Redis数据库-编程知识

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 thanthe actual 'hz' field value if dynamic-hzis 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 thatmodules 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_RESchar *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 ifthe 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 tofsynced_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 backloggets 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 & 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 anxor 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 ifthere is at least an uncovered slot.*/int cluster_slave_no_failover;  /* Prevent slave from starting a failoverif 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 ableto set in order to suppress certainnative Redis Cluster features. Check theREDISMODULE_CLUSTER_FLAG_*. */int cluster_allow_reads_when_down; /* Are reads allowed when the clusteris 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 withthe old "requirepass" directive forbackward compatibility with Redis <= 5. */int acl_pubsub_default;      /* Default ACL pub/sub channels flag */aclInfo acl_info; /* ACL info *//* Assert & 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 clusteris 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;**里面是每个数据库的存储信息，dbnum代表数据库的个数。

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主要有键值空间和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

过期键删除

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、惰性删除和定期删除。

定时删除

在设置键过期的同时，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，都检查键是否过期，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

每隔一段时间对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和定期删除两种策略的结合。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命令在执行之前都会调用expireIfNeed函数对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 && (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字典中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 longeffort = 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;} elsecurrent_perc = 0;server.stat_expired_stale_perc = (current_perc*0.05)+(server.stat_expired_stale_perc*0.95);
}

内存淘汰

淘汰策略

当Redis的运行内存超出设置的最大内存，将开启内存淘汰，也就是对键进行删除。
Redis内存淘汰策略主要分为8种。其中noeviction为默认淘汰策略

noeviction：不淘汰任何键，再有新键写入时直接报错。
volatile-random: 在设置了过期时间的键中，进行随机删除
volatile-ttl：在设置了过期时间的键中，优先删除更早期的键
volatile-lru：在设置了过期时间的键中，优先删除最久未使用的键
volitile-lfu：在设置了过期时间的键中，优先删除最少使用的键
allkeys-randome: 所有键中，进行随机删除
allkeys-lru：所有键中，优先删除最久未使用的键
allkeys-lfu：所有键中，优先删除最少使用的键

LRU算法和LFU算法都依赖redisObject中的lru字段，但是两种算法对于数据存储有些差异。

struct redisObject {unsigned type:4;unsigned encoding:4;unsigned lru:LRU_BITS; /* LRU time (relative to global lru_clock) or* LFU data (least significant 8 bits frequency* and most significant 16 bits access time). */int refcount;void *ptr;
};

LRU算法

LRU（Least Recently Used）即最近未使用。传统的LRU算法是基于链表实现的，最新操作的键会移动大表头，当进行淘汰时，只需要从表尾进行即可。
但是Redis并没有使用传统的LRU算法，因为那样会有两个问题。

使用链表维护所有的缓存数据，会带来额外的内存开销
如有有大量的键被访问时，会导致大量的链表移动操作，比较耗时，影响redis性能
Redis实现了一种近似LRU算法，使用随机采样的思想进行键值淘汰，它随机选出5个值，然后对最久未使用的键进行淘汰。

Redis对象中的Lru的24位bits用于储存键最近被访问的时间戳，可以根据时间戳计算需要淘汰的键。