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CQL BINARY PROTOCOL v1
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. CREDENTIALS
4.1.3. OPTIONS
4.1.4. QUERY
4.1.5. PREPARE
4.1.6. EXECUTE
4.1.7. 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
5. Compression
6. Data Type Serialization Formats
7. Error codes
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 while communication are initiated by the
client with the server responding to request, the protocol may likely add
server pushes in the future, so responses does not obligatory 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 (1 for the protocol defined in
this document). In other words, for this version of the protocol, version will
have one of:
0x01 Request frame for this protocol version
0x81 Response frame for this protocol version
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
0x04 CREDENTIALS
0x05 OPTIONS
0x06 SUPPORTED
0x07 QUERY
0x08 RESULT
0x09 PREPARE
0x0A EXECUTE
0x0B REGISTER
0x0C EVENT
Messages are described in Section 4.
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
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 CREDENTIALS).
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. CREDENTIALS
Provides credentials information for the purpose of identification. This
message comes as a response to an AUTHENTICATE message from the server, but
can be use later in the communication to change the authentication
information.
The body is a list of key/value informations. It is a [short] n, followed by n
pair of [string]. These key/value pairs are passed as is to the Cassandra
IAuthenticator and thus the detail of which informations is needed depends on
that authenticator.
The response to a CREDENTIALS is a READY 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 consists of a CQL query as a [long
string] followed by the [consistency] for the operation.
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><n><value_1>....<value_n><consistency>
where:
- <id> is the prepared query ID. It's the [short bytes] returned as a
response to a PREPARE message.
- <n> is a [short] indicating the number of following values.
- <value_1>...<value_n> are the [bytes] to use for bound variables in the
prepared query.
- <consistency> is the [consistency] level for the operation.
Note that the consistency is ignored by some (prepared) queries (USE, CREATE,
ALTER, TRUNCATE, ...).
The response from the server will be a RESULT message.
4.1.7. 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 7, 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. This will be sent following
a STARTUP message and must be answered by a CREDENTIALS message from the
client to provide authentication informations.
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 or EXECUTE 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><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.
- <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 specification that are composed of:
(<ksname><tablename>)?<column_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 column name
and type. 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>
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).
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 changes
updating the table the index is on. Queries that create, alter, or drop
user-defined types (availble in Cassandra 2.1+) are considered changes
updating the keyspace the type is defined in.
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 "").
Changes to user-defined types (available in Cassandra 2.1+) will result
in an "UPDATED" change for the keyspace containing the type, and the
table name will be empty.
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.
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.
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
-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. 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 replicas 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.
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