[jira] [Updated] (CASSANDRA-8831) Create a system table to expose prepared statements
[
https://issues.apache.org/jira/browse/CASSANDRA-8831?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Robert Stupp updated CASSANDRA-8831:
Resolution: Fixed
Fix Version/s: (was: 3.x)
3.10
Status: Resolved (was: Patch Available)
Thanks!
Committed with addition to NEWS.txt as
[997cb663e8c8f164873515f81bb779e435aead6d|https://github.com/apache/cassandra/commit/997cb663e8c8f164873515f81bb779e435aead6d]
to [trunk|https://github.com/apache/cassandra/tree/trunk]
> Create a system table to expose prepared statements
> ---
>
> Key: CASSANDRA-8831
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8831
> Project: Cassandra
> Issue Type: Improvement
>Reporter: Sylvain Lebresne
>Assignee: Robert Stupp
> Labels: client-impacting, docs-impacting
> Fix For: 3.10
>
>
> Because drivers abstract from users the handling of up/down nodes, they have
> to deal with the fact that when a node is restarted (or join), it won't know
> any prepared statement. Drivers could somewhat ignore that problem and wait
> for a query to return an error (that the statement is unknown by the node) to
> re-prepare the query on that node, but it's relatively inefficient because
> every time a node comes back up, you'll get bad latency spikes due to some
> queries first failing, then being re-prepared and then only being executed.
> So instead, drivers (at least the java driver but I believe others do as
> well) pro-actively re-prepare statements when a node comes up. It solves the
> latency problem, but currently every driver instance blindly re-prepare all
> statements, meaning that in a large cluster with many clients there is a lot
> of duplication of work (it would be enough for a single client to prepare the
> statements) and a bigger than necessary load on the node that started.
> An idea to solve this it to have a (cheap) way for clients to check if some
> statements are prepared on the node. There is different options to provide
> that but what I'd suggest is to add a system table to expose the (cached)
> prepared statements because:
> # it's reasonably straightforward to implement: we just add a line to the
> table when a statement is prepared and remove it when it's evicted (we
> already have eviction listeners). We'd also truncate the table on startup but
> that's easy enough). We can even switch it to a "virtual table" if/when
> CASSANDRA-7622 lands but it's trivial to do with a normal table in the
> meantime.
> # it doesn't require a change to the protocol or something like that. It
> could even be done in 2.1 if we wish to.
> # exposing prepared statements feels like a genuinely useful information to
> have (outside of the problem exposed here that is), if only for
> debugging/educational purposes.
> The exposed table could look something like:
> {noformat}
> CREATE TABLE system.prepared_statements (
>keyspace_name text,
>table_name text,
>prepared_id blob,
>query_string text,
>PRIMARY KEY (keyspace_name, table_name, prepared_id)
> )
> {noformat}
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[jira] [Updated] (CASSANDRA-8831) Create a system table to expose prepared statements
[
https://issues.apache.org/jira/browse/CASSANDRA-8831?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Robert Stupp updated CASSANDRA-8831:
Status: Patch Available (was: Open)
> Create a system table to expose prepared statements
> ---
>
> Key: CASSANDRA-8831
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8831
> Project: Cassandra
> Issue Type: Improvement
>Reporter: Sylvain Lebresne
>Assignee: Robert Stupp
> Labels: client-impacting, docs-impacting
> Fix For: 3.x
>
>
> Because drivers abstract from users the handling of up/down nodes, they have
> to deal with the fact that when a node is restarted (or join), it won't know
> any prepared statement. Drivers could somewhat ignore that problem and wait
> for a query to return an error (that the statement is unknown by the node) to
> re-prepare the query on that node, but it's relatively inefficient because
> every time a node comes back up, you'll get bad latency spikes due to some
> queries first failing, then being re-prepared and then only being executed.
> So instead, drivers (at least the java driver but I believe others do as
> well) pro-actively re-prepare statements when a node comes up. It solves the
> latency problem, but currently every driver instance blindly re-prepare all
> statements, meaning that in a large cluster with many clients there is a lot
> of duplication of work (it would be enough for a single client to prepare the
> statements) and a bigger than necessary load on the node that started.
> An idea to solve this it to have a (cheap) way for clients to check if some
> statements are prepared on the node. There is different options to provide
> that but what I'd suggest is to add a system table to expose the (cached)
> prepared statements because:
> # it's reasonably straightforward to implement: we just add a line to the
> table when a statement is prepared and remove it when it's evicted (we
> already have eviction listeners). We'd also truncate the table on startup but
> that's easy enough). We can even switch it to a "virtual table" if/when
> CASSANDRA-7622 lands but it's trivial to do with a normal table in the
> meantime.
> # it doesn't require a change to the protocol or something like that. It
> could even be done in 2.1 if we wish to.
