nimbus是storm集群的"控制器"，是storm集群的重要组成部分。我们可以通用执行bin/storm nimbus >/dev/null 2>&1 &来启动nimbus。bin/storm是一个python脚本，在这个脚本中定义了一个nimbus函数：
nimbus函数
"""Syntax: [storm nimbus]
Launches the nimbus daemon. This command should be run under
supervision with a tool like daemontools or monit.
See Setting up a Storm cluster for more information.
(https://github.com/nathanmarz/storm/wiki/Setting-up-a-Storm-cluster)
"""
cppaths = [STORM_DIR + "/log4j", STORM_DIR + "/conf"]
jvmopts = parse_args(confvalue("nimbus.childopts", cppaths)) + [
"-Dlogfile.name=nimbus.log",
"-Dlog4j.configuration=storm.log.properties",
]
exec_storm_class(
klass,
jvmtype="-server",
extrajars=cppaths,
jvmopts=jvmopts)
klass参数的默认值为backtype.storm.daemon.nimbus，backtype.storm.daemon.nimbus标识一个java类。STORM_DIR标识storm的安装目录，cppaths集合存放了log4j配置文件路径和storm配置文件storm.yaml路径，jvmopts存放传递给jvm的参数，包括log4j配文件路径、storm.yaml路径、log4j日志名称和log4j配置文件名称。
exec_storm_class函数的逻辑比较简单，具体实现如下：
exec_storm_class函数
global CONFFILE
all_args = [
"java", jvmtype, get_config_opts(),
"-Dstorm.home=" + STORM_DIR,
"-Djava.library.path=" + confvalue("java.library.path", extrajars),
"-Dstorm.conf.file=" + CONFFILE,
"-cp", get_classpath(extrajars),
] + jvmopts + [klass] + list(args)
print "Running: " + " ".join(all_args)
if fork:
os.spawnvp(os.P_WAIT, "java", all_args)
else:
os.execvp("java", all_args) # replaces the current process and never returns
get_config_opts()获取jvm的默认配置信息，confvalue("java.library.path", extrajars)获取storm使用的本地库JZMQ加载路径，get_classpath(extrajars)获取所有依赖jar包的完整路径，然后拼接一个java -cp命令运行klass的main方法。
klass默认值为backtype.storm.daemon.nimbus，所以exec_storm_class函数最终调用backtype.storm.daemon.nimbus类的main方法。
backtype.storm.daemon.nimbus类定义在nimbus.clj文件中，定义如下：
backtype.storm.daemon.nimbus类
(:import [org.apache.thrift.server THsHaServer THsHaServer$Args])
(:import [org.apache.thrift.protocol TBinaryProtocol TBinaryProtocol$Factory])
(:import [org.apache.thrift.exception])
(:import [org.apache.thrift.transport TNonblockingServerTransport TNonblockingServerSocket])
(:import [java.nio ByteBuffer])
(:import [java.io FileNotFoundException])
(:import [java.nio.channels Channels WritableByteChannel])
(:use [backtype.storm.scheduler.DefaultScheduler])
(:import [backtype.storm.scheduler INimbus SupervisorDetails WorkerSlot TopologyDetails
Cluster Topologies SchedulerAssignment SchedulerAssignmentImpl DefaultScheduler ExecutorDetails])
(:use [backtype.storm bootstrap util])
(:use [backtype.storm.config :only [validate-configs-with-schemas]])
(:use [backtype.storm.daemon common])
(:gen-class
:methods [^{:static true} [launch [backtype.storm.scheduler.INimbus] void]]))
...
;; 其他方法
...
