Created question in FIWARE Q/A platform on 04-09-2015 at 17:09
Please, ANSWER this question AT https://stackoverflow.com/questions/32401766/make-cygnus-use-webhdfs-to-write-to-local-hdfs

Question:
Make Cygnus use WebHDFS to write to local HDFS

Description:
I'm trying to make a local Orion+Cygnus persist Orion's data on a local HDFS through WebHDFS.

On Cygnus' instructions on gitub, very little is mentioned about WebHDFS, as the configuration is more about HttpFS.
On the .md OrionHDFSsink it's said that hdfs_port=50070 is for WebHDFS, as indeed my HDFS is. So I would expect by setting the port this way cygnus would automatically use WebHDFS, but on my case it doesn't seem to be working this way.

So, here's my agent_1.conf:

cygnusagent.sources = http-source
cygnusagent.sinks = hdfs-sink
cygnusagent.channels = hdfs-channel

1. source configuration
   cygnusagent.sources.http-source.channels = hdfs-channel
   cygnusagent.sources.http-source.type = org.apache.flume.source.http.HTTPSource
   cygnusagent.sources.http-source.port = 5050
   cygnusagent.sources.http-source.handler = com.telefonica.iot.cygnus.handlers.OrionRestHandler
   cygnusagent.sources.http-source.handler.notification_target = /notify
   cygnusagent.sources.http-source.handler.default_service = def_serv
   cygnusagent.sources.http-source.handler.default_service_path = def_servpath
   cygnusagent.sources.http-source.handler.events_ttl = 4
   cygnusagent.sources.http-source.interceptors = ts gi
   cygnusagent.sources.http-source.interceptors.ts.type = timestamp
   cygnusagent.sources.http-source.interceptors.gi.type = com.telefonica.iot.cygnus.interceptors.GroupingInterceptor$Builder
   cygnusagent.sources.http-source.interceptors.gi.grouping_rules_conf_file = /usr/cygnus/conf/grouping_rules.conf

1. OrionHDFSSink configuration
   cygnusagent.sinks.hdfs-sink.channel = hdfs-channel
   cygnusagent.sinks.hdfs-sink.type = com.telefonica.iot.cygnus.sinks.OrionHDFSSink
   cygnusagent.sinks.hdfs-sink.hdfs_host = localHDFS.ip
   cygnusagent.sinks.hdfs-sink.hdfs_port = 50070
   cygnusagent.sinks.hdfs-sink.hdfs_username = HDFSrootUser
   cygnusagent.sinks.hdfs-sink.attr_persistence = column

1. hdfs-channel configuration
   cygnusagent.channels.hdfs-channel.type = memory
   cygnusagent.channels.hdfs-channel.capacity = 1000
   cygnusagent.channels.hdfs-channel.transactionCapacity = 100

When I update an Entity on Orion, to whom Cygnus is subbed, Cygnus logs the following:

02 Sep 2015 20:09:12,353 INFO [2055470757@qtp-1523539038-0] (com.telefonica.iot.cygnus.handlers.OrionRestHandler.getEvents:150) - Starting transaction (1441217314-956-0000000000)
02 Sep 2015 20:09:12,362 INFO [2055470757@qtp-1523539038-0] (com.telefonica.iot.cygnus.handlers.OrionRestHandler.getEvents:236) - Received data ({ "subscriptionId" : "55e735c9b89e8535f8ca5ef2", "originator" : "localhost", "contextResponses" : [ { "contextElement" : { "type" : "Reading", "isPattern" : "false", "id" : "Reading1.1", "attributes" : [

{ "name" : "Cost", "type" : "double", "value" : "32" }

,

{ "name" : "Reading_ID", "type" : "integer", "value" : "14" }

,

{ "name" : "Threshold", "type" : "double", "value" : "30" }

,

{ "name" : "email", "type" : "string", "value" : "arthurmvieira@hotmail.com" }

] }, "statusCode" :

{ "code" : "200", "reasonPhrase" : "OK" }

} ]})
02 Sep 2015 20:09:12,366 INFO [2055470757@qtp-1523539038-0] (com.telefonica.iot.cygnus.handlers.OrionRestHandler.getEvents:258) - Event put in the channel (id=2020008711, ttl=4)
02 Sep 2015 20:09:12,432 INFO [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionSink.process:128) - Event got from the channel (id=2020008711, headers=

{fiware-servicepath=def_servpath, destination=reading1.1_reading, content-type=application/json, fiware-service=def_serv, ttl=4, transactionId=1441217314-956-0000000000, timestamp=1441217352368}

, bodyLength=812)
02 Sep 2015 20:09:12,549 INFO [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionHDFSSink.persist:356) - [hdfs-sink] Persisting data at OrionHDFSSink. HDFS file (def_serv/def_servpath/reading1.1_reading/reading1.1_reading.txt), Data (

{"recvTime":"2015-09-02T18:09:12.368Z","Cost":"32", "Cost_md":[],"Reading_ID":"14", "Reading_ID_md":[],"Threshold":"30", "Threshold_md":[],"email":"arthurmvieira@hotmail.com", "email_md":[]}

)
02 Sep 2015 20:09:12,557 ERROR [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionSink.process:143) - Persistence error (The /user/root/def_serv/def_servpath/reading1.1_reading directory could not be created in HDFS. HttpFS response: 503 Service unavailable)
02 Sep 2015 20:09:12,558 INFO [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionSink.process:173) - An event was put again in the channel (id=2020008711, ttl=3)
02 Sep 2015 20:09:12,558 INFO [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionSink.process:193) - Finishing transaction (1441217314-956-0000000000)
02 Sep 2015 20:09:13,560 INFO [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionSink.process:128) - Event got from the channel (id=2020008711, headers=