> # exposing prepared statements feels like a genuinely useful information to
> have (outside of the problem exposed here that is), if only for
> debugging/educational purposes.
> The exposed table could look something like:
> {noformat}
> CREATE TABLE system.prepared_statements (
>keyspace_name text,
>table_name text,
>prepared_id blob,
>query_string text,
>PRIMARY KEY (keyspace_name, table_name, prepared_id)
> )
> {noformat}
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[jira] [Updated] (CASSANDRA-8831) Create a system table to expose prepared statements
[
https://issues.apache.org/jira/browse/CASSANDRA-8831?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Sylvain Lebresne updated CASSANDRA-8831:
Status: Open (was: Patch Available)
> Create a system table to expose prepared statements
> ---
>
> Key: CASSANDRA-8831
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8831
> Project: Cassandra
> Issue Type: Improvement
>Reporter: Sylvain Lebresne
>Assignee: Robert Stupp
> Labels: client-impacting, docs-impacting
> Fix For: 3.x
>
>
> Because drivers abstract from users the handling of up/down nodes, they have
> to deal with the fact that when a node is restarted (or join), it won't know
> any prepared statement. Drivers could somewhat ignore that problem and wait
> for a query to return an error (that the statement is unknown by the node) to
> re-prepare the query on that node, but it's relatively inefficient because
> every time a node comes back up, you'll get bad latency spikes due to some
> queries first failing, then being re-prepared and then only being executed.
> So instead, drivers (at least the java driver but I believe others do as
> well) pro-actively re-prepare statements when a node comes up. It solves the
> latency problem, but currently every driver instance blindly re-prepare all
> statements, meaning that in a large cluster with many clients there is a lot
> of duplication of work (it would be enough for a single client to prepare the
> statements) and a bigger than necessary load on the node that started.
> An idea to solve this it to have a (cheap) way for clients to check if some
> statements are prepared on the node. There is different options to provide
> that but what I'd suggest is to add a system table to expose the (cached)
> prepared statements because:
> # it's reasonably straightforward to implement: we just add a line to the
> table when a statement is prepared and remove it when it's evicted (we
> already have eviction listeners). We'd also truncate the table on startup but
> that's easy enough). We can even switch it to a "virtual table" if/when
> CASSANDRA-7622 lands but it's trivial to do with a normal table in the
> meantime.
> # it doesn't require a change to the protocol or something like that. It
> could even be done in 2.1 if we wish to.
> # exposing prepared statements feels like a genuinely useful information to
> have (outside of the problem exposed here that is), if only for
> debugging/educational purposes.
> The exposed table could look something like:
> {noformat}
> CREATE TABLE system.prepared_statements (
>keyspace_name text,
>table_name text,
>prepared_id blob,
>query_string text,
>PRIMARY KEY (keyspace_name, table_name, prepared_id)
> )
> {noformat}
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[jira] [Updated] (CASSANDRA-8831) Create a system table to expose prepared statements
[
https://issues.apache.org/jira/browse/CASSANDRA-8831?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Robert Stupp updated CASSANDRA-8831:
Status: Patch Available (was: Open)
Rebased the branch and addressed the review comments in a separate commit. Also
triggered new CI runs.
||trunk|[branch|https://github.com/apache/cassandra/compare/trunk...snazy:8831-pstmts]|[testall|http://cassci.datastax.com/view/Dev/view/snazy/job/snazy-8831-pstmts-testall/lastSuccessfulBuild/]|[dtest|http://cassci.datastax.com/view/Dev/view/snazy/job/snazy-8831-pstmts-dtest/lastSuccessfulBuild/]
> Create a system table to expose prepared statements
> ---
>
> Key: CASSANDRA-8831
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8831
> Project: Cassandra
> Issue Type: Improvement
>Reporter: Sylvain Lebresne
>Assignee: Robert Stupp
> Labels: client-impacting, docs-impacting
> Fix For: 3.x
>
>
> Because drivers abstract from users the handling of up/down nodes, they have
> to deal with the fact that when a node is restarted (or join), it won't know
> any prepared statement. Drivers could somewhat ignore that problem and wait
> for a query to return an error (that the statement is unknown by the node) to
> re-prepare the query on that node, but it's relatively inefficient because
> every time a node comes back up, you'll get bad latency spikes due to some
> queries first failing, then being re-prepared and then only being executed.
> So instead, drivers (at least the java driver but I believe others do as
> well) pro-actively re-prepare statements when a node comes up. It solves the
> latency problem, but currently every driver instance blindly re-prepare all
> statements, meaning that in a large cluster with many clients there is a lot
> of duplication of work (it would be enough for a single client to prepare the
> statements) and a bigger than necessary load on the node that started.
