Metrics¶
ksqlDB emits a variety of JMX metrics to help you understand and monitor what its servers are doing. This reference describes each metric and grouping.
All persistent queries¶
Metrics that describe the full set of persistent queries on a given server.
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Attributes¶
Bytes consumed total
bytes-consumed-total
The total number of bytes consumed across all queries.
Created queries
created-queries
The current number of created queries running in this engine.
Error rate
error-rate
The proportion of failed queries to successful queries, indicating messages that were consumed but not processed. Messages may not be processed if, for exammple, the message contents could not be deserialized due to an incompatible schema. Alternatively, a consumed message may not have been produced, hence being effectively dropped. Such messages would also be counted toward the error rate. This can indicate problems with system configuration or issues in the queries being executed.
Error queries
error-queries
The number of queries that resulted in an error. This count can help identify issues within the curent query set.
Liveness indicator
liveness-indicator
A metric with constant value 1 indicating the server is up and emitting metrics.
Maximum messages consumed
messages-consumed-max
The maximum number of messages consumed by all active queries.
Messages consumed average
messages-consumed-avg
The average number of messages consumed across all active queries. This can indicate the average load on the system.
Messages consumed per second
messages-consumed-per-sec
The number of messages consumed per second across all queries. Higher values can indicate a higher load on the system.
Messages consumed total
messages-consumed-total
The total number of messages consumed across all queries.
Messages produced per second
messages-produced-per-sec
The number of messages produced per second across all queries. This can indicate system throughput.
Minimum messages consumed
messages-consumed-min
The minimum number of messages consumed by all active queries.
Not-running queries
not-running-queries
The number of queries that have been defined but are not currently running.
Number of active queries
num-active-queries
The current number of active queries running in this engine.
Number of idle queries
num-idle-queries
The number of queries that are currently idle, meaning that they are not processing any data.
Number of persistent queries
num-persistent-queries
The current number of persistent queries running in this engine.
Pending shutdown queries
pending-shutdown-queries
The number of queries that are in the process of shutting down, usually due to a manual command to terminate.
Rebalancing queries
rebalancing-queries
The number of queries that are currently undergoing a rebalance operation. Typically, this happens when a new worker joins a cluster or an existing one leaves.
Running queries
running-queries
The current number of persistent queries running in this engine.
Persistent query status¶
Metrics that describe the health of each persistent query.
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Attributes¶
ksqlDB query status
ksql-query-status
The current ksqlDB status of the given query.
The metric query-status shows the Kafka Streams application state.
The PAUSE / RESUME commands do not impact the Kafka Streams state, so this new metric shows when a query is paused.
Query status
query-status
The current Kafka Streams status of the given query.
The ksql-query-status metric has been added to show the ksqlDB query status.
Error status
error-status
The current error status of the given query, if the state is in ERROR state.
Persistent query production¶
Metrics that describe the producer activity of each persistent query.
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Attributes¶
Total messages
total-messages
The total number of messages produced.
Messages per second
messages-per-sec
The total number of messages produced per second.
Persistent query consumption¶
Metrics that describe the consumer activity of each persistent query.
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Attributes¶
Total messages
consumer-total-messages
The total number of messages consumed.
Messages per second
consumer-messages-per-sec
The total number of messages consumed per second.
Total bytes
consumer-total-bytes
The total number of bytes consumed.
Runtime¶
Because ksqlDB persistent queries directly compile into Kafka Streams topologies, many useful Kafka Streams metrics are emitted for each persistent query. These metrics are omitted from this reference to avoid redundancy.
HTTP server¶
ksqlDB's REST API is built using Vert.x, and consequentially exposes many Vert.x metrics directly. These metrics are omitted from this reference to avoid redundancy.
Pull queries¶
Metrics that describe the activity of pull queries on each server.
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Info
Pull query metrics must be enabled explicitly by setting
the ksql.query.pull.metrics.enabled server configuration to true.
Attributes¶
Pull query total requests
pull-query-requests-total
Total number of pull query requests.
Pull query request rate
pull-query-requests-rate
Rate of pull query requests per second.
Pull query requests error count
pull-query-requests-error-total
Total number of erroneous pull query requests.
Pull query request error rate
pull-query-requests-error-rate
Rate of erroneous pull query requests per second.
Local pull query requests count
pull-query-requests-local
Count of local pull query requests.
Local pull query requests rate
pull-query-requests-local-rate
Rate of local pull query requests per second.
Remote pull query requests count
pull-query-requests-remote
Count of remote pull query requests.
Remote pull query requests rate
pull-query-requests-remote-rate
Rate of remote pull query requests per second.
Pull query minimum request latency
pull-query-requests-latency-latency-min
Average time for a pull query request.
Pull query maximum request latency
pull-query-requests-latency-latency-max
Max time for a pull query request.
Pull query average request latency
pull-query-requests-latency-latency-avg
Average time for a pull query request.
Pull query latency 50th percentile
pull-query-requests-latency-distribution-50
Latency distribution of the 50th percentile.
Pull query latency 75th percentile
pull-query-requests-latency-distribution-75
Latency distribution of the 75th percentile.
Pull query latency 75th percentile
pull-query-requests-latency-distribution-90
Latency distribution of the 90th percentile.
Pull query latency 99th percentile
pull-query-requests-latency-distribution-99
Latency distribution of the 99th percentile.
User-defined functions¶
Metrics that describe the activity of user-defined functions, both in-built and custom added.
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Info
UDF metrics must be enabled explicitly by setting
the ksql.udf.collect.metrics server configuration to true.
Attributes¶
ksqlDB creates a series of attributes per user-defined function. The general form is:
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For example, if you had a UDF named formula, you would see these attributes:
ksql-udf-formula-avgksql-udf-formula-countksql-udf-formula-maxksql-udf-formula-rate
Here are what each of these suffixes mean.
avg
Average time for an invocation of the function.
count
Total number of invocations of the function.
max
Max time for an invocation of the function.
rate
The average number of invocations per second of the function.
Command runner¶
Metrics that describe the health of the CommandRunner thread, which
enables each node to participate in distributed computation.
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Attributes¶
Thread status
status
The status of the commandRunner thread as it processes the command topic.
RocksDB¶
Metrics that report the resource utilization for RocksDB. If RocksDB runs out of resources, it spools to disk, affecting performance.
Run the free -m command to check for high cache usage. You may see that the
process is running at its configured memory threshold.
Also, you can check the following JMX metrics for high usage.
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Attributes¶
Block cache usage
block-cache-usage
Bytes allocated for the block cache.
Note
The block-cache-usage metric is distinct from the OS page cache reported
by the free -m command.
Current size of all memory tables
cur-size-all-mem-tables
Amount of memory allocated for the write buffer.