## What changes were proposed in this pull request?
Fix the broken links in the programming guide of the Graphx Migration and understanding closures
## How was this patch tested?
By running the test cases and checking the links.
Author: Shivansh <shiv4nsh@gmail.com>
Closes#14503 from shiv4nsh/SPARK-16911.
## What changes were proposed in this pull request?
In the programming guide, the accumulator section mixes up both the old and new APIs causing it to be confusing. This is not necessary for Scala, so all references to the old API are removed. For Java, it is somewhat fixed up except for the example of a custom accumulator because I don't think an API exists yet. Python has not currently implemented the new API.
## How was this patch tested?
built doc locally
Author: Bryan Cutler <cutlerb@gmail.com>
Closes#14516 from BryanCutler/fixup-accumulator-programming-guide-SPARK-15702.
## What changes were proposed in this pull request?
Made DataFrame-based API primary
* Spark doc menu bar and other places now link to ml-guide.html, not mllib-guide.html
* mllib-guide.html keeps RDD-specific list of features, with a link at the top redirecting people to ml-guide.html
* ml-guide.html includes a "maintenance mode" announcement about the RDD-based API
* **Reviewers: please check this carefully**
* (minor) Titles for DF API no longer include "- spark.ml" suffix. Titles for RDD API have "- RDD-based API" suffix
* Moved migration guide to ml-guide from mllib-guide
* Also moved past guides from mllib-migration-guides to ml-migration-guides, with a redirect link on mllib-migration-guides
* **Reviewers**: I did not change any of the content of the migration guides.
Reorganized DataFrame-based guide:
* ml-guide.html mimics the old mllib-guide.html page in terms of content: overview, migration guide, etc.
* Moved Pipeline description into ml-pipeline.html and moved tuning into ml-tuning.html
* **Reviewers**: I did not change the content of these guides, except some intro text.
* Sidebar remains the same, but with pipeline and tuning sections added
Other:
* ml-classification-regression.html: Moved text about linear methods to new section in page
## How was this patch tested?
Generated docs locally
Author: Joseph K. Bradley <joseph@databricks.com>
Closes#14213 from jkbradley/ml-guide-2.0.
## What changes were proposed in this pull request?
Add Asynchronous Actions documentation inside action of programming guide
## How was this patch tested?
check the documentation indentation and formatting with md preview.
Author: sandy <phalodi@gmail.com>
Closes#14104 from phalodi/SPARK-16438.
This has changed from 1.6, and now stores memory off-heap using spark's off-heap support instead of in tachyon.
Author: Eric Liang <ekl@databricks.com>
Closes#13744 from ericl/spark-16025.
## What changes were proposed in this pull request?
minor typo
## How was this patch tested?
minor typo in the doc, should be self explanatory
Author: Mortada Mehyar <mortada.mehyar@gmail.com>
Closes#13639 from mortada/typo.
## What changes were proposed in this pull request?
- Deprecate old Java accumulator API; should use Scala now
- Update Java tests and examples
- Don't bother testing old accumulator API in Java 8 (too)
- (fix a misspelling too)
## How was this patch tested?
Jenkins tests
Author: Sean Owen <sowen@cloudera.com>
Closes#13606 from srowen/SPARK-15086.
## What changes were proposed in this pull request?
Update document programming-guide accumulator section (scala language)
java and python version, because the API haven't done, so I do not modify them.
## How was this patch tested?
N/A
Author: WeichenXu <WeichenXu123@outlook.com>
Closes#13441 from WeichenXu123/update_doc_accumulatorV2_clean.
## What changes were proposed in this pull request?
https://issues.apache.org/jira/browse/SPARK-13973
Following discussion with srowen the IPYTHON and IPYTHON_OPTS variables are removed. If they are set in the user's environment, pyspark will not execute and prints an error message. Failing noisily will force users to remove these options and learn the new configuration scheme, which is much more sustainable and less confusing.
## How was this patch tested?
Manual testing; set IPYTHON=1 and verified that the error message prints.
Author: pshearer <pshearer@massmutual.com>
Author: shearerp <shearerp@umich.edu>
Closes#12528 from shearerp/master.