> An idea to solve this it to have a (cheap) way for clients to check if some
> statements are prepared on the node. There is different options to provide
> that but what I'd suggest is to add a system table to expose the (cached)
> prepared statements because:
> # it's reasonably straightforward to implement: we just add a line to the
> table when a statement is prepared and remove it when it's evicted (we
> already have eviction listeners). We'd also truncate the table on startup but
> that's easy enough). We can even switch it to a "virtual table" if/when
> CASSANDRA-7622 lands but it's trivial to do with a normal table in the
> meantime.
> # it doesn't require a change to the protocol or something like that. It
> could even be done in 2.1 if we wish to.
> # exposing prepared statements feels like a genuinely useful information to
> have (outside of the problem exposed here that is), if only for
> debugging/educational purposes.
> The exposed table could look something like:
> {noformat}
> CREATE TABLE system.prepared_statements (
>keyspace_name text,
>table_name text,
>prepared_id blob,
>query_string text,
>PRIMARY KEY (keyspace_name, table_name, prepared_id)
> )
> {noformat}
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[jira] [Updated] (CASSANDRA-8831) Create a system table to expose prepared statements
[
https://issues.apache.org/jira/browse/CASSANDRA-8831?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Sylvain Lebresne updated CASSANDRA-8831:
Status: Open (was: Patch Available)
> Create a system table to expose prepared statements
> ---
>
> Key: CASSANDRA-8831
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8831
> Project: Cassandra
> Issue Type: Improvement
>Reporter: Sylvain Lebresne
>Assignee: Robert Stupp
> Labels: client-impacting, docs-impacting
> Fix For: 3.x
>
>
> Because drivers abstract from users the handling of up/down nodes, they have
> to deal with the fact that when a node is restarted (or join), it won't know
> any prepared statement. Drivers could somewhat ignore that problem and wait
> for a query to return an error (that the statement is unknown by the node) to
> re-prepare the query on that node, but it's relatively inefficient because
> every time a node comes back up, you'll get bad latency spikes due to some
> queries first failing, then being re-prepared and then only being executed.
> So instead, drivers (at least the java driver but I believe others do as
> well) pro-actively re-prepare statements when a node comes up. It solves the
> latency problem, but currently every driver instance blindly re-prepare all
> statements, meaning that in a large cluster with many clients there is a lot
> of duplication of work (it would be enough for a single client to prepare the
> statements) and a bigger than necessary load on the node that started.
> An idea to solve this it to have a (cheap) way for clients to check if some
> statements are prepared on the node. There is different options to provide
> that but what I'd suggest is to add a system table to expose the (cached)
> prepared statements because:
> # it's reasonably straightforward to implement: we just add a line to the
> table when a statement is prepared and remove it when it's evicted (we
> already have eviction listeners). We'd also truncate the table on startup but
> that's easy enough). We can even switch it to a "virtual table" if/when
> CASSANDRA-7622 lands but it's trivial to do with a normal table in the
> meantime.
> # it doesn't require a change to the protocol or something like that. It
> could even be done in 2.1 if we wish to.
> # exposing prepared statements feels like a genuinely useful information to
> have (outside of the problem exposed here that is), if only for
> debugging/educational purposes.
> The exposed table could look something like:
> {noformat}
> CREATE TABLE system.prepared_statements (
>keyspace_name text,
>table_name text,
>prepared_id blob,
>query_string text,
>PRIMARY KEY (keyspace_name, table_name, prepared_id)
> )
> {noformat}
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[jira] [Updated] (CASSANDRA-8831) Create a system table to expose prepared statements
[
https://issues.apache.org/jira/browse/CASSANDRA-8831?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Robert Stupp updated CASSANDRA-8831:
Attachment: (was: 8831-v2.txt)
> Create a system table to expose prepared statements
> ---
>
> Key: CASSANDRA-8831
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8831
> Project: Cassandra
> Issue Type: Improvement
>Reporter: Sylvain Lebresne
>Assignee: Robert Stupp
> Labels: client-impacting, docs-impacting
> Fix For: 3.x
>
>
> Because drivers abstract from users the handling of up/down nodes, they have
> to deal with the fact that when a node is restarted (or join), it won't know
> any prepared statement. Drivers could somewhat ignore that problem and wait
> for a query to return an error (that the statement is unknown by the node) to
> re-prepare the query on that node, but it's relatively inefficient because
> every time a node comes back up, you'll get bad latency spikes due to some
> queries first failing, then being re-prepared and then only being executed.
> So instead, drivers (at least the java driver but I believe others do as
> well) pro-actively re-prepare statements when a node comes up. It solves the
> latency problem, but currently every driver instance blindly re-prepare all
> statements, meaning that in a large cluster with many clients there is a lot
> of duplication of work (it would be enough for a single client to prepare the
> statements) and a bigger than necessary load on the node that started.