(defn -main []
(-launch (standalone-nimbus)))
:gen-class指示Clojure生成Java类backtype.storm.daemon.nimbus，并且声明一个静态方法launch，launch方法接收一个实现backtype.storm.scheduler.INimbus接口的实例作为参数。launch函数的参数是由standalone-nimbus函数生成的。standalone-nimbus函数定义如下：返回一个实现INimbus接口的实例。
standalone-nimbus函数
;; 实现INimbus接口
(reify INimbus
;; prepare函数为空实现
(prepare [this conf local-dir]
)
;; allSlotsAvailableForScheduling获取所有可用的slot集合
(allSlotsAvailableForScheduling [this supervisors topologies topologies-missing-assignments]
;; supervisors标识集群所有supervisor的详细信息对象SupervisorDetails的集合
(->> supervisors
;; 遍历supervisors，为supervisor的每个port生成对应的WorkerSlot对象，WorkerSlot包含两个属性节点id和port
(mapcat (fn [^SupervisorDetails s]
(for [p (.getMeta s)]
(WorkerSlot. (.getId s) p))))
set ))
(assignSlots [this topology slots]
)
(getForcedScheduler [this]
nil )
;; 获取supervisor主机名
(getHostName [this supervisors node-id]
(if-let [^SupervisorDetails supervisor (get supervisors node-id)]
(.getHost supervisor)))
))
launch函数定义如下：
launch函数
;;
;; read-storm-config函数用于读取storm集群的配置信息，参见其定义部分
(launch-server! (read-storm-config) nimbus))
launch-server!函数定义如下：
(defn launch-server! [conf nimbus]
;; 判断是否是分布式模式，如果是本地模式则抛出IllegalArgumentException
(validate-distributed-mode! conf)
;; service-handler函数是由宏defserverfn定义的，返回一个实现了Nimbus类中的Iface接口的实例，Nimbus类是由thrift框架自动生成的，Iface接口封装了service Nimbus的全部接口。
;; nimbus thrift server端提供的接口服务都是由这个实例实现的。service-handler函数参见其定义部分，service Nimbus参见storm.thrift
;; service-handler绑定实现了Nimbus类中的Iface接口的实例
(let [service-handler (service-handler conf nimbus)
options (-> (TNonblockingServerSocket. (int (conf NIMBUS-THRIFT-PORT)))
(THsHaServer$Args.)
(.workerThreads 64)
(.protocolFactory (TBinaryProtocol$Factory. false true (conf NIMBUS-THRIFT-MAX-BUFFER-SIZE)))
(.processor (Nimbus$Processor. service-handler))
)
server (THsHaServer. (do (set! (. options maxReadBufferBytes)(conf NIMBUS-THRIFT-MAX-BUFFER-SIZE)) options))]
(add-shutdown-hook-with-force-kill-in-1-sec (fn []
(.shutdown service-handler)
(.stop server)))
(log-message "Starting Nimbus server...")
(.serve server)))
read-storm-config定义如下：
read-storm-config函数
[]
;; conf绑定storm集群配置信息
(let [conf (clojurify-structure (Utils/readStormConfig))]
;; validate-configs-with-schemas函数验证配置信息的正确性并删除不正确的配置信息
(validate-configs-with-schemas conf)
conf))
read-storm-config函数调用了backtype.storm.utils.Utils类的静态方法readStormConfig，如下：
readStormConfig方法
// 调用readDefaultConfig从defaults.yaml配置文件读取默认配置信息存入ret
Map ret = readDefaultConfig();
// 获取用户自定义配置文件路径
String confFile = System.getProperty("storm.conf.file");
Map storm;
if (confFile==null || confFile.equals("")) {
storm = findAndReadConfigFile("storm.yaml", false);
} else {
// 读取用户自定义配置信息
storm = findAndReadConfigFile(confFile, true);
}
// 将用户自定义的配置信息覆盖更新到ret中
ret.putAll(storm);
// 将命令行方式提供的配置信息覆盖更新到ret中
ret.putAll(readCommandLineOpts());
// 返回覆盖更新后的配置信息ret
return ret;
}
service-handler函数定义如下：
defserverfn是一个宏，(defserverfn service-handler [conf inimbus] ... )返回一个名字为service-handler函数。宏扩展是在编译时进行的
service-handler函数
;; 调用inimbus的prepare方法，inimbus是standalone-nimbus函数返回的实现INimbus接口的实例，当前版本prepare方法为空实现
(.prepare inimbus conf (master-inimbus-dir conf))
;; 打印日志信息
(log-message "Starting Nimbus with conf " conf)
;; nimbus绑定了一个map，这个map保存了nimbus端所必需的"属性"，详见nimbus-data函数定义部分
(let [nimbus (nimbus-data conf inimbus)]
;; 调用nimbus这个map中保存的backtype.storm.nimbus.DefaultTopologyValidator对象的prepare方法，通过查看backtype.storm.nimbus.DefaultTopologyValidator类，我们可以发现prepare默认为空实现
(.prepare ^backtype.storm.nimbus.ITopologyValidator (:validator nimbus) conf)
