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https://issues.apache.org/jira/browse/SPARK-17937?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Cody Koeninger updated SPARK-17937:
-----------------------------------
Description:
Possible events for which offsets are needed:
# New partition is discovered
# Offset out of range (aka, data has been lost). It's possible to separate
this into offset too small and offset too large, but I'm not sure it matters
for us.
Possible sources of offsets:
# *Earliest* position in log
# *Latest* position in log
# *Fail* and kill the query
# *Checkpoint* position
# *User specified* per topicpartition
# *Kafka commit log*. Currently unsupported. This means users who want to
migrate from existing kafka jobs need to jump through hoops. Even if we never
want to support it, as soon as we take on SPARK-17815 we need to make sure
Kafka commit log state is clearly documented and handled.
# *Timestamp*. Currently unsupported. This could be supported with old,
inaccurate Kafka time api, or upcoming time index
# *X offsets* before or after latest / earliest position. Currently
unsupported. I think the semantics of this are super unclear by comparison
with timestamp, given that Kafka doesn't have a single range of offsets.
Currently allowed pre-query configuration, all "ORs" are exclusive:
# startingOffsets: *earliest* OR *latest* OR *User specified* json per
topicpartition (SPARK-17812)
# failOnDataLoss: true (which implies *Fail* above) OR false (which implies
*Earliest* above) In general, I see no reason this couldn't specify Latest as
an option.
Possible lifecycle times in which an offset-related event may happen:
# At initial query start
#* New partition: if startingOffsets is *Earliest* or *Latest*, use that. If
startingOffsets is *User specified* perTopicpartition, and the new partition
isn't in the map, *Fail*. Note that this is effectively undistinguishable from
new parititon during query, because partitions may have changed in between
pre-query configuration and query start, but we treat it differently, and users
in this case are SOL
#* Offset out of range on driver: We don't technically have behavior for this
case yet. Could use the value of failOnDataLoss, but it's possible people may
want to know at startup that something was wrong, even if they're ok with
earliest for a during-query out of range
#* Offset out of range on executor: seems like it should be*Fail* or
*Earliest*, based on failOnDataLoss. but it looks like this setting is
currently ignored, and the executor will just fail...
# During query
#* New partition: *Earliest*, only. This seems to be by fiat, I see no reason
this can't be configurable.
#* Offset out of range on driver: this _probably_ doesn't happen, because
we're doing explicit seeks to the latest position
#* Offset out of range on executor: ?
# At query restart
#* New partition: *Checkpoint*, fall back to *Earliest*. Again, no reason this
couldn't be configurable fall back to Latest
#* Offset out of range on driver: this _probably_ doesn't happen, because
we're doing explicit seeks to the specified position
#* Offset out of range on executor: ?
I've probably missed something, chime in.
was:
Possible events for which offsets are needed:
# New partition is discovered
# Offset out of range (aka, data has been lost). It's possible to separate
this into offset too small and offset too large, but I'm not sure it matters
for us.
Possible sources of offsets:
# *Earliest* position in log
# *Latest* position in log
# *Fail* and kill the query
# *Checkpoint* position
# *User specified* per topicpartition
# *Kafka commit log*. Currently unsupported. This means users who want to
migrate from existing kafka jobs need to jump through hoops. Even if we never
want to support it, as soon as we take on SPARK-17815 we need to make sure
Kafka commit log state is clearly documented and handled.
# *Timestamp*. Currently unsupported. This could be supported with old,
inaccurate Kafka time api, or upcoming time index
# *X offsets* before or after latest / earliest position. Currently
unsupported. I think the semantics of this are super unclear by comparison
with timestamp, given that Kafka doesn't have a single range of offsets.
Currently allowed pre-query configuration, all "ORs" are exclusive:
# startingOffsets: *earliest* OR *latest* OR *User specified* json per
topicpartition (SPARK-17812)
# failOnDataLoss: true (which implies *Fail* above) OR false (which implies
*Earliest* above) In general, I see no reason this couldn't specify Latest as
an option.
