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Posted to dev@cassandra.apache.org by Dinesh Joshi <dj...@apache.org> on 2022/02/05 20:59:06 UTC
Re: [DISCUSS] CEP-19: Trie memtable implementation
This is excellent. Thanks for opening up this CEP. It would be great to get some stats around GC allocation rate / memory pressure, read & write latencies, etc. compared to existing implementation.
Dinesh
> On Jan 18, 2022, at 2:13 AM, Branimir Lambov <bl...@apache.org> wrote:
>
> The memtable pluggability API (CEP-11) is per-table to enable memtable selection that suits specific workflows. It also makes full sense to permit per-node configuration, both to be able to modify the configuration to suit heterogeneous deployments better, as well as to test changes for improvements such as this one.
> Recognizing this, the patch comes with a modification to the API <https://github.com/blambov/cassandra/commit/24b558ba2f71a2f040804e28993cc914b31298f5> that defines memtable templates in cassandra.yaml (i.e. per node) and allows the schema to select a template (in addition to being able to specify the full memtable configuration). One could use this e.g. by adding:
> memtable_templates:
> trie:
> class: TrieMemtable
> shards: 16
> skiplist:
> class: SkipListMemtable
> memtable:
> template: skiplist
> (which defines two templates and specifies the default memtable implementation to use) to cassandra.yaml and specifying WITH memtable = {'template' : 'trie'} in the table schema.
>
> I intend to commit this modification with the memtable API (CASSANDRA-17034/CEP-11).
>
> Performance comparisons will be published soon.
>
> Regards,
> Branimir
>
> On Fri, Jan 14, 2022 at 4:15 PM Jeff Jirsa <jjirsa@gmail.com <ma...@gmail.com>> wrote:
> Sounds like a great addition
>
> Can you share some of the details around gc and latency improvements you’ve observed with the list?
>
> Any specific reason the confirmation is through schema vs yaml? Presumably it’s so a user can test per table, but this changes every host in a cluster, so the impact of a bug/regression is much higher.
>
>
>> On Jan 10, 2022, at 1:30 AM, Branimir Lambov <blambov@apache.org <ma...@apache.org>> wrote:
>>
>>
>> We would like to contribute our TrieMemtable to Cassandra.
>>
>> https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-19%3A+Trie+memtable+implementation <https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-19%3A+Trie+memtable+implementation>
>>
>> This is a new memtable solution aimed to replace the legacy implementation, developed with the following objectives:
>> - lowering the on-heap complexity and the ability to store memtable indexing structures off-heap,
>> - leveraging byte order and a trie structure to lower the memory footprint and improve mutation and lookup performance.
>>
>> The new memtable relies on CASSANDRA-6936 to translate to and from byte-ordered representations of types, and CASSANDRA-17034 / CEP-11 to plug into Cassandra. The memtable is built on multiple shards of custom in-memory single-writer multiple-reader tries, whose implementation uses a combination of state-of-the-art and novel features for greater efficiency.
>>
>> The CEP's JIRA ticket (https://issues.apache.org/jira/browse/CASSANDRA-17240 <https://issues.apache.org/jira/browse/CASSANDRA-17240>) contains the initial version of the implementation. In its current form it achieves much better garbage collection latency, significantly bigger data sizes between flushes for the same memory allocation, as well as drastically increased write throughput, and we expect the memory and garbage collection improvements to go much further with upcoming improvements to the solution.
>>
>> I am interested in hearing your thoughts on the proposal.
>>
>> Regards,
>> Branimir
>>
Re: [DISCUSS] CEP-19: Trie memtable implementation
Posted by "C. Scott Andreas" <sc...@paradoxica.net>.
Branimir, thank you for sharing these results.
The numbers are exciting - particularly the UCS test in which compaction keeps up, and your note mentioning 30% larger L0 flushes due to the more compact memory representation.
Great work.
— Scott
> On Feb 7, 2022, at 8:39 AM, Branimir Lambov <bl...@apache.org> wrote:
>
>
> Added some performance results to the ticket: https://issues.apache.org/jira/browse/CASSANDRA-17240
>
> Regards,
> Branimir
>
>> On Sat, Feb 5, 2022 at 10:59 PM Dinesh Joshi <dj...@apache.org> wrote:
>> This is excellent. Thanks for opening up this CEP. It would be great to get some stats around GC allocation rate / memory pressure, read & write latencies, etc. compared to existing implementation.
>>
>> Dinesh
>>
>>> On Jan 18, 2022, at 2:13 AM, Branimir Lambov <bl...@apache.org> wrote:
>>>
>>> The memtable pluggability API (CEP-11) is per-table to enable memtable selection that suits specific workflows. It also makes full sense to permit per-node configuration, both to be able to modify the configuration to suit heterogeneous deployments better, as well as to test changes for improvements such as this one.
>>> Recognizing this, the patch comes with a modification to the API that defines memtable templates in cassandra.yaml (i.e. per node) and allows the schema to select a template (in addition to being able to specify the full memtable configuration). One could use this e.g. by adding:
>>> memtable_templates:
>>> trie:
>>> class: TrieMemtable
>>> shards: 16
>>> skiplist:
>>> class: SkipListMemtable
>>> memtable:
>>> template: skiplist
>>> (which defines two templates and specifies the default memtable implementation to use) to cassandra.yaml and specifying WITH memtable = {'template' : 'trie'} in the table schema.
>>>
>>> I intend to commit this modification with the memtable API (CASSANDRA-17034/CEP-11).
>>>
>>> Performance comparisons will be published soon.
>>>
>>> Regards,
>>> Branimir
>>>
>>>> On Fri, Jan 14, 2022 at 4:15 PM Jeff Jirsa <jj...@gmail.com> wrote:
>>>> Sounds like a great addition
>>>>
>>>> Can you share some of the details around gc and latency improvements you’ve observed with the list?
>>>>
>>>> Any specific reason the confirmation is through schema vs yaml? Presumably it’s so a user can test per table, but this changes every host in a cluster, so the impact of a bug/regression is much higher.
>>>>
>>>>
>>>>>> On Jan 10, 2022, at 1:30 AM, Branimir Lambov <bl...@apache.org> wrote:
>>>>>>
>>>>>
>>>>> We would like to contribute our TrieMemtable to Cassandra.
>>>>>
>>>>> https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-19%3A+Trie+memtable+implementation
>>>>>
>>>>> This is a new memtable solution aimed to replace the legacy implementation, developed with the following objectives:
>>>>> - lowering the on-heap complexity and the ability to store memtable indexing structures off-heap,
>>>>> - leveraging byte order and a trie structure to lower the memory footprint and improve mutation and lookup performance.
>>>>>
>>>>> The new memtable relies on CASSANDRA-6936 to translate to and from byte-ordered representations of types, and CASSANDRA-17034 / CEP-11 to plug into Cassandra. The memtable is built on multiple shards of custom in-memory single-writer multiple-reader tries, whose implementation uses a combination of state-of-the-art and novel features for greater efficiency.
>>>>>
>>>>> The CEP's JIRA ticket (https://issues.apache.org/jira/browse/CASSANDRA-17240) contains the initial version of the implementation. In its current form it achieves much better garbage collection latency, significantly bigger data sizes between flushes for the same memory allocation, as well as drastically increased write throughput, and we expect the memory and garbage collection improvements to go much further with upcoming improvements to the solution.
