well now i know what the problem could be.
You are trying to execute a job on a cluster (== not local), but have
set the local flag to true.
env.execute(local=True)
Due to this flag the files are only copied into the tmp directory of the
node where you execute the plan, and are thus not accessible from other
worker nodes.
In order to use the Python API on a cluster you *must* have a filesystem
that is accessible by all workers (like HDFS) to which the files can be
copied. From there they can be distributed to the nodes via the DC.**
On 17.07.2016 17:33, Geoffrey Mon wrote:
I haven't yet figured out how to write a Java job to test
DistributedCache functionality between machines; I've only gotten
worker nodes to create caches from local files (on the same worker
nodes), rather than on files from the master node. The
DistributedCache test I've been using (based on the
DistributedCacheTest unit test) is here:
https://gist.github.com/GEOFBOT/041d76b47f08919305493f57ebdde0f7
I realized that this test only tested local files because I was
getting an error that the file used for the cache was not found until
I created that file on the worker node in the location specified in
the plan.
I've been trying to run a simple Python example that does word counting:
https://gist.github.com/GEOFBOT/dbdc30120fb4d71383d9e3eff5f93c1f
I've tried three different setups so far: I've tried virtual machines,
AWS virtual machine instances, and physical machines. With each setup,
I get the same errors.
Although with all three of these setups, basic Java jobs can be run
(like WordCount, PageRank), Python programs cannot be run because the
files needed to run them are not properly distributed to the worker
nodes. I've found that although the master node reads the Python
libraries and plan files (presumably to send them to the worker), the
worker node never writes any of those files to disk, despite the files
being added to the list of files in the distributed cache via
DistributedCache.writeFileInfotoConfig (which I found via remote
debugging).
When a Python program is run via pyflink, it executes but crashes as
soon as there is any sort of operation requiring mapping. The
following exception is thrown:
2016-07-17 09:39:50,857 INFO
org.apache.flink.runtime.executiongraph.ExecutionGraph -
MapPartition (PythonFlatMap -> PythonMap) (1/1)
(12fbc21f0424ab87f3ef579fbe73b0b3) switched from RUNNING to FAILED
2016-07-17 09:39:50,863 INFO
org.apache.flink.runtime.jobmanager.JobManager - Status of job
3685c180d7eb004154e8f9d94996e0cf (Flink Java Job at Sun Jul 17
09:39:49 EDT 2016) changed to FAILING.
java.lang.Exception: The user defined 'open()' method caused an
exception: An error occurred while copying the file.
at org.apache.flink.runtime.operators.BatchTask.run(BatchTask.java:481)
<snip>
Caused by: java.lang.RuntimeException: An error occurred while copying
the file.
at
org.apache.flink.api.common.cache.DistributedCache.getFile(DistributedCache.java:78)
at
org.apache.flink.python.api.streaming.data.PythonStreamer.startPython(PythonStreamer.java:102)
<snip>
Caused by: java.io.FileNotFoundException: File file:/tmp/flink does
not exist or the user running Flink ('gmon') has insufficient
permissions to access it.
at
org.apache.flink.core.fs.local.LocalFileSystem.getFileStatus(LocalFileSystem.java:109)
at org.apache.flink.runtime.filecache.FileCache.copy(FileCache.java:242)
at
org.apache.flink.runtime.filecache.FileCache$CopyProcess.call(FileCache.java:322)
<snip>
... 1 more
If the pyflink library is manually copied into place at /tmp/flink,
that error will be replaced by the following:
2016-07-17 00:10:54,342 INFO
org.apache.flink.runtime.executiongraph.ExecutionGraph -
MapPartition (PythonFlatMap -> PythonMap) (1/1)
(23591303d5b571a6b3e9b68ef51c5a8e) switched from RUNNING to FAILED
2016-07-17 00:10:54,348 INFO
org.apache.flink.runtime.jobmanager.JobManager - Status of job
e072403ffec32bd14b54416b53cb46ae (Flink Java Job at Sun Jul 17
00:10:51 EDT 2016) changed to FAILING.
