服务器结构

struct redisServer {
    /* General */
    pid_t pid;                  /* Main process pid. */
    pthread_t main_thread_id;         /* Main thread id */
    char *configfile;           /* Absolute config file path, or NULL */
    char *executable;           /* Absolute executable file path. */
    char **exec_argv;           /* Executable argv vector (copy). */
    int dynamic_hz;             /* Change hz value depending on # of clients. */
    int config_hz;              /* Configured HZ value. May be different than
                                   the actual 'hz' field value if dynamic-hz
                                   is enabled. */
    mode_t umask;               /* The umask value of the process on startup */
    int hz;                     /* serverCron() calls frequency in hertz */
    int in_fork_child;          /* indication that this is a fork child */
    redisDb *db;
    dict *commands;             /* Command table */
    dict *orig_commands;        /* Command table before command renaming. */
    aeEventLoop *el;
    rax *errors;                /* Errors table */
    unsigned int lruclock; /* Clock for LRU eviction */
    volatile sig_atomic_t shutdown_asap; /* Shutdown ordered by signal handler. */
    mstime_t shutdown_mstime;   /* Timestamp to limit graceful shutdown. */
    int last_sig_received;      /* Indicates the last SIGNAL received, if any (e.g., SIGINT or SIGTERM). */
    int shutdown_flags;         /* Flags passed to prepareForShutdown(). */
    int activerehashing;        /* Incremental rehash in serverCron() */
    int active_defrag_running;  /* Active defragmentation running (holds current scan aggressiveness) */
    char *pidfile;              /* PID file path */
    int arch_bits;              /* 32 or 64 depending on sizeof(long) */
    int cronloops;              /* Number of times the cron function run */
    char runid[CONFIG_RUN_ID_SIZE+1];  /* ID always different at every exec. */
    int sentinel_mode;          /* True if this instance is a Sentinel. */
    size_t initial_memory_usage; /* Bytes used after initialization. */
    int always_show_logo;       /* Show logo even for non-stdout logging. */
    int in_exec;                /* Are we inside EXEC? */
    int busy_module_yield_flags;         /* Are we inside a busy module? (triggered by RM_Yield). see BUSY_MODULE_YIELD_ flags. */
    const char *busy_module_yield_reply; /* When non-null, we are inside RM_Yield. */
    char *ignore_warnings;      /* Config: warnings that should be ignored. */
    int client_pause_in_transaction; /* Was a client pause executed during this Exec? */
    int thp_enabled;                 /* If true, THP is enabled. */
    size_t page_size;                /* The page size of OS. */
    /* Modules */
    dict *moduleapi;            /* Exported core APIs dictionary for modules. */
    dict *sharedapi;            /* Like moduleapi but containing the APIs that
                                   modules share with each other. */
    dict *module_configs_queue; /* Dict that stores module configurations from .conf file until after modules are loaded during startup or arguments to loadex. */
    list *loadmodule_queue;     /* List of modules to load at startup. */
    int module_pipe[2];         /* Pipe used to awake the event loop by module threads. */
    pid_t child_pid;            /* PID of current child */
    int child_type;             /* Type of current child */
    /* Networking */
    int port;                   /* TCP listening port */
    int tls_port;               /* TLS listening port */
    int tcp_backlog;            /* TCP listen() backlog */
    char *bindaddr[CONFIG_BINDADDR_MAX]; /* Addresses we should bind to */
    int bindaddr_count;         /* Number of addresses in server.bindaddr[] */
    char *bind_source_addr;     /* Source address to bind on for outgoing connections */
    char *unixsocket;           /* UNIX socket path */
    unsigned int unixsocketperm; /* UNIX socket permission (see mode_t) */
    connListener listeners[CONN_TYPE_MAX]; /* TCP/Unix/TLS even more types */
    uint32_t socket_mark_id;    /* ID for listen socket marking */
    connListener clistener;     /* Cluster bus listener */
    list *clients;              /* List of active clients */
    list *clients_to_close;     /* Clients to close asynchronously */
    list *clients_pending_write; /* There is to write or install handler. */
    list *clients_pending_read;  /* Client has pending read socket buffers. */
    list *slaves, *monitors;    /* List of slaves and MONITORs */
    client *current_client;     /* The client that triggered the command execution (External or AOF). */
    client *executing_client;   /* The client executing the current command (possibly script or module). */

#ifdef LOG_REQ_RES
    char *req_res_logfile; /* Path of log file for logging all requests and their replies. If NULL, no logging will be performed */
    unsigned int client_default_resp;
#endif

    /* Stuff for client mem eviction */
    clientMemUsageBucket* client_mem_usage_buckets;

    rax *clients_timeout_table; /* Radix tree for blocked clients timeouts. */
    int execution_nesting;      /* Execution nesting level.
                                 * e.g. call(), async module stuff (timers, events, etc.),
                                 * cron stuff (active expire, eviction) */
    rax *clients_index;         /* Active clients dictionary by client ID. */
    uint32_t paused_actions;   /* Bitmask of actions that are currently paused */
    list *postponed_clients;       /* List of postponed clients */
    pause_event client_pause_per_purpose[NUM_PAUSE_PURPOSES];
    char neterr[ANET_ERR_LEN];   /* Error buffer for anet.c */
    dict *migrate_cached_sockets;/* MIGRATE cached sockets */
    redisAtomic uint64_t next_client_id; /* Next client unique ID. Incremental. */
    int protected_mode;         /* Don't accept external connections. */
    int io_threads_num;         /* Number of IO threads to use. */
    int io_threads_do_reads;    /* Read and parse from IO threads? */
    int io_threads_active;      /* Is IO threads currently active? */
    long long events_processed_while_blocked; /* processEventsWhileBlocked() */
    int enable_protected_configs;    /* Enable the modification of protected configs, see PROTECTED_ACTION_ALLOWED_* */
    int enable_debug_cmd;            /* Enable DEBUG commands, see PROTECTED_ACTION_ALLOWED_* */
    int enable_module_cmd;           /* Enable MODULE commands, see PROTECTED_ACTION_ALLOWED_* */

