docs/content/maintenance/metrics.md

---
title: "Metrics"
weight: 9
type: docs
aliases:
- /maintenance/metrics.html
---
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# Paimon Metrics

Paimon has built a metrics system to measure the behaviours of reading and writing, like how many manifest files it scanned in the last planning, how long it took in the last commit operation, how many files it deleted in the last compact operation.

In Paimon's metrics system, metrics are updated and reported at table granularity.

There are three types of metrics provided in the Paimon metric system, `Gauge`, `Counter`, `Histogram`.
- `Gauge`: Provides a value of any type at a point in time.
- `Counter`: Used to count values by incrementing and decrementing.
- `Histogram`: Measure the statistical distribution of a set of values including the min, max, mean, standard deviation and percentile.

Paimon has supported built-in metrics to measure operations of **commits**, **scans**, **writes** and **compactions**, which can be bridged to any computing engine that supports, like Flink, Spark etc.

## Metrics List

Below is lists of Paimon built-in metrics. They are summarized into types of scan metrics, commit metrics, write metrics, write buffer metrics and compaction metrics.

### Scan Metrics

<table class="table table-bordered">
    <thead>
    <tr>
      <th class="text-left" style="width: 225pt">Metrics Name</th>
      <th class="text-left" style="width: 70pt">Type</th>
      <th class="text-left" style="width: 300pt">Description</th>
    </tr>
    </thead>
    <tbody>
        <tr>
            <td>lastScanDuration</td>
            <td>Gauge</td>
            <td>The time it took to complete the last scan.</td>
        </tr>
        <tr>
            <td>scanDuration</td>
            <td>Histogram</td>
            <td>Distributions of the time taken by the last few scans.</td>
        </tr>
        <tr>
            <td>lastScannedManifests</td>
            <td>Gauge</td>
            <td>Number of scanned manifest files in the last scan.</td>
        </tr>
        <tr>
            <td>lastScanSkippedTableFiles</td>
            <td>Gauge</td>
            <td>Total skipped table files in the last scan.</td>
        </tr>
        <tr>
            <td>lastScanResultedTableFiles</td>
            <td>Gauge</td>
            <td>Resulted table files in the last scan.</td>
        </tr>
    </tbody>
</table>

