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CQL BINARY PROTOCOL v2
Table of Contents
1. Overview
2. Frame header
2.1. version
2.2. flags
2.3. stream
2.4. opcode
2.5. length
3. Notations
4. Messages
4.1. Requests
4.1.1. STARTUP
4.1.2. AUTH_RESPONSE
4.1.3. OPTIONS
4.1.4. QUERY
4.1.5. PREPARE
4.1.6. EXECUTE
4.1.7. BATCH
4.1.8. REGISTER
4.2. Responses
4.2.1. ERROR
4.2.2. READY
4.2.3. AUTHENTICATE
4.2.4. SUPPORTED
4.2.5. RESULT
4.2.5.1. Void
4.2.5.2. Rows
4.2.5.3. Set_keyspace
4.2.5.4. Prepared
4.2.5.5. Schema_change
4.2.6. EVENT
4.2.7. AUTH_CHALLENGE
4.2.8. AUTH_SUCCESS
5. Compression
6. Data Type Serialization Formats
7. Result paging
8. Error codes
9. Changes from v1
1. Overview
The CQL binary protocol is a frame based protocol. Frames are defined as:
0 8 16 24 32
+---------+---------+---------+---------+
| version | flags | stream | opcode |
+---------+---------+---------+---------+
| length |
+---------+---------+---------+---------+
| |
. ... body ... .
. .
. .
+----------------------------------------
The protocol is big-endian (network byte order).
Each frame contains a fixed size header (8 bytes) followed by a variable size
body. The header is described in Section 2. The content of the body depends
on the header opcode value (the body can in particular be empty for some
opcode values). The list of allowed opcode is defined Section 2.3 and the
details of each corresponding message is described Section 4.
The protocol distinguishes 2 types of frames: requests and responses. Requests
are those frame sent by the clients to the server, response are the ones sent
by the server. Note however that the protocol supports server pushes (events)
so responses does not necessarily come right after a client request.
Note to client implementors: clients library should always assume that the
body of a given frame may contain more data than what is described in this
document. It will however always be safe to ignore the remaining of the frame
body in such cases. The reason is that this may allow to sometimes extend the
protocol with optional features without needing to change the protocol
version.
2. Frame header
2.1. version
The version is a single byte that indicate both the direction of the message
(request or response) and the version of the protocol in use. The up-most bit
of version is used to define the direction of the message: 0 indicates a
request, 1 indicates a responses. This can be useful for protocol analyzers to
distinguish the nature of the packet from the direction which it is moving.
The rest of that byte is the protocol version (2 for the protocol defined in
this document). In other words, for this version of the protocol, version will
have one of:
0x02 Request frame for this protocol version
0x82 Response frame for this protocol version
Please note that the while every message ship with the version, only one version
of messages is accepted on a given connection. In other words, the first message
exchanged (STARTUP) sets the version for the connection for the lifetime of this
connection.
This document describe the version 2 of the protocol. For the changes made since
version 1, see Section 9.
2.2. flags
Flags applying to this frame. The flags have the following meaning (described
by the mask that allow to select them):
0x01: Compression flag. If set, the frame body is compressed. The actual
compression to use should have been set up beforehand through the
Startup message (which thus cannot be compressed; Section 4.1.1).
0x02: Tracing flag. For a request frame, this indicate the client requires
tracing of the request. Note that not all requests support tracing.
Currently, only QUERY, PREPARE and EXECUTE queries support tracing.
Other requests will simply ignore the tracing flag if set. If a
request support tracing and the tracing flag was set, the response to
this request will have the tracing flag set and contain tracing
information.
If a response frame has the tracing flag set, its body contains
a tracing ID. The tracing ID is a [uuid] and is the first thing in
the frame body. The rest of the body will then be the usual body
corresponding to the response opcode.
The rest of the flags is currently unused and ignored.
2.3. stream
A frame has a stream id (one signed byte). When sending request messages, this
stream id must be set by the client to a positive byte (negative stream id
are reserved for streams initiated by the server; currently all EVENT messages
(section 4.2.6) have a streamId of -1). If a client sends a request message
with the stream id X, it is guaranteed that the stream id of the response to
that message will be X.