> An idea to solve this it to have a (cheap) way for clients to check if some
> statements are prepared on the node. There is different options to provide
> that but what I'd suggest is to add a system table to expose the (cached)
> prepared statements because:
> # it's reasonably straightforward to implement: we just add a line to the
> table when a statement is prepared and remove it when it's evicted (we
> already have eviction listeners). We'd also truncate the table on startup but
> that's easy enough). We can even switch it to a "virtual table" if/when
> CASSANDRA-7622 lands but it's trivial to do with a normal table in the
> meantime.
> # it doesn't require a change to the protocol or something like that. It
> could even be done in 2.1 if we wish to.
> # exposing prepared statements feels like a genuinely useful information to
> have (outside of the problem exposed here that is), if only for
> debugging/educational purposes.
> The exposed table could look something like:
> {noformat}
> CREATE TABLE system.prepared_statements (
>keyspace_name text,
>table_name text,
>prepared_id blob,
>query_string text,
>PRIMARY KEY (keyspace_name, table_name, prepared_id)
> )
> {noformat}
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[jira] [Updated] (CASSANDRA-8831) Create a system table to expose prepared statements
[
https://issues.apache.org/jira/browse/CASSANDRA-8831?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Robert Stupp updated CASSANDRA-8831:
Attachment: (was: 8831-v1.txt)
> Create a system table to expose prepared statements
> ---
>
> Key: CASSANDRA-8831
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8831
> Project: Cassandra
> Issue Type: Improvement
>Reporter: Sylvain Lebresne
>Assignee: Robert Stupp
> Labels: client-impacting, docs-impacting
> Fix For: 3.x
>
> Attachments: 8831-v2.txt
>
>
> Because drivers abstract from users the handling of up/down nodes, they have
> to deal with the fact that when a node is restarted (or join), it won't know
> any prepared statement. Drivers could somewhat ignore that problem and wait
> for a query to return an error (that the statement is unknown by the node) to
> re-prepare the query on that node, but it's relatively inefficient because
> every time a node comes back up, you'll get bad latency spikes due to some
> queries first failing, then being re-prepared and then only being executed.
> So instead, drivers (at least the java driver but I believe others do as
> well) pro-actively re-prepare statements when a node comes up. It solves the
> latency problem, but currently every driver instance blindly re-prepare all
> statements, meaning that in a large cluster with many clients there is a lot
> of duplication of work (it would be enough for a single client to prepare the
> statements) and a bigger than necessary load on the node that started.
> An idea to solve this it to have a (cheap) way for clients to check if some
> statements are prepared on the node. There is different options to provide
> that but what I'd suggest is to add a system table to expose the (cached)
> prepared statements because:
> # it's reasonably straightforward to implement: we just add a line to the
> table when a statement is prepared and remove it when it's evicted (we
> already have eviction listeners). We'd also truncate the table on startup but
> that's easy enough). We can even switch it to a "virtual table" if/when
> CASSANDRA-7622 lands but it's trivial to do with a normal table in the
> meantime.
> # it doesn't require a change to the protocol or something like that. It
> could even be done in 2.1 if we wish to.
> # exposing prepared statements feels like a genuinely useful information to
> have (outside of the problem exposed here that is), if only for
> debugging/educational purposes.
> The exposed table could look something like:
> {noformat}
> CREATE TABLE system.prepared_statements (
>keyspace_name text,
>table_name text,
>prepared_id blob,
>query_string text,
>PRIMARY KEY (keyspace_name, table_name, prepared_id)
> )
> {noformat}
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[jira] [Updated] (CASSANDRA-8831) Create a system table to expose prepared statements
[
https://issues.apache.org/jira/browse/CASSANDRA-8831?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Robert Stupp updated CASSANDRA-8831:
Attachment: (was: 8831-3.0-v1.txt)
> Create a system table to expose prepared statements
> ---
>
> Key: CASSANDRA-8831
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8831
> Project: Cassandra
> Issue Type: Improvement
>Reporter: Sylvain Lebresne
>Assignee: Robert Stupp
> Labels: client-impacting, docs-impacting
> Fix For: 3.x
>
> Attachments: 8831-v2.txt
>
>
> Because drivers abstract from users the handling of up/down nodes, they have
> to deal with the fact that when a node is restarted (or join), it won't know
> any prepared statement. Drivers could somewhat ignore that problem and wait
> for a query to return an error (that the statement is unknown by the node) to
> re-prepare the query on that node, but it's relatively inefficient because
> every time a node comes back up, you'll get bad latency spikes due to some
> queries first failing, then being re-prepared and then only being executed.
> So instead, drivers (at least the java driver but I believe others do as
> well) pro-actively re-prepare statements when a node comes up. It solves the
> latency problem, but currently every driver instance blindly re-prepare all
> statements, meaning that in a large cluster with many clients there is a lot
> of duplication of work (it would be enough for a single client to prepare the
> statements) and a bigger than necessary load on the node that started.