### Commit Metrics

<table class="table table-bordered">
    <thead>
    <tr>
      <th class="text-left" style="width: 225pt">Metrics Name</th>
      <th class="text-left" style="width: 70pt">Type</th>
      <th class="text-left" style="width: 300pt">Description</th>
    </tr>
    </thead>
    <tbody>
        <tr>
            <td>lastCommitDuration</td>
            <td>Gauge</td>
            <td>The time it took to complete the last commit.</td>
        </tr>
        <tr>
            <td>commitDuration</td>
            <td>Histogram</td>
            <td>Distributions of the time taken by the last few commits.</td>
        </tr>
        <tr>
            <td>lastCommitAttempts</td>
            <td>Gauge</td>
            <td>The number of attempts the last commit made.</td>
        </tr>
        <tr>
            <td>lastTableFilesAdded</td>
            <td>Gauge</td>
            <td>Number of added table files in the last commit, including newly created data files and compacted after.</td>
        </tr>
        <tr>
            <td>lastTableFilesDeleted</td>
            <td>Gauge</td>
            <td>Number of deleted table files in the last commit, which comes from compacted before.</td>
        </tr>
        <tr>
            <td>lastTableFilesAppended</td>
            <td>Gauge</td>
            <td>Number of appended table files in the last commit, which means the newly created data files.</td>
        </tr>
        <tr>
            <td>lastTableFilesCommitCompacted</td>
            <td>Gauge</td>
            <td>Number of compacted table files in the last commit, including compacted before and after.</td>
        </tr>
        <tr>
            <td>lastChangelogFilesAppended</td>
            <td>Gauge</td>
            <td>Number of appended changelog files in last commit.</td>
        </tr>
        <tr>
            <td>lastChangelogFileCommitCompacted</td>
            <td>Gauge</td>
            <td>Number of compacted changelog files in last commit.</td>
        </tr>
        <tr>
            <td>lastGeneratedSnapshots</td>
            <td>Gauge</td>
            <td>Number of snapshot files generated in the last commit, maybe 1 snapshot or 2 snapshots.</td>
        </tr>
        <tr>
            <td>lastDeltaRecordsAppended</td>
            <td>Gauge</td>
            <td>Delta records count in last commit with APPEND commit kind.</td>
        </tr>
        <tr>
            <td>lastChangelogRecordsAppended</td>
            <td>Gauge</td>
            <td>Changelog records count in last commit with APPEND commit kind.</td>
        </tr>
        <tr>
            <td>lastDeltaRecordsCommitCompacted</td>
            <td>Gauge</td>
            <td>Delta records count in last commit with COMPACT commit kind.</td>
        </tr>
        <tr>
            <td>lastChangelogRecordsCommitCompacted</td>
            <td>Gauge</td>
            <td>Changelog records count in last commit with COMPACT commit kind.</td>
        </tr>
        <tr>
            <td>lastPartitionsWritten</td>
            <td>Gauge</td>
            <td>Number of partitions written in the last commit.</td>
        </tr>
        <tr>
            <td>lastBucketsWritten</td>
            <td>Gauge</td>
            <td>Number of buckets written in the last commit.</td>
        </tr>
        <tr>
            <td>lastCompactionInputFileSize</td>
            <td>Gauge</td>
            <td>Total size of the input files for the last compaction.</td>
        </tr>
        <tr>
            <td>lastCompactionOutputFileSize</td>
            <td>Gauge</td>
            <td>Total size of the output files for the last compaction.</td>
        </tr>
    </tbody>
</table>

### Write Buffer Metrics

<table class="table table-bordered">
    <thead>
    <tr>
      <th class="text-left" style="width: 225pt">Metrics Name</th>
      <th class="text-left" style="width: 70pt">Type</th>
      <th class="text-left" style="width: 300pt">Description</th>
    </tr>
    </thead>
    <tbody>
        <tr>
            <td>numWriters</td>
            <td>Gauge</td>
            <td>Number of writers in this parallelism.</td>
        </tr>
        <tr>
            <td>bufferPreemptCount</td>
            <td>Gauge</td>
            <td>The total number of memory preempted.</td>
        </tr>
        <tr>
            <td>usedWriteBufferSizeByte</td>
            <td>Gauge</td>
            <td>Current used write buffer size in byte.</td>
        </tr>
        <tr>
            <td>totalWriteBufferSizeByte</td>
            <td>Gauge</td>
            <td>The total write buffer size configured in byte.</td>
        </tr>
    </tbody>
</table>