;; cleanup-corrupt-topologies!函数的主要功能就是将在nimbus服务器{storm.local.dir}/nimbus/stormdist/路径中不存在的topology id从zookeeper的/storms/路径中删除，即删除在nimbus服务器上缺失jar包、topology信息和配置信息的当前正在运行的topology，
;; cleanup-corrupt-topologies!函数参见其定义部分
(cleanup-corrupt-topologies! nimbus)
;; 更新当前storm集群上topology的状态
(doseq [storm-id (.active-storms (:storm-cluster-state nimbus))]
;; transition!函数主要功能就是负责topology状态转换，规定了当topology由一种状态转换成另一种新状态时，需要做哪些处理操作，参见其定义部分
(transition! nimbus storm-id :startup))
;; 通过schedule-recurring函数向storm定时器添加了一个"周期任务"检查心跳，重新分配任务，清理不活跃的topology，mk-assignments函数的主要功能就是检查心跳和重新分配任务。关于storm定时器详细分析请见"storm定时器timer源码分析"；关于mk-assignments函数请见"storm任务分配源码分析"
;; do-cleanup函数主要功能就是清理不活跃的topology，请参加其定义部分
(schedule-recurring (:timer nimbus)
0
(conf NIMBUS-MONITOR-FREQ-SECS)
(fn []
(when (conf NIMBUS-REASSIGN)
(locking (:submit-lock nimbus)
(mk-assignments nimbus)))
(do-cleanup nimbus)
))
;; Schedule Nimbus inbox cleaner
;; 通过schedule-recurring函数向storm定时器添加一个"周期任务"删除nimbus服务器上的过期jar包
(schedule-recurring (:timer nimbus)
0
(conf NIMBUS-CLEANUP-INBOX-FREQ-SECS)
(fn []
(clean-inbox (inbox nimbus) (conf NIMBUS-INBOX-JAR-EXPIRATION-SECS))
))
(reify Nimbus$Iface
;; submitTopologyWithOpts函数负责topology的提交，有关该函数的详细分析请参见"storm源码分析之topology提交过程"
(^void submitTopologyWithOpts
[this ^String storm-name ^String uploadedJarLocation ^String serializedConf ^StormTopology topology
^SubmitOptions submitOptions]
(try
(assert (not-nil? submitOptions))
(validate-topology-name! storm-name)
(check-storm-active! nimbus storm-name false)
(let [topo-conf (from-json serializedConf)]
(try
(validate-configs-with-schemas topo-conf)
(catch IllegalArgumentException ex
(throw (InvalidTopologyException. (.getMessage ex)))))
(.validate ^backtype.storm.nimbus.ITopologyValidator (:validator nimbus)
storm-name
topo-conf
topology))
(swap! (:submitted-count nimbus) inc)
(let [storm-id (str storm-name "-" @(:submitted-count nimbus) "-" (current-time-secs))
storm-conf (normalize-conf
conf
(-> serializedConf
from-json
(assoc STORM-ID storm-id)
(assoc TOPOLOGY-NAME storm-name))
topology)
total-storm-conf (merge conf storm-conf)
topology (normalize-topology total-storm-conf topology)
storm-cluster-state (:storm-cluster-state nimbus)]
(system-topology! total-storm-conf topology) ;; this validates the structure of the topology
(log-message "Received topology submission for " storm-name " with conf " storm-conf)
;; lock protects against multiple topologies being submitted at once and
;; cleanup thread killing topology in b/w assignment and starting the topology
(locking (:submit-lock nimbus)
(setup-storm-code conf storm-id uploadedJarLocation storm-conf topology)
(.setup-heartbeats! storm-cluster-state storm-id)
(let [thrift-status->kw-status {TopologyInitialStatus/INACTIVE :inactive
TopologyInitialStatus/ACTIVE :active}]
(start-storm nimbus storm-name storm-id (thrift-status->kw-status (.get_initial_status submitOptions))))
(mk-assignments nimbus)))
(catch Throwable e
(log-warn-error e "Topology submission exception. (topology name='" storm-name "')")
(throw e))))
;; submitTopology函数调用了submitTopologyWithOpts函数
(^void submitTopology
[this ^String storm-name ^String uploadedJarLocation ^String serializedConf ^StormTopology topology]
(.submitTopologyWithOpts this storm-name uploadedJarLocation serializedConf topology
(SubmitOptions. TopologyInitialStatus/ACTIVE)))
;; killTopology函数见名知意，调用了killTopologyWithOpts函数
(^void killTopology [this ^String name]
(.killTopologyWithOpts this name (KillOptions.)))