>>>>>
>>>>> I am interested in hearing your thoughts on the proposal.
>>>>>
>>>>> Regards,
>>>>> Branimir
>>>>>
>>
Re: [DISCUSS] CEP-19: Trie memtable implementation
Posted by "benedict@apache.org" <be...@apache.org>.
FWIW, I think the proposed approach to configuration is fine.
I think selecting a choice for the user should be done simply and deterministically. We should probably default to Trie based memtables for users with a fresh config file, and we can consider changing the default in a later release for those with an old config file that does not specify an implementation.
From: Dinesh Joshi <dj...@apache.org>
Date: Tuesday, 8 February 2022 at 20:21
To: dev@cassandra.apache.org <de...@cassandra.apache.org>
Subject: Re: [DISCUSS] CEP-19: Trie memtable implementation
Thank you for sharing the perf test results.
Going back to the schema vs yaml configuration. I am concerned users may pick the wrong implementation for their use-case. Is there any chance for us to automatically pick a MemTable implementation based on heuristics? Do we foresee users ever picking the existing SkipList implementation over the Trie Given the performance tests, it seems the Trie implementation is the clear winner.
To be clear, I am not suggesting we remove the existing implementation. I am for maintaining a pluggable API for various components.
Dinesh
On Feb 7, 2022, at 8:39 AM, Branimir Lambov <bl...@apache.org>> wrote:
Added some performance results to the ticket: https://issues.apache.org/jira/browse/CASSANDRA-17240
Regards,
Branimir
On Sat, Feb 5, 2022 at 10:59 PM Dinesh Joshi <dj...@apache.org>> wrote:
This is excellent. Thanks for opening up this CEP. It would be great to get some stats around GC allocation rate / memory pressure, read & write latencies, etc. compared to existing implementation.
Dinesh
On Jan 18, 2022, at 2:13 AM, Branimir Lambov <bl...@apache.org>> wrote:
The memtable pluggability API (CEP-11) is per-table to enable memtable selection that suits specific workflows. It also makes full sense to permit per-node configuration, both to be able to modify the configuration to suit heterogeneous deployments better, as well as to test changes for improvements such as this one.
Recognizing this, the patch comes with a modification to the API<https://github.com/blambov/cassandra/commit/24b558ba2f71a2f040804e28993cc914b31298f5> that defines memtable templates in cassandra.yaml (i.e. per node) and allows the schema to select a template (in addition to being able to specify the full memtable configuration). One could use this e.g. by adding:
memtable_templates:
trie:
class: TrieMemtable
shards: 16
skiplist:
class: SkipListMemtable
memtable:
template: skiplist
(which defines two templates and specifies the default memtable implementation to use) to cassandra.yaml and specifying WITH memtable = {'template' : 'trie'} in the table schema.
I intend to commit this modification with the memtable API (CASSANDRA-17034/CEP-11).
Performance comparisons will be published soon.
Regards,
Branimir
On Fri, Jan 14, 2022 at 4:15 PM Jeff Jirsa <jj...@gmail.com>> wrote:
Sounds like a great addition
Can you share some of the details around gc and latency improvements you’ve observed with the list?
Any specific reason the confirmation is through schema vs yaml? Presumably it’s so a user can test per table, but this changes every host in a cluster, so the impact of a bug/regression is much higher.
On Jan 10, 2022, at 1:30 AM, Branimir Lambov <bl...@apache.org>> wrote:
We would like to contribute our TrieMemtable to Cassandra.
https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-19%3A+Trie+memtable+implementation
This is a new memtable solution aimed to replace the legacy implementation, developed with the following objectives:
- lowering the on-heap complexity and the ability to store memtable indexing structures off-heap,
- leveraging byte order and a trie structure to lower the memory footprint and improve mutation and lookup performance.
The new memtable relies on CASSANDRA-6936 to translate to and from byte-ordered representations of types, and CASSANDRA-17034 / CEP-11 to plug into Cassandra. The memtable is built on multiple shards of custom in-memory single-writer multiple-reader tries, whose implementation uses a combination of state-of-the-art and novel features for greater efficiency.
The CEP's JIRA ticket (https://issues.apache.org/jira/browse/CASSANDRA-17240) contains the initial version of the implementation. In its current form it achieves much better garbage collection latency, significantly bigger data sizes between flushes for the same memory allocation, as well as drastically increased write throughput, and we expect the memory and garbage collection improvements to go much further with upcoming improvements to the solution.
I am interested in hearing your thoughts on the proposal.
Regards,
Branimir
Re: [DISCUSS] CEP-19: Trie memtable implementation
Posted by Branimir Lambov <bl...@apache.org>.
Let us continue the configuration discussion in the CEP-11 JIRA (
https://issues.apache.org/jira/browse/CASSANDRA-17034).
Any further comments on the alternate memtable? Are we ready for a vote?
Regards,
Branimir
On Wed, Feb 9, 2022 at 12:13 PM Bowen Song <bo...@bso.ng> wrote:
> TBH, I don't have an opinion on the configuration. I just want to say that
> if at the end we decide the configuration in the YAML should override the
> table schema, I would like to recommend that we specifying a list of
> whitelisted (or blacklisted) "templates" in the YAML file, and the template
> chosen by the table schema is used if it's enabled, otherwise fallback to a
> default template, which could be the first element in the whitelist if
> that's used, or a separate configuration entry if a blacklist is used. The
> list should be optional in the YAML, and an empty list or the absent of it
> means everything is enabled.
>
> Advantage of this:
>
> 1. it doesn't require the operator to configure this, as an empty or
> absent list by default enables all templates and should work fine in most
> cases.
>
> 2. it allows the operator to whitelist / blacklist any template if ever
> needed (e.g. due to a bug), and also allow them to choose a fallback option.
>
> 3. the table schema has priority as long as the chosen template is not
> explicitly disabled by the YAML.
>
> 4. it allows the operator to selectively disable some templates without
> forcing all tables to use the same template specified by the YAML.
>
>
> On 09/02/2022 09:43, benedict@apache.org wrote:
>
> Why not have some default templates that can be specified by the schema
> without touching the yaml, but overridden in the yaml as necessary?
>
>
>
> *From: *Branimir Lambov <bl...@apache.org> <bl...@apache.org>
> *Date: *Wednesday, 9 February 2022 at 09:35
> *To: *dev@cassandra.apache.org <de...@cassandra.apache.org>
> <de...@cassandra.apache.org>
> *Subject: *Re: [DISCUSS] CEP-19: Trie memtable implementation
>
> If I understand this correctly, you prefer _not_ to have an option to give
> the configuration explicitly in the schema. I.e. force the configurations
> ("templates" in current terms) to be specified in the yaml, and only allow
> tables to specify which one to use among them?
>
>
>
> This does sound at least as good to me, and I'll happily change the API.
>
>
>
> Regards,
>
> Branimir
>
>
>
> On Tue, Feb 8, 2022 at 10:40 PM Dinesh Joshi <dj...@apache.org> wrote:
>
> My quick reading of the code suggests that schema will override the
> operator's default preference in the YAML. In the event of a bug in the new
> implementation, there could be situation where the operator might need to
> override this via the YAML.