    /* RDB / AOF loading information */
    volatile sig_atomic_t loading; /* We are loading data from disk if true */
    volatile sig_atomic_t async_loading; /* We are loading data without blocking the db being served */
    off_t loading_total_bytes;
    off_t loading_rdb_used_mem;
    off_t loading_loaded_bytes;
    time_t loading_start_time;
    off_t loading_process_events_interval_bytes;
    /* Fields used only for stats */
    time_t stat_starttime;          /* Server start time */
    long long stat_numcommands;     /* Number of processed commands */
    long long stat_numconnections;  /* Number of connections received */
    long long stat_expiredkeys;     /* Number of expired keys */
    double stat_expired_stale_perc; /* Percentage of keys probably expired */
    long long stat_expired_time_cap_reached_count; /* Early expire cycle stops.*/
    long long stat_expire_cycle_time_used; /* Cumulative microseconds used. */
    long long stat_evictedkeys;     /* Number of evicted keys (maxmemory) */
    long long stat_evictedclients;  /* Number of evicted clients */
    long long stat_total_eviction_exceeded_time;  /* Total time over the memory limit, unit us */
    monotime stat_last_eviction_exceeded_time;  /* Timestamp of current eviction start, unit us */
    long long stat_keyspace_hits;   /* Number of successful lookups of keys */
    long long stat_keyspace_misses; /* Number of failed lookups of keys */
    long long stat_active_defrag_hits;      /* number of allocations moved */
    long long stat_active_defrag_misses;    /* number of allocations scanned but not moved */
    long long stat_active_defrag_key_hits;  /* number of keys with moved allocations */
    long long stat_active_defrag_key_misses;/* number of keys scanned and not moved */
    long long stat_active_defrag_scanned;   /* number of dictEntries scanned */
    long long stat_total_active_defrag_time; /* Total time memory fragmentation over the limit, unit us */
    monotime stat_last_active_defrag_time; /* Timestamp of current active defrag start */
    size_t stat_peak_memory;        /* Max used memory record */
    long long stat_aof_rewrites;    /* number of aof file rewrites performed */
    long long stat_aofrw_consecutive_failures; /* The number of consecutive failures of aofrw */
    long long stat_rdb_saves;       /* number of rdb saves performed */
    long long stat_fork_time;       /* Time needed to perform latest fork() */
    double stat_fork_rate;          /* Fork rate in GB/sec. */
    long long stat_total_forks;     /* Total count of fork. */
    long long stat_rejected_conn;   /* Clients rejected because of maxclients */
    long long stat_sync_full;       /* Number of full resyncs with slaves. */
    long long stat_sync_partial_ok; /* Number of accepted PSYNC requests. */
    long long stat_sync_partial_err;/* Number of unaccepted PSYNC requests. */
    list *slowlog;                  /* SLOWLOG list of commands */
    long long slowlog_entry_id;     /* SLOWLOG current entry ID */
    long long slowlog_log_slower_than; /* SLOWLOG time limit (to get logged) */
    unsigned long slowlog_max_len;     /* SLOWLOG max number of items logged */
    struct malloc_stats cron_malloc_stats; /* sampled in serverCron(). */
    redisAtomic long long stat_net_input_bytes; /* Bytes read from network. */
    redisAtomic long long stat_net_output_bytes; /* Bytes written to network. */
    redisAtomic long long stat_net_repl_input_bytes; /* Bytes read during replication, added to stat_net_input_bytes in 'info'. */
    redisAtomic long long stat_net_repl_output_bytes; /* Bytes written during replication, added to stat_net_output_bytes in 'info'. */
    size_t stat_current_cow_peak;   /* Peak size of copy on write bytes. */
    size_t stat_current_cow_bytes;  /* Copy on write bytes while child is active. */
    monotime stat_current_cow_updated;  /* Last update time of stat_current_cow_bytes */
    size_t stat_current_save_keys_processed;  /* Processed keys while child is active. */
    size_t stat_current_save_keys_total;  /* Number of keys when child started. */
    size_t stat_rdb_cow_bytes;      /* Copy on write bytes during RDB saving. */
    size_t stat_aof_cow_bytes;      /* Copy on write bytes during AOF rewrite. */
    size_t stat_module_cow_bytes;   /* Copy on write bytes during module fork. */
    double stat_module_progress;   /* Module save progress. */
    size_t stat_clients_type_memory[CLIENT_TYPE_COUNT];/* Mem usage by type */
    size_t stat_cluster_links_memory; /* Mem usage by cluster links */
    long long stat_unexpected_error_replies; /* Number of unexpected (aof-loading, replica to master, etc.) error replies */
    long long stat_total_error_replies; /* Total number of issued error replies ( command + rejected errors ) */
    long long stat_dump_payload_sanitizations; /* Number deep dump payloads integrity validations. */
    long long stat_io_reads_processed; /* Number of read events processed by IO / Main threads */
    long long stat_io_writes_processed; /* Number of write events processed by IO / Main threads */
    redisAtomic long long stat_total_reads_processed; /* Total number of read events processed */
    redisAtomic long long stat_total_writes_processed; /* Total number of write events processed */
    long long stat_client_qbuf_limit_disconnections;  /* Total number of clients reached query buf length limit */
    long long stat_client_outbuf_limit_disconnections;  /* Total number of clients reached output buf length limit */
    /* The following two are used to track instantaneous metrics, like
     * number of operations per second, network traffic. */
    struct {
        long long last_sample_base;  /* The divisor of last sample window */
        long long last_sample_value; /* The dividend of last sample window */
        long long samples[STATS_METRIC_SAMPLES];
        int idx;
    } inst_metric[STATS_METRIC_COUNT];
    long long stat_reply_buffer_shrinks; /* Total number of output buffer shrinks */
    long long stat_reply_buffer_expands; /* Total number of output buffer expands */
    monotime el_start;
    /* The following two are used to record the max number of commands executed in one eventloop.
     * Note that commands in transactions are also counted. */
    long long el_cmd_cnt_start;
    long long el_cmd_cnt_max;
    /* The sum of active-expire, active-defrag and all other tasks done by cron and beforeSleep,
       but excluding read, write and AOF, which are counted by other sets of metrics. */
    monotime el_cron_duration; 
    durationStats duration_stats[EL_DURATION_TYPE_NUM];