java.lang.Exception: The user defined 'open()' method caused an
exception: External process for task MapPartition (PythonFlatMap ->
PythonMap) terminated prematurely.
python3: can't open file
'/tmp/flink-dist-cache-724a9274-f984-429c-a0bf-4f5f23c5cfbc/e072403ffec32bd14b54416b53cb46ae/flink/plan.py':
[Errno 2] No such file or directory
at org.apache.flink.runtime.operators.BatchTask.run(BatchTask.java:481)
<snip>
Caused by: java.lang.RuntimeException: External process for task
MapPartition (PythonFlatMap -> PythonMap) terminated prematurely.
python3: can't open file
'/tmp/flink-dist-cache-724a9274-f984-429c-a0bf-4f5f23c5cfbc/e072403ffec32bd14b54416b53cb46ae/flink/plan.py':
[Errno 2] No such file or directory
at
org.apache.flink.python.api.streaming.data.PythonStreamer.startPython(PythonStreamer.java:144)
at
org.apache.flink.python.api.streaming.data.PythonStreamer.open(PythonStreamer.java:92)
at
org.apache.flink.python.api.functions.PythonMapPartition.open(PythonMapPartition.java:48)
<snip>
... 3 more
Both of these exceptions point to Flink not properly copying the
requested files. Has anyone else successfully run Python jobs on a
Flink cluster, or is there a bug preventing successful operation?
Unfortunately, I am relying on using a Flink cluster to run a Python
job for some scientific data that needs to be completed soon.
Thank for your assistance,
Geoffrey
On Sun, Jul 17, 2016 at 4:04 AM Chesnay Schepler <ches...@apache.org
<mailto:ches...@apache.org>> wrote:
Please also post the job you're trying to run.
On 17.07.2016 08:43, Geoffrey Mon wrote:
The Java program I used to test DistributedCache was faulty since
it actually created the cache from files on the machine on which
the program was running (i.e. the worker node).
I tried implementing a cluster again, this time using two actual
machines instead of virtual machines. I found the same error of
the Python libraries and plan file not being found in the
temporary directory. Has anyone else been able to successfully
set up a Flink cluster to run Python jobs? I've been beginning to
suspect that there may be some issues with running Python jobs on
Flink clusters that are present in Flink.
Cheers,
Geoffrey
On Fri, Jul 15, 2016 at 11:28 AM Geoffrey Mon <geof...@gmail.com
<mailto:geof...@gmail.com>> wrote:
I wrote a simple Java plan that reads a file in the
distributed cache and uses the first line from that file in a
map operation. Sure enough, it works locally, but fails when
the job is sent to a taskmanager on a worker node. Since
DistributedCache seems to work for everyone else, I'm
thinking that maybe some sort of file permissions are not
properly set such that Flink is not able to successfully
write distributed cache files.
I used inotify-tools to watch the temporary files directory
on both the master node and worker node. When the plan is
being prepared, the jobmanager node wrote the Python modules
and plan file to the temporary files directory. However, on
the worker node, the directory tree was created, but the job
failed before any of the module or plan files were even
attempted to be written. Interestingly enough, there were no
error messages or warnings about the cache.
Cheers,
Geoffrey
On Fri, Jul 15, 2016 at 4:15 AM Chesnay Schepler
<ches...@apache.org <mailto:ches...@apache.org>> wrote:
Could you write a java job that uses the Distributed
cache to distribute files?
If this fails then the DC is faulty, if it doesn't
something in the Python API is wrong.