This allow to deal with the asynchronous nature of the protocol. If a client
sends multiple messages simultaneously (without waiting for responses), there
is no guarantee on the order of the responses. For instance, if the client
writes REQ_1, REQ_2, REQ_3 on the wire (in that order), the server might
respond to REQ_3 (or REQ_2) first. Assigning different stream id to these 3
requests allows the client to distinguish to which request an received answer
respond to. As there can only be 128 different simultaneous stream, it is up
to the client to reuse stream id.
Note that clients are free to use the protocol synchronously (i.e. wait for
the response to REQ_N before sending REQ_N+1). In that case, the stream id
can be safely set to 0. Clients should also feel free to use only a subset of
the 128 maximum possible stream ids if it is simpler for those
implementation.
2.4. opcode
An integer byte that distinguish the actual message:
0x00 ERROR
0x01 STARTUP
0x02 READY
0x03 AUTHENTICATE
0x05 OPTIONS
0x06 SUPPORTED
0x07 QUERY
0x08 RESULT
0x09 PREPARE
0x0A EXECUTE
0x0B REGISTER
0x0C EVENT
0x0D BATCH
0x0E AUTH_CHALLENGE
0x0F AUTH_RESPONSE
0x10 AUTH_SUCCESS
Messages are described in Section 4.
(Note that there is no 0x04 message in this version of the protocol)
2.5. length
A 4 byte integer representing the length of the body of the frame (note:
currently a frame is limited to 256MB in length).
3. Notations
To describe the layout of the frame body for the messages in Section 4, we
define the following:
[int] A 4 byte integer
[short] A 2 byte unsigned integer
[string] A [short] n, followed by n bytes representing an UTF-8
string.
[long string] An [int] n, followed by n bytes representing an UTF-8 string.
[uuid] A 16 bytes long uuid.
[string list] A [short] n, followed by n [string].
[bytes] A [int] n, followed by n bytes if n >= 0. If n < 0,
no byte should follow and the value represented is `null`.
[short bytes] A [short] n, followed by n bytes if n >= 0.
[option] A pair of <id><value> where <id> is a [short] representing
the option id and <value> depends on that option (and can be
of size 0). The supported id (and the corresponding <value>)
will be described when this is used.
[option list] A [short] n, followed by n [option].
[inet] An address (ip and port) to a node. It consists of one
[byte] n, that represents the address size, followed by n
[byte] representing the IP address (in practice n can only be
either 4 (IPv4) or 16 (IPv6)), following by one [int]
representing the port.
[consistency] A consistency level specification. This is a [short]
representing a consistency level with the following
correspondance:
0x0000 ANY
0x0001 ONE
0x0002 TWO
0x0003 THREE
0x0004 QUORUM
0x0005 ALL
0x0006 LOCAL_QUORUM
0x0007 EACH_QUORUM
0x0008 SERIAL
0x0009 LOCAL_SERIAL
0x000A LOCAL_ONE
[string map] A [short] n, followed by n pair <k><v> where <k> and <v>
are [string].
[string multimap] A [short] n, followed by n pair <k><v> where <k> is a
[string] and <v> is a [string list].
4. Messages
4.1. Requests
Note that outside of their normal responses (described below), all requests
can get an ERROR message (Section 4.2.1) as response.
4.1.1. STARTUP
Initialize the connection. The server will respond by either a READY message
(in which case the connection is ready for queries) or an AUTHENTICATE message
(in which case credentials will need to be provided using AUTH_RESPONSE).
This must be the first message of the connection, except for OPTIONS that can
be sent before to find out the options supported by the server. Once the
connection has been initialized, a client should not send any more STARTUP
message.
The body is a [string map] of options. Possible options are:
- "CQL_VERSION": the version of CQL to use. This option is mandatory and
currenty, the only version supported is "3.0.0". Note that this is
different from the protocol version.
- "COMPRESSION": the compression algorithm to use for frames (See section 5).
This is optional, if not specified no compression will be used.
4.1.2. AUTH_RESPONSE
Answers a server authentication challenge.