    /* Configuration */
    int verbosity;                  /* Loglevel in redis.conf */
    int maxidletime;                /* Client timeout in seconds */
    int tcpkeepalive;               /* Set SO_KEEPALIVE if non-zero. */
    int active_expire_enabled;      /* Can be disabled for testing purposes. */
    int active_expire_effort;       /* From 1 (default) to 10, active effort. */
    int lazy_expire_disabled;       /* If > 0, don't trigger lazy expire */
    int active_defrag_enabled;
    int sanitize_dump_payload;      /* Enables deep sanitization for ziplist and listpack in RDB and RESTORE. */
    int skip_checksum_validation;   /* Disable checksum validation for RDB and RESTORE payload. */
    int jemalloc_bg_thread;         /* Enable jemalloc background thread */
    size_t active_defrag_ignore_bytes; /* minimum amount of fragmentation waste to start active defrag */
    int active_defrag_threshold_lower; /* minimum percentage of fragmentation to start active defrag */
    int active_defrag_threshold_upper; /* maximum percentage of fragmentation at which we use maximum effort */
    int active_defrag_cycle_min;       /* minimal effort for defrag in CPU percentage */
    int active_defrag_cycle_max;       /* maximal effort for defrag in CPU percentage */
    unsigned long active_defrag_max_scan_fields; /* maximum number of fields of set/hash/zset/list to process from within the main dict scan */
    size_t client_max_querybuf_len; /* Limit for client query buffer length */
    int dbnum;                      /* Total number of configured DBs */
    int supervised;                 /* 1 if supervised, 0 otherwise. */
    int supervised_mode;            /* See SUPERVISED_* */
    int daemonize;                  /* True if running as a daemon */
    int set_proc_title;             /* True if change proc title */
    char *proc_title_template;      /* Process title template format */
    clientBufferLimitsConfig client_obuf_limits[CLIENT_TYPE_OBUF_COUNT];
    int pause_cron;                 /* Don't run cron tasks (debug) */
    int latency_tracking_enabled;   /* 1 if extended latency tracking is enabled, 0 otherwise. */
    double *latency_tracking_info_percentiles; /* Extended latency tracking info output percentile list configuration. */
    int latency_tracking_info_percentiles_len;
    /* AOF persistence */
    int aof_enabled;                /* AOF configuration */
    int aof_state;                  /* AOF_(ON|OFF|WAIT_REWRITE) */
    int aof_fsync;                  /* Kind of fsync() policy */
    char *aof_filename;             /* Basename of the AOF file and manifest file */
    char *aof_dirname;              /* Name of the AOF directory */
    int aof_no_fsync_on_rewrite;    /* Don't fsync if a rewrite is in prog. */
    int aof_rewrite_perc;           /* Rewrite AOF if % growth is > M and... */
    off_t aof_rewrite_min_size;     /* the AOF file is at least N bytes. */
    off_t aof_rewrite_base_size;    /* AOF size on latest startup or rewrite. */
    off_t aof_current_size;         /* AOF current size (Including BASE + INCRs). */
    off_t aof_last_incr_size;       /* The size of the latest incr AOF. */
    off_t aof_last_incr_fsync_offset; /* AOF offset which is already requested to be synced to disk.
                                       * Compare with the aof_last_incr_size. */
    int aof_flush_sleep;            /* Micros to sleep before flush. (used by tests) */
    int aof_rewrite_scheduled;      /* Rewrite once BGSAVE terminates. */
    sds aof_buf;      /* AOF buffer, written before entering the event loop */
    int aof_fd;       /* File descriptor of currently selected AOF file */
    int aof_selected_db; /* Currently selected DB in AOF */
    time_t aof_flush_postponed_start; /* UNIX time of postponed AOF flush */
    time_t aof_last_fsync;            /* UNIX time of last fsync() */
    time_t aof_rewrite_time_last;   /* Time used by last AOF rewrite run. */
    time_t aof_rewrite_time_start;  /* Current AOF rewrite start time. */
    time_t aof_cur_timestamp;       /* Current record timestamp in AOF */
    int aof_timestamp_enabled;      /* Enable record timestamp in AOF */
    int aof_lastbgrewrite_status;   /* C_OK or C_ERR */
    unsigned long aof_delayed_fsync;  /* delayed AOF fsync() counter */
    int aof_rewrite_incremental_fsync;/* fsync incrementally while aof rewriting? */
    int rdb_save_incremental_fsync;   /* fsync incrementally while rdb saving? */
    int aof_last_write_status;      /* C_OK or C_ERR */
    int aof_last_write_errno;       /* Valid if aof write/fsync status is ERR */
    int aof_load_truncated;         /* Don't stop on unexpected AOF EOF. */
    int aof_use_rdb_preamble;       /* Specify base AOF to use RDB encoding on AOF rewrites. */
    redisAtomic int aof_bio_fsync_status; /* Status of AOF fsync in bio job. */
    redisAtomic int aof_bio_fsync_errno;  /* Errno of AOF fsync in bio job. */
    aofManifest *aof_manifest;       /* Used to track AOFs. */
    int aof_disable_auto_gc;         /* If disable automatically deleting HISTORY type AOFs?
                                        default no. (for testings). */