On 15.07.2016 08:06, Geoffrey Mon wrote:
I've come across similar issues when trying to set up
Flink on Amazon EC2 instances. Presumably there is
something wrong with my setup? Here is the
flink-conf.yaml I am using:
https://gist.githubusercontent.com/GEOFBOT/3ffc9b21214174ae750cc3fdb2625b71/raw/flink-conf.yaml
Thanks,
Geoffrey
On Wed, Jul 13, 2016 at 1:15 PM Geoffrey Mon
<geof...@gmail.com <mailto:geof...@gmail.com>> wrote:
Hello,
Here is the TaskManager log on pastebin:
http://pastebin.com/XAJ56gn4
I will look into whether the files were created.
By the way, the cluster is made with virtual
machines running on BlueData EPIC. I don't know if
that might be related to the problem.
Thanks,
Geoffrey
On Wed, Jul 13, 2016 at 6:12 AM Chesnay Schepler
<ches...@apache.org <mailto:ches...@apache.org>> wrote:
Hello Geoffrey,
How often does this occur?
Flink distributes the user-code and the python
library using the Distributed Cache.
Either the file is deleted right after being
created for some reason, or the DC returns a
file name before the file was created (which
shouldn't happen, it should block it is available).
If you are up to debugging this i would suggest
looking into FileCache class and verifying
whether the file in question is in fact created.
The logs of the TaskManager of which the
exception occurs could be of interest too; could
you send them to me?
Regards,
Chesnay
On 13.07.2016 04:11, Geoffrey Mon wrote:
Hello all,
I've set up Flink on a very small cluster of
one master node and five worker nodes,
following the instructions in the documentation
(https://ci.apache.org/projects/flink/flink-docs-master/setup/cluster_setup.html).
I can run the included examples like WordCount
and PageRank across the entire cluster, but
when I try to run simple Python examples, I
sometimes get a strange error on the first
PythonMapPartition about the temporary folders
that contain the streams of data between Python
and Java.
If I run jobs on only the taskmanager on the
master node, Python examples run fine. However,
if the jobs use the worker nodes, then I get
the following error:
org.apache.flink.client.program.ProgramInvocationException:
The program execution failed: Job execution failed.
at
org.apache.flink.client.program.ClusterClient.run(ClusterClient.java:378)
<snip>
Caused by:
org.apache.flink.runtime.client.JobExecutionException:
Job execution failed.
at
org.apache.flink.runtime.jobmanager.JobManager$$anonfun$handleMessage$1$$anonfun$applyOrElse$7.apply$mcV$sp(JobManager.scala:806)
<snip>
Caused by: java.lang.Exception: The user
defined 'open()' method caused an exception:
External process for task MapPartition
(PythonMap) terminated prematurely.
python: can't open file
'/home/bluedata/flink/tmp/flink-dist-cache-d1958549-3d58-4554-b286-cb4b1cdb9060/52feefa8892e61ba9a187f7684c84ada/flink/plan.py':
[Errno 2] No such file or directory
at
org.apache.flink.runtime.operators.BatchTask.run(BatchTask.java:481)
<snip>
Caused by: java.lang.RuntimeException: External
process for task MapPartition (PythonMap)
terminated prematurely.
python: can't open file
'/home/bluedata/flink/tmp/flink-dist-cache-d1958549-3d58-4554-b286-cb4b1cdb9060/52feefa8892e61ba9a187f7684c84ada/flink/plan.py':
[Errno 2] No such file or directory
at
org.apache.flink.python.api.streaming.data.PythonStreamer.startPython(PythonStreamer.java:144)
at
org.apache.flink.python.api.streaming.data.PythonStreamer.open(PythonStreamer.java:92)
at
org.apache.flink.python.api.functions.PythonMapPartition.open(PythonMapPartition.java:48)
at
org.apache.flink.api.common.functions.util.FunctionUtils.openFunction(FunctionUtils.java:38)
at
org.apache.flink.runtime.operators.BatchTask.run(BatchTask.java:477)
... 5 more
I'm suspecting this issue has something to do
with the data sending between the master and
the workers, but I haven't been able to find
any solutions. Presumably the temporary files
weren't received properly and thus were not
created properly?
Thanks in advance.
Cheers,
Geoffrey