Authentication in the protocol is SASL based. The server sends authentication
challenges (a bytes token) to which the client answer with this message. Those
exchanges continue until the server accepts the authentication by sending a
AUTH_SUCCESS message after a client AUTH_RESPONSE. It is however that client that
initiate the exchange by sending an initial AUTH_RESPONSE in response to a
server AUTHENTICATE request.
The body of this message is a single [bytes] token. The details of what this
token contains (and when it can be null/empty, if ever) depends on the actual
authenticator used.
The response to a AUTH_RESPONSE is either a follow-up AUTH_CHALLENGE message,
an AUTH_SUCCESS message or an ERROR message.
4.1.3. OPTIONS
Asks the server to return what STARTUP options are supported. The body of an
OPTIONS message should be empty and the server will respond with a SUPPORTED
message.
4.1.4. QUERY
Performs a CQL query. The body of the message must be:
<query><query_parameters>
where <query> is a [long string] representing the query and
<query_parameters> must be
<consistency><flags>[<n><value_1>...<value_n>][<result_page_size>][<paging_state>][<serial_consistency>]
where:
- <consistency> is the [consistency] level for the operation.
- <flags> is a [byte] whose bits define the options for this query and
in particular influence what the remainder of the message contains.
A flag is set if the bit corresponding to its `mask` is set. Supported
flags are, given there mask:
0x01: Values. In that case, a [short] <n> followed by <n> [bytes]
values are provided. Those value are used for bound variables in
the query.
0x02: Skip_metadata. If present, the Result Set returned as a response
to that query (if any) will have the NO_METADATA flag (see
Section 4.2.5.2).
0x04: Page_size. In that case, <result_page_size> is an [int]
controlling the desired page size of the result (in CQL3 rows).
See the section on paging (Section 7) for more details.
0x08: With_paging_state. If present, <paging_state> should be present.
<paging_state> is a [bytes] value that should have been returned
in a result set (Section 4.2.5.2). If provided, the query will be
executed but starting from a given paging state. This also to
continue paging on a different node from the one it has been
started (See Section 7 for more details).
0x10: With serial consistency. If present, <serial_consistency> should be
present. <serial_consistency> is the [consistency] level for the
serial phase of conditional updates. That consitency can only be
either SERIAL or LOCAL_SERIAL and if not present, it defaults to
SERIAL. This option will be ignored for anything else that a
conditional update/insert.
Note that the consistency is ignored by some queries (USE, CREATE, ALTER,
TRUNCATE, ...).
The server will respond to a QUERY message with a RESULT message, the content
of which depends on the query.
4.1.5. PREPARE
Prepare a query for later execution (through EXECUTE). The body consists of
the CQL query to prepare as a [long string].
The server will respond with a RESULT message with a `prepared` kind (0x0004,
see Section 4.2.5).
4.1.6. EXECUTE
Executes a prepared query. The body of the message must be:
<id><query_parameters>
where <id> is the prepared query ID. It's the [short bytes] returned as a
response to a PREPARE message. As for <query_parameters>, it has the exact
same definition than in QUERY (see Section 4.1.4).
The response from the server will be a RESULT message.
4.1.7. BATCH
Allows executing a list of queries (prepared or not) as a batch (note that
only DML statements are accepted in a batch). The body of the message must
be:
<type><n><query_1>...<query_n><consistency>
where:
- <type> is a [byte] indicating the type of batch to use:
- If <type> == 0, the batch will be "logged". This is equivalent to a
normal CQL3 batch statement.
- If <type> == 1, the batch will be "unlogged".
- If <type> == 2, the batch will be a "counter" batch (and non-counter
statements will be rejected).
- <n> is a [short] indicating the number of following queries.
- <query_1>...<query_n> are the queries to execute. A <query_i> must be of the
form:
<kind><string_or_id><n><value_1>...<value_n>
where:
- <kind> is a [byte] indicating whether the following query is a prepared
one or not. <kind> value must be either 0 or 1.
- <string_or_id> depends on the value of <kind>. If <kind> == 0, it should be
a [long string] query string (as in QUERY, the query string might contain
bind markers). Otherwise (that is, if <kind> == 1), it should be a
[short bytes] representing a prepared query ID.