>
>
>
> On Feb 8, 2022, at 12:29 PM, Jeremiah D Jordan <je...@gmail.com>
> wrote:
>
>
>
> I don’t really see most users touching the default implementation. I
> would expect the main reason someone would change would be
>
> 1. They run into some bug that is only in one of the implementations.
>
> 2. They have persistent memory and so want to use
> https://issues.apache.org/jira/browse/CASSANDRA-13981
>
>
>
> Given that I doubt most people will touch it, I think it is good to give
> advanced operators the ability to have more control over switching to
> things that have new performance characteristics. So I like the idea that
> the proposed configuration approach which allows someone to change to a new
> implementation one node at a time and only for specific tables.
>
>
>
> On Feb 8, 2022, at 2:21 PM, Dinesh Joshi <dj...@apache.org> wrote:
>
>
>
> Thank you for sharing the perf test results.
>
>
>
> Going back to the schema vs yaml configuration. I am concerned users may
> pick the wrong implementation for their use-case. Is there any chance for
> us to automatically pick a MemTable implementation based on heuristics? Do
> we foresee users ever picking the existing SkipList implementation over the
> Trie Given the performance tests, it seems the Trie implementation is the
> clear winner.
>
>
>
> To be clear, I am not suggesting we remove the existing implementation. I
> am for maintaining a pluggable API for various components.
>
>
>
> Dinesh
>
>
>
> On Feb 7, 2022, at 8:39 AM, Branimir Lambov <bl...@apache.org> wrote:
>
>
>
> Added some performance results to the ticket:
> https://issues.apache.org/jira/browse/CASSANDRA-17240
>
>
>
> Regards,
>
> Branimir
>
>
>
> On Sat, Feb 5, 2022 at 10:59 PM Dinesh Joshi <dj...@apache.org> wrote:
>
> This is excellent. Thanks for opening up this CEP. It would be great to
> get some stats around GC allocation rate / memory pressure, read & write
> latencies, etc. compared to existing implementation.
>
>
>
> Dinesh
>
>
>
> On Jan 18, 2022, at 2:13 AM, Branimir Lambov <bl...@apache.org> wrote:
>
>
>
> The memtable pluggability API (CEP-11) is per-table to enable memtable
> selection that suits specific workflows. It also makes full sense to permit
> per-node configuration, both to be able to modify the configuration to suit
> heterogeneous deployments better, as well as to test changes for
> improvements such as this one.
>
> Recognizing this, the patch comes with a modification to the API
> <https://github.com/blambov/cassandra/commit/24b558ba2f71a2f040804e28993cc914b31298f5>
> that defines memtable templates in cassandra.yaml (i.e. per node) and
> allows the schema to select a template (in addition to being able to
> specify the full memtable configuration). One could use this e.g. by adding:
>
> *memtable_templates*:
> *trie*:
> *class*: TrieMemtable
> *shards*: 16
> *skiplist*:
> *class*: SkipListMemtable*memtable*:
> *template*: skiplist
>
> (which defines two templates and specifies the default memtable
> implementation to use) to cassandra.yaml and specifying *WITH memtable =
> {'template' : 'trie'} *in the table schema.
>
>
>
> I intend to commit this modification with the memtable API
> (CASSANDRA-17034/CEP-11).
>
>
>
> Performance comparisons will be published soon.
>
>
>
> Regards,
>
> Branimir
>
>
>
> On Fri, Jan 14, 2022 at 4:15 PM Jeff Jirsa <jj...@gmail.com> wrote:
>
> Sounds like a great addition
>
>
>
> Can you share some of the details around gc and latency improvements
> you’ve observed with the list?
>
>
>
> Any specific reason the confirmation is through schema vs yaml? Presumably
> it’s so a user can test per table, but this changes every host in a
> cluster, so the impact of a bug/regression is much higher.
>
>
>
>
>
> On Jan 10, 2022, at 1:30 AM, Branimir Lambov <bl...@apache.org> wrote:
>
>
>
> We would like to contribute our TrieMemtable to Cassandra.
>
>
>
>
> https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-19%3A+Trie+memtable+implementation
>
>
>
> This is a new memtable solution aimed to replace the legacy
> implementation, developed with the following objectives:
>
> - lowering the on-heap complexity and the ability to store memtable
> indexing structures off-heap,
>
> - leveraging byte order and a trie structure to lower the memory footprint
> and improve mutation and lookup performance.
>
>
>
> The new memtable relies on CASSANDRA-6936 to translate to and from
> byte-ordered representations of types, and CASSANDRA-17034 / CEP-11 to plug
> into Cassandra. The memtable is built on multiple shards of custom
> in-memory single-writer multiple-reader tries, whose implementation uses a
> combination of state-of-the-art and novel features for greater efficiency.
>
>
>
> The CEP's JIRA ticket (
> https://issues.apache.org/jira/browse/CASSANDRA-17240) contains the
> initial version of the implementation. In its current form it achieves much
> better garbage collection latency, significantly bigger data sizes between
> flushes for the same memory allocation, as well as drastically increased
> write throughput, and we expect the memory and garbage collection
> improvements to go much further with upcoming improvements to the solution.
>
>
>
> I am interested in hearing your thoughts on the proposal.
>
>
>
> Regards,
>
> Branimir
>
>
>
>
>
>
>
>
>
>
>
>
Re: [DISCUSS] CEP-19: Trie memtable implementation
Posted by Bowen Song <bo...@bso.ng>.
TBH, I don't have an opinion on the configuration. I just want to say
that if at the end we decide the configuration in the YAML should
override the table schema, I would like to recommend that we specifying
a list of whitelisted (or blacklisted) "templates" in the YAML file, and
the template chosen by the table schema is used if it's enabled,
otherwise fallback to a default template, which could be the first
element in the whitelist if that's used, or a separate configuration
entry if a blacklist is used. The list should be optional in the YAML,
and an empty list or the absent of it means everything is enabled.
Advantage of this:
1. it doesn't require the operator to configure this, as an empty or
absent list by default enables all templates and should work fine in
most cases.
2. it allows the operator to whitelist / blacklist any template if ever
needed (e.g. due to a bug), and also allow them to choose a fallback option.
3. the table schema has priority as long as the chosen template is not
explicitly disabled by the YAML.
4. it allows the operator to selectively disable some templates without
forcing all tables to use the same template specified by the YAML.
On 09/02/2022 09:43, benedict@apache.org wrote:
>
> Why not have some default templates that can be specified by the
> schema without touching the yaml, but overridden in the yaml as necessary?
>
> *From: *Branimir Lambov <bl...@apache.org>
> *Date: *Wednesday, 9 February 2022 at 09:35
> *To: *dev@cassandra.apache.org <de...@cassandra.apache.org>
> *Subject: *Re: [DISCUSS] CEP-19: Trie memtable implementation
>
> If I understand this correctly, you prefer _not_ to have an option to
> give the configuration explicitly in the schema. I.e. force the
> configurations ("templates" in current terms) to be specified in the
> yaml, and only allow tables to specify which one to use among them?
>
> This does sound at least as good to me, and I'll happily change the API.