> An idea to solve this it to have a (cheap) way for clients to check if some
> statements are prepared on the node. There is different options to provide
> that but what I'd suggest is to add a system table to expose the (cached)
> prepared statements because:
> # it's reasonably straightforward to implement: we just add a line to the
> table when a statement is prepared and remove it when it's evicted (we
> already have eviction listeners). We'd also truncate the table on startup but
> that's easy enough). We can even switch it to a "virtual table" if/when
> CASSANDRA-7622 lands but it's trivial to do with a normal table in the
> meantime.
> # it doesn't require a change to the protocol or something like that. It
> could even be done in 2.1 if we wish to.
> # exposing prepared statements feels like a genuinely useful information to
> have (outside of the problem exposed here that is), if only for
> debugging/educational purposes.
> The exposed table could look something like:
> {noformat}
> CREATE TABLE system.prepared_statements (
>keyspace_name text,
>table_name text,
>prepared_id blob,
>query_string text,
>PRIMARY KEY (keyspace_name, table_name, prepared_id)
> )
> {noformat}
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[jira] [Updated] (CASSANDRA-8831) Create a system table to expose prepared statements
[
https://issues.apache.org/jira/browse/CASSANDRA-8831?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Jonathan Ellis updated CASSANDRA-8831:
--
Labels: client-impacting docs-impacting (was: client-impacting
doc-impacting)
> Create a system table to expose prepared statements
> ---
>
> Key: CASSANDRA-8831
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8831
> Project: Cassandra
> Issue Type: Improvement
>Reporter: Sylvain Lebresne
>Assignee: Robert Stupp
> Labels: client-impacting, docs-impacting
> Fix For: 3.x
>
> Attachments: 8831-3.0-v1.txt, 8831-v1.txt, 8831-v2.txt
>
>
> Because drivers abstract from users the handling of up/down nodes, they have
> to deal with the fact that when a node is restarted (or join), it won't know
> any prepared statement. Drivers could somewhat ignore that problem and wait
> for a query to return an error (that the statement is unknown by the node) to
> re-prepare the query on that node, but it's relatively inefficient because
> every time a node comes back up, you'll get bad latency spikes due to some
> queries first failing, then being re-prepared and then only being executed.
> So instead, drivers (at least the java driver but I believe others do as
> well) pro-actively re-prepare statements when a node comes up. It solves the
> latency problem, but currently every driver instance blindly re-prepare all
> statements, meaning that in a large cluster with many clients there is a lot
> of duplication of work (it would be enough for a single client to prepare the
> statements) and a bigger than necessary load on the node that started.
> An idea to solve this it to have a (cheap) way for clients to check if some
> statements are prepared on the node. There is different options to provide
> that but what I'd suggest is to add a system table to expose the (cached)
> prepared statements because:
> # it's reasonably straightforward to implement: we just add a line to the
> table when a statement is prepared and remove it when it's evicted (we
> already have eviction listeners). We'd also truncate the table on startup but
> that's easy enough). We can even switch it to a "virtual table" if/when
> CASSANDRA-7622 lands but it's trivial to do with a normal table in the
> meantime.
> # it doesn't require a change to the protocol or something like that. It
> could even be done in 2.1 if we wish to.
> # exposing prepared statements feels like a genuinely useful information to
> have (outside of the problem exposed here that is), if only for
> debugging/educational purposes.
> The exposed table could look something like:
> {noformat}
> CREATE TABLE system.prepared_statements (
>keyspace_name text,
>table_name text,
>prepared_id blob,
>query_string text,
>PRIMARY KEY (keyspace_name, table_name, prepared_id)
> )
> {noformat}
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[jira] [Updated] (CASSANDRA-8831) Create a system table to expose prepared statements
[
https://issues.apache.org/jira/browse/CASSANDRA-8831?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Tyler Hobbs updated CASSANDRA-8831:
---
Labels: client-impacting doc-impacting (was: )
> Create a system table to expose prepared statements
> ---
>
> Key: CASSANDRA-8831
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8831
> Project: Cassandra
> Issue Type: Improvement
>Reporter: Sylvain Lebresne
>Assignee: Robert Stupp
> Labels: client-impacting, doc-impacting
> Fix For: 3.0
>
> Attachments: 8831-3.0-v1.txt, 8831-v1.txt, 8831-v2.txt
>
>
> Because drivers abstract from users the handling of up/down nodes, they have
> to deal with the fact that when a node is restarted (or join), it won't know
> any prepared statement. Drivers could somewhat ignore that problem and wait
> for a query to return an error (that the statement is unknown by the node) to
> re-prepare the query on that node, but it's relatively inefficient because
> every time a node comes back up, you'll get bad latency spikes due to some
> queries first failing, then being re-prepared and then only being executed.
