Slack digest for #general - 2019-08-26

[Apache Pulsar Slack]

2019-08-25 09:14:04 UTC - WingerPun: @WingerPun has joined the channel
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2019-08-25 16:48:16 UTC - Chris Bartholomew: That doc refers to synchronous 
replication. This medium article explains the difference between asynchronous 
and synchronous replication: 
<https://medium.com/@pckeyan/apache-pulsar-geo-replication-ad4f0ca3224b>
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2019-08-25 22:19:23 UTC - Igor Zubchenok: up
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2019-08-25 22:20:24 UTC - Igor Zubchenok: I implemented small ping service that 
measures message time of delivery by creating both producer and consumer for a 
topic. And send a message every 10 ms.
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2019-08-25 22:37:07 UTC - Igor Zubchenok: What I see strange is these peaks.
The same peak pattern at the same moment happens at both servers if I run test 
from two different location.
It happens every 5-6.5 seconds
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2019-08-25 22:38:54 UTC - Igor Zubchenok: 
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2019-08-25 22:58:49 UTC - Igor Zubchenok: Another strange point is increasing 
time of delivery from 2ms to 13ms between peaks. If I zoom it looks like:
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2019-08-25 22:59:14 UTC - Igor Zubchenok: 
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2019-08-26 01:39:53 UTC - Igor Zubchenok: I measured CPU very often and found 
that broker process CPU increases during peaks.
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2019-08-26 02:48:58 UTC - Luke Lu: Hey guys, has anyone here seen the 
“head-scratching” subscription stats, where no messages are coming in for a 
while and there is a constant backlog on a connected consumer waiting for data. 
 Shouldn’t the subscription backlog go to zero in this case? This is using the 
websocket API:
```
    "SomeSubscription" : {
      "msgRateOut" : 0.0,
      "msgThroughputOut" : 0.0,
      "msgRateRedeliver" : 0.0,
      "msgBacklog" : 377,
      "blockedSubscriptionOnUnackedMsgs" : false,
      "msgDelayed" : 0,
      "unackedMessages" : 0,
      "type" : "Exclusive",
      "activeConsumerName" : "de307",
      "msgRateExpired" : 0.0,
      "consumers" : [ {
        "msgRateOut" : 0.0,
        "msgThroughputOut" : 0.0,
        "msgRateRedeliver" : 0.0,
        "consumerName" : "de307",
        "availablePermits" : 635,
        "unackedMessages" : 0,
        "blockedConsumerOnUnackedMsgs" : false,
        "metadata" : { },
        "connectedSince" : "2019-08-25T15:38:05.655Z",
        "clientVersion" : "2.4.0",
        "address" : "/10.36.33.96:49970"
      } ],
      "isReplicated" : false
    }
```
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2019-08-26 07:15:09 UTC - xue: I modify broker.conf, functionsWorkerEnabled = 
false, all clusters can be started successfully, function-worker can be started 
separately, through bin/pulsar-admin namespaces-clusters--cluster 
&lt;existing-clusters&gt;, &lt;new-cluster&gt; public/functions commands to 
solve another problem, when doing geo replication test. Wait, is the 
pulsarFunctionsCluster attribute in the functions_worker.yml file configured to 
be the name of all clusters, or the name of the local cluster?
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2019-08-26 07:18:06 UTC - xue: pulsarFunctionsCluster: pulsar-cluster，or 
pulsarFunctionsCluster: pulsar-cluster,pulsar-cluster2?
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2019-08-26 08:17:18 UTC - Emanuel: @Emanuel has joined the channel
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2019-08-26 08:20:27 UTC - Emanuel: Hey guys, is it possible to use pulsar SQL 
from pulsar functions or alternatively from a flink processor? 
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