Possible lifecycle times in which an offset-related event may happen:
# At initial query start
#* New partition: if startingOffsets is *Earliest* or *Latest*, use that. If
startingOffsets is *User specified* perTopicpartition, and the new partition
isn't in the map, *Fail*. Note that this is effectively undistinguishable from
new parititon during query, because partitions may have changed in between
pre-query configuration and query start, but we treat it differently, and users
in this case are SOL
#* Offset out of range on driver: We don't technically have behavior for this
case yet. Could use the value of failOnDataLoss, but it's possible people may
want to know at startup that something was wrong, even if they're ok with
earliest for a during-query out of range
#* Offset out of range on executor: *Fail* or *Earliest*, based on
failOnDataLoss.
# During query
#* New partition: *Earliest*, only. This seems to be by fiat, I see no reason
this can't be configurable.
#* Offset out of range on driver: this _probably_ doesn't happen, because
we're doing explicit seeks to the latest position
#* Offset out of range on executor: *Fail* or *Earliest*, based on
failOnDataLoss
# At query restart
#* New partition: *Checkpoint*, fall back to *Earliest*. Again, no reason this
couldn't be configurable fall back to Latest
#* Offset out of range on driver: this _probably_ doesn't happen, because
we're doing explicit seeks to the specified position
#* Offset out of range on executor: *Fail* or *Earliest*, based on
failOnDataLoss
I've probably missed something, chime in.
> Clarify Kafka offset semantics for Structured Streaming
> -------------------------------------------------------
>
> Key: SPARK-17937
> URL: https://issues.apache.org/jira/browse/SPARK-17937
> Project: Spark
> Issue Type: Sub-task
> Reporter: Cody Koeninger
>
> Possible events for which offsets are needed:
> # New partition is discovered
> # Offset out of range (aka, data has been lost). It's possible to separate
> this into offset too small and offset too large, but I'm not sure it matters
> for us.
> Possible sources of offsets:
> # *Earliest* position in log
> # *Latest* position in log
> # *Fail* and kill the query
> # *Checkpoint* position
> # *User specified* per topicpartition
> # *Kafka commit log*. Currently unsupported. This means users who want to
> migrate from existing kafka jobs need to jump through hoops. Even if we
> never want to support it, as soon as we take on SPARK-17815 we need to make
> sure Kafka commit log state is clearly documented and handled.
> # *Timestamp*. Currently unsupported. This could be supported with old,
> inaccurate Kafka time api, or upcoming time index
> # *X offsets* before or after latest / earliest position. Currently
> unsupported. I think the semantics of this are super unclear by comparison
> with timestamp, given that Kafka doesn't have a single range of offsets.
> Currently allowed pre-query configuration, all "ORs" are exclusive:
> # startingOffsets: *earliest* OR *latest* OR *User specified* json per
> topicpartition (SPARK-17812)
> # failOnDataLoss: true (which implies *Fail* above) OR false (which implies
> *Earliest* above) In general, I see no reason this couldn't specify Latest
> as an option.
> Possible lifecycle times in which an offset-related event may happen:
> # At initial query start
> #* New partition: if startingOffsets is *Earliest* or *Latest*, use that. If
> startingOffsets is *User specified* perTopicpartition, and the new partition
> isn't in the map, *Fail*. Note that this is effectively undistinguishable
> from new parititon during query, because partitions may have changed in
> between pre-query configuration and query start, but we treat it differently,
> and users in this case are SOL
> #* Offset out of range on driver: We don't technically have behavior for this
> case yet. Could use the value of failOnDataLoss, but it's possible people
> may want to know at startup that something was wrong, even if they're ok with
> earliest for a during-query out of range
> #* Offset out of range on executor: seems like it should be*Fail* or
> *Earliest*, based on failOnDataLoss. but it looks like this setting is
> currently ignored, and the executor will just fail...
> # During query
> #* New partition: *Earliest*, only. This seems to be by fiat, I see no
> reason this can't be configurable.
> #* Offset out of range on driver: this _probably_ doesn't happen, because
> we're doing explicit seeks to the latest position
> #* Offset out of range on executor: ?
> # At query restart
> #* New partition: *Checkpoint*, fall back to *Earliest*. Again, no reason
> this couldn't be configurable fall back to Latest
> #* Offset out of range on driver: this _probably_ doesn't happen, because
> we're doing explicit seeks to the specified position
> #* Offset out of range on executor: ?
> I've probably missed something, chime in.
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