- <n> is a [short] indicating the number (possibly 0) of following values.
- <value_1>...<value_n> are the [bytes] to use for bound variables.
- <consistency> is the [consistency] level for the operation.
The server will respond with a RESULT message with a `Void` kind (0x0001,
see Section 4.2.5).
4.1.8. REGISTER
Register this connection to receive some type of events. The body of the
message is a [string list] representing the event types to register to. See
section 4.2.6 for the list of valid event types.
The response to a REGISTER message will be a READY message.
Please note that if a client driver maintains multiple connections to a
Cassandra node and/or connections to multiple nodes, it is advised to
dedicate a handful of connections to receive events, but to *not* register
for events on all connections, as this would only result in receiving
multiple times the same event messages, wasting bandwidth.
4.2. Responses
This section describes the content of the frame body for the different
responses. Please note that to make room for future evolution, clients should
support extra informations (that they should simply discard) to the one
described in this document at the end of the frame body.
4.2.1. ERROR
Indicates an error processing a request. The body of the message will be an
error code ([int]) followed by a [string] error message. Then, depending on
the exception, more content may follow. The error codes are defined in
Section 8, along with their additional content if any.
4.2.2. READY
Indicates that the server is ready to process queries. This message will be
sent by the server either after a STARTUP message if no authentication is
required, or after a successful CREDENTIALS message.
The body of a READY message is empty.
4.2.3. AUTHENTICATE
Indicates that the server require authentication, and which authentication
mechanism to use.
The authentication is SASL based and thus consists on a number of server
challenges (AUTH_CHALLENGE, Section 4.2.7) followed by client responses
(AUTH_RESPONSE, Section 4.1.2). The Initial exchange is however boostrapped
by an initial client response. The details of that exchange (including how
much challenge-response pair are required) are specific to the authenticator
in use. The exchange ends when the server sends an AUTH_SUCCESS message or
an ERROR message.
This message will be sent following a STARTUP message if authentication is
required and must be answered by a AUTH_RESPONSE message from the client.
The body consists of a single [string] indicating the full class name of the
IAuthenticator in use.
4.2.4. SUPPORTED
Indicates which startup options are supported by the server. This message
comes as a response to an OPTIONS message.
The body of a SUPPORTED message is a [string multimap]. This multimap gives
for each of the supported STARTUP options, the list of supported values.
4.2.5. RESULT
The result to a query (QUERY, PREPARE, EXECUTE or BATCH messages).
The first element of the body of a RESULT message is an [int] representing the
`kind` of result. The rest of the body depends on the kind. The kind can be
one of:
0x0001 Void: for results carrying no information.
0x0002 Rows: for results to select queries, returning a set of rows.
0x0003 Set_keyspace: the result to a `use` query.
0x0004 Prepared: result to a PREPARE message.
0x0005 Schema_change: the result to a schema altering query.
The body for each kind (after the [int] kind) is defined below.
4.2.5.1. Void
The rest of the body for a Void result is empty. It indicates that a query was
successful without providing more information.
4.2.5.2. Rows
Indicates a set of rows. The rest of body of a Rows result is:
<metadata><rows_count><rows_content>
where:
- <metadata> is composed of:
<flags><columns_count>[<paging_state>][<global_table_spec>?<col_spec_1>...<col_spec_n>]
where:
- <flags> is an [int]. The bits of <flags> provides information on the
formatting of the remaining informations. A flag is set if the bit
corresponding to its `mask` is set. Supported flags are, given there
mask:
0x0001 Global_tables_spec: if set, only one table spec (keyspace
and table name) is provided as <global_table_spec>. If not
set, <global_table_spec> is not present.
0x0002 Has_more_pages: indicates whether this is not the last
page of results and more should be retrieve. If set, the
<paging_state> will be present. The <paging_state> is a
[bytes] value that should be used in QUERY/EXECUTE to
continue paging and retrieve the remained of the result for
this query (See Section 7 for more details).
0x0004 No_metadata: if set, the <metadata> is only composed of
these <flags>, the <column_count> and optionally the
<paging_state> (depending on the Has_more_pages flage) but
no other information (so no <global_table_spec> nor <col_spec_i>).
