Hi,
Thanks for the offer, I'd be happy to review your PR. Just wait a bit
until I have opened a proper ticket for that. I still need to think more
about the design. Among other things, I have to check what ES dev team
did for other big data ES IO (es_hadoop) on that particular point.
Besides, I think we also need to deal with the id at read time not only
at write time. I'll give some details in the ticket.
Le 15/11/2017 à 20:08, Chet Aldrich a écrit :
Given that this seems like a change that should probably happen, and
I’d like to help contribute if possible, a few questions and my
current opinion:
So I’m leaning towards approach B here, which is:
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>
I think that the reduction in user-friendliness may be outweighed by
the fact that this obviates some of the issues surrounding a failure
when finishing a bundle. Additionally, this /forces/ the user to
provide a document id, which I think is probably better practice.
Yes as I wrote before, I think it is better to force the user to provide
an id (at least for index updates, exactly-one semantics is a larger
beam subject than this IO scope). Regarding design, plan b is not the
better one IMHO because it changes the IO public API. I'm more in favor
of plan a with the ability for the user to tell what field is his doc id.
This will also probably lead to fewer frustrations around “magic” code
that just pulls something in if it happens to be there, and doesn’t if
not. We’ll need to rely on the user catching this functionality in the
docs or the code itself to take advantage of it.
IMHO it’d be generally better to enforce this at compile time because
it does have an effect on whether the pipeline produces duplicates on
failure. Additionally, we get the benefit of relatively intuitive
behavior where if the user passes in the same Key value, it’ll update
a record in ES, and if the key is different then it will create a new
record.
Totally agree, id enforcement at compile time, no auto-generation
Curious to hear thoughts on this. If this seems reasonable I’ll go
ahead and create a JIRA for tracking and start working on a PR for
this. Also, if it’d be good to loop in the dev mailing list before
starting let me know, I’m pretty new to this.
I'll create the ticket and we will loop on design in the comments.
Best
Etienne
Chet
On Nov 15, 2017, at 12:53 AM, Etienne Chauchot <[email protected]
<mailto:[email protected]>> 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 [email protected] <mailto:[email protected]> because
it seems like he’s been doing work related to the elastic sink.