>
> Regards,
>
> Branimir
>
> On Tue, Feb 8, 2022 at 10:40 PM Dinesh Joshi <dj...@apache.org> wrote:
>
> My quick reading of the code suggests that schema will override
> the operator's default preference in the YAML. In the event of a
> bug in the new implementation, there could be situation where the
> operator might need to override this via the YAML.
>
>
>
> On Feb 8, 2022, at 12:29 PM, Jeremiah D Jordan
> <je...@gmail.com> wrote:
>
> I don’t really see most users touching the default
> implementation. I would expect the main reason someone would
> change would be
>
> 1. They run into some bug that is only in one of the
> implementations.
>
> 2. They have persistent memory and so want to use
> https://issues.apache.org/jira/browse/CASSANDRA-13981
>
> Given that I doubt most people will touch it, I think it is
> good to give advanced operators the ability to have more
> control over switching to things that have new performance
> characteristics. So I like the idea that the proposed
> configuration approach which allows someone to change to a new
> implementation one node at a time and only for specific tables.
>
>
>
> On Feb 8, 2022, at 2:21 PM, Dinesh Joshi
> <dj...@apache.org> wrote:
>
> Thank you for sharing the perf test results.
>
> Going back to the schema vs yaml configuration. I am
> concerned users may pick the wrong implementation for
> their use-case. Is there any chance for us to
> automatically pick a MemTable implementation based on
> heuristics? Do we foresee users ever picking the existing
> SkipList implementation over the Trie Given the
> performance tests, it seems the Trie implementation is the
> clear winner.
>
> To be clear, I am not suggesting we remove the existing
> implementation. I am for maintaining a pluggable API for
> various components.
>
> Dinesh
>
>
>
> On Feb 7, 2022, at 8:39 AM, Branimir Lambov
> <bl...@apache.org> wrote:
>
> Added some performance results to the ticket:
> https://issues.apache.org/jira/browse/CASSANDRA-17240
>
> Regards,
>
> Branimir
>
> On Sat, Feb 5, 2022 at 10:59 PM Dinesh Joshi
> <dj...@apache.org> wrote:
>
> This is excellent. Thanks for opening up this CEP.
> It would be great to get some stats around GC
> allocation rate / memory pressure, read & write
> latencies, etc. compared to existing implementation.
>
> Dinesh
>
>
>
> On Jan 18, 2022, at 2:13 AM, Branimir Lambov
> <bl...@apache.org> wrote:
>
> The memtable pluggability API (CEP-11) is
> per-table to enable memtable selection
> that suits specific workflows. It also makes
> full sense to permit per-node configuration,
> both to be able to modify the configuration to
> suit heterogeneous deployments better, as well
> as to test changes for improvements such as
> this one.
>
> Recognizing this, the patch comes with a
> modification to the API
> <https://github.com/blambov/cassandra/commit/24b558ba2f71a2f040804e28993cc914b31298f5>
> that defines memtable templates in
> cassandra.yaml (i.e. per node) and allows the
> schema to select a template (in addition to
> being able to specify the full memtable
> configuration). One could use this e.g. by adding:
>
> *memtable_templates*:
> *trie*:
> *class*: TrieMemtable
> *shards*: 16
> *skiplist*:
> *class*: SkipListMemtable
> *memtable*:
> *template*: skiplist
>
> (which defines two templates and specifies the
> default memtable implementation to use) to
> cassandra.yaml and specifying *WITH memtable =
> {'template' : 'trie'} *in the table schema.
>
> I intend to commit this modification with the
> memtable API (CASSANDRA-17034/CEP-11).
>
> Performance comparisons will be published soon.
>
> Regards,
>
> Branimir
>
> On Fri, Jan 14, 2022 at 4:15 PM Jeff Jirsa
> <jj...@gmail.com> wrote:
>
> Sounds like a great addition
>
> Can you share some of the details around
> gc and latency improvements you’ve
> observed with the list?
>
> Any specific reason the confirmation is
> through schema vs yaml? Presumably it’s so
> a user can test per table, but this
> changes every host in a cluster, so the
> impact of a bug/regression is much higher.
>
>
>
> On Jan 10, 2022, at 1:30 AM, Branimir
> Lambov <bl...@apache.org> wrote:
>
>
>
> We would like to contribute our
> TrieMemtable to Cassandra.
>
> https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-19%3A+Trie+memtable+implementation
>
> This is a new memtable solution aimed
> to replace the legacy implementation,
> developed with the following objectives:
>
> - lowering the on-heap complexity and
> the ability to store memtable indexing
> structures off-heap,
>
> - leveraging byte order and a trie
> structure to lower the memory
> footprint and improve mutation and
> lookup performance.
>
> The new memtable relies on
> CASSANDRA-6936 to translate to and
> from byte-ordered representations of
> types, and CASSANDRA-17034 / CEP-11 to
> plug into Cassandra. The memtable is
> built on multiple shards of custom
> in-memory single-writer
> multiple-reader tries, whose
> implementation uses a combination of
> state-of-the-art and novel features
> for greater efficiency.
>
> The CEP's JIRA ticket
> (https://issues.apache.org/jira/browse/CASSANDRA-17240)
> contains the initial version of the
> implementation. In its current form it
> achieves much better garbage
> collection latency, significantly
> bigger data sizes between flushes for
> the same memory allocation, as well as
> drastically increased write
> throughput, and we expect the memory
> and garbage collection improvements to
> go much further with upcoming
> improvements to the solution.
>
> I am interested in hearing your
> thoughts on the proposal.
>
> Regards,
>
> Branimir
>
Re: [DISCUSS] CEP-19: Trie memtable implementation
Posted by "benedict@apache.org" <be...@apache.org>.
Why not have some default templates that can be specified by the schema without touching the yaml, but overridden in the yaml as necessary?
From: Branimir Lambov <bl...@apache.org>
Date: Wednesday, 9 February 2022 at 09:35
To: dev@cassandra.apache.org <de...@cassandra.apache.org>
Subject: Re: [DISCUSS] CEP-19: Trie memtable implementation
If I understand this correctly, you prefer _not_ to have an option to give the configuration explicitly in the schema. I.e. force the configurations ("templates" in current terms) to be specified in the yaml, and only allow tables to specify which one to use among them?
This does sound at least as good to me, and I'll happily change the API.
Regards,
Branimir
On Tue, Feb 8, 2022 at 10:40 PM Dinesh Joshi <dj...@apache.org>> wrote:
My quick reading of the code suggests that schema will override the operator's default preference in the YAML. In the event of a bug in the new implementation, there could be situation where the operator might need to override this via the YAML.
On Feb 8, 2022, at 12:29 PM, Jeremiah D Jordan <je...@gmail.com>> wrote:
I don’t really see most users touching the default implementation. I would expect the main reason someone would change would be
1. They run into some bug that is only in one of the implementations.
2. They have persistent memory and so want to use https://issues.apache.org/jira/browse/CASSANDRA-13981
Given that I doubt most people will touch it, I think it is good to give advanced operators the ability to have more control over switching to things that have new performance characteristics. So I like the idea that the proposed configuration approach which allows someone to change to a new implementation one node at a time and only for specific tables.
On Feb 8, 2022, at 2:21 PM, Dinesh Joshi <dj...@apache.org>> wrote:
Thank you for sharing the perf test results.