This will only ever be the case if this was requested
during the query (see QUERY and RESULT messages).
- <columns_count> is an [int] representing the number of columns selected
by the query this result is of. It defines the number of <col_spec_i>
elements in and the number of element for each row in <rows_content>.
- <global_table_spec> is present if the Global_tables_spec is set in
<flags>. If present, it is composed of two [string] representing the
(unique) keyspace name and table name the columns return are of.
- <col_spec_i> specifies the columns returned in the query. There is
<column_count> such column specifications that are composed of:
(<ksname><tablename>)?<name><type>
The initial <ksname> and <tablename> are two [string] are only present
if the Global_tables_spec flag is not set. The <column_name> is a
[string] and <type> is an [option] that correspond to the description
(what this description is depends a bit on the context: in results to
selects, this will be either the user chosen alias or the selection used
(often a colum name, but it can be a function call too). In results to
a PREPARE, this will be either the name of the bind variable corresponding
or the column name for the variable if it is "anonymous") and type of
the corresponding result. The option for <type> is either a native
type (see below), in which case the option has no value, or a
'custom' type, in which case the value is a [string] representing
the full qualified class name of the type represented. Valid option
ids are:
0x0000 Custom: the value is a [string], see above.
0x0001 Ascii
0x0002 Bigint
0x0003 Blob
0x0004 Boolean
0x0005 Counter
0x0006 Decimal
0x0007 Double
0x0008 Float
0x0009 Int
0x000A Text
0x000B Timestamp
0x000C Uuid
0x000D Varchar
0x000E Varint
0x000F Timeuuid
0x0010 Inet
0x0020 List: the value is an [option], representing the type
of the elements of the list.
0x0021 Map: the value is two [option], representing the types of the
keys and values of the map
0x0022 Set: the value is an [option], representing the type
of the elements of the set
- <rows_count> is an [int] representing the number of rows present in this
result. Those rows are serialized in the <rows_content> part.
- <rows_content> is composed of <row_1>...<row_m> where m is <rows_count>.
Each <row_i> is composed of <value_1>...<value_n> where n is
<columns_count> and where <value_j> is a [bytes] representing the value
returned for the jth column of the ith row. In other words, <rows_content>
is composed of (<rows_count> * <columns_count>) [bytes].
4.2.5.3. Set_keyspace
The result to a `use` query. The body (after the kind [int]) is a single
[string] indicating the name of the keyspace that has been set.
4.2.5.4. Prepared
The result to a PREPARE message. The rest of the body of a Prepared result is:
<id><metadata><result_metadata>
where:
- <id> is [short bytes] representing the prepared query ID.
- <metadata> is defined exactly as for a Rows RESULT (See section 4.2.5.2; you
can however assume that the Has_more_pages flag is always off) and
is the specification for the variable bound in this prepare statement.
- <result_metadata> is defined exactly as <metadata> but correspond to the
metadata for the resultSet that execute this query will yield. Note that
<result_metadata> may be empty (have the No_metadata flag and 0 columns, See
section 4.2.5.2) and will be for any query that is not a Select. There is
in fact never a guarantee that this will non-empty so client should protect
themselves accordingly. The presence of this information is an
optimization that allows to later execute the statement that has been
prepared without requesting the metadata (Skip_metadata flag in EXECUTE).
Clients can safely discard this metadata if they do not want to take
advantage of that optimization.
Note that prepared query ID return is global to the node on which the query
has been prepared. It can be used on any connection to that node and this
until the node is restarted (after which the query must be reprepared).
4.2.5.5. Schema_change
The result to a schema altering query (creation/update/drop of a
keyspace/table/index). The body (after the kind [int]) is composed of 3
[string]:
<change><keyspace><table>
where:
- <change> describe the type of change that has occured. It can be one of
"CREATED", "UPDATED" or "DROPPED".
- <keyspace> is the name of the affected keyspace or the keyspace of the
affected table.
- <table> is the name of the affected table. <table> will be empty (i.e.
the empty string "") if the change was affecting a keyspace and not a
table.
Note that queries to create and drop an index are considered as change
updating the table the index is on.