## What changes were proposed in this pull request?
Add simple clarification that Spark can be cross-built for other Scala versions.
## How was this patch tested?
Automated doc build
Author: Sean Owen <sowen@cloudera.com>
Closes#12757 from srowen/SPARK-14882.
## What changes were proposed in this pull request?
Added screenshot + minor fixes to improve reading
## How was this patch tested?
Manual
Author: Jacek Laskowski <jacek@japila.pl>
Closes#12569 from jaceklaskowski/docs-accumulators.
## What changes were proposed in this pull request?
We provide a very limited set of cluster management script in Spark for Tachyon, although Tachyon itself provides a much better version of it. Given now Spark users can simply use Tachyon as a normal file system and does not require extensive configurations, we can remove this management capabilities to simplify Spark bash scripts.
Note that this also reduces coupling between a 3rd party external system and Spark's release scripts, and would eliminate possibility for failures such as Tachyon being renamed or the tar balls being relocated.
## How was this patch tested?
N/A
Author: Reynold Xin <rxin@databricks.com>
Closes#11400 from rxin/release-script.
## What changes were proposed in this pull request?
This PR tries to fix all typos in all markdown files under `docs` module,
and fixes similar typos in other comments, too.
## How was the this patch tested?
manual tests.
Author: Dongjoon Hyun <dongjoon@apache.org>
Closes#11300 from dongjoon-hyun/minor_fix_typos.
Clarify that reduce functions need to be commutative, and fold functions do not
See https://github.com/apache/spark/pull/11091
Author: Sean Owen <sowen@cloudera.com>
Closes#11217 from srowen/SPARK-13339.
Clarify that modifying a driver local variable won't have the desired effect in cluster modes, and may or may not work as intended in local mode
Author: Sean Owen <sowen@cloudera.com>
Closes#10866 from srowen/SPARK-12760.
…local vs cluster
srowen thanks for the PR at https://github.com/apache/spark/pull/10866! sorry it took me a while.
This is related to https://github.com/apache/spark/pull/10866, basically the assignment in the lambda expression in the python example is actually invalid
```
In [1]: data = [1, 2, 3, 4, 5]
In [2]: counter = 0
In [3]: rdd = sc.parallelize(data)
In [4]: rdd.foreach(lambda x: counter += x)
File "<ipython-input-4-fcb86c182bad>", line 1
rdd.foreach(lambda x: counter += x)
^
SyntaxError: invalid syntax
```
Author: Mortada Mehyar <mortada.mehyar@gmail.com>
Closes#10867 from mortada/doc_python_fix.
This PR adds Scala, Java and Python examples to show how to use Accumulator and Broadcast in Spark Streaming to support checkpointing.
Author: Shixiong Zhu <shixiong@databricks.com>
Closes#10385 from zsxwing/accumulator-broadcast-example.
The current default storage level of Python persist API is MEMORY_ONLY_SER. This is different from the default level MEMORY_ONLY in the official document and RDD APIs.
davies Is this inconsistency intentional? Thanks!
Updates: Since the data is always serialized on the Python side, the storage levels of JAVA-specific deserialization are not removed, such as MEMORY_ONLY.
Updates: Based on the reviewers' feedback. In Python, stored objects will always be serialized with the [Pickle](https://docs.python.org/2/library/pickle.html) library, so it does not matter whether you choose a serialized level. The available storage levels in Python include `MEMORY_ONLY`, `MEMORY_ONLY_2`, `MEMORY_AND_DISK`, `MEMORY_AND_DISK_2`, `DISK_ONLY`, `DISK_ONLY_2` and `OFF_HEAP`.
Author: gatorsmile <gatorsmile@gmail.com>
Closes#10092 from gatorsmile/persistStorageLevel.
Remove Hadoop third party distro page, and move Hadoop cluster config info to configuration page
CC pwendell
Author: Sean Owen <sowen@cloudera.com>
Closes#9298 from srowen/SPARK-11305.
Update `lineLengths.persist();` to `lineLengths.persist(StorageLevel.MEMORY_ONLY());` because `JavaRDD#persist` needs a parameter of `StorageLevel`.