Going back to the schema vs yaml configuration. I am concerned users may pick the wrong implementation for their use-case. Is there any chance for us to automatically pick a MemTable implementation based on heuristics? Do we foresee users ever picking the existing SkipList implementation over the Trie Given the performance tests, it seems the Trie implementation is the clear winner.
To be clear, I am not suggesting we remove the existing implementation. I am for maintaining a pluggable API for various components.
Dinesh
On Feb 7, 2022, at 8:39 AM, Branimir Lambov <bl...@apache.org>> wrote:
Added some performance results to the ticket: https://issues.apache.org/jira/browse/CASSANDRA-17240
Regards,
Branimir
On Sat, Feb 5, 2022 at 10:59 PM Dinesh Joshi <dj...@apache.org>> wrote:
This is excellent. Thanks for opening up this CEP. It would be great to get some stats around GC allocation rate / memory pressure, read & write latencies, etc. compared to existing implementation.
Dinesh
On Jan 18, 2022, at 2:13 AM, Branimir Lambov <bl...@apache.org>> wrote:
The memtable pluggability API (CEP-11) is per-table to enable memtable selection that suits specific workflows. It also makes full sense to permit per-node configuration, both to be able to modify the configuration to suit heterogeneous deployments better, as well as to test changes for improvements such as this one.
Recognizing this, the patch comes with a modification to the API<https://github.com/blambov/cassandra/commit/24b558ba2f71a2f040804e28993cc914b31298f5> that defines memtable templates in cassandra.yaml (i.e. per node) and allows the schema to select a template (in addition to being able to specify the full memtable configuration). One could use this e.g. by adding:
memtable_templates:
trie:
class: TrieMemtable
shards: 16
skiplist:
class: SkipListMemtable
memtable:
template: skiplist
(which defines two templates and specifies the default memtable implementation to use) to cassandra.yaml and specifying WITH memtable = {'template' : 'trie'} in the table schema.
I intend to commit this modification with the memtable API (CASSANDRA-17034/CEP-11).
Performance comparisons will be published soon.
Regards,
Branimir
On Fri, Jan 14, 2022 at 4:15 PM Jeff Jirsa <jj...@gmail.com>> wrote:
Sounds like a great addition
Can you share some of the details around gc and latency improvements you’ve observed with the list?
Any specific reason the confirmation is through schema vs yaml? Presumably it’s so a user can test per table, but this changes every host in a cluster, so the impact of a bug/regression is much higher.
On Jan 10, 2022, at 1:30 AM, Branimir Lambov <bl...@apache.org>> wrote:
We would like to contribute our TrieMemtable to Cassandra.
https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-19%3A+Trie+memtable+implementation
This is a new memtable solution aimed to replace the legacy implementation, developed with the following objectives:
- lowering the on-heap complexity and the ability to store memtable indexing structures off-heap,
- leveraging byte order and a trie structure to lower the memory footprint and improve mutation and lookup performance.
The new memtable relies on CASSANDRA-6936 to translate to and from byte-ordered representations of types, and CASSANDRA-17034 / CEP-11 to plug into Cassandra. The memtable is built on multiple shards of custom in-memory single-writer multiple-reader tries, whose implementation uses a combination of state-of-the-art and novel features for greater efficiency.
The CEP's JIRA ticket (https://issues.apache.org/jira/browse/CASSANDRA-17240) contains the initial version of the implementation. In its current form it achieves much better garbage collection latency, significantly bigger data sizes between flushes for the same memory allocation, as well as drastically increased write throughput, and we expect the memory and garbage collection improvements to go much further with upcoming improvements to the solution.
I am interested in hearing your thoughts on the proposal.
Regards,
Branimir
Re: [DISCUSS] CEP-19: Trie memtable implementation
Posted by Branimir Lambov <bl...@apache.org>.
If I understand this correctly, you prefer _not_ to have an option to give
the configuration explicitly in the schema. I.e. force the configurations
("templates" in current terms) to be specified in the yaml, and only allow
tables to specify which one to use among them?
This does sound at least as good to me, and I'll happily change the API.
Regards,
Branimir
On Tue, Feb 8, 2022 at 10:40 PM Dinesh Joshi <dj...@apache.org> wrote:
> My quick reading of the code suggests that schema will override the
> operator's default preference in the YAML. In the event of a bug in the new
> implementation, there could be situation where the operator might need to
> override this via the YAML.
>
> On Feb 8, 2022, at 12:29 PM, Jeremiah D Jordan <je...@gmail.com>
> wrote:
>
> I don’t really see most users touching the default implementation. I
> would expect the main reason someone would change would be
> 1. They run into some bug that is only in one of the implementations.
> 2. They have persistent memory and so want to use
> https://issues.apache.org/jira/browse/CASSANDRA-13981
>
> Given that I doubt most people will touch it, I think it is good to give
> advanced operators the ability to have more control over switching to
> things that have new performance characteristics. So I like the idea that
> the proposed configuration approach which allows someone to change to a new
> implementation one node at a time and only for specific tables.
>
> On Feb 8, 2022, at 2:21 PM, Dinesh Joshi <dj...@apache.org> wrote:
>
> Thank you for sharing the perf test results.
>
> Going back to the schema vs yaml configuration. I am concerned users may
> pick the wrong implementation for their use-case. Is there any chance for
> us to automatically pick a MemTable implementation based on heuristics? Do
> we foresee users ever picking the existing SkipList implementation over the
> Trie Given the performance tests, it seems the Trie implementation is the
> clear winner.
>
> To be clear, I am not suggesting we remove the existing implementation. I
> am for maintaining a pluggable API for various components.
>
> Dinesh
>
> On Feb 7, 2022, at 8:39 AM, Branimir Lambov <bl...@apache.org> wrote:
>
> Added some performance results to the ticket:
> https://issues.apache.org/jira/browse/CASSANDRA-17240
>
> Regards,
> Branimir
>
> On Sat, Feb 5, 2022 at 10:59 PM Dinesh Joshi <dj...@apache.org> wrote:
>
>> This is excellent. Thanks for opening up this CEP. It would be great to
>> get some stats around GC allocation rate / memory pressure, read & write
>> latencies, etc. compared to existing implementation.
>>
>> Dinesh
>>
>> On Jan 18, 2022, at 2:13 AM, Branimir Lambov <bl...@apache.org> wrote:
>>
>> The memtable pluggability API (CEP-11) is per-table to enable memtable
>> selection that suits specific workflows. It also makes full sense to permit
>> per-node configuration, both to be able to modify the configuration to suit
>> heterogeneous deployments better, as well as to test changes for
>> improvements such as this one.
>> Recognizing this, the patch comes with a modification to the API
>> <https://github.com/blambov/cassandra/commit/24b558ba2f71a2f040804e28993cc914b31298f5>
>> that defines memtable templates in cassandra.yaml (i.e. per node) and
>> allows the schema to select a template (in addition to being able to
>> specify the full memtable configuration). One could use this e.g. by adding:
>>
>> memtable_templates:
>> trie:
>> class: TrieMemtable
>> shards: 16
>> skiplist:
>> class: SkipListMemtable
>> memtable:
>> template: skiplist
>>
>> (which defines two templates and specifies the default memtable
>> implementation to use) to cassandra.yaml and specifying WITH memtable =
>> {'template' : 'trie'} in the table schema.