{fiware-servicepath=def_servpath, destination=reading1.1_reading, content-type=application/json, fiware-service=def_serv, ttl=3, transactionId=1441217314-956-0000000000, timestamp=1441217352368}

, bodyLength=812)
02 Sep 2015 20:09:13,574 INFO [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionHDFSSink.persist:356) - [hdfs-sink] Persisting data at OrionHDFSSink. HDFS file (def_serv/def_servpath/reading1.1_reading/reading1.1_reading.txt), Data (

{"recvTime":"2015-09-02T18:09:12.368Z","Cost":"32", "Cost_md":[],"Reading_ID":"14", "Reading_ID_md":[],"Threshold":"30", "Threshold_md":[],"email":"arthurmvieira@hotmail.com", "email_md":[]}

)
02 Sep 2015 20:09:13,574 ERROR [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionSink.process:143) - Persistence error (The /user/root/def_serv/def_servpath/reading1.1_reading directory could not be created in HDFS. HttpFS response: 503 Service unavailable)
02 Sep 2015 20:09:13,575 INFO [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionSink.process:173) - An event was put again in the channel (id=2020008711, ttl=2)
02 Sep 2015 20:09:13,575 INFO [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionSink.process:193) - Finishing transaction (1441217314-956-0000000000)
02 Sep 2015 20:09:15,576 INFO [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionSink.process:128) - Event got from the channel (id=2020008711, headers=

{fiware-servicepath=def_servpath, destination=reading1.1_reading, content-type=application/json, fiware-service=def_serv, ttl=2, transactionId=1441217314-956-0000000000, timestamp=1441217352368}

, bodyLength=812)
02 Sep 2015 20:09:15,590 INFO [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionHDFSSink.persist:356) - [hdfs-sink] Persisting data at OrionHDFSSink. HDFS file (def_serv/def_servpath/reading1.1_reading/reading1.1_reading.txt), Data (

{"recvTime":"2015-09-02T18:09:12.368Z","Cost":"32", "Cost_md":[],"Reading_ID":"14", "Reading_ID_md":[],"Threshold":"30", "Threshold_md":[],"email":"arthurmvieira@hotmail.com", "email_md":[]}

)
02 Sep 2015 20:09:15,599 ERROR [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionSink.process:143) - Persistence error (The /user/root/def_serv/def_servpath/reading1.1_reading directory could not be created in HDFS. HttpFS response: 503 Service unavailable)
02 Sep 2015 20:09:15,600 INFO [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionSink.process:173) - An event was put again in the channel (id=2020008711, ttl=1)
02 Sep 2015 20:09:15,600 INFO [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionSink.process:193) - Finishing transaction (1441217314-956-0000000000)
02 Sep 2015 20:09:18,601 INFO [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionSink.process:128) - Event got from the channel (id=2020008711, headers=

{fiware-servicepath=def_servpath, destination=reading1.1_reading, content-type=application/json, fiware-service=def_serv, ttl=1, transactionId=1441217314-956-0000000000, timestamp=1441217352368}

, bodyLength=812)
02 Sep 2015 20:09:18,615 INFO [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionHDFSSink.persist:356) - [hdfs-sink] Persisting data at OrionHDFSSink. HDFS file (def_serv/def_servpath/reading1.1_reading/reading1.1_reading.txt), Data (

{"recvTime":"2015-09-02T18:09:12.368Z","Cost":"32", "Cost_md":[],"Reading_ID":"14", "Reading_ID_md":[],"Threshold":"30", "Threshold_md":[],"email":"arthurmvieira@hotmail.com", "email_md":[]}

)
02 Sep 2015 20:09:18,618 ERROR [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionSink.process:143) - Persistence error (The /user/root/def_serv/def_servpath/reading1.1_reading directory could not be created in HDFS. HttpFS response: 503 Service unavailable)
02 Sep 2015 20:09:18,621 INFO [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionSink.process:173) - An event was put again in the channel (id=2020008711, ttl=0)
02 Sep 2015 20:09:18,621 INFO [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionSink.process:193) - Finishing transaction (1441217314-956-0000000000)
02 Sep 2015 20:09:22,622 INFO [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionSink.process:128) - Event got from the channel (id=2020008711, headers=

{fiware-servicepath=def_servpath, destination=reading1.1_reading, content-type=application/json, fiware-service=def_serv, ttl=0, transactionId=1441217314-956-0000000000, timestamp=1441217352368}

, bodyLength=812)
02 Sep 2015 20:09:22,635 INFO [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionHDFSSink.persist:356) - [hdfs-sink] Persisting data at OrionHDFSSink. HDFS file (def_serv/def_servpath/reading1.1_reading/reading1.1_reading.txt), Data (

{"recvTime":"2015-09-02T18:09:12.368Z","Cost":"32", "Cost_md":[],"Reading_ID":"14", "Reading_ID_md":[],"Threshold":"30", "Threshold_md":[],"email":"arthurmvieira@hotmail.com", "email_md":[]}

)
02 Sep 2015 20:09:22,635 ERROR [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionSink.process:143) - Persistence error (The /user/root/def_serv/def_servpath/reading1.1_reading directory could not be created in HDFS. HttpFS response: 503 Service unavailable)
02 Sep 2015 20:09:22,635 WARN [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionSink.process:163) - The event TTL has expired, it is no more re-injected in the channel (id=2020008711, ttl=0)
02 Sep 2015 20:09:22,635 INFO [SinkRunner-PollingRunner-DefaultSinkProcessor] (com.telefonica.iot.cygnus.sinks.OrionSink.process:193) - Finishing transaction (1441217314-956-0000000000)

So you can see it's trying to use HttpFS, as it logs the response:

HttpFS response: 503 Service unavailable

...on each writing try.

How should I configure the agent to use WebHDFS?

Thank you