Author: Keiji Yoshida <yoshida.keiji.84@gmail.com>
Closes#8372 from yosssi/patch-1.
Clarify what may cause long-running Spark apps to preserve shuffle files
Author: Sean Owen <sowen@cloudera.com>
Closes#6901 from srowen/SPARK-5836 and squashes the following commits:
a9faef0 [Sean Owen] Clarify what may cause long-running Spark apps to preserve shuffle files
Update build to use Java 7, and remove some comments and special-case support for Java 6.
Author: Sean Owen <sowen@cloudera.com>
Closes#6265 from srowen/SPARK-7733 and squashes the following commits:
59bda4e [Sean Owen] Update build to use Java 7, and remove some comments and special-case support for Java 6
Adds a section in the RDD persistence section of the programming-guide docs detailing Spark-Tachyon version compatibility as discussed in [[SPARK-6391]](https://issues.apache.org/jira/browse/SPARK-6391).
Author: Calvin Jia <jia.calvin@gmail.com>
Closes#6382 from calvinjia/spark-6391 and squashes the following commits:
113e863 [Calvin Jia] Move compatibility info to the offheap storage level section.
7942dc5 [Calvin Jia] Add a section in the programming-guide docs for Tachyon compatibility.
sqlCtx -> sqlContext
You can check the docs by:
```
$ cd docs
$ SKIP_SCALADOC=1 jekyll serve
```
cc shivaram
Author: Davies Liu <davies@databricks.com>
Closes#5442 from davies/r_docs and squashes the following commits:
7a12ec6 [Davies Liu] remove rdd in R docs
8496b26 [Davies Liu] remove the docs related to RDD
e23b9d6 [Davies Liu] delete R docs for RDD API
222e4ff [Davies Liu] Merge branch 'master' into r_docs
89684ce [Davies Liu] Merge branch 'r_docs' of github.com:davies/spark into r_docs
f0a10e1 [Davies Liu] address comments from @shivaram
f61de71 [Davies Liu] Update pairRDD.R
3ef7cf3 [Davies Liu] use + instead of function(a,b) a+b
2f10a77 [Davies Liu] address comments from @cafreeman
9c2a062 [Davies Liu] mention R api together with Python API
23f751a [Davies Liu] Fill in SparkR examples in programming guide
The change per SPARK-4397 makes implicit objects in SparkContext to be found by the compiler automatically. So that we don't need to import the o.a.s.SparkContext._ explicitly any more and can remove some statements around the "implicit conversions" from the latest Programming Guides (1.3.0 and higher)
Author: Dice <poleon.kd@gmail.com>
Closes#6234 from daisukebe/patch-1 and squashes the following commits:
b77ecd9 [Dice] fix a typo
45dfcd3 [Dice] rewording per Sean's advice
a094bcf [Dice] Adding a note for users on any previous releases
a29be5f [Dice] Updating Programming Guides per SPARK-4397
Just a few minor fixes in the guide, so a new JIRA issue was not created per the guidelines.
Author: Mike Dusenberry <dusenberrymw@gmail.com>
Closes#6240 from dusenberrymw/Fix_Programming_Guide_Typos and squashes the following commits:
ffa76eb [Mike Dusenberry] Fixing a few basic typos in the Programming Guide.
The contribution is my original work. I license the work to the project under the project's open source license.
Small typo in the programming guide.
Author: Eric Chiang <eric.chiang.m@gmail.com>
Closes#5599 from ericchiang/docs-typo and squashes the following commits:
1177942 [Eric Chiang] fixed doc
I've updated the Spark Programming Guide to add a section on the shuffle operation providing some background on what it does. I've also addressed some of its performance impacts.
I've included documentation to address the following issues:
https://issues.apache.org/jira/browse/SPARK-5836https://issues.apache.org/jira/browse/SPARK-3441https://issues.apache.org/jira/browse/SPARK-5750https://issues.apache.org/jira/browse/SPARK-4227 is related but can be addressed in a separate PR since it involves updates to the Spark Configuration Guide.