;; storm-name绑定kill的topology名称，KillOptions是一个thrift数据结构，只有个属性wait_secs，表示延迟多长时间执行kill
(^void killTopologyWithOpts [this ^String storm-name ^KillOptions options]
;; check-storm-active!检查topology是否是"active"，如果不活跃则抛出异常
(check-storm-active! nimbus storm-name true)
;; 如果设置了延迟时间，wait-amt绑定延迟时间
(let [wait-amt (if (.is_set_wait_secs options)
(.get_wait_secs options)
)]
;; transition-name!函数主要功能就是根据storm-name获取topology id，然后调用transition!函数，topology由当前状态转换到:kill状态，:kill状态是一个"临时状态"，最终修改topology状态为:killed，:killed状态为"持久状态"
;; 通过state-transitions函数我们可以知道无论从哪种状态转换到:kill状态，都将调用kill-transition函数，kill-transition通过调用delay-event向storm定时器添加一个定时任务，这个定时任务的主要功能就是负责topology由:killed状态
;; 转换到:remove状态，这时将调用remove-storm!函数清理topology
(transition-name! nimbus storm-name [:kill wait-amt] true)
))
;; rebalance函数可以重新设置topology的进程数和各个component的并行度，RebalanceOptions是thirft数据结构，有三个属性rebalance的延迟时间、新的进程数，新的并行度
(^void rebalance [this ^String storm-name ^RebalanceOptions options]
;; check-storm-active!检查topology是否是"active"，如果不活跃则抛出异常
(check-storm-active! nimbus storm-name true)
;; 如果设置了延迟时间，wait-amt绑定延迟时间
(let [wait-amt (if (.is_set_wait_secs options)
(.get_wait_secs options))
;; 如果设置了新的进程数，num-workers绑定新进程数
num-workers (if (.is_set_num_workers options)
(.get_num_workers options))
;; 如果设置了新的组件并行度，executor-overrides绑定新组件并行度
executor-overrides (if (.is_set_num_executors options)
(.get_num_executors options)
{})]
(doseq [[c num-executors] executor-overrides]
(when (<= num-executors 0)
(throw (InvalidTopologyException. "Number of executors must be greater than 0"))
))
;; transition-name!函数主要功能就是根据storm-name获取topology id，然后调用transition!函数，topology由当前状态转换到:rebalance状态，:rebalance状态是一个"临时状态"，最终修改topology状态为:rebalancing，:rebalancing状态为"持久状态"
;; 通过state-transitions函数我们可以知道只允许从:active和:inactive状态转换到:rebalance状态，并调用rebalance-transition函数，rebalance-transition通过调用delay-event向storm定时器添加一个定时任务，这个定时任务的主要功能就是负责topology由:rebalancing状态
;; 转换到:do-rebalance状态，并调用do-rebalance函数（重新设置topology的进程数和组件并行度，然后调用mk-assignments函数重新进行任务分配），然后将topology状态修改成:rebalancing的前一个状态
(transition-name! nimbus storm-name [:rebalance wait-amt num-workers executor-overrides] true)
))
;; 激活topology，将topology状态修改成:active，处理过程与killTopologyWithOpts、rebalance相似
(activate [this storm-name]
(transition-name! nimbus storm-name :activate true)
)
;; 将topology状态修改成:inactive，deactivate处理过程与activate相似
(deactivate [this storm-name]
(transition-name! nimbus storm-name :inactivate true))
;; beginFileUpload()函数获取nimbus存放jar的目录
(beginFileUpload [this]
(let [fileloc (str (inbox nimbus) "/stormjar-" (uuid) ".jar")]
(.put (:uploaders nimbus)
fileloc
(Channels/newChannel (FileOutputStream. fileloc)))
(log-message "Uploading file from client to " fileloc)
fileloc
))
;; 上传jar包文件
(^void uploadChunk [this ^String location ^ByteBuffer chunk]
(let [uploaders (:uploaders nimbus)
^WritableByteChannel channel (.get uploaders location)]
(when-not channel
(throw (RuntimeException.
