TRACING
Enables or disables request tracing for all nodes in the cluster.
Enables and disables tracing for transactions on all nodes in the cluster. Use tracing to
troubleshoot performance problems. Detailed transaction information related Cassandra
internal operations is captured in the system_traces keyspace. When a query
runs a session id displays in the query results and an entry with the high-level details
such as session id and client, and session length, is written to the
system_traces.session table. More detailed data for each operation
Cassandra performed is written to the system_traces.events table.
Tracing information is saved for 24 hours. To save tracing data longer than 24 hours, copy it to another location. For information about probabilistic tracing, see Cassandra 3.0 documentation.
The session id is used by the SHOW SESSION tracing_session_id command to display detailed event information.
Synopsis
TRACING [ON | OFF]| Syntax conventions | Description |
|---|---|
| UPPERCASE | Literal keyword. |
| Lowercase | Not literal. |
Italics |
Variable value. Replace with a user-defined value. |
[] |
Optional. Square brackets ( [] ) surround optional command
arguments. Do not type the square brackets. |
( ) |
Group. Parentheses ( ( ) ) identify a group to choose from. Do
not type the parentheses. |
| |
Or. A vertical bar ( | ) separates alternative elements. Type
any one of the elements. Do not type the vertical bar. |
... |
Repeatable. An ellipsis ( ... ) indicates that you can repeat
the syntax element as often as required. |
'Literal string' |
Single quotation ( ' ) marks must surround literal strings in
CQL statements. Use single quotation marks to preserve upper case. |
{ key : value } |
Map collection. Braces ( { } ) enclose map collections or key
value pairs. A colon separates the key and the value. |
<datatype1,datatype2> |
Set, list, map, or tuple. Angle brackets ( < > ) enclose
data types in a set, list, map, or tuple. Separate the data types with a comma.
|
cql_statement; |
End CQL statement. A semicolon ( ; ) terminates all CQL
statements. |
[--] |
Separate the command line options from the command arguments with two hyphens (
-- ). This syntax is useful when arguments might be mistaken for
command line options. |
' <schema> ... </schema> ' |
Search CQL only: Single quotation marks ( ' ) surround an
entire XML schema declaration. |
@xml_entity='xml_entity_type' |
Search CQL only: Identify the entity and literal value to overwrite the XML element in the schema and solrConfig files. |
Examples
Tracing a write request
This example shows tracing activity on a 3-node cluster created by ccm on Mac OSX. Using a keyspace that has a replication factor of 3 and an employee table similar to the one in "Using a compound primary key," the tracing shows that the coordinator performs the following actions:
- Identifies the target nodes for replication of the row.
- Writes the row to the commitlog and memtable.
- Confirms completion of the request.
Turn on tracing:
TRACING ON
Insert a record into the cyclist_name table:
INSERT INTO cycling.cyclist_name ( id, lastname, firstname ) VALUES ( e7ae5cf3-d358-4d99-b900-85902fda9bb0, 'FRAME', 'Alex' );
The request and each step are captured and displayed.
Tracing session: 9b378c70-b114-11e6-89b5-b7fad52e1885
activity | timestamp | source | source_elapsed | client
-----------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------+-----------+----------------+-----------
Execute CQL3 query | 2016-11-22 16:34:34.300000 | 127.0.0.1 | 0 | 127.0.0.1
Parsing INSERT INTO cycling.cyclist_name (id, lastname, firstname) VALUES (e7ae5cf3-d358-4d99-b900-85902fda9bb0, 'FRAME','Alex'); [Native-Transport-Requests-1] | 2016-11-22 16:34:34.305000 | 127.0.0.1 | 5935 | 127.0.0.1
Preparing statement [Native-Transport-Requests-1] | 2016-11-22 16:34:34.308000 | 127.0.0.1 | 9199 | 127.0.0.1
Determining replicas for mutation [Native-Transport-Requests-1] | 2016-11-22 16:34:34.330000 | 127.0.0.1 | 30530 | 127.0.0.1
Appending to commitlog [MutationStage-3] | 2016-11-22 16:34:34.330000 | 127.0.0.1 | 30979 | 127.0.0.1
Adding to cyclist_name memtable [MutationStage-3] | 2016-11-22 16:34:34.330000 | 127.0.0.1 | 31510 | 127.0.0.1
Request complete | 2016-11-22 16:34:34.333633 | 127.0.0.1 | 33633 | 127.0.0.1Tracing a sequential scan
SELECT * FROM cycling.cyclist_name ;
id | firstname | lastname
--------------------------------------+-----------+-----------------
e7ae5cf3-d358-4d99-b900-85902fda9bb0 | Alex | FRAME
fb372533-eb95-4bb4-8685-6ef61e994caa | Michael | MATTHEWS
5b6962dd-3f90-4c93-8f61-eabfa4a803e2 | Marianne | VOS
220844bf-4860-49d6-9a4b-6b5d3a79cbfb | Paolo | TIRALONGO
6ab09bec-e68e-48d9-a5f8-97e6fb4c9b47 | Steven | KRUIKSWIJK
e7cd5752-bc0d-4157-a80f-7523add8dbcd | Anna | VAN DER BREGGEN
(6 rows)
Tracing session: 117c1440-b116-11e6-89b5-b7fad52e1885
activity | timestamp | source | source_elapsed | client
-------------------------------------------------------------------------------------------------------------------------------+----------------------------+-----------+----------------+-----------
Execute CQL3 query | 2016-11-22 16:45:02.212000 | 127.0.0.1 | 0 | 127.0.0.1
Parsing SELECT * FROM cycling.cyclist_name ; [Native-Transport-Requests-1] | 2016-11-22 16:45:02.212000 | 127.0.0.1 | 372 | 127.0.0.1
Preparing statement [Native-Transport-Requests-1] | 2016-11-22 16:45:02.212000 | 127.0.0.1 | 541 | 127.0.0.1
Computing ranges to query [Native-Transport-Requests-1] | 2016-11-22 16:45:02.213000 | 127.0.0.1 | 807 | 127.0.0.1
Submitting range requests on 257 ranges with a concurrency of 257 (0.3 rows per range expected) [Native-Transport-Requests-1] | 2016-11-22 16:45:02.213000 | 127.0.0.1 | 1632 | 127.0.0.1
Submitted 1 concurrent range requests [Native-Transport-Requests-1] | 2016-11-22 16:45:02.215000 | 127.0.0.1 | 3002 | 127.0.0.1
Executing seq scan across 1 sstables for (min(-9223372036854775808), min(-9223372036854775808)] [ReadStage-2] | 2016-11-22 16:45:02.215000 | 127.0.0.1 | 3130 | 127.0.0.1
Read 6 live and 0 tombstone cells [ReadStage-2] | 2016-11-22 16:45:02.216000 | 127.0.0.1 | 3928 | 127.0.0.1
Request complete | 2016-11-22 16:45:02.216252 | 127.0.0.1 | 4252 | 127.0.0.1