Author: Ilya Ganelin <ilya.ganelin@capitalone.com>
Author: Ilya Ganelin <ilganeli@gmail.com>
Closes#5074 from ilganeli/SPARK-5750 and squashes the following commits:
6178e24 [Ilya Ganelin] Update programming-guide.md
7a0b96f [Ilya Ganelin] Update programming-guide.md
2c5df08 [Ilya Ganelin] Merge branch 'SPARK-5750' of github.com:ilganeli/spark into SPARK-5750
dffbd2d [Ilya Ganelin] [SPARK-5750] Slight wording update
1ff4eb4 [Ilya Ganelin] Merge remote-tracking branch 'upstream/master' into SPARK-5750
85f9c6e [Ilya Ganelin] Update programming-guide.md
349d1fa [Ilya Ganelin] Added cross linkf or configuration page
eeb5a7a [Ilya Ganelin] [SPARK-5750] Added some minor fixes
dd5cc9d [Ilya Ganelin] [SPARK-5750] Fixed some factual inaccuracies with regards to shuffle internals.
a8adb57 [Ilya Ganelin] [SPARK-5750] Incoporated feedback from Sean Owen
9954bbe [Ilya Ganelin] Merge remote-tracking branch 'upstream/master' into SPARK-5750
159dd1c [Ilya Ganelin] [SPARK-5750] Style fixes from rxin.
75ef67b [Ilya Ganelin] [SPARK-5750][SPARK-3441][SPARK-5836] Added documentation explaining the shuffle operation and included errata from a number of other JIRAs
As for "notebook --pylab inline" is not supported any more, update the related documentation for this.
Author: Cong Yue <yuecong1104@gmail.com>
Closes#5111 from yuecong/patch-1 and squashes the following commits:
872df76 [Cong Yue] Update the command to use IPython notebook
Author: Kamil Smuga <smugakamil@gmail.com>
Author: stderr <smugakamil@gmail.com>
Closes#5120 from kamilsmuga/master and squashes the following commits:
fee3281 [Kamil Smuga] more python api links fixed for docs
13240cb [Kamil Smuga] resolved merge conflicts with upstream/master
6649b3b [Kamil Smuga] fix broken docs links to Python API
92f03d7 [stderr] Fix links to pyspark api
Author: Sandy Ryza <sandy@cloudera.com>
Closes#2490 from sryza/sandy-spark-3642 and squashes the following commits:
aae3340 [Sandy Ryza] SPARK-3642. Document the nuances of broadcast variables
Hi all - I've added a writeup on how closures work within Spark to help clarify the general case for this problem and similar problems. I hope this addresses the issue and would love any feedback.
Author: Ilya Ganelin <ilya.ganelin@capitalone.com>
Closes#4696 from ilganeli/SPARK-4423 and squashes the following commits:
c5dc498 [Ilya Ganelin] Fixed typo
07b78e8 [Ilya Ganelin] Updated to fix capitalization
48c1983 [Ilya Ganelin] Updated to fix capitalization and clarify wording
2fd2a07 [Ilya Ganelin] Incoporated a few more minor fixes. Fixed a bug in python code. Added semicolons for java
4772f99 [Ilya Ganelin] Incorporated latest feedback
448bd79 [Ilya Ganelin] Updated some verbage and added section links
5dbbda5 [Ilya Ganelin] Improved some wording
d374d3a [Ilya Ganelin] Merge remote-tracking branch 'upstream/master' into SPARK-4423
2600668 [Ilya Ganelin] Minor edits
c768ab2 [Ilya Ganelin] Updated documentation to add a section on closures. This helps understand confusing behavior of foreach and map functions when attempting to modify variables outside of the scope of an RDD action or transformation
This change encapsulates all the logic involved in launching a Spark job
into a small Java library that can be easily embedded into other applications.
The overall goal of this change is twofold, as described in the bug:
- Provide a public API for launching Spark processes. This is a common request
from users and currently there's no good answer for it.
- Remove a lot of the duplicated code and other coupling that exists in the
different parts of Spark that deal with launching processes.