4.2.6. EVENT
And event pushed by the server. A client will only receive events for the
type it has REGISTER to. The body of an EVENT message will start by a
[string] representing the event type. The rest of the message depends on the
event type. The valid event types are:
- "TOPOLOGY_CHANGE": events related to change in the cluster topology.
Currently, events are sent when new nodes are added to the cluster, and
when nodes are removed. The body of the message (after the event type)
consists of a [string] and an [inet], corresponding respectively to the
type of change ("NEW_NODE", "REMOVED_NODE", or "MOVED_NODE") followed
by the address of the new/removed/moved node.
- "STATUS_CHANGE": events related to change of node status. Currently,
up/down events are sent. The body of the message (after the event type)
consists of a [string] and an [inet], corresponding respectively to the
type of status change ("UP" or "DOWN") followed by the address of the
concerned node.
- "SCHEMA_CHANGE": events related to schema change. The body of the message
(after the event type) consists of 3 [string] corresponding respectively
to the type of schema change ("CREATED", "UPDATED" or "DROPPED"),
followed by the name of the affected keyspace and the name of the
affected table within that keyspace. For changes that affect a keyspace
directly, the table name will be empty (i.e. the empty string "").
All EVENT message have a streamId of -1 (Section 2.3).
Please note that "NEW_NODE" and "UP" events are sent based on internal Gossip
communication and as such may be sent a short delay before the binary
protocol server on the newly up node is fully started. Clients are thus
advise to wait a short time before trying to connect to the node (1 seconds
should be enough), otherwise they may experience a connection refusal at
first.
It is possible for the same event to be sent multiple times. Therefore,
a client library should ignore the same event if it has already been notified
of a change.
4.2.7. AUTH_CHALLENGE
A server authentication challenge (see AUTH_RESPONSE (Section 4.1.2) for more
details).
The body of this message is a single [bytes] token. The details of what this
token contains (and when it can be null/empty, if ever) depends on the actual
authenticator used.
Clients are expected to answer the server challenge by an AUTH_RESPONSE
message.
4.2.7. AUTH_SUCCESS
Indicate the success of the authentication phase. See Section 4.2.3 for more
details.
The body of this message is a single [bytes] token holding final information
from the server that the client may require to finish the authentication
process. What that token contains and whether it can be null depends on the
actual authenticator used.
5. Compression
Frame compression is supported by the protocol, but then only the frame body
is compressed (the frame header should never be compressed).
Before being used, client and server must agree on a compression algorithm to
use, which is done in the STARTUP message. As a consequence, a STARTUP message
must never be compressed. However, once the STARTUP frame has been received
by the server can be compressed (including the response to the STARTUP
request). Frame do not have to be compressed however, even if compression has
been agreed upon (a server may only compress frame above a certain size at its
discretion). A frame body should be compressed if and only if the compressed
flag (see Section 2.2) is set.
As of this version 2 of the protocol, the following compressions are available:
- lz4 (https://code.google.com/p/lz4/). In that, note that the 4 first bytes
of the body will be the uncompressed length (followed by the compressed
bytes).
- snappy (https://code.google.com/p/snappy/). This compression might not be
available as it depends on a native lib (server-side) that might not be
avaivable on some installation.
6. Data Type Serialization Formats
This sections describes the serialization formats for all CQL data types
supported by Cassandra through the native protocol. These serialization
formats should be used by client drivers to encode values for EXECUTE
messages. Cassandra will use these formats when returning values in
RESULT messages.
All values are represented as [bytes] in EXECUTE and RESULT messages.
The [bytes] format includes an int prefix denoting the length of the value.
For that reason, the serialization formats described here will not include
a length component.
For legacy compatibility reasons, note that most non-string types support
"empty" values (i.e. a value with zero length). An empty value is distinct
from NULL, which is encoded with a negative length.
As with the rest of the native protocol, all encodings are big-endian.
6.1. ascii
A sequence of bytes in the ASCII range [0, 127]. Bytes with values outside of
this range will result in a validation error.
6.2 bigint
An eight-byte two's complement integer.
6.3 blob
Any sequence of bytes.
6.4 boolean
A single byte. A value of 0 denotes "false"; any other value denotes "true".