"File for that location does not exist (or timed out)")))
(.write channel chunk)
(.put uploaders location channel)
))
;; 上传jar包完成，关闭Channel
(^void finishFileUpload [this ^String location]
(let [uploaders (:uploaders nimbus)
^WritableByteChannel channel (.get uploaders location)]
(when-not channel
(throw (RuntimeException.
"File for that location does not exist (or timed out)")))
(.close channel)
(log-message "Finished uploading file from client: " location)
(.remove uploaders location)
))
;; 获取文件输入流
(^String beginFileDownload [this ^String file]
(let [is (BufferFileInputStream. file)
id (uuid)]
(.put (:downloaders nimbus) id is)
id
))
;; 读取文件
(^ByteBuffer downloadChunk [this ^String id]
(let [downloaders (:downloaders nimbus)
^BufferFileInputStream is (.get downloaders id)]
(when-not is
(throw (RuntimeException.
"Could not find input stream for that id")))
(let [ret (.read is)]
(.put downloaders id is)
(when (empty? ret)
(.remove downloaders id))
(ByteBuffer/wrap ret)
)))
;; 获取storm集群配置信息
(^String getNimbusConf [this]
(to-json (:conf nimbus)))
;; 获取topology配置信息
(^String getTopologyConf [this ^String id]
(to-json (try-read-storm-conf conf id)))
;; 获取StormTopology
(^StormTopology getTopology [this ^String id]
(system-topology! (try-read-storm-conf conf id) (try-read-storm-topology conf id)))
(^StormTopology getUserTopology [this ^String id]
(try-read-storm-topology conf id))
;; 获取当前集群的汇总信息包括supervisor汇总信息，nimbus启动时间，所有活跃topology汇总信息
(^ClusterSummary getClusterInfo [this]
(let [storm-cluster-state (:storm-cluster-state nimbus)
;; supervisor-infos绑定supervisor id->SupervisorInfo对象键值对的map
;; SupervisorInfo定义：(defrecord SupervisorInfo [time-secs hostname assignment-id used-ports meta scheduler-meta uptime-secs])
supervisor-infos (all-supervisor-info storm-cluster-state)
;; TODO: need to get the port info about supervisors...
;; in standalone just look at metadata, otherwise just say N/A?
;; 根据SupervisorInfo数据创建SupervisorSummary数据
supervisor-summaries (dofor [[id info] supervisor-infos]
(let [ports (set (:meta info)) ;;TODO: this is only true for standalone
]
(SupervisorSummary. (:hostname info)
(:uptime-secs info)
(count ports)
(count (:used-ports info))
id )
))
;; nimbus-uptime绑定nimbus启动时间
nimbus-uptime ((:uptime nimbus))
;; bases绑定集群上所有活跃topology的StormBase数据集合
bases (topology-bases storm-cluster-state)
;; topology-summaries绑定活跃topology的TopologySummary数据
topology-summaries (dofor [[id base] bases]
(let [assignment (.assignment-info storm-cluster-state id nil)]
(TopologySummary. id
(:storm-name base)
(->> (:executor->node+port assignment)
keys
(mapcat executor-id->tasks)
count)
(->> (:executor->node+port assignment)
keys
count)
(->> (:executor->node+port assignment)
vals
set
count)
(time-delta (:launch-time-secs base))
(extract-status-str base))
))]
;; 创建ClusterSummary数据
(ClusterSummary. supervisor-summaries
nimbus-uptime
topology-summaries)
))
;; 获取指定storm-id的topology的TopologyInfo数据
(^TopologyInfo getTopologyInfo [this ^String storm-id]
;; storm-cluster-state绑定StormClusterState对象
(let [storm-cluster-state (:storm-cluster-state nimbus)
;; task->component绑定任务id->组件名称键值对的map，形如：{1 "boltA", 2 "boltA", 3 "boltA", 4 "boltA", 5 "boltB", 6 "boltB"}
task->component (storm-task-info (try-read-storm-topology conf storm-id) (try-read-storm-conf conf storm-id))
;; bases绑storm-id的StormBase
base (.storm-base storm-cluster-state storm-id nil)