> So instead, drivers (at least the java driver but I believe others do as
> well) pro-actively re-prepare statements when a node comes up. It solves the
> latency problem, but currently every driver instance blindly re-prepare all
> statements, meaning that in a large cluster with many clients there is a lot
> of duplication of work (it would be enough for a single client to prepare the
> statements) and a bigger than necessary load on the node that started.
> An idea to solve this it to have a (cheap) way for clients to check if some
> statements are prepared on the node. There is different options to provide
> that but what I'd suggest is to add a system table to expose the (cached)
> prepared statements because:
> # it's reasonably straightforward to implement: we just add a line to the
> table when a statement is prepared and remove it when it's evicted (we
> already have eviction listeners). We'd also truncate the table on startup but
> that's easy enough). We can even switch it to a "virtual table" if/when
> CASSANDRA-7622 lands but it's trivial to do with a normal table in the
> meantime.
> # it doesn't require a change to the protocol or something like that. It
> could even be done in 2.1 if we wish to.
> # exposing prepared statements feels like a genuinely useful information to
> have (outside of the problem exposed here that is), if only for
> debugging/educational purposes.
> The exposed table could look something like:
> {noformat}
> CREATE TABLE system.prepared_statements (
>keyspace_name text,
>table_name text,
>prepared_id blob,
>query_string text,
>PRIMARY KEY (keyspace_name, table_name, prepared_id)
> )
> {noformat}
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[jira] [Updated] (CASSANDRA-8831) Create a system table to expose prepared statements
[
https://issues.apache.org/jira/browse/CASSANDRA-8831?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Aleksey Yeschenko updated CASSANDRA-8831:
-
Reviewer: Sylvain Lebresne
> Create a system table to expose prepared statements
> ---
>
> Key: CASSANDRA-8831
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8831
> Project: Cassandra
> Issue Type: Improvement
>Reporter: Sylvain Lebresne
>Assignee: Robert Stupp
> Fix For: 3.0
>
> Attachments: 8831-3.0-v1.txt, 8831-v1.txt, 8831-v2.txt
>
>
> Because drivers abstract from users the handling of up/down nodes, they have
> to deal with the fact that when a node is restarted (or join), it won't know
> any prepared statement. Drivers could somewhat ignore that problem and wait
> for a query to return an error (that the statement is unknown by the node) to
> re-prepare the query on that node, but it's relatively inefficient because
> every time a node comes back up, you'll get bad latency spikes due to some
> queries first failing, then being re-prepared and then only being executed.
> So instead, drivers (at least the java driver but I believe others do as
> well) pro-actively re-prepare statements when a node comes up. It solves the
> latency problem, but currently every driver instance blindly re-prepare all
> statements, meaning that in a large cluster with many clients there is a lot
> of duplication of work (it would be enough for a single client to prepare the
> statements) and a bigger than necessary load on the node that started.
> An idea to solve this it to have a (cheap) way for clients to check if some
> statements are prepared on the node. There is different options to provide
> that but what I'd suggest is to add a system table to expose the (cached)
> prepared statements because:
> # it's reasonably straightforward to implement: we just add a line to the
> table when a statement is prepared and remove it when it's evicted (we
> already have eviction listeners). We'd also truncate the table on startup but
> that's easy enough). We can even switch it to a "virtual table" if/when
> CASSANDRA-7622 lands but it's trivial to do with a normal table in the
> meantime.
> # it doesn't require a change to the protocol or something like that. It
> could even be done in 2.1 if we wish to.
> # exposing prepared statements feels like a genuinely useful information to
> have (outside of the problem exposed here that is), if only for
> debugging/educational purposes.
> The exposed table could look something like:
> {noformat}
> CREATE TABLE system.prepared_statements (
>keyspace_name text,
>table_name text,
>prepared_id blob,
>query_string text,
>PRIMARY KEY (keyspace_name, table_name, prepared_id)
> )
> {noformat}
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[jira] [Updated] (CASSANDRA-8831) Create a system table to expose prepared statements
[
https://issues.apache.org/jira/browse/CASSANDRA-8831?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Robert Stupp updated CASSANDRA-8831:
Attachment: 8831-3.0-v1.txt
Attached patch against trunk (3.0)
> Create a system table to expose prepared statements
> ---
>
> Key: CASSANDRA-8831
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8831
> Project: Cassandra
> Issue Type: Improvement
>Reporter: Sylvain Lebresne
>Assignee: Robert Stupp
> Fix For: 3.0
>
> Attachments: 8831-3.0-v1.txt, 8831-v1.txt, 8831-v2.txt
>
>
> Because drivers abstract from users the handling of up/down nodes, they have
> to deal with the fact that when a node is restarted (or join), it won't know
> any prepared statement. Drivers could somewhat ignore that problem and wait
> for a query to return an error (that the statement is unknown by the node) to
> re-prepare the query on that node, but it's relatively inefficient because
> every time a node comes back up, you'll get bad latency spikes due to some
> queries first failing, then being re-prepared and then only being executed.