(However, it is recommended that a value of 1 be used to represent "true".)
6.5 decimal
The decimal format represents an arbitrary-precision number. It contains an
[int] "scale" component followed by a varint encoding (see section 6.17)
of the unscaled value. The encoded value represents "<unscaled>E<-scale>".
In other words, "<unscaled> * 10 ^ (-1 * <scale>)".
6.6 double
An eight-byte floating point number in the IEEE 754 binary64 format.
6.7 float
An four-byte floating point number in the IEEE 754 binary32 format.
6.8 inet
A 4 byte or 16 byte sequence denoting an IPv4 or IPv6 address, respectively.
6.9 int
A four-byte two's complement integer.
6.10 list
A [short] n indicating the number of elements in the list, followed by n
elements. Each element is [short bytes] representing the serialized value.
6.11 map
A [short] n indicating the number of key/value pairs in the map, followed by
n entries. Each entry is composed of two [short bytes] representing the key
and value.
6.12 set
A [short] n indicating the number of elements in the set, followed by n
elements. Each element is [short bytes] representing the serialized value.
6.13 text
A sequence of bytes conforming to the UTF-8 specifications.
6.14 timestamp
An eight-byte two's complement integer representing a millisecond-precision
offset from the unix epoch (00:00:00, January 1st, 1970). Negative values
represent a negative offset from the epoch.
6.15 uuid
A 16 byte sequence representing any valid UUID as defined by RFC 4122.
6.16 varchar
An alias of the "text" type.
6.17 varint
A variable-length two's complement encoding of a signed integer.
The following examples may help implementors of this spec:
Value | Encoding
------|---------
0 | 0x00
1 | 0x01
127 | 0x7F
128 | 0x0080
129 | 0x0081
-1 | 0xFF
-128 | 0x80
-129 | 0xFF7F
Note that positive numbers must use a most-significant byte with a value
less than 0x80, because a most-significant bit of 1 indicates a negative
value. Implementors should pad positive values that have a MSB >= 0x80
with a leading 0x00 byte.
6.18 timeuuid
A 16 byte sequence representing a version 1 UUID as defined by RFC 4122.
7. Result paging
The protocol allows for paging the result of queries. For that, the QUERY and
EXECUTE messages have a <result_page_size> value that indicate the desired
page size in CQL3 rows.
If a positive value is provided for <result_page_size>, the result set of the
RESULT message returned for the query will contain at most the
<result_page_size> first rows of the query result. If that first page of result
contains the full result set for the query, the RESULT message (of kind `Rows`)
will have the Has_more_pages flag *not* set. However, if some results are not
part of the first response, the Has_more_pages flag will be set and the result
will contain a <paging_state> value. In that case, the <paging_state> value
should be used in a QUERY or EXECUTE message (that has the *same* query than
the original one or the behavior is undefined) to retrieve the next page of
results.
Only CQL3 queries that return a result set (RESULT message with a Rows `kind`)
support paging. For other type of queries, the <result_page_size> value is
ignored.
Note to client implementors:
- While <result_page_size> can be as low as 1, it will likely be detrimental
to performance to pick a value too low. A value below 100 is probably too
low for most use cases.
- Clients should not rely on the actual size of the result set returned to
decide if there is more result to fetch or not. Instead, they should always
check the Has_more_pages flag (unless they did not enabled paging for the query
obviously). Clients should also not assert that no result will have more than
<result_page_size> results. While the current implementation always respect
the exact value of <result_page_size>, we reserve ourselves the right to return
slightly smaller or bigger pages in the future for performance reasons.
8. Error codes
The supported error codes are described below:
0x0000 Server error: something unexpected happened. This indicates a
server-side bug.
0x000A Protocol error: some client message triggered a protocol
violation (for instance a QUERY message is sent before a STARTUP
one has been sent)
0x0100 Bad credentials: CREDENTIALS request failed because Cassandra
did not accept the provided credentials.
0x1000 Unavailable exception. The rest of the ERROR message body will be
<cl><required><alive>
where:
<cl> is the [consistency] level of the query having triggered
the exception.