;; assignment绑定该topology的AssignmentInfo信息，(defrecord Assignment [master-code-dir node->host executor->node+port executor->start-time-secs])
assignment (.assignment-info storm-cluster-state storm-id nil)
;; beats绑定该topology所有executor-id->心跳信息的map
beats (.executor-beats storm-cluster-state storm-id (:executor->node+port assignment))
;; all-components绑定该topology所有component-id集合
all-components (-> task->component reverse-map keys)
;; errors绑定component-id->组件错误信息的map
errors (->> all-components
(map (fn [c] [c (get-errors storm-cluster-state storm-id c)]))
(into {}))
;; executor-summaries绑定ExecutorSummary集合
executor-summaries (dofor [[executor [node port]] (:executor->node+port assignment)]
(let [host (-> assignment :node->host (get node))
heartbeat (get beats executor)
stats (:stats heartbeat)
stats (if stats
(stats/thriftify-executor-stats stats))]
(doto
(ExecutorSummary. (thriftify-executor-id executor)
(-> executor first task->component)
host
port
(nil-to-zero (:uptime heartbeat)))
(.set_stats stats))
))
]
;; 创建TopologyInfo对象
(TopologyInfo. storm-id
(:storm-name base)
(time-delta (:launch-time-secs base))
executor-summaries
(extract-status-str base)
errors
)
))
Shutdownable
(shutdown [this]
(log-message "Shutting down master")
(cancel-timer (:timer nimbus))
(.disconnect (:storm-cluster-state nimbus))
(.cleanup (:downloaders nimbus))
(.cleanup (:uploaders nimbus))
(log-message "Shut down master")
)
DaemonCommon
(waiting? [this]
(timer-waiting? (:timer nimbus))))))
nimbus-data函数定义如下：
nimbus-data函数
(let [forced-scheduler (.getForcedScheduler inimbus)]
;; 保存storm集群的配置信息
{:conf conf
;; 保存inimbus实例
:inimbus inimbus
;; 初始化topology提交总数为0
:submitted-count (atom 0)
;; 调用cluster.clj中的mk-storm-cluster-state函数创建StormClusterState实例，StormClusterState实例封装了与zookeeper交互的接口
:storm-cluster-state (cluster/mk-storm-cluster-state conf)
;; 保存"提交锁"，在topology提交时，需要先获取该锁，然后才能提交，这样可以防止一次提交多个topology，也保证了topology之间操作的互斥性
:submit-lock (Object.)
;; 初始化心跳缓存
:heartbeats-cache (atom {})
;; 创建下载TimeCacheMap缓存，关于TimeCacheMap缓存会在以后文章中单独分析，在此不做介绍
:downloaders (file-cache-map conf)
;; 创建上传TimeCacheMap缓存
:uploaders (file-cache-map conf)
;; 保存一个返回值为"当前时间"-"nimbus启动时间"的函数，调用该函数可以获取nimbus启动多长时间
:uptime (uptime-computer)
;; 通过java反射创建一个NIMBUS-TOPOLOGY-VALIDATOR指定的validator对象，默认为backtype.storm.nimbus.DefaultTopologyValidator对象
:validator (new-instance (conf NIMBUS-TOPOLOGY-VALIDATOR))
;; mk-timer函数会创建一个"定时线程"，关于定时线程会在以后文章中单位分析，在此不做介绍
:timer (mk-timer :kill-fn (fn [t]
(log-error t "Error when processing event")
;; exit-process!函数通过调用java的Runtime类的exit(int status)方法终止进程，并传达状态码20
(exit-process! 20 "Error when processing an event")
))
;; 由mk-scheduler函数创建scheduler调度器，通过分析mk-scheduler函数，可以发现在没有配置用户自定义的scheduler情况下，mk-scheduler函数默认返回DefaultScheduler，mk-scheduler函数参见其定义部分
:scheduler (mk-scheduler conf inimbus)
}))
mk-scheduler函数定义如下：
mk-scheduler函数
;; 当前版本getForcedScheduler函数返回nil
(let [forced-scheduler (.getForcedScheduler inimbus)
;; scheduler绑定IScheduler接口的实现
;; cond等价于java中的switch，我们可以发现首先检查forced-scheduler，如果forced-scheduler为nil，则检查是否有用户自定义的scheduler，如果没有则
;; 使用默认的DefaultScheduler
scheduler (cond
forced-scheduler
(do (log-message "Using forced scheduler from INimbus " (class forced-scheduler))
forced-scheduler)
(conf STORM-SCHEDULER)
(do (log-message "Using custom scheduler: " (conf STORM-SCHEDULER))
(-> (conf STORM-SCHEDULER) new-instance))
:else
(do (log-message "Using default scheduler")
(DefaultScheduler.)))]