    /* RDB persistence */
    long long dirty;                /* Changes to DB from the last save */
    long long dirty_before_bgsave;  /* Used to restore dirty on failed BGSAVE */
    long long rdb_last_load_keys_expired;  /* number of expired keys when loading RDB */
    long long rdb_last_load_keys_loaded;   /* number of loaded keys when loading RDB */
    struct saveparam *saveparams;   /* Save points array for RDB */
    int saveparamslen;              /* Number of saving points */
    char *rdb_filename;             /* Name of RDB file */
    int rdb_compression;            /* Use compression in RDB? */
    int rdb_checksum;               /* Use RDB checksum? */
    int rdb_del_sync_files;         /* Remove RDB files used only for SYNC if
                                       the instance does not use persistence. */
    time_t lastsave;                /* Unix time of last successful save */
    time_t lastbgsave_try;          /* Unix time of last attempted bgsave */
    time_t rdb_save_time_last;      /* Time used by last RDB save run. */
    time_t rdb_save_time_start;     /* Current RDB save start time. */
    int rdb_bgsave_scheduled;       /* BGSAVE when possible if true. */
    int rdb_child_type;             /* Type of save by active child. */
    int lastbgsave_status;          /* C_OK or C_ERR */
    int stop_writes_on_bgsave_err;  /* Don't allow writes if can't BGSAVE */
    int rdb_pipe_read;              /* RDB pipe used to transfer the rdb data */
                                    /* to the parent process in diskless repl. */
    int rdb_child_exit_pipe;        /* Used by the diskless parent allow child exit. */
    connection **rdb_pipe_conns;    /* Connections which are currently the */
    int rdb_pipe_numconns;          /* target of diskless rdb fork child. */
    int rdb_pipe_numconns_writing;  /* Number of rdb conns with pending writes. */
    char *rdb_pipe_buff;            /* In diskless replication, this buffer holds data */
    int rdb_pipe_bufflen;           /* that was read from the rdb pipe. */
    int rdb_key_save_delay;         /* Delay in microseconds between keys while
                                     * writing aof or rdb. (for testings). negative
                                     * value means fractions of microseconds (on average). */
    int key_load_delay;             /* Delay in microseconds between keys while
                                     * loading aof or rdb. (for testings). negative
                                     * value means fractions of microseconds (on average). */
    /* Pipe and data structures for child -> parent info sharing. */
    int child_info_pipe[2];         /* Pipe used to write the child_info_data. */
    int child_info_nread;           /* Num of bytes of the last read from pipe */
    /* Propagation of commands in AOF / replication */
    redisOpArray also_propagate;    /* Additional command to propagate. */
    int replication_allowed;        /* Are we allowed to replicate? */
    /* Logging */
    char *logfile;                  /* Path of log file */
    int syslog_enabled;             /* Is syslog enabled? */
    char *syslog_ident;             /* Syslog ident */
    int syslog_facility;            /* Syslog facility */
    int crashlog_enabled;           /* Enable signal handler for crashlog.
                                     * disable for clean core dumps. */
    int memcheck_enabled;           /* Enable memory check on crash. */
    int use_exit_on_panic;          /* Use exit() on panic and assert rather than
                                     * abort(). useful for Valgrind. */
    /* Shutdown */
    int shutdown_timeout;           /* Graceful shutdown time limit in seconds. */
    int shutdown_on_sigint;         /* Shutdown flags configured for SIGINT. */
    int shutdown_on_sigterm;        /* Shutdown flags configured for SIGTERM. */

