define CLUSTER_MF_PAUSE_MULT 2 /* Master pause manual failover mult. */
#define CLUSTER_SLAVE_MIGRATION_DELAY 5000 /* Delay for slave migration. */

/* Redirection errors returned by getNodeByQuery(). */
#define CLUSTER_REDIR_NONE 0          /* Node can serve the request. */
#define CLUSTER_REDIR_CROSS_SLOT 1    /* -CROSSSLOT request. */
#define CLUSTER_REDIR_UNSTABLE 2      /* -TRYAGAIN redirection required */
#define CLUSTER_REDIR_ASK 3           /* -ASK redirection required. */
#define CLUSTER_REDIR_MOVED 4         /* -MOVED redirection required. */
#define CLUSTER_REDIR_DOWN_STATE 5    /* -CLUSTERDOWN, global state. */
#define CLUSTER_REDIR_DOWN_UNBOUND 6  /* -CLUSTERDOWN, unbound slot. */
#define CLUSTER_REDIR_DOWN_RO_STATE 7 /* -CLUSTERDOWN, allow reads. */

struct clusterNode;

/* clusterLink encapsulates everything needed to talk with a remote node. */
typedef struct clusterLink {
    mstime_t ctime;             /* Link creation time */
    connection *conn;           /* Connection to remote node */
    sds sndbuf;                 /* Packet send buffer */
    char *rcvbuf;               /* Packet reception buffer */
    size_t rcvbuf_len;          /* Used size of rcvbuf */
    size_t rcvbuf_alloc;        /* Allocated size of rcvbuf */
    struct clusterNode *node;   /* Node related to this link. Initialized to NULL when unknown */
    int inbound;                /* 1 if this link is an inbound link accepted from the related node */
} clusterLink;

/* Cluster node flags and macros. */
#define CLUSTER_NODE_MASTER 1     /* The node is a master */
#define CLUSTER_NODE_SLAVE 2      /* The node is a slave */
#define CLUSTER_NODE_PFAIL 4      /* Failure? Need acknowledge */
#define CLUSTER_NODE_FAIL 8       /* The node is believed to be malfunctioning */
#define CLUSTER_NODE_MYSELF 16    /* This node is myself */
#define CLUSTER_NODE_HANDSHAKE 32 /* We have still to exchange the first ping */
#define CLUSTER_NODE_NOADDR   64  /* We don't know the address of this node */
#define CLUSTER_NODE_MEET 128     /* Send a MEET message to this node */
#define CLUSTER_NODE_MIGRATE_TO 256 /* Master eligible for replica migration. */
#define CLUSTER_NODE_NOFAILOVER 512 /* Slave will not try to failover. */
#define CLUSTER_NODE_NULL_NAME "\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"

#define nodeIsMaster(n) ((n)->flags & CLUSTER_NODE_MASTER)
#define nodeIsSlave(n) ((n)->flags & CLUSTER_NODE_SLAVE)
#define nodeInHandshake(n) ((n)->flags & CLUSTER_NODE_HANDSHAKE)
#define nodeHasAddr(n) (!((n)->flags & CLUSTER_NODE_NOADDR))
#define nodeWithoutAddr(n) ((n)->flags & CLUSTER_NODE_NOADDR)
#define nodeTimedOut(n) ((n)->flags & CLUSTER_NODE_PFAIL)
#define nodeFailed(n) ((n)->flags & CLUSTER_NODE_FAIL)
#define nodeCantFailover(n) ((n)->flags & CLUSTER_NODE_NOFAILOVER)

/* Reasons why a slave is not able to failover. */
#define CLUSTER_CANT_FAILOVER_NONE 0
#define CLUSTER_CANT_FAILOVER_DATA_AGE 1
#define CLUSTER_CANT_FAILOVER_WAITING_DELAY 2
#define CLUSTER_CANT_FAILOVER_EXPIRED 3
#define CLUSTER_CANT_FAILOVER_WAITING_VOTES 4
#define CLUSTER_CANT_FAILOVER_RELOG_PERIOD (60*5) /* seconds. */

/* clusterState todo_before_sleep flags. */
#define CLUSTER_TODO_HANDLE_FAILOVER (1<<0)
#define CLUSTER_TODO_UPDATE_STATE (1<<1)
#define CLUSTER_TODO_SAVE_CONFIG (1<<2)
#define CLUSTER_TODO_FSYNC_CONFIG (1<<3)
#define CLUSTER_TODO_HANDLE_MANUALFAILOVER (1<<4)