A lot of the duplication was due to different code needed to build an
application's classpath (and the bootstrapper needed to run the driver in
certain situations), and also different code needed to parse spark-submit
command line options in different contexts. The change centralizes those
as much as possible so that all code paths can rely on the library for
handling those appropriately.
Author: Marcelo Vanzin <vanzin@cloudera.com>
Closes#3916 from vanzin/SPARK-4924 and squashes the following commits:
18c7e4d [Marcelo Vanzin] Fix make-distribution.sh.
2ce741f [Marcelo Vanzin] Add lots of quotes.
3b28a75 [Marcelo Vanzin] Update new pom.
a1b8af1 [Marcelo Vanzin] Merge branch 'master' into SPARK-4924
897141f [Marcelo Vanzin] Review feedback.
e2367d2 [Marcelo Vanzin] Merge branch 'master' into SPARK-4924
28cd35e [Marcelo Vanzin] Remove stale comment.
b1d86b0 [Marcelo Vanzin] Merge branch 'master' into SPARK-4924
00505f9 [Marcelo Vanzin] Add blurb about new API in the programming guide.
5f4ddcc [Marcelo Vanzin] Better usage messages.
92a9cfb [Marcelo Vanzin] Fix Win32 launcher, usage.
6184c07 [Marcelo Vanzin] Rename field.
4c19196 [Marcelo Vanzin] Update comment.
7e66c18 [Marcelo Vanzin] Fix pyspark tests.
0031a8e [Marcelo Vanzin] Review feedback.
c12d84b [Marcelo Vanzin] Review feedback. And fix spark-submit on Windows.
e2d4d71 [Marcelo Vanzin] Simplify some code used to launch pyspark.
43008a7 [Marcelo Vanzin] Don't make builder extend SparkLauncher.
b4d6912 [Marcelo Vanzin] Use spark-submit script in SparkLauncher.
28b1434 [Marcelo Vanzin] Add a comment.
304333a [Marcelo Vanzin] Fix propagation of properties file arg.
bb67b93 [Marcelo Vanzin] Remove unrelated Yarn change (that is also wrong).
8ec0243 [Marcelo Vanzin] Add missing newline.
95ddfa8 [Marcelo Vanzin] Fix handling of --help for spark-class command builder.
72da7ec [Marcelo Vanzin] Rename SparkClassLauncher.
62978e4 [Marcelo Vanzin] Minor cleanup of Windows code path.
9cd5b44 [Marcelo Vanzin] Make all non-public APIs package-private.
e4c80b6 [Marcelo Vanzin] Reorganize the code so that only SparkLauncher is public.
e50dc5e [Marcelo Vanzin] Merge branch 'master' into SPARK-4924
de81da2 [Marcelo Vanzin] Fix CommandUtils.
86a87bf [Marcelo Vanzin] Merge branch 'master' into SPARK-4924
2061967 [Marcelo Vanzin] Merge branch 'master' into SPARK-4924
46d46da [Marcelo Vanzin] Clean up a test and make it more future-proof.
b93692a [Marcelo Vanzin] Merge branch 'master' into SPARK-4924
ad03c48 [Marcelo Vanzin] Revert "Fix a thread-safety issue in "local" mode."
0b509d0 [Marcelo Vanzin] Merge branch 'master' into SPARK-4924
23aa2a9 [Marcelo Vanzin] Read java-opts from conf dir, not spark home.
7cff919 [Marcelo Vanzin] Javadoc updates.
eae4d8e [Marcelo Vanzin] Fix new unit tests on Windows.
e570fb5 [Marcelo Vanzin] Merge branch 'master' into SPARK-4924
44cd5f7 [Marcelo Vanzin] Add package-info.java, clean up javadocs.
f7cacff [Marcelo Vanzin] Remove "launch Spark in new thread" feature.
7ed8859 [Marcelo Vanzin] Some more feedback.
54cd4fd [Marcelo Vanzin] Merge branch 'master' into SPARK-4924
61919df [Marcelo Vanzin] Clean leftover debug statement.
aae5897 [Marcelo Vanzin] Use launcher classes instead of jars in non-release mode.
e584fc3 [Marcelo Vanzin] Rework command building a little bit.