> So instead, drivers (at least the java driver but I believe others do as
> well) pro-actively re-prepare statements when a node comes up. It solves the
> latency problem, but currently every driver instance blindly re-prepare all
> statements, meaning that in a large cluster with many clients there is a lot
> of duplication of work (it would be enough for a single client to prepare the
> statements) and a bigger than necessary load on the node that started.
> An idea to solve this it to have a (cheap) way for clients to check if some
> statements are prepared on the node. There is different options to provide
> that but what I'd suggest is to add a system table to expose the (cached)
> prepared statements because:
> # it's reasonably straightforward to implement: we just add a line to the
> table when a statement is prepared and remove it when it's evicted (we
> already have eviction listeners). We'd also truncate the table on startup but
> that's easy enough). We can even switch it to a "virtual table" if/when
> CASSANDRA-7622 lands but it's trivial to do with a normal table in the
> meantime.
> # it doesn't require a change to the protocol or something like that. It
> could even be done in 2.1 if we wish to.
> # exposing prepared statements feels like a genuinely useful information to
> have (outside of the problem exposed here that is), if only for
> debugging/educational purposes.
> The exposed table could look something like:
> {noformat}
> CREATE TABLE system.prepared_statements (
>keyspace_name text,
>table_name text,
>prepared_id blob,
>query_string text,
>PRIMARY KEY (keyspace_name, table_name, prepared_id)
> )
> {noformat}
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[jira] [Updated] (CASSANDRA-8831) Create a system table to expose prepared statements
[
https://issues.apache.org/jira/browse/CASSANDRA-8831?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Robert Stupp updated CASSANDRA-8831:
Fix Version/s: 3.0
> Create a system table to expose prepared statements
> ---
>
> Key: CASSANDRA-8831
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8831
> Project: Cassandra
> Issue Type: Improvement
>Reporter: Sylvain Lebresne
>Assignee: Robert Stupp
> Fix For: 3.0
>
> Attachments: 8831-v1.txt, 8831-v2.txt
>
>
> Because drivers abstract from users the handling of up/down nodes, they have
> to deal with the fact that when a node is restarted (or join), it won't know
> any prepared statement. Drivers could somewhat ignore that problem and wait
> for a query to return an error (that the statement is unknown by the node) to
> re-prepare the query on that node, but it's relatively inefficient because
> every time a node comes back up, you'll get bad latency spikes due to some
> queries first failing, then being re-prepared and then only being executed.
> So instead, drivers (at least the java driver but I believe others do as
> well) pro-actively re-prepare statements when a node comes up. It solves the
> latency problem, but currently every driver instance blindly re-prepare all
> statements, meaning that in a large cluster with many clients there is a lot
> of duplication of work (it would be enough for a single client to prepare the
> statements) and a bigger than necessary load on the node that started.
> An idea to solve this it to have a (cheap) way for clients to check if some
> statements are prepared on the node. There is different options to provide
> that but what I'd suggest is to add a system table to expose the (cached)
> prepared statements because:
> # it's reasonably straightforward to implement: we just add a line to the
> table when a statement is prepared and remove it when it's evicted (we
> already have eviction listeners). We'd also truncate the table on startup but
> that's easy enough). We can even switch it to a "virtual table" if/when
> CASSANDRA-7622 lands but it's trivial to do with a normal table in the
> meantime.
> # it doesn't require a change to the protocol or something like that. It
> could even be done in 2.1 if we wish to.
> # exposing prepared statements feels like a genuinely useful information to
> have (outside of the problem exposed here that is), if only for
> debugging/educational purposes.
> The exposed table could look something like:
> {noformat}
> CREATE TABLE system.prepared_statements (
>keyspace_name text,
>table_name text,
>prepared_id blob,
>query_string text,
>PRIMARY KEY (keyspace_name, table_name, prepared_id)
> )
> {noformat}
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[jira] [Updated] (CASSANDRA-8831) Create a system table to expose prepared statements
[
https://issues.apache.org/jira/browse/CASSANDRA-8831?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Robert Stupp updated CASSANDRA-8831:
Attachment: 8831-v2.txt
bq. {{use_keyspace_name}} vs. {{keyspace_name}}
For 2.1 the {{USE}}d keyspace might not have any effect. But for 3.0 (UDFs) it
has. Additionally the {{prepared_id}} is calculated upon the current keyspace
and the statement.
Your other comments make sense - so I'll adopt them.
bq. writing them all every minute
It just synchronizes against the table every minute - so it's basically more a
_delayed/async write_. But you're right, only the first prepare would really
hit the (mem)table, meaning that the actual write is cheap - so I'll remove the
scheduled thing.
Attached v2 of the patch incorporates the changes.
bq. security concerns
We could add a configuration field to turn this feature on and off. WDYT?