;; 先调用prepare函数
(.prepare scheduler conf)
;; 然后返回scheduler
scheduler
))
cleanup-corrupt-topologies!函数定义如下：
cleanup-corrupt-topologies!函数
;; 获取nimbus这个map中保存的StormCluterState实例
(let [storm-cluster-state (:storm-cluster-state nimbus)
;; code-ids绑定了nimbus服务器上{storm.local.dir}/nimbus/stormdist/目录下所有子目录的名称，即提交给nimbus的所有topology的id
code-ids (set (code-ids (:conf nimbus)))
;; active-topologies绑定zookeeper上/storms/目录中所有文件名称，即当前storm集群上正在运行的topology的id
active-topologies (set (.active-storms storm-cluster-state))
;; corrupt-topologies绑定active-topologies和code-ids的差集，即当前正在运行的，但丢失jar包、topology信息和配置信息的topology的id
corrupt-topologies (set/difference active-topologies code-ids)]
;; 将id包含在corrupt-topologies集合的topology的分配信息从zookeeper的/assignments目录删除，同时将StormBase信息从zookeeper的/storms目录删除
(doseq [corrupt corrupt-topologies]
(log-message "Corrupt topology " corrupt " has state on zookeeper but doesn't have a local dir on Nimbus. Cleaning up...")
(.remove-storm! storm-cluster-state corrupt)
)))
transition!函数定义如下：
transition!函数的作用十分重要，负责topology状态转换，在启动nimbus场景下，event的值为":startup"关键字，error-on-no-transition?的值为false。transition!函数有两个重载版本。
transition!函数
([nimbus storm-id event]
(transition! nimbus storm-id event false))
([nimbus storm-id event error-on-no-transition?]
;; 加锁
(locking (:submit-lock nimbus)
;; system-events绑定一个集合#{:startup}
(let [system-events #{:startup}
;; 在启动nimbus场景下，event绑定[:startup]，event-args为nil
[event & event-args] (if (keyword? event) [event] event)
;; 从zookeeper上获取topology的状态，一个map对象，绑定到status上
status (topology-status nimbus storm-id)]
;; handles the case where event was scheduled but topology has been removed
(if-not status
;; 如果status为nil则记录日志，transition!函数执行结束
(log-message "Cannot apply event " event " to " storm-id " because topology no longer exists")
;; 如果status不为nil，get-event绑定一个函数
(let [get-event (fn [m e]
(if (contains? m e)
(m e)
(let [msg (str "No transition for event: " event
", status: " status,
" storm-id: " storm-id)]
(if error-on-no-transition?
(throw-runtime msg)
(do (when-not (contains? system-events event)
(log-message msg))
nil))
)))
;; state-transitions函数返回一个状态转换映射map，这个map中规定了由一种状态可以转换到哪些状态，并且在状态转换后执行哪些处理（即调用哪个函数），参见其定义部分
;; 通过分析state-transitions函数，我们可以发现只有当topology的当前状态为":killed"和":rebalancing"时，才允许转换到":startup"状态，如果当前状态是其他状态，transition将为nil
;; 我们先讨论其他状态，这时transition为nil，接着transition通过if判断将绑定一个(fn [] nil)函数，这样new-status将为nil。所以在启动nimbus场景下，topology由其他状态转换到":startup"状态时，transition!函数什么都没做
transition (-> (state-transitions nimbus storm-id status)
(get (:type status))
(get-event event))
transition (if (or (nil? transition)
(keyword? transition))
(fn [] transition)
transition)
new-status (apply transition event-args)
new-status (if (keyword? new-status)
{:type new-status}
new-status)]
(when new-status
(set-topology-status! nimbus storm-id new-status)))))
)))
1、如果topology由":killed"转换到":startup"（kill topology的过程中，nimbus挂掉了，当重启nimbus时就有可能出现这种状态转换）时，transition将绑定
storm-id
(:kill-time-secs status)
:remove)
nil)
new-status值为transition绑定的函数的返回值nil。transition绑定的函数通过调用delay-event函数将#(transition! nimbus storm-id :remove false)函数添加到storm定时器中，然后由storm定时器执行该函数，该函数再次调用了transition!函数，不过这次是由":killed"转换到":remove"， 调用函数