525ef5b [Marcelo Vanzin] Rework Unix spark-class to handle argument with newlines.
8ac4e92 [Marcelo Vanzin] Minor test cleanup.
e946a99 [Marcelo Vanzin] Merge PySparkLauncher into SparkSubmitCliLauncher.
c617539 [Marcelo Vanzin] Review feedback round 1.
fc6a3e2 [Marcelo Vanzin] Merge branch 'master' into SPARK-4924
f26556b [Marcelo Vanzin] Fix a thread-safety issue in "local" mode.
2f4e8b4 [Marcelo Vanzin] Changes needed to make this work with SPARK-4048.
799fc20 [Marcelo Vanzin] Merge branch 'master' into SPARK-4924
bb5d324 [Marcelo Vanzin] Merge branch 'master' into SPARK-4924
53faef1 [Marcelo Vanzin] Merge branch 'master' into SPARK-4924
a7936ef [Marcelo Vanzin] Fix pyspark tests.
656374e [Marcelo Vanzin] Mima fixes.
4d511e7 [Marcelo Vanzin] Fix tools search code.
7a01e4a [Marcelo Vanzin] Fix pyspark on Yarn.
1b3f6e9 [Marcelo Vanzin] Call SparkSubmit from spark-class launcher for unknown classes.
25c5ae6 [Marcelo Vanzin] Centralize SparkSubmit command line parsing.
27be98a [Marcelo Vanzin] Modify Spark to use launcher lib.
6f70eea [Marcelo Vanzin] [SPARK-4924] Add a library for launching Spark jobs programatically.
Author: RobertZK <technoguyrob@gmail.com>
Author: Robert Krzyzanowski <technoguyrob@gmail.com>
Closes#4840 from robertzk/patch-1 and squashes the following commits:
d286215 [RobertZK] lambda fix per @laserson
5937989 [Robert Krzyzanowski] Fix python typo
This looks like a simple typo ```SparkContext.newHadoopRDD``` instead of ```SparkContext.newAPIHadoopRDD``` as in actual http://spark.apache.org/docs/1.2.1/api/scala/index.html#org.apache.spark.SparkContext
Author: Alexander <abezzubov@nflabs.com>
Closes#4718 from bzz/hadoop-InputFormats-doc-fix and squashes the following commits:
680a4c4 [Alexander] Fix typo in docs on custom Hadoop InputFormats
Looking at the code, I believe this remark about `take(n)` computing partitions on the driver is no longer correct. Apologies if I'm wrong.
This came up in http://stackoverflow.com/q/28436559/3318517.
Author: Daniel Darabos <darabos.daniel@gmail.com>
Closes#4533 from darabos/patch-2 and squashes the following commits:
cc80f3a [Daniel Darabos] Remove outdated remark about take(n).
- Add meta description tags on some of the most important doc pages
- Shorten the titles of some pages to have more relevant keywords; for
example there's no reason to have "Spark SQL Programming Guide - Spark
1.2.0 documentation", we can just say "Spark SQL - Spark 1.2.0
documentation".
Author: Matei Zaharia <matei@databricks.com>
Closes#4381 from mateiz/docs-seo and squashes the following commits:
4940563 [Matei Zaharia] [SPARK-5608] Improve SEO of Spark documentation pages
Author: Sandy Ryza <sandy@cloudera.com>
Closes#4251 from sryza/sandy-spark-5458 and squashes the following commits:
460827a [Sandy Ryza] Python too
d2dc160 [Sandy Ryza] SPARK-5458. Refer to aggregateByKey instead of combineByKey in docs
I've added documentation clarifying the particular lack of clarity highlighted in the relevant JIRA. I've also added code examples for this issue to clarify the explanation.