>>
>> I intend to commit this modification with the memtable API
>> (CASSANDRA-17034/CEP-11).
>>
>> Performance comparisons will be published soon.
>>
>> Regards,
>> Branimir
>>
>> On Fri, Jan 14, 2022 at 4:15 PM Jeff Jirsa <jj...@gmail.com> wrote:
>>
>>> Sounds like a great addition
>>>
>>> Can you share some of the details around gc and latency improvements
>>> you’ve observed with the list?
>>>
>>> Any specific reason the confirmation is through schema vs yaml?
>>> Presumably it’s so a user can test per table, but this changes every host
>>> in a cluster, so the impact of a bug/regression is much higher.
>>>
>>>
>>> On Jan 10, 2022, at 1:30 AM, Branimir Lambov <bl...@apache.org> wrote:
>>>
>>>
>>> We would like to contribute our TrieMemtable to Cassandra.
>>>
>>>
>>> https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-19%3A+Trie+memtable+implementation
>>>
>>> This is a new memtable solution aimed to replace the legacy
>>> implementation, developed with the following objectives:
>>> - lowering the on-heap complexity and the ability to store memtable
>>> indexing structures off-heap,
>>> - leveraging byte order and a trie structure to lower the memory
>>> footprint and improve mutation and lookup performance.
>>>
>>> The new memtable relies on CASSANDRA-6936 to translate to and from
>>> byte-ordered representations of types, and CASSANDRA-17034 / CEP-11 to plug
>>> into Cassandra. The memtable is built on multiple shards of custom
>>> in-memory single-writer multiple-reader tries, whose implementation uses a
>>> combination of state-of-the-art and novel features for greater efficiency.
>>>
>>> The CEP's JIRA ticket (
>>> https://issues.apache.org/jira/browse/CASSANDRA-17240) contains the
>>> initial version of the implementation. In its current form it achieves much
>>> better garbage collection latency, significantly bigger data sizes between
>>> flushes for the same memory allocation, as well as drastically increased
>>> write throughput, and we expect the memory and garbage collection
>>> improvements to go much further with upcoming improvements to the solution.
>>>
>>> I am interested in hearing your thoughts on the proposal.
>>>
>>> Regards,
>>> Branimir
>>>
>>>
>>
>
>
>
Re: [DISCUSS] CEP-19: Trie memtable implementation
Posted by Dinesh Joshi <dj...@apache.org>.
My quick reading of the code suggests that schema will override the operator's default preference in the YAML. In the event of a bug in the new implementation, there could be situation where the operator might need to override this via the YAML.
> On Feb 8, 2022, at 12:29 PM, Jeremiah D Jordan <je...@gmail.com> wrote:
>
> I don’t really see most users touching the default implementation. I would expect the main reason someone would change would be
> 1. They run into some bug that is only in one of the implementations.
> 2. They have persistent memory and so want to use https://issues.apache.org/jira/browse/CASSANDRA-13981 <https://issues.apache.org/jira/browse/CASSANDRA-13981>
>
> Given that I doubt most people will touch it, I think it is good to give advanced operators the ability to have more control over switching to things that have new performance characteristics. So I like the idea that the proposed configuration approach which allows someone to change to a new implementation one node at a time and only for specific tables.
>
>> On Feb 8, 2022, at 2:21 PM, Dinesh Joshi <djoshi@apache.org <ma...@apache.org>> wrote:
>>
>> Thank you for sharing the perf test results.
>>
>> Going back to the schema vs yaml configuration. I am concerned users may pick the wrong implementation for their use-case. Is there any chance for us to automatically pick a MemTable implementation based on heuristics? Do we foresee users ever picking the existing SkipList implementation over the Trie Given the performance tests, it seems the Trie implementation is the clear winner.
>>
>> To be clear, I am not suggesting we remove the existing implementation. I am for maintaining a pluggable API for various components.
>>
>> Dinesh
>>
>>> On Feb 7, 2022, at 8:39 AM, Branimir Lambov <blambov@apache.org <ma...@apache.org>> wrote:
>>>
>>> Added some performance results to the ticket: https://issues.apache.org/jira/browse/CASSANDRA-17240 <https://issues.apache.org/jira/browse/CASSANDRA-17240>
>>>
>>> Regards,
>>> Branimir
>>>
>>> On Sat, Feb 5, 2022 at 10:59 PM Dinesh Joshi <djoshi@apache.org <ma...@apache.org>> wrote:
>>> This is excellent. Thanks for opening up this CEP. It would be great to get some stats around GC allocation rate / memory pressure, read & write latencies, etc. compared to existing implementation.
>>>
>>> Dinesh
>>>
>>>> On Jan 18, 2022, at 2:13 AM, Branimir Lambov <blambov@apache.org <ma...@apache.org>> wrote:
>>>>
>>>> The memtable pluggability API (CEP-11) is per-table to enable memtable selection that suits specific workflows. It also makes full sense to permit per-node configuration, both to be able to modify the configuration to suit heterogeneous deployments better, as well as to test changes for improvements such as this one.
>>>> Recognizing this, the patch comes with a modification to the API <https://github.com/blambov/cassandra/commit/24b558ba2f71a2f040804e28993cc914b31298f5> that defines memtable templates in cassandra.yaml (i.e. per node) and allows the schema to select a template (in addition to being able to specify the full memtable configuration). One could use this e.g. by adding:
>>>> memtable_templates:
>>>> trie:
>>>> class: TrieMemtable
>>>> shards: 16
>>>> skiplist:
>>>> class: SkipListMemtable
>>>> memtable:
>>>> template: skiplist
>>>> (which defines two templates and specifies the default memtable implementation to use) to cassandra.yaml and specifying WITH memtable = {'template' : 'trie'} in the table schema.
>>>>
>>>> I intend to commit this modification with the memtable API (CASSANDRA-17034/CEP-11).
>>>>
>>>> Performance comparisons will be published soon.
>>>>
>>>> Regards,
>>>> Branimir
>>>>
>>>> On Fri, Jan 14, 2022 at 4:15 PM Jeff Jirsa <jjirsa@gmail.com <ma...@gmail.com>> wrote:
>>>> Sounds like a great addition
>>>>
>>>> Can you share some of the details around gc and latency improvements you’ve observed with the list?
>>>>
>>>> Any specific reason the confirmation is through schema vs yaml? Presumably it’s so a user can test per table, but this changes every host in a cluster, so the impact of a bug/regression is much higher.
>>>>
>>>>
>>>>> On Jan 10, 2022, at 1:30 AM, Branimir Lambov <blambov@apache.org <ma...@apache.org>> wrote:
>>>>>
>>>>>
>>>>> We would like to contribute our TrieMemtable to Cassandra.
>>>>>
>>>>> https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-19%3A+Trie+memtable+implementation <https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-19%3A+Trie+memtable+implementation>
>>>>>
>>>>> This is a new memtable solution aimed to replace the legacy implementation, developed with the following objectives:
>>>>> - lowering the on-heap complexity and the ability to store memtable indexing structures off-heap,
>>>>> - leveraging byte order and a trie structure to lower the memory footprint and improve mutation and lookup performance.
