THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
Status
Current state: Under Discussion
Discussion thread: https://mail-archives.apache.org/mod_mbox/flink-dev/201902.mbox/browser
JIRA:
Released: <Flink Version>
Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).
Motivation
Flink has defined a few standard metrics for jobs, tasks and operators. It also supports custom metrics in various scenarios. However, so far there is no standard or conventional metric definition for the connectors. Each connector defines their own metrics at the moment. This complicates operation and monitoring. Admittedly, different connectors may have different metrics, but some commonly used metrics can probably be standardized. This FLIP proposes a set of standard connector metrics that each connector should emit if applicable. The metrics proposed in this FLIP will serve as a convention for the connector implementations.
Public Interfaces
We propose to introduce a set of conventional / standard metrics for the connectors.
Source Metrics
Name | Type | Unit | Description |
numBytesIn | Counter | Bytes | The total number of input bytes since the source started |
numBytesInPerSec | Meter | Bytes/Sec | The input bytes per second |
numRecordsIn | Counter | Records | The total number of input records since the source started |
numRecordsInPerSec | Meter | Records/Sec | The input records per second |
| numRecordsInErrors | Counter | Records | The total number of record that failed to consume |
recordSize | Histogram | Bytes | The size of a record |
fetchLatency | Histogram | ms | The latency occurred before Flink fetched the record. fetchLatency = FetchTime - EventTime |
latency | Histogram | ms | The latency occurred before the record is emitted by the source connector. latency = EmitTime - EventTime |
idleTime | Gauge | ms | The time in milliseconds that the source has not processed any record. idleTime = CurrentTime - LastRecordProcessTime |
Sink Metrics
Name | Type | Unit | Description |
numBytesOut | Counter | Bytes | The total number of output bytes since the source started |
numBytesOutPerSec | Meter | Bytes/Sec | The output bytes per second |
numRecordsOut | Counter | Records | The total number of output records since the source started |
numRecordsOutPerSec | Meter | Records/Sec | The output records per second |
| numRecordsOutErrors | Counter | Record | The total number of records failed to send |
recordSize | Histogram | Bytes | The size of a record |
sendTime | Histogram | ms | The time it takes to send a record |
Note:
- A connector implementation does not have report all the following metrics. But the connectors that do report these metrics should conform to this convention.
- The histogram metrics are usually very expensive, so it is strongly recommended that the connectors do not report them by default. But give the options to the users to enable them on demand.
Scope
The metric group for each source and sink would be the same as ordinary operator scope, i.e. default to <host>.taskmanager.<tm_id>.<job_name>.<operator_name>.<subtask_index>
Additional connector specific metrics should also use the same scope.
Native Connector Metrics
If the connector has its original metrics, the original metric names should still be kept, even some of the original metrics are exposed with standard metric names.
Proposed Changes
- Add the proposed metrics to the existing connectors.
- Mark the old metrics as deprecated if necessary.
- Correct the scope and metric names of the connectors if needed.
Compatibility, Deprecation, and Migration Plan
This FLIP proposes adding new metrics to the connectors and mark the old duplicate metrics as deprecated if necessary.
After some releases, we would like to remove some of the old metrics that are duplicates of the new standard metrics. But there is no strict timeline for that.
Test Plan
Standard connector metric test suites will be created to ensure the connector names are implemented correctly.
Rejected Alternatives
None