    /* Replication (master) */
    char replid[CONFIG_RUN_ID_SIZE+1];  /* My current replication ID. */
    char replid2[CONFIG_RUN_ID_SIZE+1]; /* replid inherited from master*/
    long long master_repl_offset;   /* My current replication offset */
    long long second_replid_offset; /* Accept offsets up to this for replid2. */
    redisAtomic long long fsynced_reploff_pending;/* Largest replication offset to
                                     * potentially have been fsynced, applied to
                                       fsynced_reploff only when AOF state is AOF_ON
                                       (not during the initial rewrite) */
    long long fsynced_reploff;      /* Largest replication offset that has been confirmed to be fsynced */
    int slaveseldb;                 /* Last SELECTed DB in replication output */
    int repl_ping_slave_period;     /* Master pings the slave every N seconds */
    replBacklog *repl_backlog;      /* Replication backlog for partial syncs */
    long long repl_backlog_size;    /* Backlog circular buffer size */
    time_t repl_backlog_time_limit; /* Time without slaves after the backlog
                                       gets released. */
    time_t repl_no_slaves_since;    /* We have no slaves since that time.
                                       Only valid if server.slaves len is 0. */
    int repl_min_slaves_to_write;   /* Min number of slaves to write. */
    int repl_min_slaves_max_lag;    /* Max lag of <count> slaves to write. */
    int repl_good_slaves_count;     /* Number of slaves with lag <= max_lag. */
    int repl_diskless_sync;         /* Master send RDB to slaves sockets directly. */
    int repl_diskless_load;         /* Slave parse RDB directly from the socket.
                                     * see REPL_DISKLESS_LOAD_* enum */
    int repl_diskless_sync_delay;   /* Delay to start a diskless repl BGSAVE. */
    int repl_diskless_sync_max_replicas;/* Max replicas for diskless repl BGSAVE
                                         * delay (start sooner if they all connect). */
    size_t repl_buffer_mem;         /* The memory of replication buffer. */
    list *repl_buffer_blocks;       /* Replication buffers blocks list
                                     * (serving replica clients and repl backlog) */
    /* Replication (slave) */
    char *masteruser;               /* AUTH with this user and masterauth with master */
    sds masterauth;                 /* AUTH with this password with master */
    char *masterhost;               /* Hostname of master */
    int masterport;                 /* Port of master */
    int repl_timeout;               /* Timeout after N seconds of master idle */
    client *master;     /* Client that is master for this slave */
    client *cached_master; /* Cached master to be reused for PSYNC. */
    int repl_syncio_timeout; /* Timeout for synchronous I/O calls */
    int repl_state;          /* Replication status if the instance is a slave */
    off_t repl_transfer_size; /* Size of RDB to read from master during sync. */
    off_t repl_transfer_read; /* Amount of RDB read from master during sync. */
    off_t repl_transfer_last_fsync_off; /* Offset when we fsync-ed last time. */
    connection *repl_transfer_s;     /* Slave -> Master SYNC connection */
    int repl_transfer_fd;    /* Slave -> Master SYNC temp file descriptor */
    char *repl_transfer_tmpfile; /* Slave-> master SYNC temp file name */
    time_t repl_transfer_lastio; /* Unix time of the latest read, for timeout */
    int repl_serve_stale_data; /* Serve stale data when link is down? */
    int repl_slave_ro;          /* Slave is read only? */
    int repl_slave_ignore_maxmemory;    /* If true slaves do not evict. */
    time_t repl_down_since; /* Unix time at which link with master went down */
    int repl_disable_tcp_nodelay;   /* Disable TCP_NODELAY after SYNC? */
    int slave_priority;             /* Reported in INFO and used by Sentinel. */
    int replica_announced;          /* If true, replica is announced by Sentinel */
    int slave_announce_port;        /* Give the master this listening port. */
    char *slave_announce_ip;        /* Give the master this ip address. */
    int propagation_error_behavior; /* Configures the behavior of the replica
                                     * when it receives an error on the replication stream */
    int repl_ignore_disk_write_error;   /* Configures whether replicas panic when unable to
                                         * persist writes to AOF. */
    /* The following two fields is where we store master PSYNC replid/offset
     * while the PSYNC is in progress. At the end we'll copy the fields into
     * the server->master client structure. */
    char master_replid[CONFIG_RUN_ID_SIZE+1];  /* Master PSYNC runid. */
    long long master_initial_offset;           /* Master PSYNC offset. */
    int repl_slave_lazy_flush;          /* Lazy FLUSHALL before loading DB? */
    /* Synchronous replication. */
    list *clients_waiting_acks;         /* Clients waiting in WAIT or WAITAOF. */
    int get_ack_from_slaves;            /* If true we send REPLCONF GETACK. */
    /* Limits */
    unsigned int maxclients;            /* Max number of simultaneous clients */
    unsigned long long maxmemory;   /* Max number of memory bytes to use */
    ssize_t maxmemory_clients;       /* Memory limit for total client buffers */
    int maxmemory_policy;           /* Policy for key eviction */
    int maxmemory_samples;          /* Precision of random sampling */
    int maxmemory_eviction_tenacity;/* Aggressiveness of eviction processing */
    int lfu_log_factor;             /* LFU logarithmic counter factor. */
    int lfu_decay_time;             /* LFU counter decay factor. */
    long long proto_max_bulk_len;   /* Protocol bulk length maximum size. */
    int oom_score_adj_values[CONFIG_OOM_COUNT];   /* Linux oom_score_adj configuration */
    int oom_score_adj;                            /* If true, oom_score_adj is managed */
    int disable_thp;                              /* If true, disable THP by syscall */
    /* Blocked clients */
    unsigned int blocked_clients;   /* # of clients executing a blocking cmd.*/
    unsigned int blocked_clients_by_type[BLOCKED_NUM];
    list *unblocked_clients; /* list of clients to unblock before next loop */
    list *ready_keys;        /* List of readyList structures for BLPOP &amp; co */
    /* Client side caching. */
    unsigned int tracking_clients;  /* # of clients with tracking enabled.*/
    size_t tracking_table_max_keys; /* Max number of keys in tracking table. */
    list *tracking_pending_keys; /* tracking invalidation keys pending to flush */
    list *pending_push_messages; /* pending publish or other push messages to flush */
    /* Sort parameters - qsort_r() is only available under BSD so we
     * have to take this state global, in order to pass it to sortCompare() */
    int sort_desc;
    int sort_alpha;
    int sort_bypattern;
    int sort_store;
    /* Zip structure config, see redis.conf for more information  */
    size_t hash_max_listpack_entries;
    size_t hash_max_listpack_value;
    size_t set_max_intset_entries;
    size_t set_max_listpack_entries;
    size_t set_max_listpack_value;
    size_t zset_max_listpack_entries;
    size_t zset_max_listpack_value;
    size_t hll_sparse_max_bytes;
    size_t stream_node_max_bytes;
    long long stream_node_max_entries;
    /* List parameters */
    int list_max_listpack_size;
    int list_compress_depth;
    /* time cache */
    redisAtomic time_t unixtime; /* Unix time sampled every cron cycle. */
    time_t timezone;            /* Cached timezone. As set by tzset(). */
    int daylight_active;        /* Currently in daylight saving time. */
    mstime_t mstime;            /* 'unixtime' in milliseconds. */
    ustime_t ustime;            /* 'unixtime' in microseconds. */
    mstime_t cmd_time_snapshot; /* Time snapshot of the root execution nesting. */
    size_t blocking_op_nesting; /* Nesting level of blocking operation, used to reset blocked_last_cron. */
    long long blocked_last_cron; /* Indicate the mstime of the last time we did cron jobs from a blocking operation */
    /* Pubsub */
    dict *pubsub_channels;  /* Map channels to list of subscribed clients */
    dict *pubsub_patterns;  /* A dict of pubsub_patterns */
    int notify_keyspace_events; /* Events to propagate via Pub/Sub. This is an
                                   xor of NOTIFY_... flags. */
    dict *pubsubshard_channels;  /* Map shard channels to list of subscribed clients */
    /* Cluster */
    int cluster_enabled;      /* Is cluster enabled? */
    int cluster_port;         /* Set the cluster port for a node. */
    mstime_t cluster_node_timeout; /* Cluster node timeout. */
    mstime_t cluster_ping_interval;    /* A debug configuration for setting how often cluster nodes send ping messages. */
    char *cluster_configfile; /* Cluster auto-generated config file name. */
    struct clusterState *cluster;  /* State of the cluster */
    int cluster_migration_barrier; /* Cluster replicas migration barrier. */
    int cluster_allow_replica_migration; /* Automatic replica migrations to orphaned masters and from empty masters */
    int cluster_slave_validity_factor; /* Slave max data age for failover. */
    int cluster_require_full_coverage; /* If true, put the cluster down if
                                          there is at least an uncovered slot.*/
    int cluster_slave_no_failover;  /* Prevent slave from starting a failover
                                       if the master is in failure state. */
    char *cluster_announce_ip;  /* IP address to announce on cluster bus. */
    char *cluster_announce_hostname;  /* hostname to announce on cluster bus. */
    char *cluster_announce_human_nodename;  /* Human readable node name assigned to a node. */
    int cluster_preferred_endpoint_type; /* Use the announced hostname when available. */
    int cluster_announce_port;     /* base port to announce on cluster bus. */
    int cluster_announce_tls_port; /* TLS port to announce on cluster bus. */
    int cluster_announce_bus_port; /* bus port to announce on cluster bus. */
    int cluster_module_flags;      /* Set of flags that Redis modules are able
                                      to set in order to suppress certain
                                      native Redis Cluster features. Check the
                                      REDISMODULE_CLUSTER_FLAG_*. */
    int cluster_allow_reads_when_down; /* Are reads allowed when the cluster
                                        is down? */
    int cluster_config_file_lock_fd;   /* cluster config fd, will be flocked. */
    unsigned long long cluster_link_msg_queue_limit_bytes;  /* Memory usage limit on individual link msg queue */
    int cluster_drop_packet_filter; /* Debug config that allows tactically
                                   * dropping packets of a specific type */
    /* Scripting */
    mstime_t busy_reply_threshold;  /* Script / module timeout in milliseconds */
    int pre_command_oom_state;         /* OOM before command (script?) was started */
    int script_disable_deny_script;    /* Allow running commands marked "no-script" inside a script. */
    /* Lazy free */
    int lazyfree_lazy_eviction;
    int lazyfree_lazy_expire;
    int lazyfree_lazy_server_del;
    int lazyfree_lazy_user_del;
    int lazyfree_lazy_user_flush;
    /* Latency monitor */
    long long latency_monitor_threshold;
    dict *latency_events;
    /* ACLs */
    char *acl_filename;           /* ACL Users file. NULL if not configured. */
    unsigned long acllog_max_len; /* Maximum length of the ACL LOG list. */
    sds requirepass;              /* Remember the cleartext password set with
                                     the old "requirepass" directive for
                                     backward compatibility with Redis <= 5. */
    int acl_pubsub_default;      /* Default ACL pub/sub channels flag */
    aclInfo acl_info; /* ACL info */
    /* Assert &amp; bug reporting */
    int watchdog_period;  /* Software watchdog period in ms. 0 = off */
    /* System hardware info */
    size_t system_memory_size;  /* Total memory in system as reported by OS */
    /* TLS Configuration */
    int tls_cluster;
    int tls_replication;
    int tls_auth_clients;
    redisTLSContextConfig tls_ctx_config;
    /* cpu affinity */
    char *server_cpulist; /* cpu affinity list of redis server main/io thread. */
    char *bio_cpulist; /* cpu affinity list of bio thread. */
    char *aof_rewrite_cpulist; /* cpu affinity list of aof rewrite process. */
    char *bgsave_cpulist; /* cpu affinity list of bgsave process. */
    /* Sentinel config */
    struct sentinelConfig *sentinel_config; /* sentinel config to load at startup time. */
    /* Coordinate failover info */
    mstime_t failover_end_time; /* Deadline for failover command. */
    int force_failover; /* If true then failover will be forced at the
                         * deadline, otherwise failover is aborted. */
    char *target_replica_host; /* Failover target host. If null during a
                                * failover then any replica can be used. */
    int target_replica_port; /* Failover target port */
    int failover_state; /* Failover state */
    int cluster_allow_pubsubshard_when_down; /* Is pubsubshard allowed when the cluster
                                                is down, doesn't affect pubsub global. */
    long reply_buffer_peak_reset_time; /* The amount of time (in milliseconds) to wait between reply buffer peak resets */
    int reply_buffer_resizing_enabled; /* Is reply buffer resizing enabled (1 by default) */
    /* Local environment */
    char *locale_collate;
};