>>>>>
>>>>> The new memtable relies on CASSANDRA-6936 to translate to and from byte-ordered representations of types, and CASSANDRA-17034 / CEP-11 to plug into Cassandra. The memtable is built on multiple shards of custom in-memory single-writer multiple-reader tries, whose implementation uses a combination of state-of-the-art and novel features for greater efficiency.
>>>>>
>>>>> The CEP's JIRA ticket (https://issues.apache.org/jira/browse/CASSANDRA-17240 <https://issues.apache.org/jira/browse/CASSANDRA-17240>) contains the initial version of the implementation. In its current form it achieves much better garbage collection latency, significantly bigger data sizes between flushes for the same memory allocation, as well as drastically increased write throughput, and we expect the memory and garbage collection improvements to go much further with upcoming improvements to the solution.
>>>>>
>>>>> I am interested in hearing your thoughts on the proposal.
>>>>>
>>>>> Regards,
>>>>> Branimir
>>>>>
>>>
>>
>
Re: [DISCUSS] CEP-19: Trie memtable implementation
Posted by Jeremiah D Jordan <je...@gmail.com>.
I don’t really see most users touching the default implementation. I would expect the main reason someone would change would be
1. They run into some bug that is only in one of the implementations.
2. They have persistent memory and so want to use https://issues.apache.org/jira/browse/CASSANDRA-13981 <https://issues.apache.org/jira/browse/CASSANDRA-13981>
Given that I doubt most people will touch it, I think it is good to give advanced operators the ability to have more control over switching to things that have new performance characteristics. So I like the idea that the proposed configuration approach which allows someone to change to a new implementation one node at a time and only for specific tables.
> On Feb 8, 2022, at 2:21 PM, Dinesh Joshi <dj...@apache.org> wrote:
>
> Thank you for sharing the perf test results.
>
> Going back to the schema vs yaml configuration. I am concerned users may pick the wrong implementation for their use-case. Is there any chance for us to automatically pick a MemTable implementation based on heuristics? Do we foresee users ever picking the existing SkipList implementation over the Trie Given the performance tests, it seems the Trie implementation is the clear winner.
>
> To be clear, I am not suggesting we remove the existing implementation. I am for maintaining a pluggable API for various components.
>
> Dinesh
>
>> On Feb 7, 2022, at 8:39 AM, Branimir Lambov <blambov@apache.org <ma...@apache.org>> wrote:
>>
>> Added some performance results to the ticket: https://issues.apache.org/jira/browse/CASSANDRA-17240 <https://issues.apache.org/jira/browse/CASSANDRA-17240>
>>
>> Regards,
>> Branimir
>>
>> On Sat, Feb 5, 2022 at 10:59 PM Dinesh Joshi <djoshi@apache.org <ma...@apache.org>> wrote:
>> This is excellent. Thanks for opening up this CEP. It would be great to get some stats around GC allocation rate / memory pressure, read & write latencies, etc. compared to existing implementation.
>>
>> Dinesh
>>
>>> On Jan 18, 2022, at 2:13 AM, Branimir Lambov <blambov@apache.org <ma...@apache.org>> wrote:
>>>
>>> The memtable pluggability API (CEP-11) is per-table to enable memtable selection that suits specific workflows. It also makes full sense to permit per-node configuration, both to be able to modify the configuration to suit heterogeneous deployments better, as well as to test changes for improvements such as this one.
>>> Recognizing this, the patch comes with a modification to the API <https://github.com/blambov/cassandra/commit/24b558ba2f71a2f040804e28993cc914b31298f5> that defines memtable templates in cassandra.yaml (i.e. per node) and allows the schema to select a template (in addition to being able to specify the full memtable configuration). One could use this e.g. by adding:
>>> memtable_templates:
>>> trie:
>>> class: TrieMemtable
>>> shards: 16
>>> skiplist:
>>> class: SkipListMemtable
>>> memtable:
>>> template: skiplist
>>> (which defines two templates and specifies the default memtable implementation to use) to cassandra.yaml and specifying WITH memtable = {'template' : 'trie'} in the table schema.
>>>
>>> I intend to commit this modification with the memtable API (CASSANDRA-17034/CEP-11).
>>>
>>> Performance comparisons will be published soon.
>>>
>>> Regards,
>>> Branimir
>>>
>>> On Fri, Jan 14, 2022 at 4:15 PM Jeff Jirsa <jjirsa@gmail.com <ma...@gmail.com>> wrote:
>>> Sounds like a great addition
>>>
>>> Can you share some of the details around gc and latency improvements you’ve observed with the list?
>>>
>>> Any specific reason the confirmation is through schema vs yaml? Presumably it’s so a user can test per table, but this changes every host in a cluster, so the impact of a bug/regression is much higher.
>>>
>>>
>>>> On Jan 10, 2022, at 1:30 AM, Branimir Lambov <blambov@apache.org <ma...@apache.org>> wrote:
>>>>
>>>>
>>>> We would like to contribute our TrieMemtable to Cassandra.
>>>>
>>>> https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-19%3A+Trie+memtable+implementation <https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-19%3A+Trie+memtable+implementation>
>>>>
>>>> This is a new memtable solution aimed to replace the legacy implementation, developed with the following objectives:
>>>> - lowering the on-heap complexity and the ability to store memtable indexing structures off-heap,
>>>> - leveraging byte order and a trie structure to lower the memory footprint and improve mutation and lookup performance.
>>>>
>>>> The new memtable relies on CASSANDRA-6936 to translate to and from byte-ordered representations of types, and CASSANDRA-17034 / CEP-11 to plug into Cassandra. The memtable is built on multiple shards of custom in-memory single-writer multiple-reader tries, whose implementation uses a combination of state-of-the-art and novel features for greater efficiency.
>>>>
>>>> The CEP's JIRA ticket (https://issues.apache.org/jira/browse/CASSANDRA-17240 <https://issues.apache.org/jira/browse/CASSANDRA-17240>) contains the initial version of the implementation. In its current form it achieves much better garbage collection latency, significantly bigger data sizes between flushes for the same memory allocation, as well as drastically increased write throughput, and we expect the memory and garbage collection improvements to go much further with upcoming improvements to the solution.
>>>>
>>>> I am interested in hearing your thoughts on the proposal.
>>>>
>>>> Regards,
>>>> Branimir
>>>>
>>
>
Re: [DISCUSS] CEP-19: Trie memtable implementation
Posted by Dinesh Joshi <dj...@apache.org>.
Thank you for sharing the perf test results.
Going back to the schema vs yaml configuration. I am concerned users may pick the wrong implementation for their use-case. Is there any chance for us to automatically pick a MemTable implementation based on heuristics? Do we foresee users ever picking the existing SkipList implementation over the Trie Given the performance tests, it seems the Trie implementation is the clear winner.
To be clear, I am not suggesting we remove the existing implementation. I am for maintaining a pluggable API for various components.
Dinesh
> On Feb 7, 2022, at 8:39 AM, Branimir Lambov <bl...@apache.org> wrote:
>
> Added some performance results to the ticket: https://issues.apache.org/jira/browse/CASSANDRA-17240 <https://issues.apache.org/jira/browse/CASSANDRA-17240>
>
> Regards,
> Branimir
>
> On Sat, Feb 5, 2022 at 10:59 PM Dinesh Joshi <djoshi@apache.org <ma...@apache.org>> wrote:
> This is excellent. Thanks for opening up this CEP. It would be great to get some stats around GC allocation rate / memory pressure, read & write latencies, etc. compared to existing implementation.