<required> is an [int] representing the number of node that
should be alive to respect <cl>
<alive> is an [int] representing the number of replica that
were known to be alive when the request has been
processed (since an unavailable exception has been
triggered, there will be <alive> < <required>)
0x1001 Overloaded: the request cannot be processed because the
coordinator node is overloaded
0x1002 Is_bootstrapping: the request was a read request but the
coordinator node is bootstrapping
0x1003 Truncate_error: error during a truncation error.
0x1100 Write_timeout: Timeout exception during a write request. The rest
of the ERROR message body will be
<cl><received><blockfor><writeType>
where:
<cl> is the [consistency] level of the query having triggered
the exception.
<received> is an [int] representing the number of nodes having
acknowledged the request.
<blockfor> is an [int] representing the number of replica whose
acknowledgement is required to achieve <cl>.
<writeType> is a [string] that describe the type of the write
that timeouted. The value of that string can be one
of:
- "SIMPLE": the write was a non-batched
non-counter write.
- "BATCH": the write was a (logged) batch write.
If this type is received, it means the batch log
has been successfully written (otherwise a
"BATCH_LOG" type would have been send instead).
- "UNLOGGED_BATCH": the write was an unlogged
batch. Not batch log write has been attempted.
- "COUNTER": the write was a counter write
(batched or not).
- "BATCH_LOG": the timeout occured during the
write to the batch log when a (logged) batch
write was requested.
0x1200 Read_timeout: Timeout exception during a read request. The rest
of the ERROR message body will be
<cl><received><blockfor><data_present>
where:
<cl> is the [consistency] level of the query having triggered
the exception.
<received> is an [int] representing the number of nodes having
answered the request.
<blockfor> is an [int] representing the number of replica whose
response is required to achieve <cl>. Please note that it
is possible to have <received> >= <blockfor> if
<data_present> is false. And also in the (unlikely)
case were <cl> is achieved but the coordinator node
timeout while waiting for read-repair
acknowledgement.
<data_present> is a single byte. If its value is 0, it means
the replica that was asked for data has not
responded. Otherwise, the value is != 0.
0x2000 Syntax_error: The submitted query has a syntax error.
0x2100 Unauthorized: The logged user doesn't have the right to perform
the query.
0x2200 Invalid: The query is syntactically correct but invalid.
0x2300 Config_error: The query is invalid because of some configuration issue
0x2400 Already_exists: The query attempted to create a keyspace or a
table that was already existing. The rest of the ERROR message
body will be <ks><table> where:
<ks> is a [string] representing either the keyspace that
already exists, or the keyspace in which the table that
already exists is.
<table> is a [string] representing the name of the table that
already exists. If the query was attempting to create a
keyspace, <table> will be present but will be the empty
string.
0x2500 Unprepared: Can be thrown while a prepared statement tries to be
executed if the provide prepared statement ID is not known by
this host. The rest of the ERROR message body will be [short
bytes] representing the unknown ID.
9. Changes from v1
* Protocol is versioned to allow old client connects to a newer server, if a
newer client connects to an older server, it needs to check if it gets a
ProtocolException on connection and try connecting with a lower version.
* A query can now have bind variables even though the statement is not
prepared; see Section 4.1.4.
* A new BATCH message allows to batch a set of queries (prepared or not); see
Section 4.1.7.
* Authentication now uses SASL. Concretely, the CREDENTIALS message has been
removed and replaced by a server/client challenges/responses exchanges (done
through the new AUTH_RESPONSE/AUTH_CHALLENGE messages). See Section 4.2.3 for
details.
* Query paging has been added (Section 7): QUERY and EXECUTE message have an
additional <result_page_size> [int] and <paging_state> [bytes], and
the Rows kind of RESULT message has an additional flag and <paging_state>
value. Note that paging is optional, and a client that do not want to handle
can simply avoid including the Page_size flag and parameter in QUERY and
EXECUTE.
* QUERY and EXECUTE statements can request for the metadata to be skipped in
the result set returned (for efficiency reasons) if said metadata are known
in advance. Furthermore, the result to a PREPARE (section 4.2.5.4) now
includes the metadata for the result of executing the statement just
prepared (though those metadata will be empty for non SELECT statements).