fhueske commented on a change in pull request #8330: [FLINK-12388][docs] Update
the production readiness checklist
URL: https://github.com/apache/flink/pull/8330#discussion_r282917921
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File path: docs/ops/production_ready.md
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@@ -22,79 +22,54 @@ specific language governing permissions and limitations
under the License.
-->
+The production readiness checklist provides an overview of configuration
options that should be carefully considered before bringing an Apache Flink job
into production.
+While the Flink community has attempted to provide sensible defaults for each
configuration, it is important to review this list and ensure the options
chosen are sufficient for your needs.
+
* ToC
{:toc}
-## Production Readiness Checklist
-
-Purpose of this production readiness checklist is to provide a condensed
overview of configuration options that are
-important and need **careful considerations** if you plan to bring your Flink
job into **production**. For most of these options
-Flink provides out-of-the-box defaults to make usage and adoption of Flink
easier. For many users and scenarios, those
-defaults are good starting points for development and completely sufficient
for "one-shot" jobs.
-
-However, once you are planning to bring a Flink application to production the
requirements typically increase. For example,
-you want your job to be (re-)scalable and to have a good upgrade story for
your job and new Flink versions.
-
-In the following, we present a collection of configuration options that you
should check before your job goes into production.
-
-### Set maximum parallelism for operators explicitly
-
-Maximum parallelism is a configuration parameter that is newly introduced in
Flink 1.2 and has important implications
-for the (re-)scalability of your Flink job. This parameter, which can be set
on a per-job and/or per-operator granularity,
-determines the maximum parallelism to which you can scale operators. It is
important to understand that (as of now) there
-is **no way to change** this parameter after your job has been started, except
for restarting your job completely
-from scratch (i.e. with a new state, and not from a previous
checkpoint/savepoint). Even if Flink would provide some way
-to change maximum parallelism for existing savepoints in the future, you can
already assume that for large states this is
-likely a long running operation that you want to avoid. At this point, you
might wonder why not just to use a very high
-value as default for this parameter. The reason behind this is that high
maximum parallelism can have some impact on your
-application's performance and even state sizes, because Flink has to maintain
certain metadata for its ability to rescale which
-can increase with the maximum parallelism. In general, you should choose a max
parallelism that is high enough to fit your
-future needs in scalability, but keeping it as low as possible can give
slightly better performance. In particular,
-a maximum parallelism higher that 128 will typically result in slightly bigger
state snapshots from the keyed backends.
+### Set An Explicit Max Parallelism
-Notice that maximum parallelism must fulfill the following conditions:
+The max parallelism, set on a per-job and per-operator granularity, determines
the maximum parallelism to which a stateful operator can scale.
+There is currently **no way to change** the maximum parallelism of an operator
after a job has started without discarding that operators state.
+The reason maximum parallelism exists, versus allowing stateful operators to
be infinitely scalable, is that it has some impact on your application's
performance and state size.
+Flink has to maintain specific metadata for its ability to rescale state which
grows linearly with max parallelism.
Review comment:
nit: AFAIK it does not grow linearly but logarithmic. (the key group id
needs one more bit for each power-of-two step). Maybe just drop "linearly"?
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