>
> Dinesh
>
>> On Jan 18, 2022, at 2:13 AM, Branimir Lambov <blambov@apache.org <ma...@apache.org>> wrote:
>>
>> The memtable pluggability API (CEP-11) is per-table to enable memtable selection that suits specific workflows. It also makes full sense to permit per-node configuration, both to be able to modify the configuration to suit heterogeneous deployments better, as well as to test changes for improvements such as this one.
>> Recognizing this, the patch comes with a modification to the API <https://github.com/blambov/cassandra/commit/24b558ba2f71a2f040804e28993cc914b31298f5> that defines memtable templates in cassandra.yaml (i.e. per node) and allows the schema to select a template (in addition to being able to specify the full memtable configuration). One could use this e.g. by adding:
>> memtable_templates:
>> trie:
>> class: TrieMemtable
>> shards: 16
>> skiplist:
>> class: SkipListMemtable
>> memtable:
>> template: skiplist
>> (which defines two templates and specifies the default memtable implementation to use) to cassandra.yaml and specifying WITH memtable = {'template' : 'trie'} in the table schema.
>>
>> I intend to commit this modification with the memtable API (CASSANDRA-17034/CEP-11).
>>
>> Performance comparisons will be published soon.
>>
>> Regards,
>> Branimir
>>
>> On Fri, Jan 14, 2022 at 4:15 PM Jeff Jirsa <jjirsa@gmail.com <ma...@gmail.com>> wrote:
>> Sounds like a great addition
>>
>> Can you share some of the details around gc and latency improvements you’ve observed with the list?
>>
>> Any specific reason the confirmation is through schema vs yaml? Presumably it’s so a user can test per table, but this changes every host in a cluster, so the impact of a bug/regression is much higher.
>>
>>
>>> On Jan 10, 2022, at 1:30 AM, Branimir Lambov <blambov@apache.org <ma...@apache.org>> wrote:
>>>
>>>
>>> We would like to contribute our TrieMemtable to Cassandra.
>>>
>>> https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-19%3A+Trie+memtable+implementation <https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-19%3A+Trie+memtable+implementation>
>>>
>>> This is a new memtable solution aimed to replace the legacy implementation, developed with the following objectives:
>>> - lowering the on-heap complexity and the ability to store memtable indexing structures off-heap,
>>> - leveraging byte order and a trie structure to lower the memory footprint and improve mutation and lookup performance.
>>>
>>> The new memtable relies on CASSANDRA-6936 to translate to and from byte-ordered representations of types, and CASSANDRA-17034 / CEP-11 to plug into Cassandra. The memtable is built on multiple shards of custom in-memory single-writer multiple-reader tries, whose implementation uses a combination of state-of-the-art and novel features for greater efficiency.
>>>
>>> The CEP's JIRA ticket (https://issues.apache.org/jira/browse/CASSANDRA-17240 <https://issues.apache.org/jira/browse/CASSANDRA-17240>) contains the initial version of the implementation. In its current form it achieves much better garbage collection latency, significantly bigger data sizes between flushes for the same memory allocation, as well as drastically increased write throughput, and we expect the memory and garbage collection improvements to go much further with upcoming improvements to the solution.
>>>
>>> I am interested in hearing your thoughts on the proposal.
>>>
>>> Regards,
>>> Branimir
>>>
>
Re: [DISCUSS] CEP-19: Trie memtable implementation
Posted by Branimir Lambov <bl...@apache.org>.
Added some performance results to the ticket:
https://issues.apache.org/jira/browse/CASSANDRA-17240
Regards,
Branimir
On Sat, Feb 5, 2022 at 10:59 PM Dinesh Joshi <dj...@apache.org> wrote:
> This is excellent. Thanks for opening up this CEP. It would be great to
> get some stats around GC allocation rate / memory pressure, read & write
> latencies, etc. compared to existing implementation.
>
> Dinesh
>
> On Jan 18, 2022, at 2:13 AM, Branimir Lambov <bl...@apache.org> wrote:
>
> The memtable pluggability API (CEP-11) is per-table to enable memtable
> selection that suits specific workflows. It also makes full sense to permit
> per-node configuration, both to be able to modify the configuration to suit
> heterogeneous deployments better, as well as to test changes for
> improvements such as this one.
> Recognizing this, the patch comes with a modification to the API
> <https://github.com/blambov/cassandra/commit/24b558ba2f71a2f040804e28993cc914b31298f5>
> that defines memtable templates in cassandra.yaml (i.e. per node) and
> allows the schema to select a template (in addition to being able to
> specify the full memtable configuration). One could use this e.g. by adding:
>
> memtable_templates:
> trie:
> class: TrieMemtable
> shards: 16
> skiplist:
> class: SkipListMemtable
> memtable:
> template: skiplist
>
> (which defines two templates and specifies the default memtable
> implementation to use) to cassandra.yaml and specifying WITH memtable =
> {'template' : 'trie'} in the table schema.
>
> I intend to commit this modification with the memtable API
> (CASSANDRA-17034/CEP-11).
>
> Performance comparisons will be published soon.
>
> Regards,
> Branimir
>
> On Fri, Jan 14, 2022 at 4:15 PM Jeff Jirsa <jj...@gmail.com> wrote:
>
>> Sounds like a great addition
>>
>> Can you share some of the details around gc and latency improvements
>> you’ve observed with the list?
>>
>> Any specific reason the confirmation is through schema vs yaml?
>> Presumably it’s so a user can test per table, but this changes every host
>> in a cluster, so the impact of a bug/regression is much higher.
>>
>>
>> On Jan 10, 2022, at 1:30 AM, Branimir Lambov <bl...@apache.org> wrote:
>>
>>
>> We would like to contribute our TrieMemtable to Cassandra.
>>
>>
>> https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-19%3A+Trie+memtable+implementation
>>
>> This is a new memtable solution aimed to replace the legacy
>> implementation, developed with the following objectives:
>> - lowering the on-heap complexity and the ability to store memtable
>> indexing structures off-heap,
>> - leveraging byte order and a trie structure to lower the memory
>> footprint and improve mutation and lookup performance.
>>
>> The new memtable relies on CASSANDRA-6936 to translate to and from
>> byte-ordered representations of types, and CASSANDRA-17034 / CEP-11 to plug
>> into Cassandra. The memtable is built on multiple shards of custom
>> in-memory single-writer multiple-reader tries, whose implementation uses a
>> combination of state-of-the-art and novel features for greater efficiency.
>>
>> The CEP's JIRA ticket (
>> https://issues.apache.org/jira/browse/CASSANDRA-17240) contains the
>> initial version of the implementation. In its current form it achieves much
>> better garbage collection latency, significantly bigger data sizes between
>> flushes for the same memory allocation, as well as drastically increased
>> write throughput, and we expect the memory and garbage collection
>> improvements to go much further with upcoming improvements to the solution.
>>
>> I am interested in hearing your thoughts on the proposal.
>>
>> Regards,
>> Branimir
>>
>>
>