hadoop/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/OzoneMetrics.md

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HDFS Ozone Metrics
===============

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Overview
--------

The container metrics that is used in HDFS Ozone.

### Storage Container Metrics

The metrics for various storage container operations in HDFS Ozone.

Storage container is an optional service that can be enabled by setting
'ozone.enabled' to true.
These metrics are only available when ozone is enabled.

Storage Container Metrics maintains a set of generic metrics for all
container RPC calls that can be made to a datandoe/container.

Along with the total number of RPC calls containers maintain a set of metrics
for each RPC call. Following is the set of counters maintained for each RPC
operation.

*Total number of operation* - We maintain an array which counts how
many times a specific operation has been performed.
Eg.`NumCreateContainer` tells us how many times create container has been
invoked on this datanode.

*Total number of pending operation* - This is an array which counts how
many times a specific operation is waitting to be processed from the client
point of view.
Eg.`NumPendingCreateContainer` tells us how many create container requests that
waitting to be processed.

*Average latency of each pending operation in nanoseconds* - The average latency
of the operation from the client point of view.
Eg. `CreateContainerLatencyAvgTime` - This tells us the average latency of
Create Container from the client point of view.

*Number of bytes involved in a specific command* - This is an array that is
maintained for all operations, but makes sense only for read and write
operations.

While it is possible to read the bytes in update container, it really makes
no sense, since no data stream involved. Users are advised to use this
metric only when it makes sense. Eg. `BytesReadChunk` -- Tells us how
many bytes have been read from this data using Read Chunk operation.

*Average Latency of each operation* - The average latency of the operation.
Eg. `LatencyCreateContainerAvgTime` - This tells us the average latency of
Create Container.

*Quantiles for each of these operations* - The 50/75/90/95/99th percentile
of these operations. Eg. `CreateContainerNanos60s50thPercentileLatency` --
gives latency of the create container operations at the 50th percentile latency
(1 minute granularity). We report 50th, 75th, 90th, 95th and 99th percentile
for all RPCs.

So this leads to the containers reporting these counters for each of these
RPC operations.

| Name | Description |
|:---- |:---- |
| `NumOps` | Total number of container operations |
| `CreateContainer` | Create container operation |
| `ReadContainer` | Read container operation |
| `UpdateContainer` | Update container operations |
| `DeleteContainer` | Delete container operations |
| `ListContainer` | List container operations |
| `PutKey` | Put key operations |
| `GetKey` | Get key operations |
| `DeleteKey` | Delete key operations |
| `ListKey` | List key operations |
| `ReadChunk` | Read chunk operations |
| `DeleteChunk` | Delete chunk operations |
| `WriteChunk` | Write chunk operations|
| `ListChunk` | List chunk operations |
| `CompactChunk` | Compact chunk operations |
| `PutSmallFile` | Put small file operations |
| `GetSmallFile` | Get small file operations |
| `CloseContainer` | Close container operations |

### Storage Container Manager Metrics

The metrics for containers that managed by Storage Container Manager.

Storage Container Manager (SCM) is a master service which keeps track of
replicas of storage containers. It also manages all data nodes and their
states, dealing with container reports and dispatching commands for execution.

Following are the counters for containers:

| Name | Description |
|:---- |:---- |
| `LastContainerReportSize` | Total size in bytes of all containers |
| `LastContainerReportUsed` | Total number of bytes used by all containers |
| `LastContainerReportKeyCount` | Total number of keys in all containers |
| `LastContainerReportReadBytes` | Total number of bytes have been read from all containers |
| `LastContainerReportWriteBytes` | Total number of bytes have been written into all containers |
| `LastContainerReportReadCount` | Total number of times containers have been read from |
| `LastContainerReportWriteCount` | Total number of times containers have been written to |

### Key Space Metrics

The metrics for various key space manager operations in HDFS Ozone.

key space manager (KSM) is a service that similar to the Namenode in HDFS.
In the current design of KSM, it maintains metadata of all volumes, buckets and keys.
These metrics are only available when ozone is enabled.

Following is the set of counters maintained for each key space operation.

*Total number of operation* - We maintain an array which counts how
many times a specific operation has been performed.
Eg.`NumVolumeCreate` tells us how many times create volume has been
invoked in KSM.

*Total number of failed operation* - This type operation is opposite to the above
operation.
Eg.`NumVolumeCreateFails` tells us how many times create volume has been invoked
failed in KSM.

Following are the counters for each of key space operations.

| Name | Description |
|:---- |:---- |
| `VolumeCreate` | Create volume operation |
| `VolumeUpdates` | Update volume property operation |
| `VolumeInfos` | Get volume information operation |
| `VolumeCheckAccesses` | Check volume access operation |
| `VolumeDeletes` | Delete volume operation |
| `VolumeLists` | List volume operation |
| `BucketCreates` | Create bucket operation |
| `BucketInfos` | Get bucket information operation |
| `BucketUpdates` | Update bucket property operation |
| `BucketDeletes` | Delete bucket operation |
| `BucketLists` | List bucket operation |
| `KeyAllocate` | Allocate key operation |
| `KeyLookup` | Look up key operation |
| `KeyDeletes` | Delete key operation |
| `KeyLists` | List key operation |