redisServer的参数比较多,主要的是**redisDb *db;**里面每个数据库存储信息dbnum代表数据库的个数。
redisServer

数据库结构

每个数据库是由redisDb结构组成的。

/* Redis database representation. There are multiple databases identified
 * by integers from 0 (the default database) up to the max configured
 * database. The database number is the 'id' field in the structure. */
typedef struct redisDb {
    dict *dict;                 /* The keyspace for this DB */
    dict *expires;              /* Timeout of keys with a timeout set */
    dict *blocking_keys;        /* Keys with clients waiting for data (BLPOP)*/
    dict *blocking_keys_unblock_on_nokey;   /* Keys with clients waiting for
                                             * data, and should be unblocked if key is deleted (XREADEDGROUP).
                                             * This is a subset of blocking_keys*/
    dict *ready_keys;           /* Blocked keys that received a PUSH */
    dict *watched_keys;         /* WATCHED keys for MULTI/EXEC CAS */
    int id;                     /* Database ID */
    long long avg_ttl;          /* Average TTL, just for stats */
    unsigned long expires_cursor; /* Cursor of the active expire cycle. */
    list *defrag_later;         /* List of key names to attempt to defrag one by one, gradually. */
    clusterSlotToKeyMapping *slots_to_keys; /* Array of slots to keys. Only used in cluster mode (db 0). */
} redisDb;