/* Message types.
 *
 * Note that the PING, PONG and MEET messages are actually the same exact
 * kind of packet. PONG is the reply to ping, in the exact format as a PING,
 * while MEET is a special PING that forces the receiver to add the sender
 * as a node (if it is not already in the list). */
#define CLUSTERMSG_TYPE_PING 0          /* Ping */
#define CLUSTERMSG_TYPE_PONG 1          /* Pong (reply to Ping) */
#define CLUSTERMSG_TYPE_MEET 2          /* Meet "let's join" message */
#define CLUSTERMSG_TYPE_FAIL 3          /* Mark node xxx as failing */
#define CLUSTERMSG_TYPE_PUBLISH 4       /* Pub/Sub Publish propagation */
#define CLUSTERMSG_TYPE_FAILOVER_AUTH_REQUEST 5 /* May I failover? */
#define CLUSTERMSG_TYPE_FAILOVER_AUTH_ACK 6     /* Yes, you have my vote */
#define CLUSTERMSG_TYPE_UPDATE 7        /* Another node slots configuration */
#define CLUSTERMSG_TYPE_MFSTART 8       /* Pause clients for manual failover */
#define CLUSTERMSG_TYPE_MODULE 9        /* Module cluster API message. */
#define CLUSTERMSG_TYPE_PUBLISHSHARD 10 /* Pub/Sub Publish shard propagation */
#define CLUSTERMSG_TYPE_COUNT 11        /* Total number of message types. */

/* Flags that a module can set in order to prevent certain Redis Cluster
 * features to be enabled. Useful when implementing a different distributed
 * system on top of Redis Cluster message bus, using modules. */
#define CLUSTER_MODULE_FLAG_NONE 0
#define CLUSTER_MODULE_FLAG_NO_FAILOVER (1<<1)
#define CLUSTER_MODULE_FLAG_NO_REDIRECTION (1<<2)

/* This structure represent elements of node->fail_reports. */
typedef struct clusterNodeFailReport {
    struct clusterNode *node;  /* Node reporting the failure condition. */
    mstime_t time;             /* Time of the last report from this node. */
} clusterNodeFailReport;

typedef struct clusterNode {
    mstime_t ctime; /* Node object creation time. */
    char name[CLUSTER_NAMELEN]; /* Node name, hex string, sha1-size */
    int flags;      /* CLUSTER_NODE_... */
    uint64_t configEpoch; /* Last configEpoch observed for this node */
    unsigned char slots[CLUSTER_SLOTS/8]; /* slots handled by this node */
    uint16_t *slot_info_pairs; /* Slots info represented as (start/end) pair (consecutive index). */
    int slot_info_pairs_count; /* Used number of slots in slot_info_pairs */
    int numslots;   /* Number of slots handled by this node */
    int numslaves;  /* Number of slave nodes, if this is a master */
    struct clusterNode **slaves; /* pointers to slave nodes */
    struct clusterNode *slaveof; /* pointer to the master node. Note that it
                                    may be NULL even if the node is a slave
                                    if we don't have the master node in our
                                    tables. */
    unsigned long long last_in_ping_gossip; /* The number of the last carried in the ping gossip section */
    mstime_t ping_sent;      /* Unix time we sent latest ping */
    mstime_t pong_received;  /* Unix time we received the pong */
    mstime_t data_received;  /* Unix time we received any data */
    mstime_t fail_time;      /* Unix time when FAIL flag was set */
    mstime_t voted_time;     /* Last time we voted for a slave of this master */
    mstime_t repl_offset_time;  /* Unix time we received offset for this node */
    mstime_t orphaned_time;     /* Starting time of orphaned master condition */
    long long repl_offset;      /* Last known repl offset for this node. */
    char ip[NET_IP_STR_LEN];    /* Latest known IP address of this node */
    sds hostname;               /* The known hostname for this node */
    int port;                   /* Latest known clients port (TLS or plain). */
    int pport;                  /* Latest known clients plaintext port. Only used
                                   if the main clients port is for TLS. */
    int cport;                  /* Latest known cluster port of this node. */
    clusterLink *link;          /* TCP/IP link established toward this node */
    clusterLink *inbound_link;  /* TCP/IP link accepted from this node */
    list *fail_reports;         /* List of nodes signaling this as failing */
} clusterNode;

