[jira] [Commented] (CASSANDRA-4539) potential backwards incompatibility in native protocol
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https://issues.apache.org/jira/browse/CASSANDRA-4539?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=13450286#comment-13450286
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paul cannon commented on CASSANDRA-4539:
+1.
potential backwards incompatibility in native protocol
--
Key: CASSANDRA-4539
URL: https://issues.apache.org/jira/browse/CASSANDRA-4539
Project: Cassandra
Issue Type: Improvement
Components: API
Affects Versions: 1.2.0 beta 1
Reporter: paul cannon
Assignee: Sylvain Lebresne
Priority: Minor
Labels: cql, native_protocol
Fix For: 1.2.0 beta 1
Attachments: 4539.txt
In the text of the native_protocol.spec document, it explains the format for
a notation called {{[option]}}, which should represent {{a pair of
idvalue}}.
In doing a first-draft implementation of the protocol for the python driver,
though, I found that I had a misunderstanding. I read that section as saying
that {{value}} was a {{[value]}}, and that it could have a length of 0
(i.e., the {{[int]}} on the front of the {{[value]}} could be 0). However, it
turns out that {{value}} might not be there at all, or might be *two*
{{[value]}}'s, depending on the option id and message context.
I'm not a fan of this, since
* A protocol parsing library can't simply implement a single function to
read in {{[option]}}'s, since the length of the value part is dependent on
the message context
* If we add a new native data type (a new option id which could be used
inside a {{col_spec_i}} in a RESULT message), then older clients will not
know how to read past the value part. Of course they won't know how to
interpret the data or deserialize later rows of that unknown type - that's
not the problem - the problem is that the older client should be able just to
mark that column as unparseable and still handle the rest of the columns.
Can we make {{value}} be a {{[value]}}, the contents of which can be
re-interpreted as a {{[string]}}, an {{[option]}}, two {{[option]}}'s, or
whatever?
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[jira] [Commented] (CASSANDRA-4539) potential backwards incompatibility in native protocol
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https://issues.apache.org/jira/browse/CASSANDRA-4539?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=13447834#comment-13447834
]
Sylvain Lebresne commented on CASSANDRA-4539:
-
bq. I read that section as saying that value was a [value]
Hum, I see how one could be confused :). Though the idea is really that the two
are not related at all. I've renamed [value] to [bytes] in commit 06269b9 to
hopefully make if more clear that those are not related.
Now the main _raison d'être_ of [option] is to have a compact way to describe
the type in the query response metadata. For that, and given that it's
something sent very frequently, I really think we should keep it the way it is.
I'm all for making client library implementers job easy as much as possible but
adding even one byte per type is just not worth it in that case. And I don't
think it's much of a problem in the case we add new data type as long as we fix
the option ids for a given protocol version. And if we add a new type, the
server can very well use the 'custom' option id until we decide to bump the
protocol version to add a specific option id for that new type.
Now for STARTUP, I'll admit that reusing [option] might have been a bit
overkill. It would probably be simpler/more flexible to change STARTUP to take
some mapstring, string (and to have OPTIONS messages to return a mapstring,
[string list]. I'll make that change.
potential backwards incompatibility in native protocol
--
Key: CASSANDRA-4539
URL: https://issues.apache.org/jira/browse/CASSANDRA-4539
Project: Cassandra
Issue Type: Improvement
Components: API
Affects Versions: 1.2.0 beta 1
Reporter: paul cannon
Assignee: Sylvain Lebresne
Priority: Minor
Labels: cql, native_protocol
Fix For: 1.2.0 beta 1
In the text of the native_protocol.spec document, it explains the format for
a notation called {{[option]}}, which should represent {{a pair of
idvalue}}.
In doing a first-draft implementation of the protocol for the python driver,
though, I found that I had a misunderstanding. I read that section as saying
that {{value}} was a {{[value]}}, and that it could have a length of 0
(i.e., the {{[int]}} on the front of the {{[value]}} could be 0). However, it
turns out that {{value}} might not be there at all, or might be *two*
{{[value]}}'s, depending on the option id and message context.
I'm not a fan of this, since
* A protocol parsing library can't simply implement a single function to
read in {{[option]}}'s, since the length of the value part is dependent on
the message context
* If we add a new native data type (a new option id which could be used
inside a {{col_spec_i}} in a RESULT message), then older clients will not
know how to read past the value part. Of course they won't know how to
interpret the data or deserialize later rows of that unknown type - that's
not the problem - the problem is that the older client should be able just to
mark that column as unparseable and still handle the rest of the columns.
Can we make {{value}} be a {{[value]}}, the contents of which can be
re-interpreted as a {{[string]}}, an {{[option]}}, two {{[option]}}'s, or
whatever?
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[jira] [Commented] (CASSANDRA-4539) potential backwards incompatibility in native protocol
[
https://issues.apache.org/jira/browse/CASSANDRA-4539?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=13434599#comment-13434599
]
paul cannon commented on CASSANDRA-4539:
Another potential problem is if a client program wants to use a STARTUP option
not yet understood by the driver. If an option's value part is always a
{{[value]}}, then the driver doesn't have to guess how to send that argument to
the server.
(It might also be worthwhile to make the values in STARTUP optionlists always
be {{[string]}} s, so that apps don't have to bother with potentially encoding
binary values themselves when the driver doesn't recognize those options.)
potential backwards incompatibility in native protocol
--
Key: CASSANDRA-4539
URL: https://issues.apache.org/jira/browse/CASSANDRA-4539
Project: Cassandra
Issue Type: Improvement
Components: API
Affects Versions: 1.2
Reporter: paul cannon
Assignee: Sylvain Lebresne
Priority: Minor
Labels: cql, native_protocol
Fix For: 1.2
In the text of the native_protocol.spec document, it explains the format for
a notation called {{[option]}}, which should represent {{a pair of
idvalue}}.
In doing a first-draft implementation of the protocol for the python driver,
though, I found that I had a misunderstanding. I read that section as saying
that {{value}} was a {{[value]}}, and that it could have a length of 0
(i.e., the {{[int]}} on the front of the {{[value]}} could be 0). However, it
turns out that {{value}} might not be there at all, or might be *two*
{{[value]}}'s, depending on the option id and message context.
I'm not a fan of this, since
* A protocol parsing library can't simply implement a single function to
read in {{[option]}}'s, since the length of the value part is dependent on
the message context
* If we add a new native data type (a new option id which could be used
inside a {{col_spec_i}} in a RESULT message), then older clients will not
know how to read past the value part. Of course they won't know how to
interpret the data or deserialize later rows of that unknown type - that's
not the problem - the problem is that the older client should be able just to
mark that column as unparseable and still handle the rest of the columns.
Can we make {{value}} be a {{[value]}}, the contents of which can be
re-interpreted as a {{[string]}}, an {{[option]}}, two {{[option]}}'s, or
whatever?
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