Author: Ilya Ganelin <ilya.ganelin@capitalone.com>
Closes#4022 from ilganeli/SPARK-733 and squashes the following commits:
587def5 [Ilya Ganelin] Updated to clarify verbage
df3afd7 [Ilya Ganelin] Revert "Partially updated task metrics to make some vars private"
3f6c512 [Ilya Ganelin] Revert "Completed refactoring to make vars in TaskMetrics class private"
58034fb [Ilya Ganelin] Merge remote-tracking branch 'upstream/master' into SPARK-733
4dc2cdb [Ilya Ganelin] Merge remote-tracking branch 'upstream/master' into SPARK-733
3a38db1 [Ilya Ganelin] Verified documentation update by building via jekyll
33b5a2d [Ilya Ganelin] Added code examples for java and python
1fd59b2 [Ilya Ganelin] Updated documentation for accumulators to highlight lazy evaluation issue
5525c20 [Ilya Ganelin] Completed refactoring to make vars in TaskMetrics class private
c64da4f [Ilya Ganelin] Partially updated task metrics to make some vars private
Grammatical error in Programming Guide document
Author: lewuathe <lewuathe@me.com>
Closes#3412 from Lewuathe/typo-programming-guide and squashes the following commits:
a3e2f00 [lewuathe] Typo in Programming Guide markdown
https://issues.apache.org/jira/browse/SPARK-3628
In current implementation, the accumulator will be updated for every successfully finished task, even the task is from a resubmitted stage, which makes the accumulator counter-intuitive
In this patch, I changed the way for the DAGScheduler to update the accumulator,
DAGScheduler maintains a HashTable, mapping the stage id to the received <accumulator_id , value> pairs. Only when the stage becomes independent, (no job needs it any more), we accumulate the values of the <accumulator_id , value> pairs, when a task finished, we check if the HashTable has contained such stageId, it saves the accumulator_id, value only when the task is the first finished task of a new stage or the stage is running for the first attempt...
Author: CodingCat <zhunansjtu@gmail.com>
Closes#2524 from CodingCat/SPARK-732-1 and squashes the following commits:
701a1e8 [CodingCat] roll back change on Accumulator.scala
1433e6f [CodingCat] make MIMA happy
b233737 [CodingCat] address Matei's comments
02261b8 [CodingCat] rollback some changes
6b0aff9 [CodingCat] update document
2b2e8cf [CodingCat] updateAccumulator
83b75f8 [CodingCat] style fix
84570d2 [CodingCat] re-enable the bad accumulator guard
1e9e14d [CodingCat] add NPE guard
21b6840 [CodingCat] simplify the patch
88d1f03 [CodingCat] fix rebase error
f74266b [CodingCat] add test case for resubmitted result stage
5cf586f [CodingCat] de-duplicate on task level
138f9b3 [CodingCat] make MIMA happy
67593d2 [CodingCat] make if allowing duplicate update as an option of accumulator
This patch adds error-detection logic to throw an exception when attempting to create multiple active SparkContexts in the same JVM, since this is currently unsupported and has been known to cause confusing behavior (see SPARK-2243 for more details).
**The solution implemented here is only a partial fix.** A complete fix would have the following properties:
1. Only one SparkContext may ever be under construction at any given time.
2. Once a SparkContext has been successfully constructed, any subsequent construction attempts should fail until the active SparkContext is stopped.
3. If the SparkContext constructor throws an exception, then all resources created in the constructor should be cleaned up (SPARK-4194).
4. If a user attempts to create a SparkContext but the creation fails, then the user should be able to create new SparkContexts.
This PR only provides 2) and 4); we should be able to provide all of these properties, but the correct fix will involve larger changes to SparkContext's construction / initialization, so we'll target it for a different Spark release.
### The correct solution:
I think that the correct way to do this would be to move the construction of SparkContext's dependencies into a static method in the SparkContext companion object. Specifically, we could make the default SparkContext constructor `private` and change it to accept a `SparkContextDependencies` object that contains all of SparkContext's dependencies (e.g. DAGScheduler, ContextCleaner, etc.). Secondary constructors could call a method on the SparkContext companion object to create the `SparkContextDependencies` and pass the result to the primary SparkContext constructor. For example:
```scala
class SparkContext private (deps: SparkContextDependencies) {
def this(conf: SparkConf) {
this(SparkContext.getDeps(conf))
}
}
object SparkContext(
private[spark] def getDeps(conf: SparkConf): SparkContextDependencies = synchronized {
if (anotherSparkContextIsActive) { throw Exception(...) }
var dagScheduler: DAGScheduler = null
try {
dagScheduler = new DAGScheduler(...)