/* Slot to keys for a single slot. The keys in the same slot are linked together
 * using dictEntry metadata. */
typedef struct slotToKeys {
    uint64_t count;             /* Number of keys in the slot. */
    dictEntry *head;            /* The first key-value entry in the slot. */
} slotToKeys;

/* Slot to keys mapping for all slots, opaque outside this file. */
struct clusterSlotToKeyMapping {
    slotToKeys by_slot[CLUSTER_SLOTS];
};

/* Dict entry metadata for cluster mode, used for the Slot to Key API to form a
 * linked list of the entries belonging to the same slot. */
typedef struct clusterDictEntryMetadata {
    dictEntry *prev;            /* Prev entry with key in the same slot */
    dictEntry *next;            /* Next entry with key in the same slot */
} clusterDictEntryMetadata;


typedef struct clusterState {
    clusterNode *myself;  /* This node */
    uint64_t currentEpoch;
    int state;            /* CLUSTER_OK, CLUSTER_FAIL, ... */
    int size;             /* Num of master nodes with at least one slot */
    dict *nodes;          /* Hash table of name -> clusterNode structures */
    dict *nodes_black_list; /* Nodes we don't re-add for a few seconds. */
    clusterNode *migrating_slots_to[CLUSTER_SLOTS];
    clusterNode *importing_slots_from[CLUSTER_SLOTS];
    clusterNode *slots[CLUSTER_SLOTS];
    rax *slots_to_channels;
    /* The following fields are used to take the slave state on elections. */
    mstime_t failover_auth_time; /* Time of previous or next election. */
    int failover_auth_count;    /* Number of votes received so far. */
    int failover_auth_sent;     /* True if we already asked for votes. */
    int failover_auth_rank;     /* This slave rank for current auth request. */
    uint64_t failover_auth_epoch; /* Epoch of the current election. */
    int cant_failover_reason;   /* Why a slave is currently not able to
                                   failover. See the CANT_FAILOVER_* macros. */
    /* Manual failover state in common. */
    mstime_t mf_end;            /* Manual failover time limit (ms unixtime).
                                   It is zero if there is no MF in progress. */
    /* Manual failover state of master. */
    clusterNode *mf_slave;      /* Slave performing the manual failover. */
    /* Manual failover state of slave. */
    long long mf_master_offset; /* Master offset the slave needs to start MF
                                   or -1 if still not received. */
    int mf_can_start;           /* If non-zero signal that the manual failover
                                   can start requesting masters vote. */
    /* The following fields are used by masters to take state on elections. */
    uint64_t lastVoteEpoch;     /* Epoch of the last vote granted. */
    int todo_before_sleep; /* Things to do in clusterBeforeSleep(). */
    /* Stats */
    /* Messages received and sent by type. */
    long long stats_bus_messages_sent[CLUSTERMSG_TYPE_COUNT];
    long long stats_bus_messages_received[CLUSTERMSG_TYPE_COUNT];
    long long stats_pfail_nodes;    /* Number of nodes in PFAIL status,
                                       excluding nodes without address. */
    unsigned long long stat_cluster_links_buffer_limit_exceeded;  /* Total number of cluster links freed due to exceeding buffer limit */
} clusterState;

/* Redis cluster messages header */

/* Initially we don't know our "name", but we'll find it once we connect
 * to the first node, using the getsockname() function. Then we'll use this
 * address for all the next messages. */
typedef struct {
    char nodename[CLUSTER_NAMELEN];
    uint32_t ping_sent;
    uint32_t pong_received;
    char ip[NET_IP_STR_LEN];  /* IP address last time it was seen */
    uint16_t port;              /* base port last time it was seen */
    uint16_t cport;             /* cluster port last time it was seen */
    uint16_t flags;             /* node->flags copy */
    uint16_t pport;             /* plaintext-port, when base port is TLS */
    uint16_t notused1;
} clusterMsgDataGossip;

typedef struct {
    char nodename[CLUSTER_NAMELEN];
} clusterMsgDataFail;

typedef struct {
    uint32_t channel_len;
    uint32_t message_len;
    unsigned char bulk_data[8]; /* 8 bytes just as placeholder. */
} clusterMsgDataPublish;

typedef struct {
    uint64_t configEpoch; /* Config epoch of the specified instance. */
    char nodename[CLUSTER_NAMELEN]; /* Name of the slots owner. */
    unsigned char slots[CLUSTER_SLOTS/8]; /* Slots bitmap. */
} clusterMsgDataUpdate;

typedef struct {
    uint64_t module_id;     /* ID of the sender module. */
    uint32_t len;           /* ID of the sender module. */
    uint8_t type;           /* Type from 0 to 255. */
    unsigned char bulk_data[3]; /* 3 bytes just as placeholder. */
} clusterMsgModule;

