[
https://issues.apache.org/jira/browse/HADOOP-2247?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Arun C Murthy updated HADOOP-2247:
----------------------------------
Status: Open (was: Patch Available)
Couple of comments:
1. To kill maps:
bq. 2. (num-fetch-fail-notifications/num-reducers) >= max-allowed, here
max-allowed = 0.5
should be (num-fetch-fail-notifications / *num-currently_running-reducers* ) >=
max-allowed. This is to ensure that long-tails do not hold up the job. For e.g.
if we had a lost TT and a bad map, we will need to wait too long for the last
couple of reduces to finish; and hence the idea is to use
*num-currently_running-reducers*.
For cases where the maps are long-lived and non-trivial the
_max-completion-time_ of the mapper used to gate the notifications to the JT
from the reducer should help.
2. We don't need to maintain a mapping from mapId -> maxRetries, just a global
variable should work i.e. we don't need to customize it per mapId.
3. Please change all hard-coded factors (such as divide-by-two) to final
variables. (I see at least one instance: *minShuffleRunDuration / 2*)
> Mappers fail easily due to repeated failures
> --------------------------------------------
>
> Key: HADOOP-2247
> URL: https://issues.apache.org/jira/browse/HADOOP-2247
> Project: Hadoop
> Issue Type: Bug
> Affects Versions: 0.15.0
> Environment: 1400 Node hadoop cluster
> Reporter: Srikanth Kakani
> Assignee: Amar Kamat
> Priority: Blocker
> Fix For: 0.15.2
>
> Attachments: HADOOP-2220.patch, HADOOP-2220.patch
>
>
> Related to HADOOP-2220, problem introduced in HADOOP-1158
> At this scale hardcoding the number of fetch failures to a static number: in
> this case 3 is never going to work. Although the jobs we are running are
> loading the systems 3 failures can randomly occur within the lifetime of a
> map. Even fetching the data can cause enough load for so many failures to
> occur.
> We believe that number of tasks and size of cluster should be taken into
> account. Based on which we believe that a ratio between total fetch attempts
> and total failed attempts should be taken into consideration.
> Given our experience with a task should be declared "Too many fetch failures"
> based on:
> failures > n /*could be 3*/ && (failures/total attempts) > k% /*could be
> 30-40%*/
> Basically the first factor is to give some headstart to the second factor,
> second factor then takes into account the cluster size and the task size.
> Additionally we could take recency into account, say failures and attempts in
> last one hour. We do not want to make it too small.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