> Create a system table to expose prepared statements
> ---
>
> Key: CASSANDRA-8831
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8831
> Project: Cassandra
> Issue Type: Improvement
>Reporter: Sylvain Lebresne
>Assignee: Robert Stupp
> Attachments: 8831-v1.txt, 8831-v2.txt
>
>
> Because drivers abstract from users the handling of up/down nodes, they have
> to deal with the fact that when a node is restarted (or join), it won't know
> any prepared statement. Drivers could somewhat ignore that problem and wait
> for a query to return an error (that the statement is unknown by the node) to
> re-prepare the query on that node, but it's relatively inefficient because
> every time a node comes back up, you'll get bad latency spikes due to some
> queries first failing, then being re-prepared and then only being executed.
> So instead, drivers (at least the java driver but I believe others do as
> well) pro-actively re-prepare statements when a node comes up. It solves the
> latency problem, but currently every driver instance blindly re-prepare all
> statements, meaning that in a large cluster with many clients there is a lot
> of duplication of work (it would be enough for a single client to prepare the
> statements) and a bigger than necessary load on the node that started.
> An idea to solve this it to have a (cheap) way for clients to check if some
> statements are prepared on the node. There is different options to provide
> that but what I'd suggest is to add a system table to expose the (cached)
> prepared statements because:
> # it's reasonably straightforward to implement: we just add a line to the
> table when a statement is prepared and remove it when it's evicted (we
> already have eviction listeners). We'd also truncate the table on startup but
> that's easy enough). We can even switch it to a "virtual table" if/when
> CASSANDRA-7622 lands but it's trivial to do with a normal table in the
> meantime.
> # it doesn't require a change to the protocol or something like that. It
> could even be done in 2.1 if we wish to.
> # exposing prepared statements feels like a genuinely useful information to
> have (outside of the problem exposed here that is), if only for
> debugging/educational purposes.
> The exposed table could look something like:
> {noformat}
> CREATE TABLE system.prepared_statements (
>keyspace_name text,
>table_name text,
>prepared_id blob,
>query_string text,
>PRIMARY KEY (keyspace_name, table_name, prepared_id)
> )
> {noformat}
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[jira] [Updated] (CASSANDRA-8831) Create a system table to expose prepared statements
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]
Robert Stupp updated CASSANDRA-8831:
Attachment: 8831-v1.txt
Alright - it's really not a big thing to code.
[Git branch|https://github.com/snazy/cassandra/tree/8831-sys-pstmt] (based on
2.1) + attached patch 8831-v1.txt include unit test.
Table has the layout you've proposed - except that I had to add the column
{{use_keyspace_name}} has been added (since the {{USE}}d keyspace influences
the CQL).
I implemented it as "persists changes to the table every minute".
> Create a system table to expose prepared statements
> ---
>
> Key: CASSANDRA-8831
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8831
> Project: Cassandra
> Issue Type: Improvement
>Reporter: Sylvain Lebresne
> Attachments: 8831-v1.txt
>
>
> Because drivers abstract from users the handling of up/down nodes, they have
> to deal with the fact that when a node is restarted (or join), it won't know
> any prepared statement. Drivers could somewhat ignore that problem and wait
> for a query to return an error (that the statement is unknown by the node) to
> re-prepare the query on that node, but it's relatively inefficient because
> every time a node comes back up, you'll get bad latency spikes due to some
> queries first failing, then being re-prepared and then only being executed.
> So instead, drivers (at least the java driver but I believe others do as
> well) pro-actively re-prepare statements when a node comes up. It solves the
> latency problem, but currently every driver instance blindly re-prepare all
> statements, meaning that in a large cluster with many clients there is a lot
> of duplication of work (it would be enough for a single client to prepare the
> statements) and a bigger than necessary load on the node that started.
> An idea to solve this it to have a (cheap) way for clients to check if some
> statements are prepared on the node. There is different options to provide
> that but what I'd suggest is to add a system table to expose the (cached)
> prepared statements because:
> # it's reasonably straightforward to implement: we just add a line to the
> table when a statement is prepared and remove it when it's evicted (we
> already have eviction listeners). We'd also truncate the table on startup but
> that's easy enough). We can even switch it to a "virtual table" if/when
> CASSANDRA-7622 lands but it's trivial to do with a normal table in the
> meantime.
> # it doesn't require a change to the protocol or something like that. It
> could even be done in 2.1 if we wish to.
> # exposing prepared statements feels like a genuinely useful information to
> have (outside of the problem exposed here that is), if only for
> debugging/educational purposes.
> The exposed table could look something like:
> {noformat}
> CREATE TABLE system.prepared_statements (
>keyspace_name text,
>table_name text,
>prepared_id blob,
>query_string text,
>PRIMARY KEY (keyspace_name, table_name, prepared_id)
> )
> {noformat}
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