[...]
} catch {
case e: Exception =>
Option(dagScheduler).foreach(_.stop())
[...]
}
SparkContextDependencies(dagScheduler, ....)
}
}
```
This gives us mutual exclusion and ensures that any resources created during the failed SparkContext initialization are properly cleaned up.
This indirection is necessary to maintain binary compatibility. In retrospect, it would have been nice if SparkContext had no private constructors and could only be created through builder / factory methods on its companion object, since this buys us lots of flexibility and makes dependency injection easier.
### Alternative solutions:
As an alternative solution, we could refactor SparkContext's primary constructor to perform all object creation in a giant `try-finally` block. Unfortunately, this will require us to turn a bunch of `vals` into `vars` so that they can be assigned from the `try` block. If we still want `vals`, we could wrap each `val` in its own `try` block (since the try block can return a value), but this will lead to extremely messy code and won't guard against the introduction of future code which doesn't properly handle failures.
The more complex approach outlined above gives us some nice dependency injection benefits, so I think that might be preferable to a `var`-ification.
### This PR's solution:
- At the start of the constructor, check whether some other SparkContext is active; if so, throw an exception.
- If another SparkContext might be under construction (or has thrown an exception during construction), allow the new SparkContext to begin construction but log a warning (since resources might have been leaked from a failed creation attempt).
- At the end of the SparkContext constructor, check whether some other SparkContext constructor has raced and successfully created an active context. If so, throw an exception.
This guarantees that no two SparkContexts will ever be active and exposed to users (since we check at the very end of the constructor). If two threads race to construct SparkContexts, then one of them will win and another will throw an exception.
This exception can be turned into a warning by setting `spark.driver.allowMultipleContexts = true`. The exception is disabled in unit tests, since there are some suites (such as Hive) that may require more significant refactoring to clean up their SparkContexts. I've made a few changes to other suites' test fixtures to properly clean up SparkContexts so that the unit test logs contain fewer warnings.
Author: Josh Rosen <joshrosen@databricks.com>
Closes#3121 from JoshRosen/SPARK-4180 and squashes the following commits:
23c7123 [Josh Rosen] Merge remote-tracking branch 'origin/master' into SPARK-4180
d38251b [Josh Rosen] Address latest round of feedback.
c0987d3 [Josh Rosen] Accept boolean instead of SparkConf in methods.
85a424a [Josh Rosen] Incorporate more review feedback.
372d0d3 [Josh Rosen] Merge remote-tracking branch 'origin/master' into SPARK-4180
f5bb78c [Josh Rosen] Update mvn build, too.
d809cb4 [Josh Rosen] Improve handling of failed SparkContext creation attempts.
79a7e6f [Josh Rosen] Fix commented out test
a1cba65 [Josh Rosen] Merge remote-tracking branch 'origin/master' into SPARK-4180
7ba6db8 [Josh Rosen] Add utility to set system properties in tests.
4629d5c [Josh Rosen] Set spark.driver.allowMultipleContexts=true in tests.
ed17e14 [Josh Rosen] Address review feedback; expose hack workaround for existing unit tests.
1c66070 [Josh Rosen] Merge remote-tracking branch 'origin/master' into SPARK-4180
06c5c54 [Josh Rosen] Add / improve SparkContext cleanup in streaming BasicOperationsSuite
d0437eb [Josh Rosen] StreamingContext.stop() should stop SparkContext even if StreamingContext has not been started yet.
c4d35a2 [Josh Rosen] Log long form of creation site to aid debugging.
918e878 [Josh Rosen] Document "one SparkContext per JVM" limitation.
afaa7e3 [Josh Rosen] [SPARK-4180] Prevent creations of multiple active SparkContexts.
Author: zsxwing <zsxwing@gmail.com>
Closes#3226 from zsxwing/SPARK-4363 and squashes the following commits:
8109914 [zsxwing] Update the Broadcast example
