I think it's also related to the discussion Romain raised on the dev mailing
list (gap between batch size, checkpointing & bundles).
Regards
JB
On 11/15/2017 09:53 AM, Etienne Chauchot wrote:
Hi Chet,
What you say is totally true, docs written using ElasticSearchIO will always
have an ES generated id. But it might change in the future, indeed it might be a
good thing to allow the user to pass an id. Just in 5 seconds thinking, I see 3
possible designs for that.
a.(simplest) use a json special field for the id, if it is provided by the user
in the input json then it is used, auto-generated id otherwise.
b. (a bit less user friendly) PCollection<KV> with K as an id. But forces the
user to do a Pardo before writing to ES to output KV pairs of <id, json>
c. (a lot more complex) Allow the IO to serialize/deserialize java beans and
have an String id field. Matching java types to ES types is quite tricky, so,
for now we just relied on the user to serialize his beans into json and let ES
match the types automatically.
Related to the problems you raise bellow:
1. Well, the bundle is the commit entity of beam. Consider the case of
ESIO.batchSize being < to bundle size. While processing records, when the number
of elements reaches batchSize, an ES bulk insert will be issued but no
finishBundle. If there is a problem later on in the bundle processing before the
finishBundle, the checkpoint will still be at the beginning of the bundle, so
all the bundle will be retried leading to duplicate documents. Thanks for
raising that! I'm CCing the dev list so that someone could correct me on the
checkpointing mecanism if I'm missing something. Besides I'm thinking about
forcing the user to provide an id in all cases to workaround this issue.
2. Correct.
Best,
Etienne
Le 15/11/2017 à 02:16, Chet Aldrich a écrit :
Hello all!
So I’ve been using the ElasticSearchIO sink for a project (unfortunately it’s
Elasticsearch 5.x, and so I’ve been messing around with the latest RC) and I’m
finding that it doesn’t allow for changing the document ID, but only lets you
pass in a record, which means that the document ID is auto-generated. See this
line for what specifically is happening:
https://github.com/apache/beam/blob/master/sdks/java/io/elasticsearch/src/main/java/org/apache/beam/sdk/io/elasticsearch/ElasticsearchIO.java#L838
Essentially the data part of the document is being placed but it doesn’t allow
for other properties, such as the document ID, to be set.
This leads to two problems:
1. Beam doesn’t necessarily guarantee exactly-once execution for a given item
in a PCollection, as I understand it. This means that you may get more than
one record in Elastic for a given item in a PCollection that you pass in.
2. You can’t do partial updates to an index. If you run a batch job once, and
then run the batch job again on the same index without clearing it, you just
double everything in there.
Is there any good way around this?
I’d be happy to try writing up a PR for this in theory, but not sure how to
best approach it. Also would like to figure out a way to get around this in
the meantime, if anyone has any ideas.
Best,
Chet
P.S. CCed echauc...@gmail.com <mailto:echauc...@gmail.com> because it seems
like he’s been doing work related to the elastic sink.
--
Jean-Baptiste Onofré
jbono...@apache.org
http://blog.nanthrax.net
Talend - http://www.talend.com