redisDb主要有键值空间过期集合两个字典组成。其中dict包含所有的键值对儿信息,expires包含键的过期信息
redisDb

过期删除

如果一个键已经过期,怎么被删除呐?删除策略已经有三种定时删除惰性删除定期删除

定时删除

设置过期的同时,创建一个timer,让timer在键过期时立即执行对键的删除。

  • 优点:对内存友好
  • 缺点:对CPU不友好

惰性删除

键过期后不做任何处理,但是当从键空间中获取键时,都检查是否过期,如果过期的话,就删除键,否则就正常返回

  • 优点:对CPU友好
  • 缺点:对内存不友好

定期删除

每隔一段时间数据库进行一次检查,删除里面的过期键。至于每次遍历多少个库,遍历多少个键,则有配置决定。
定期删除时定时删除和惰性删除两种策略的一种整合折中。

Redis过期键删除策略

Redis服务器实际上使用的是惰性删除定期删除两种策略结合通过两种策略的配合,可以很好的合理利用CPU时间和避免浪费内存空间之间取得平衡

惰性删除实现

惰性删除主要有expireIfNeed函数实现,所有读写数据库的Redis命令执行之前都会调用expireIfNeed函数输入键从数据库进行删除。

/* This function is called when we are going to perform some operation
 * in a given key, but such key may be already logically expired even if
 * it still exists in the database. The main way this function is called
 * is via lookupKey*() family of functions.
 *
 * The behavior of the function depends on the replication role of the
 * instance, because by default replicas do not delete expired keys. They
 * wait for DELs from the master for consistency matters. However even
 * replicas will try to have a coherent return value for the function,
 * so that read commands executed in the replica side will be able to
 * behave like if the key is expired even if still present (because the
 * master has yet to propagate the DEL).
 *
 * In masters as a side effect of finding a key which is expired, such
 * key will be evicted from the database. Also this may trigger the
 * propagation of a DEL/UNLINK command in AOF / replication stream.
 *
 * On replicas, this function does not delete expired keys by default, but
 * it still returns 1 if the key is logically expired. To force deletion
 * of logically expired keys even on replicas, use the EXPIRE_FORCE_DELETE_EXPIRED
 * flag. Note though that if the current client is executing
 * replicated commands from the master, keys are never considered expired.
 *
 * On the other hand, if you just want expiration check, but need to avoid
 * the actual key deletion and propagation of the deletion, use the
 * EXPIRE_AVOID_DELETE_EXPIRED flag.
 *
 * The return value of the function is 0 if the key is still valid,
 * otherwise the function returns 1 if the key is expired. */
int expireIfNeeded(redisDb *db, robj *key, int flags) {
    if (server.lazy_expire_disabled) return 0;
    if (!keyIsExpired(db,key)) return 0;

    /* If we are running in the context of a replica, instead of
     * evicting the expired key from the database, we return ASAP:
     * the replica key expiration is controlled by the master that will
     * send us synthesized DEL operations for expired keys. The
     * exception is when write operations are performed on writable
     * replicas.
     *
     * Still we try to return the right information to the caller,
     * that is, 0 if we think the key should be still valid, 1 if
     * we think the key is expired at this time.
     *
     * When replicating commands from the master, keys are never considered
     * expired. */
    if (server.masterhost != NULL) {
        if (server.current_client &amp;& (server.current_client->flags & CLIENT_MASTER)) return 0;
        if (!(flags & EXPIRE_FORCE_DELETE_EXPIRED)) return 1;
    }

    /* In some cases we're explicitly instructed to return an indication of a
     * missing key without actually deleting it, even on masters. */
    if (flags & EXPIRE_AVOID_DELETE_EXPIRED)
        return 1;

    /* If 'expire' action is paused, for whatever reason, then don't expire any key.
     * Typically, at the end of the pause we will properly expire the key OR we
     * will have failed over and the new primary will send us the expire. */
    if (isPausedActionsWithUpdate(PAUSE_ACTION_EXPIRE)) return 1;

    /* The key needs to be converted from static to heap before deleted */
    int static_key = key->refcount == OBJ_STATIC_REFCOUNT;
    if (static_key) {
        key = createStringObject(key->ptr, sdslen(key->ptr));
    }
    /* Delete the key */
    deleteExpiredKeyAndPropagate(db,key);
    if (static_key) {
        decrRefCount(key);
    }
    return 1;
}

惰性删除

定期删除实现

定期删除有activeExpireCycle实现。每当Redis的服务器周期性操作serverCron函数执行时,activeExpireCycle函数就会被调用。在规定时间内,分多次遍历服务器中的各个数据库,从数据库的expires字典随机检查一部分键的过期时间,并删除其中的过期键。

void activeExpireCycle(int type) {
    /* Adjust the running parameters according to the configured expire
     * effort. The default effort is 1, and the maximum configurable effort
     * is 10. */
    unsigned long
    effort = server.active_expire_effort-1, /* Rescale from 0 to 9. */
    config_keys_per_loop = ACTIVE_EXPIRE_CYCLE_KEYS_PER_LOOP +
                           ACTIVE_EXPIRE_CYCLE_KEYS_PER_LOOP/4*effort,
    config_cycle_fast_duration = ACTIVE_EXPIRE_CYCLE_FAST_DURATION +
                                 ACTIVE_EXPIRE_CYCLE_FAST_DURATION/4*effort,
    config_cycle_slow_time_perc = ACTIVE_EXPIRE_CYCLE_SLOW_TIME_PERC +
                                  2*effort,
    config_cycle_acceptable_stale = ACTIVE_EXPIRE_CYCLE_ACCEPTABLE_STALE-
                                    effort;

    /* This function has some global state in order to continue the work
     * incrementally across calls. */
    static unsigned int current_db = 0; /* Next DB to test. */
    static int timelimit_exit = 0;      /* Time limit hit in previous call? */
    static long long last_fast_cycle = 0; /* When last fast cycle ran. */

    int j, iteration = 0;
    int dbs_per_call = CRON_DBS_PER_CALL;
    long long start = ustime(), timelimit, elapsed;