/* The cluster supports optional extension messages that can be sent
 * along with ping/pong/meet messages to give additional info in a 
 * consistent manner. */
typedef enum {
    CLUSTERMSG_EXT_TYPE_HOSTNAME,
    CLUSTERMSG_EXT_TYPE_FORGOTTEN_NODE,
} clusterMsgPingtypes; 

/* Helper function for making sure extensions are eight byte aligned. */
#define EIGHT_BYTE_ALIGN(size) ((((size) + 7) / 8) * 8)

typedef struct {
    char hostname[1]; /* The announced hostname, ends with \0. */
} clusterMsgPingExtHostname;

typedef struct {
    char name[CLUSTER_NAMELEN]; /* Node name. */
    uint64_t ttl; /* Remaining time to blacklist the node, in seconds. */
} clusterMsgPingExtForgottenNode;

static_assert(sizeof(clusterMsgPingExtForgottenNode) % 8 == 0, "");

typedef struct {
    uint32_t length; /* Total length of this extension message (including this header) */
    uint16_t type; /* Type of this extension message (see clusterMsgPingExtTypes) */
    uint16_t unused; /* 16 bits of padding to make this structure 8 byte aligned. */
    union {
        clusterMsgPingExtHostname hostname;
        clusterMsgPingExtForgottenNode forgotten_node;
    } ext[]; /* Actual extension information, formatted so that the data is 8 
              * byte aligned, regardless of its content. */
} clusterMsgPingExt;

union clusterMsgData {
    /* PING, MEET and PONG */
    struct {
        /* Array of N clusterMsgDataGossip structures */
        clusterMsgDataGossip gossip[1];
        /* Extension data that can optionally be sent for ping/meet/pong
         * messages. We can't explicitly define them here though, since
         * the gossip array isn't the real length of the gossip data. */
    } ping;

    /* FAIL */
    struct {
        clusterMsgDataFail about;
    } fail;

    /* PUBLISH */
    struct {
        clusterMsgDataPublish msg;
    } publish;

    /* UPDATE */
    struct {
        clusterMsgDataUpdate nodecfg;
    } update;

    /* MODULE */
    struct {
        clusterMsgModule msg;
    } module;
};

#define CLUSTER_PROTO_VER 1 /* Cluster bus protocol version. */

typedef struct {
    char sig[4];        /* Signature "RCmb" (Redis Cluster message bus). */
    uint32_t totlen;    /* Total length of this message */
    uint16_t ver;       /* Protocol version, currently set to 1. */
    uint16_t port;      /* TCP base port number. */
    uint16_t type;      /* Message type */
    uint16_t count;     /* Only used for some kind of messages. */
    uint64_t currentEpoch;  /* The epoch accordingly to the sending node. */
    uint64_t configEpoch;   /* The config epoch if it's a master, or the last
                               epoch advertised by its master if it is a
                               slave. */
    uint64_t offset;    /* Master replication offset if node is a master or
                           processed replication offset if node is a slave. */
    char sender[CLUSTER_NAMELEN]; /* Name of the sender node */
    unsigned char myslots[CLUSTER_SLOTS/8];
    char slaveof[CLUSTER_NAMELEN];
    char myip[NET_IP_STR_LEN];    /* Sender IP, if not all zeroed. */
    uint16_t extensions; /* Number of extensions sent along with this packet. */
    char notused1[30];   /* 30 bytes reserved for future usage. */
    uint16_t pport;      /* Sender TCP plaintext port, if base port is TLS */
    uint16_t cport;      /* Sender TCP cluster bus port */
    uint16_t flags;      /* Sender node flags */
    unsigned char state; /* Cluster state from the POV of the sender */
    unsigned char mflags[3]; /* Message flags: CLUSTERMSG_FLAG[012]_... */
    union clusterMsgData data;
} clusterMsg;