### Compaction Metrics

<table class="table table-bordered">
    <thead>
    <tr>
      <th class="text-left" style="width: 225pt">Metrics Name</th>
      <th class="text-left" style="width: 70pt">Type</th>
      <th class="text-left" style="width: 300pt">Description</th>
    </tr>
    </thead>
    <tbody>
        <tr>
            <td>maxLevel0FileCount</td>
            <td>Gauge</td>
            <td>The maximum number of level 0 files currently handled by this task. This value will become larger if asynchronous compaction cannot be done in time.</td>
        </tr>
        <tr>
            <td>avgLevel0FileCount</td>
            <td>Gauge</td>
            <td>The average number of level 0 files currently handled by this task. This value will become larger if asynchronous compaction cannot be done in time.</td>
        </tr>
        <tr>
            <td>compactionThreadBusy</td>
            <td>Gauge</td>
            <td>The maximum business of compaction threads in this task. Currently, there is only one compaction thread in each parallelism, so value of business ranges from 0 (idle) to 100 (compaction running all the time).</td>
        </tr>
        <tr>
            <td>avgCompactionTime</td>
            <td>Gauge</td>
            <td>The average runtime of compaction threads, calculated based on recorded compaction time data in milliseconds. The value represents the average duration of compaction operations. Higher values indicate longer average compaction times, which may suggest the need for performance optimization.</td>
        </tr>
       <tr>
            <td>compactionCompletedCount</td>
            <td>Counter</td>
            <td>The total number of compactions that have completed.</td>
        </tr>
        <tr>
            <td>compactionQueuedCount</td>
            <td>Counter</td>
            <td>The total number of compactions that are queued/running.</td>
        </tr>
        <tr>
            <td>compactionTotalCount</td>
            <td>Counter</td>
            <td>The total number of compactions.</td>
        </tr>
        <tr>
            <td>maxCompactionInputSize</td>
            <td>Gauge</td>
            <td>The maximum input file size for this task's compaction.</td>
        </tr>
        <tr>
            <td>avgCompactionInputSize</td>
            <td>Gauge</td>
            <td>The average input file size for this task's compaction.</td>
        </tr>
        <tr>
            <td>maxCompactionOutputSize</td>
            <td>Gauge</td>
            <td>The maximum output file size for this task's compaction.</td>
        </tr>
        <tr>
            <td>avgCompactionOutputSize</td>
            <td>Gauge</td>
            <td>The average output file size for this task's compaction.</td>
        </tr>
        <tr>
            <td>maxTotalFileSize</td>
            <td>Gauge</td>
            <td>The maximum total file size of an active (currently being written) bucket.</td>
        </tr>
        <tr>
            <td>avgTotalFileSize</td>
            <td>Gauge</td>
            <td>The average total file size of all active (currently being written) buckets.</td>
        </tr>
    </tbody>
</table>

## Bridging To Flink

Paimon has implemented bridging metrics to Flink's metrics system, which can be reported by Flink, and the lifecycle of metric groups are managed by Flink.

Please join the `<scope>.<infix>.<metric_name>` to get the complete metric identifier when using Flink to access Paimon, `metric_name` can be got from [Metric List]({{< ref "maintenance/metrics#metrics-list" >}}).

For example, the identifier of metric `lastPartitionsWritten` for table `word_count` in Flink job named `insert_word_count` is:

`localhost.taskmanager.localhost:60340-775a20.insert_word_count.Global Committer : word_count.0.paimon.table.word_count.commit.lastPartitionsWritten`.

From Flink Web-UI, go to the committer operator's metrics, it's shown as:

`0.Global_Committer___word_count.paimon.table.word_count.commit.lastPartitionsWritten`.

{{< hint info >}}
1. Please refer to [System Scope](https://nightlies.apache.org/flink/flink-docs-master/docs/ops/metrics/#system-scope) to understand Flink `scope`
2. Scan metrics are only supported by Flink versions >= 1.18
{{< /hint >}}

