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Version: Nightly

Trace Data Modeling

warning

This section currently in the experimental stage and may be adjusted in future versions.

In this section, we will cover how trace data is modeled in GreptimeDB as tables.

We reuse the concept of Pipeline for trace data modeling. However, note that at the moment, only built-in pipelines are supported.

Data Model Versioning​

First, the data types and features in GreptimeDB are evolving. For forward-compatibility, we use the pipeline name for data model versioning. Currently we have the following built-in pipeline for trace:

  • greptime_trace_v1: The recommended data model for trace tables.

Specify the data model in OpenTelemetry OTLP/HTTP requests with the x-greptime-pipeline-name header. Use x-greptime-pipeline-name: greptime_trace_v1 for new trace tables.

We may introduce new data models by adding new available pipeline names. Note that a new pipeline may not be compatible with previous ones, so you are recommended to use it in a new table.

Data Model​

The greptime_trace_v1 data model is pretty straight-forward. By default, trace data is stored in a table named opentelemetry_traces. You can customize the table name by specifying the x-greptime-trace-table-name header in your OTLP/HTTP requests.

  • It maps most common data fields from OpenTelemetry Trace data model to GreptimeDB's table columns.
  • service_name is extracted from resource_attributes["service.name"] and used as a Tag (part of the Primary Key).
  • timestamp is the start time of the span and is used as the Time Index.
  • A new duration_nano column is generated using end_time - start_time.
  • All attributes fields are flattened into columns using the name pattern: [span|resource|scope]_attributes.[attribute_key].
    • Note: resource_attributes.service.name is excluded from flattening as it is already stored in the service_name column.
    • If the attribute value is a compound type like Array or Kvlist, it is serialized to JSON type of GreptimeDB.
  • Compound fields, span_links and span_events are stored as JSON type.

The table will be automatically generated when your first data item arrived. It also follows our schema-less principle to update the table schema automatically for new columns, for example, the new attribute fields.

For greptime_trace_v1, GreptimeDB also reconciles attribute column types while the schema evolves. When a trace table already exists, the existing table schema is authoritative for compatible incoming values. Scalar values can be coerced to an existing compatible column type, and existing Int64 attribute columns may be widened to Float64 when incoming values contain both integers and floats. If a span still cannot be written, GreptimeDB may reject that span while accepting the other spans in the request.

A typical table structure generated from OpenTelemetry django instrument is like:

timestamp                                  | 2025-05-07 10:03:29.657544
timestamp_end                              | 2025-05-07 10:03:29.661714
duration_nano                              | 4169970
trace_id                                   | fb60d19aa36fdcb7d14a71ca0b9b42ae
span_id                                    | 49806a2671f2ddcb
span_kind                                  | SPAN_KIND_SERVER
span_name                                  | POST todos/
span_status_code                           | STATUS_CODE_UNSET
span_status_message                        |
trace_state                                |
scope_name                                 | opentelemetry.instrumentation.django
scope_version                              | 0.51b0
service_name                               | myproject
span_attributes.http.request.method        | POST
span_attributes.url.full                   |
span_attributes.server.address             | django:8000
span_attributes.network.peer.address       |
span_attributes.server.port                | 8000
span_attributes.network.peer.port          |
span_attributes.http.response.status_code  | 201
span_attributes.network.protocol.version   | 1.1
resource_attributes.telemetry.sdk.language | python
resource_attributes.telemetry.sdk.name     | opentelemetry
resource_attributes.telemetry.sdk.version  | 1.30.0
span_events                                | []
span_links                                 | []
parent_span_id                             | eccc18b6fc210f31
span_attributes.db.system                  |
span_attributes.db.name                    |
span_attributes.db.statement               |
span_attributes.url.scheme                 | http
span_attributes.url.path                   | /todos/
span_attributes.client.address             | 10.89.0.5
span_attributes.client.port                | 44302
span_attributes.user_agent.original        | python-requests/2.32.3
span_attributes.http.route                 | todos/

To check the table definition, you can use show create table opentelemetry_traces statement. An output like this is expected:

Table        | opentelemetry_traces
Create Table | CREATE TABLE IF NOT EXISTS "opentelemetry_traces" (                                           +
             |   "timestamp" TIMESTAMP(9) NOT NULL,                                                    +
             |   "timestamp_end" TIMESTAMP(9) NULL,                                                    +
             |   "duration_nano" BIGINT UNSIGNED NULL,                                                 +
             |   "trace_id" STRING NULL SKIPPING INDEX WITH(granularity = '10240', type = 'BLOOM'),    +
             |   "span_id" STRING NULL,                                                                +
             |   "span_kind" STRING NULL,                                                              +
             |   "span_name" STRING NULL,                                                              +
             |   "span_status_code" STRING NULL,                                                       +
             |   "span_status_message" STRING NULL,                                                    +
             |   "trace_state" STRING NULL,                                                            +
             |   "scope_name" STRING NULL,                                                             +
             |   "scope_version" STRING NULL,                                                          +
             |   "service_name" STRING NULL SKIPPING INDEX WITH(granularity = '10240', type = 'BLOOM'),+
             |   "span_attributes.http.request.method" STRING NULL,                                    +
             |   "span_attributes.url.full" STRING NULL,                                               +
             |   "span_attributes.server.address" STRING NULL,                                         +
             |   "span_attributes.network.peer.address" STRING NULL,                                   +
             |   "span_attributes.server.port" BIGINT NULL,                                            +
             |   "span_attributes.network.peer.port" BIGINT NULL,                                      +
             |   "span_attributes.http.response.status_code" BIGINT NULL,                              +
             |   "span_attributes.network.protocol.version" STRING NULL,                               +
             |   "resource_attributes.telemetry.sdk.language" STRING NULL,                             +
             |   "resource_attributes.telemetry.sdk.name" STRING NULL,                                 +
             |   "resource_attributes.telemetry.sdk.version" STRING NULL,                              +
             |   "span_events" JSON NULL,                                                              +
             |   "span_links" JSON NULL,                                                               +
             |   "parent_span_id" STRING NULL,                                                         +
             |   "span_attributes.db.system" STRING NULL,                                              +
             |   "span_attributes.db.name" STRING NULL,                                                +
             |   "span_attributes.db.statement" STRING NULL,                                           +
             |   "span_attributes.url.scheme" STRING NULL,                                             +
             |   "span_attributes.url.path" STRING NULL,                                               +
             |   "span_attributes.client.address" STRING NULL,                                         +
             |   "span_attributes.client.port" BIGINT NULL,                                            +
             |   "span_attributes.user_agent.original" STRING NULL,                                    +
             |   "span_attributes.http.route" STRING NULL,                                             +
             |   TIME INDEX ("timestamp"),                                                             +
             |   PRIMARY KEY ("service_name")                                                          +
             | )                                                                                       +
             | PARTITION ON COLUMNS ("trace_id") (                                                     +
             |   trace_id < '1',                                                                       +
             |   trace_id >= 'f',                                                                      +
             |   trace_id >= '1' AND trace_id < '2',                                                   +
             |   trace_id >= '2' AND trace_id < '3',                                                   +
             |   trace_id >= '3' AND trace_id < '4',                                                   +
             |   trace_id >= '4' AND trace_id < '5',                                                   +
             |   trace_id >= '5' AND trace_id < '6',                                                   +
             |   trace_id >= '6' AND trace_id < '7',                                                   +
             |   trace_id >= '7' AND trace_id < '8',                                                   +
             |   trace_id >= '8' AND trace_id < '9',                                                   +
             |   trace_id >= '9' AND trace_id < 'a',                                                   +
             |   trace_id >= 'a' AND trace_id < 'b',                                                   +
             |   trace_id >= 'b' AND trace_id < 'c',                                                   +
             |   trace_id >= 'c' AND trace_id < 'd',                                                   +
             |   trace_id >= 'd' AND trace_id < 'e',                                                   +
             |   trace_id >= 'e' AND trace_id < 'f'                                                    +
             | )                                                                                       +
             | ENGINE=mito                                                                             +
             | WITH(                                                                                   +
             |   append_mode = 'true',                                                                 +
             |   table_data_model = 'greptime_trace_v1'                                                +
             | )

Partition Rules​

We included default partition rules for trace table on the trace_id column based on the first character of it. This is optimised for retrieve trace spans by the trace id.

The partition rule introduces 16 partitions for the table. It is suitable for a 3-5 datanode setup.

To customize the partition rule, you can:

  1. Create a new table ahead-of-time by copying the DDL output by show create table on original table, update the PARTITION ON section to include your own rules.
  2. Use x-greptime-hints HTTP header in your OTLP ingestion request, include a hint trace_table_partitions=n where n is the partition number. Set n to 0 or 1 to disable partitioning.

Index​

We include skipping index on service_name, trace_id, and parent_span_id for most typical queries.

In real-world, you may want to speed up queries on other fields like an attribute field. It's possible by apply additional index on these fields using alter table statement.

Unlike partition rules, index can be created on existing table and be affective on new data.

Partial Success​

When a trace request contains multiple spans, GreptimeDB may accept the spans that can be written and reject only the spans that fail deterministic validation, such as incompatible schema or values. In this case the OTLP response contains a partial_success section with rejected_spans and error_message. If all spans are rejected, GreptimeDB returns 400 Bad Request.

Append-only Mode​

By default, trace table created by OpenTelemetry API are in append only mode.

TTL​

You can apply TTL on trace table.

Auxiliary Tables​

When you ingest trace data, GreptimeDB automatically creates two auxiliary tables to facilitate searching for services and operations. These tables are named by appending _services and _operations to your main trace table name.

By default, these are named opentelemetry_traces_services and opentelemetry_traces_operations. If you customize the main trace table name using the x-greptime-trace-table-name HTTP header, the auxiliary tables will be named accordingly (e.g., <custom_table_name>_services and <custom_table_name>_operations).

Services Table (opentelemetry_traces_services)​

This table stores the list of unique service names found in the trace data.

  • Columns:
    • timestamp: A constant timestamp (2100-01-01 00:00:00) used for all entries.
    • service_name: The name of the service (Tag).

Operations Table (opentelemetry_traces_operations)​

This table stores the list of unique operations (service, span name, and span kind) found in the trace data.

  • Columns:
    • timestamp: A constant timestamp (2100-01-01 00:00:00) used for all entries.
    • service_name: The name of the service (Tag).
    • span_name: The name of the span (Tag).
    • span_kind: The kind of the span (Tag).