    /* If 'expire' action is paused, for whatever reason, then don't expire any key.
     * Typically, at the end of the pause we will properly expire the key OR we
     * will have failed over and the new primary will send us the expire. */
    if (isPausedActionsWithUpdate(PAUSE_ACTION_EXPIRE)) return;

    if (type == ACTIVE_EXPIRE_CYCLE_FAST) {
        /* Don't start a fast cycle if the previous cycle did not exit
         * for time limit, unless the percentage of estimated stale keys is
         * too high. Also never repeat a fast cycle for the same period
         * as the fast cycle total duration itself. */
        if (!timelimit_exit &&
            server.stat_expired_stale_perc < config_cycle_acceptable_stale)
            return;

        if (start < last_fast_cycle + (long long)config_cycle_fast_duration*2)
            return;

        last_fast_cycle = start;
    }

    /* We usually should test CRON_DBS_PER_CALL per iteration, with
     * two exceptions:
     *
     * 1) Don't test more DBs than we have.
     * 2) If last time we hit the time limit, we want to scan all DBs
     * in this iteration, as there is work to do in some DB and we don't want
     * expired keys to use memory for too much time. */
    if (dbs_per_call > server.dbnum || timelimit_exit)
        dbs_per_call = server.dbnum;

    /* We can use at max 'config_cycle_slow_time_perc' percentage of CPU
     * time per iteration. Since this function gets called with a frequency of
     * server.hz times per second, the following is the max amount of
     * microseconds we can spend in this function. */
    timelimit = config_cycle_slow_time_perc*1000000/server.hz/100;
    timelimit_exit = 0;
    if (timelimit <= 0) timelimit = 1;

    if (type == ACTIVE_EXPIRE_CYCLE_FAST)
        timelimit = config_cycle_fast_duration; /* in microseconds. */

    /* Accumulate some global stats as we expire keys, to have some idea
     * about the number of keys that are already logically expired, but still
     * existing inside the database. */
    long total_sampled = 0;
    long total_expired = 0;

    /* Try to smoke-out bugs (server.also_propagate should be empty here) */
    serverAssert(server.also_propagate.numops == 0);

    for (j = 0; j < dbs_per_call && timelimit_exit == 0; j++) {
        /* Scan callback data including expired and checked count per iteration. */
        expireScanData data;

        redisDb *db = server.db+(current_db % server.dbnum);
        data.db = db;

        /* Increment the DB now so we are sure if we run out of time
         * in the current DB we'll restart from the next. This allows to
         * distribute the time evenly across DBs. */
        current_db++;

        /* Continue to expire if at the end of the cycle there are still
         * a big percentage of keys to expire, compared to the number of keys
         * we scanned. The percentage, stored in config_cycle_acceptable_stale
         * is not fixed, but depends on the Redis configured "expire effort". */
        do {
            unsigned long num, slots;
            iteration++;

            /* If there is nothing to expire try next DB ASAP. */
            if ((num = dictSize(db->expires)) == 0) {
                db->avg_ttl = 0;
                break;
            }
            slots = dictSlots(db->expires);
            data.now = mstime();

            /* When there are less than 1% filled slots, sampling the key
             * space is expensive, so stop here waiting for better times...
             * The dictionary will be resized asap. */
            if (slots > DICT_HT_INITIAL_SIZE &&
                (num*100/slots < 1)) break;

            /* The main collection cycle. Scan through keys among keys
             * with an expire set, checking for expired ones. */
            data.sampled = 0;
            data.expired = 0;
            data.ttl_sum = 0;
            data.ttl_samples = 0;

            if (num > config_keys_per_loop)
                num = config_keys_per_loop;

            /* Here we access the low level representation of the hash table
             * for speed concerns: this makes this code coupled with dict.c,
             * but it hardly changed in ten years.
             *
             * Note that certain places of the hash table may be empty,
             * so we want also a stop condition about the number of
             * buckets that we scanned. However scanning for free buckets
             * is very fast: we are in the cache line scanning a sequential
             * array of NULL pointers, so we can scan a lot more buckets
             * than keys in the same time. */
            long max_buckets = num*20;
            long checked_buckets = 0;

            while (data.sampled < num && checked_buckets < max_buckets) {
                db->expires_cursor = dictScan(db->expires, db->expires_cursor,
                                              expireScanCallback, &data);
                checked_buckets++;
            }
            total_expired += data.expired;
            total_sampled += data.sampled;

            /* Update the average TTL stats for this database. */
            if (data.ttl_samples) {
                long long avg_ttl = data.ttl_sum / data.ttl_samples;

                /* Do a simple running average with a few samples.
                 * We just use the current estimate with a weight of 2%
                 * and the previous estimate with a weight of 98%. */
                if (db->avg_ttl == 0) db->avg_ttl = avg_ttl;
                db->avg_ttl = (db->avg_ttl/50)*49 + (avg_ttl/50);
            }

            /* We can't block forever here even if there are many keys to
             * expire. So after a given amount of milliseconds return to the
             * caller waiting for the other active expire cycle. */
            if ((iteration & 0xf) == 0) { /* check once every 16 iterations. */
                elapsed = ustime()-start;
                if (elapsed > timelimit) {
                    timelimit_exit = 1;
                    server.stat_expired_time_cap_reached_count++;
                    break;
                }
            }
            /* We don't repeat the cycle for the current database if there are
             * an acceptable amount of stale keys (logically expired but yet
             * not reclaimed). */
        } while (data.sampled == 0 ||
                 (data.expired * 100 / data.sampled) > config_cycle_acceptable_stale);
    }

    elapsed = ustime()-start;
    server.stat_expire_cycle_time_used += elapsed;
    latencyAddSampleIfNeeded("expire-cycle",elapsed/1000);

    /* Update our estimate of keys existing but yet to be expired.
     * Running average with this sample accounting for 5%. */
    double current_perc;
    if (total_sampled) {
        current_perc = (double)total_expired/total_sampled;
    } else
        current_perc = 0;
    server.stat_expired_stale_perc = (current_perc*0.05)+
                                     (server.stat_expired_stale_perc*0.95);
}

原文地址:https://blog.csdn.net/kgcourage/article/details/134767250

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