/* clusterMsg defines the gossip wire protocol exchanged among Redis cluster
 * members, which can be running different versions of redis-server bits,
 * especially during cluster rolling upgrades.
 *
 * Therefore, fields in this struct should remain at the same offset from
 * release to release. The static asserts below ensures that incompatible
 * changes in clusterMsg be caught at compile time.
 */

static_assert(offsetof(clusterMsg, sig) == 0, "unexpected field offset");
static_assert(offsetof(clusterMsg, totlen) == 4, "unexpected field offset");
static_assert(offsetof(clusterMsg, ver) == 8, "unexpected field offset");
static_assert(offsetof(clusterMsg, port) == 10, "unexpected field offset");
static_assert(offsetof(clusterMsg, type) == 12, "unexpected field offset");
static_assert(offsetof(clusterMsg, count) == 14, "unexpected field offset");
static_assert(offsetof(clusterMsg, currentEpoch) == 16, "unexpected field offset");
static_assert(offsetof(clusterMsg, configEpoch) == 24, "unexpected field offset");
static_assert(offsetof(clusterMsg, offset) == 32, "unexpected field offset");
static_assert(offsetof(clusterMsg, sender) == 40, "unexpected field offset");
static_assert(offsetof(clusterMsg, myslots) == 80, "unexpected field offset");
static_assert(offsetof(clusterMsg, slaveof) == 2128, "unexpected field offset");
static_assert(offsetof(clusterMsg, myip) == 2168, "unexpected field offset");
static_assert(offsetof(clusterMsg, extensions) == 2214, "unexpected field offset");
static_assert(offsetof(clusterMsg, notused1) == 2216, "unexpected field offset");
static_assert(offsetof(clusterMsg, pport) == 2246, "unexpected field offset");
static_assert(offsetof(clusterMsg, cport) == 2248, "unexpected field offset");
static_assert(offsetof(clusterMsg, flags) == 2250, "unexpected field offset");
static_assert(offsetof(clusterMsg, state) == 2252, "unexpected field offset");
static_assert(offsetof(clusterMsg, mflags) == 2253, "unexpected field offset");
static_assert(offsetof(clusterMsg, data) == 2256, "unexpected field offset");

#define CLUSTERMSG_MIN_LEN (sizeof(clusterMsg)-sizeof(union clusterMsgData))

/* Message flags better specify the packet content or are used to
 * provide some information about the node state. */
#define CLUSTERMSG_FLAG0_PAUSED (1<<0) /* Master paused for manual failover. */
#define CLUSTERMSG_FLAG0_FORCEACK (1<<1) /* Give ACK to AUTH_REQUEST even if
                                            master is up. */
#define CLUSTERMSG_FLAG0_EXT_DATA (1<<2) /* Message contains extension data */

/* ---------------------- API exported outside cluster.c -------------------- */
void clusterInit(void);
void clusterInitListeners(void);
void clusterCron(void);
void clusterBeforeSleep(void);
clusterNode *getNodeByQuery(client *c, struct redisCommand *cmd, robj **argv, int argc, int *hashslot, int *ask);
int verifyClusterNodeId(const char *name, int length);
clusterNode *clusterLookupNode(const char *name, int length);
int clusterRedirectBlockedClientIfNeeded(client *c);
void clusterRedirectClient(client *c, clusterNode *n, int hashslot, int error_code);
void migrateCloseTimedoutSockets(void);
int verifyClusterConfigWithData(void);
unsigned long getClusterConnectionsCount(void);
int clusterSendModuleMessageToTarget(const char *target, uint64_t module_id, uint8_t type, const char *payload, uint32_t len);
void clusterPropagatePublish(robj *channel, robj *message, int sharded);
unsigned int keyHashSlot(char *key, int keylen);
void slotToKeyAddEntry(dictEntry *entry, redisDb *db);
void slotToKeyDelEntry(dictEntry *entry, redisDb *db);
void slotToKeyReplaceEntry(dictEntry *entry, redisDb *db);
void slotToKeyInit(redisDb *db);
void slotToKeyFlush(redisDb *db);
void slotToKeyDestroy(redisDb *db);
void clusterUpdateMyselfFlags(void);
void clusterUpdateMyselfIp(void);
void slotToChannelAdd(sds channel);
void slotToChannelDel(sds channel);
void clusterUpdateMyselfHostname(void);

#endif /* __CLUSTER_H */