ribbon的ServerListRefreshInterval

序

ribbon有個參數能夠用來調整刷新server list的時間間隔參數。

ServerListRefreshInterval

ribbon-core-2.2.0-sources.jar!/com/netflix/client/config/CommonClientConfigKey.java

public static final IClientConfigKey<Integer> ServerListRefreshInterval = new CommonClientConfigKey<Integer>("ServerListRefreshInterval"){};

PollingServerListUpdater

ribbon-loadbalancer-2.2.0-sources.jar!/com/netflix/loadbalancer/PollingServerListUpdater.java

private static long getRefreshIntervalMs(IClientConfig clientConfig) {
        return clientConfig.get(CommonClientConfigKey.ServerListRefreshInterval, LISTOFSERVERS_CACHE_REPEAT_INTERVAL);
    }
    
    @Override
    public synchronized void start(final UpdateAction updateAction) {
        if (isActive.compareAndSet(false, true)) {
            final Runnable wrapperRunnable = new Runnable() {
                @Override
                public void run() {
                    if (!isActive.get()) {
                        if (scheduledFuture != null) {
                            scheduledFuture.cancel(true);
                        }
                        return;
                    }
                    try {
                        updateAction.doUpdate();
                        lastUpdated = System.currentTimeMillis();
                    } catch (Exception e) {
                        logger.warn("Failed one update cycle", e);
                    }
                }
            };

            scheduledFuture = getRefreshExecutor().scheduleWithFixedDelay(
                    wrapperRunnable,
                    initialDelayMs,
                    refreshIntervalMs,
                    TimeUnit.MILLISECONDS
            );
        } else {
            logger.info("Already active, no-op");
        }
    }

DynamicServerListLoadBalancer

ribbon-loadbalancer-2.2.0-sources.jar!/com/netflix/loadbalancer/DynamicServerListLoadBalancer.java

protected final ServerListUpdater.UpdateAction updateAction = new ServerListUpdater.UpdateAction() {
        @Override
        public void doUpdate() {
            updateListOfServers();
        }
    };
@VisibleForTesting
    public void updateListOfServers() {
        List<T> servers = new ArrayList<T>();
        if (serverListImpl != null) {
            servers = serverListImpl.getUpdatedListOfServers();
            LOGGER.debug("List of Servers for {} obtained from Discovery client: {}",
                    getIdentifier(), servers);

            if (filter != null) {
                servers = filter.getFilteredListOfServers(servers);
                LOGGER.debug("Filtered List of Servers for {} obtained from Discovery client: {}",
                        getIdentifier(), servers);
            }
        }
        updateAllServerList(servers);
    }
/**
     * Update the AllServer list in the LoadBalancer if necessary and enabled
     * 
     * @param ls
     */
    protected void updateAllServerList(List<T> ls) {
        // other threads might be doing this - in which case, we pass
        if (serverListUpdateInProgress.compareAndSet(false, true)) {
            for (T s : ls) {
                s.setAlive(true); // set so that clients can start using these
                                  // servers right away instead
                // of having to wait out the ping cycle.
            }
            setServersList(ls);
            super.forceQuickPing();
            serverListUpdateInProgress.set(false);
        }
    }

這裏設置list的時候，順帶調用了forceQuickPing()方法

BaseLoadBalancer#forceQuickPing

ribbon-loadbalancer-2.2.0-sources.jar!/com/netflix/loadbalancer/BaseLoadBalancer.java

/*
     * Force an immediate ping, if we're not currently pinging and don't have a
     * quick-ping already scheduled.
     */
    public void forceQuickPing() {
        if (canSkipPing()) {
            return;
        }
        if (logger.isDebugEnabled()) {
            logger.debug("LoadBalancer:  forceQuickPing invoked");
        }
        Pinger ping = new Pinger(pingStrategy);
        try {
            ping.runPinger();
        } catch (Throwable t) {
            logger.error("Throwable caught while running forceQuickPing() for "
                    + name, t);
        }
    }