<table class="table table-bordered">
    <thead>
    <tr>
      <th class="text-left" style="width: 130pt"></th>
      <th class="text-left" style="width: 280pt">Scope</th>
      <th class="text-left" style="width: 250pt">Infix</th>
    </tr>
    </thead>
    <tbody>
        <tr>
            <td>Scan Metrics</td>
            <td>&lt;host&gt;.jobmanager.&lt;job_name&gt;</td>
            <td>&lt;source_operator_name&gt;.coordinator. enumerator.paimon.table.&lt;table_name&gt;.scan</td>
        </tr>
        <tr>
            <td>Commit Metrics</td>
            <td>&lt;host&gt;.taskmanager.&lt;tm_id&gt;.&lt;job_name&gt;.&lt;committer_operator_name&gt;.&lt;subtask_index&gt;</td>
            <td>paimon.table.&lt;table_name&gt;.commit</td>
        </tr>
        <tr>
            <td>Write Metrics</td>
            <td>&lt;host&gt;.taskmanager.&lt;tm_id&gt;.&lt;job_name&gt;.&lt;writer_operator_name&gt;.&lt;subtask_index&gt;</td>
            <td>paimon.table.&lt;table_name&gt;.partition.&lt;partition_string&gt;.bucket.&lt;bucket_index&gt;.writer</td>
        </tr>
        <tr>
            <td>Write Buffer Metrics</td>
            <td>&lt;host&gt;.taskmanager.&lt;tm_id&gt;.&lt;job_name&gt;.&lt;writer_operator_name&gt;.&lt;subtask_index&gt;</td>
            <td>paimon.table.&lt;table_name&gt;.writeBuffer</td>
        </tr>
        <tr>
            <td>Compaction Metrics</td>
            <td>&lt;host&gt;.taskmanager.&lt;tm_id&gt;.&lt;job_name&gt;.&lt;writer_operator_name&gt;.&lt;subtask_index&gt;</td>
            <td>paimon.table.&lt;table_name&gt;.partition.&lt;partition_string&gt;.bucket.&lt;bucket_index&gt;.compaction</td>
        </tr>
        <tr>
            <td>Flink Source Metrics</td>
            <td>&lt;host&gt;.taskmanager.&lt;tm_id&gt;.&lt;job_name&gt;.&lt;source_operator_name&gt;.&lt;subtask_index&gt;</td>
            <td>-</td>
        </tr>
        <tr>
            <td>Flink Sink Metrics</td>
            <td>&lt;host&gt;.taskmanager.&lt;tm_id&gt;.&lt;job_name&gt;.&lt;committer_operator_name&gt;.&lt;subtask_index&gt;</td>
            <td>-</td>
        </tr>  
    </tbody>
</table>

### Flink Connector Standard Metrics

When using Flink to read and write, Paimon has implemented some key standard Flink connector metrics to measure the source latency and output of sink, see [FLIP-33: Standardize Connector Metrics](https://cwiki.apache.org/confluence/display/FLINK/FLIP-33%3A+Standardize+Connector+Metrics). Flink source / sink metrics implemented are listed here.

#### Source Metrics (Flink)

<table class="table table-bordered">
    <thead>
    <tr>
      <th class="text-left" style="width: 225pt">Metrics Name</th>
      <th class="text-left" style="width: 65pt">Level</th>
      <th class="text-left" style="width: 70pt">Type</th>
      <th class="text-left" style="width: 300pt">Description</th>
    </tr>
    </thead>
    <tbody>
        <tr>
            <td>currentEmitEventTimeLag</td>
            <td>Flink Source Operator</td>
            <td>Gauge</td>
            <td>Time difference between sending the record out of source and file creation.</td>
        </tr>
        <tr>
            <td>currentFetchEventTimeLag</td>
            <td>Flink Source Operator</td>
            <td>Gauge</td>
            <td>Time difference between reading the data file and file creation.</td>
        </tr>
    </tbody>
</table>

{{< hint info >}}
Please note that if you specified `consumer-id` in your streaming query, the level of source metrics should turn into the reader operator, which is behind the `Monitor` operator.
{{< /hint >}}

#### Sink Metrics (Flink)

<table class="table table-bordered">
    <thead>
    <tr>
      <th class="text-left" style="width: 225pt">Metrics Name</th>
      <th class="text-left" style="width: 65pt">Level</th>
      <th class="text-left" style="width: 70pt">Type</th>
      <th class="text-left" style="width: 300pt">Description</th>
    </tr>
    </thead>
    <tbody>
        <tr>
            <td>numBytesOut</td>
            <td>Table</td>
            <td>Counter</td>
            <td>The total number of output bytes.</td>
        </tr>
        <tr>
            <td>numBytesOutPerSecond</td>
            <td>Table</td>
            <td>Meter</td>
            <td>The output bytes per second.</td>
        </tr>
        <tr>
            <td>numRecordsOut</td>
            <td>Table</td>
            <td>Counter</td>
            <td>The total number of output records.</td>
        </tr>
        <tr>
            <td>numRecordsOutPerSecond</td>
            <td>Table</td>
            <td>Meter</td>
            <td>The output records per second.</td>
        </tr>  
    </tbody>
</table>