(log-message "Killing topology: " storm-id)
;; 删除zookeeper上该topology的StormBase信息和分配信息
(.remove-storm! (:storm-cluster-state nimbus)
storm-id)
nil)
2、如果topology由":rebalancing"转换到":startup"（rebalance topology的过程中，nimbus挂掉了，当重启nimbus时就有可能出现这种状态转换）时，transition将绑定
storm-id
(:delay-secs status)
:do-rebalance)
nil)
new-status值为transition绑定的函数的返回值nil。transition绑定的函数通过调用delay-event函数将#(transition! nimbus storm-id :do-rebalance false)函数添加到storm定时器中，然后由storm定时器执行该函数，该函数再次调用了transition!函数，不过这次是由":rebalancing"转换到":do-rebalance"，调用函数
(do-rebalance nimbus storm-id status)
(:old-status status))
由于这个函数返回:rebalancing状态的前一个状态，所以storm定时器所执行的定时任务会将topology的状态由:rebalancing修改成前一个状态。以上就是启动nimbus场景下，topology可能的状态转换处理过程。 delay-event函数定义如下：主要功能就是将#(transition! nimbus storm-id event false)函数作为"定时任务"添加到storm定时器中。
(log-message "Delaying event " event " for " delay-secs " secs for " storm-id)
(schedule (:timer nimbus)
delay-secs
#(transition! nimbus storm-id event false)
))
state-transitions函数定义如下：
state-transitions函数
{:active {:inactivate :inactive
:activate nil
:rebalance (rebalance-transition nimbus storm-id status)
:kill (kill-transition nimbus storm-id)
}
:inactive {:activate :active
:inactivate nil
:rebalance (rebalance-transition nimbus storm-id status)
:kill (kill-transition nimbus storm-id)
}
:killed {:startup (fn [] (delay-event nimbus
storm-id
(:kill-time-secs status)
:remove)
nil)
:kill (kill-transition nimbus storm-id)
:remove (fn []
(log-message "Killing topology: " storm-id)
(.remove-storm! (:storm-cluster-state nimbus)
storm-id)
nil)
}
:rebalancing {:startup (fn [] (delay-event nimbus
storm-id
(:delay-secs status)
:do-rebalance)
nil)
:kill (kill-transition nimbus storm-id)
:do-rebalance (fn []
(do-rebalance nimbus storm-id status)
(:old-status status))
}})
do-cleanup函数定义如下：
do-cleanup函数
(let [storm-cluster-state (:storm-cluster-state nimbus)
conf (:conf nimbus)
submit-lock (:submit-lock nimbus)]
;; to-cleanup-ids绑定需要清理的topology的id，即不再活跃的topology的id，cleanup-storm-ids函数参见其定义部分
(let [to-cleanup-ids (locking submit-lock
(cleanup-storm-ids conf storm-cluster-state))]
(when-not (empty? to-cleanup-ids)
(doseq [id to-cleanup-ids]
(log-message "Cleaning up " id)
;; 从zookeeper上删除/workerbeats/{id}节点（清理其心跳信息）
(.teardown-heartbeats! storm-cluster-state id)
;; 从zookeeper上删除/errors/{id}节点（清理其错误信息）
(.teardown-topology-errors! storm-cluster-state id)
;; 从nimbus服务器上删除{storm.local.dir}/nimbus/stormdist/{id}目录（删除其jar包，topology信息，配置信息）
(rmr (master-stormdist-root conf id))
;; 将该topology的心跳信息从nimbus的心跳缓存中删除
(swap! (:heartbeats-cache nimbus) dissoc id))
))))
cleanup-storm-ids函数定义如下：
cleanup-storm-ids函数
;; heartbeat-ids绑定有心跳的topology的id集合
(let [heartbeat-ids (set (.heartbeat-storms storm-cluster-state))
;; error-ids绑定有错误信息的topology的id集合
error-ids (set (.error-topologies storm-cluster-state))
;; code-ids绑定在nimbus服务器上有jar包的topology的id集合
code-ids (code-ids conf)
;; assigned-ids绑定当前活跃的topology的id集合
assigned-ids (set (.active-storms storm-cluster-state))]
;; heartbeat-ids、error-ids、code-ids的并集再与assigned-ids做差集就是不活跃的topology的id
(set/difference (set/union heartbeat-ids error-ids code-ids) assigned-ids)
))
以上就是nimbus启动源码分析。