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Update documentation

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Andrew Noyes 2020-06-28 20:56:44 +00:00
parent 1c30adce74
commit b1d5e99494
2 changed files with 14 additions and 23 deletions
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35
documentation/sphinx/source/developer-guide.rst
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@ -845,30 +845,21 @@ Metrics module
Reads in the metrics module are not transactional and may require rpcs to complete. Reads in the metrics module are not transactional and may require rpcs to complete.
The key ``\xff\xff/metrics/data_distribution_stats/<begin>`` represent stats about the shard that begins at ``<begin>``. The value is a json object with a "ShardBytes" field. More fields may be added in the future. ``\xff\xff/metrics/data_distribution_stats/<begin>`` represent stats about the shard that begins at ``<begin>``
A user can see stats about data distribution like so:: >>> for k, v in db.get_range_startswith('\xff\xff/metrics/data_distribution_stats/', limit=3):
TODO update with "Storages" field, add table with schema like in health keys, and document caveats. ShardBytes is an estimate.
>>> for k, v in db.get_range_startswith('\xff\xff/metrics/data_distribution_stats/'):
... print(k, v) ... print(k, v)
... ...
('\xff\xff/metrics/data_distribution_stats/', '{"ShardBytes":330000}') ('\xff\xff/metrics/data_distribution_stats/', '{"ShardBytes":3828000,"Storages":["697f39751849d70067eabd1b079478a5"]}')
('\xff\xff/metrics/data_distribution_stats/mako00509', '{"ShardBytes":330000}') ('\xff\xff/metrics/data_distribution_stats/mako00079', '{"ShardBytes":2013000,"Storages":["697f39751849d70067eabd1b079478a5"]}')
('\xff\xff/metrics/data_distribution_stats/mako0099', '{"ShardBytes":330000}') ('\xff\xff/metrics/data_distribution_stats/mako00126', '{"ShardBytes":3201000,"Storages":["697f39751849d70067eabd1b079478a5"]}')
('\xff\xff/metrics/data_distribution_stats/mako01468', '{"ShardBytes":297000}')
('\xff\xff/metrics/data_distribution_stats/mako023', '{"ShardBytes":264000}') ========================= ======== ===============
('\xff\xff/metrics/data_distribution_stats/mako0289', '{"ShardBytes":297000}') **Field** **Type** **Description**
('\xff\xff/metrics/data_distribution_stats/mako037', '{"ShardBytes":330000}') ------------------------- -------- ---------------
('\xff\xff/metrics/data_distribution_stats/mako042', '{"ShardBytes":264000}') ShardBytes number An estimate of the sum of kv sizes for this shard.
('\xff\xff/metrics/data_distribution_stats/mako0457', '{"ShardBytes":297000}') Storages [string] A list of the storage process ids currently responsible for this shard.
('\xff\xff/metrics/data_distribution_stats/mako0524', '{"ShardBytes":264000}') ========================= ======== ===============
('\xff\xff/metrics/data_distribution_stats/mako058', '{"ShardBytes":297000}')
('\xff\xff/metrics/data_distribution_stats/mako064', '{"ShardBytes":297000}')
('\xff\xff/metrics/data_distribution_stats/mako0718', '{"ShardBytes":264000}')
('\xff\xff/metrics/data_distribution_stats/mako083', '{"ShardBytes":297000}')
('\xff\xff/metrics/data_distribution_stats/mako0909', '{"ShardBytes":741000}')
Keys starting with ``\xff\xff/metrics/health/`` represent stats about the health of the cluster, suitable for application-level throttling. Keys starting with ``\xff\xff/metrics/health/`` represent stats about the health of the cluster, suitable for application-level throttling.
Some of this information is also available in ``\xff\xff/status/json``, but these keys are significantly cheaper (in terms of server resources) to read. Some of this information is also available in ``\xff\xff/status/json``, but these keys are significantly cheaper (in terms of server resources) to read.
@ -920,7 +911,7 @@ storageQueue number The number of bytes of mutations that need to
Caveats Caveats
~~~~~~~ ~~~~~~~
#. ``\xff\xff/metrics/health/`` These keys may return data that's several seconds old, and the data may not be available for a brief period during recovery. This will be indicated by the keys briefly not being present when read. Clients should be prepared for these keys to be absent. #. ``\xff\xff/metrics/health/`` These keys may return data that's several seconds old, and the data may not be available for a brief period during recovery. This will be indicated by the keys being absent.
Performance considerations Performance considerations
========================== ==========================

2
fdbclient/NativeAPI.actor.cpp
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@ -596,7 +596,7 @@ public:
static Standalone<RangeResultRef> healthMetricsToKVPairs(const HealthMetrics& metrics, KeyRangeRef kr) { static Standalone<RangeResultRef> healthMetricsToKVPairs(const HealthMetrics& metrics, KeyRangeRef kr) {
Standalone<RangeResultRef> result; Standalone<RangeResultRef> result;
if (kr.contains(LiteralStringRef("\xff\xff/metrics/health/aggregate"))) { if (kr.contains(LiteralStringRef("\xff\xff/metrics/health/aggregate")) && metrics.worstStorageDurabilityLag != 0) {
json_spirit::mObject statsObj; json_spirit::mObject statsObj;
statsObj["batchLimited"] = metrics.batchLimited; statsObj["batchLimited"] = metrics.batchLimited;
statsObj["tpsLimit"] = metrics.tpsLimit; statsObj["tpsLimit"] = metrics.tpsLimit;