Prometheus is the metrics store behind most monitoring stacks. MaestroHub provides four dedicated nodes for evaluating PromQL at an instant or over a range, listing the metric names a server knows, and pushing samples through the remote_write protocol within your pipelines.
Configuration Quick Reference
| Field | What you choose | Details |
|---|
| Parameters | Connection, Function, Function Parameters, Timeout Override | Select the connection profile, function, configure function parameters with expression support, and optionally override timeout. |
| Settings | Description, Timeout (seconds), Retry on Timeout, Retry on Fail, On Error | Node description, maximum execution time, retry behavior on timeout or failure, and error handling strategy. All execution settings default to pipeline-level values. |
Prometheus Instant Query Node
| Function Name | Purpose | Common Use Cases |
|---|
| Instant Query | Evaluate a PromQL expression (query) at one instant (time: RFC 3339, now, or unix seconds; defaults to now) | Current values, alert conditions, single-point lookups |
Prometheus Range Query Node
| Function Name | Purpose | Common Use Cases |
|---|
| Range Query | Evaluate a PromQL expression (query) from start to end every step (a duration such as 60s) | Trend charts, windowed reports, backfills |
Prometheus Write Samples Node
Push samples through remote_write. Every item in data is one sample: value, an optional timestamp (defaults to the event time), an optional metric and labels that override the function's defaults.
| Function Name | Purpose | Common Use Cases |
|---|
| Write Samples | Send the data samples under metric with labels | Publishing pipeline KPIs, bridging PLC readings into monitoring |
Prometheus List Metrics Node
| Function Name | Purpose | Common Use Cases |
|---|
| List Metrics | List the metric names the server knows, filtered by a series selector (match) when one is given | Discovery, dashboard builders |
Output
Every Prometheus node delivers its data under result, and execution facts (success, functionId, durationMs, timestamp) under _metadata:
| Node | Expression | Description |
|---|
| Instant Query, Range Query | $node["Name"].result.resultType | What PromQL evaluated to — vector (an instant query), matrix (a range query), scalar or string |
| $node["Name"].result.series | One object per series — its labels (the metric name under __name__) and its points, each a unix-seconds timestamp and a value. $node["Name"].result.series[0].points[0].value reads a value |
| $node["Name"].result.warnings | Warnings the server attached to the evaluation, null when there are none |
| List Metrics | $node["Name"].result.metrics | The metric names, as strings |
| $node["Name"].result.metricCount | How many names were listed |
| $node["Name"].result.warnings | Warnings the server attached, null when there are none |
| Write Samples | $node["Name"].result.samplesWritten | Samples sent in the remote_write request — one per data item |
| $node["Name"].result.statusCode | The HTTP status the remote_write endpoint answered with; a non-2xx answer fails the node instead |
The call's own facts ride along under _metadata next to the four every connected node carries: $node["Name"]._metadata.query after an Instant or Range Query, $node["Name"]._metadata.step after a Range Query, and $node["Name"]._metadata.writeURL after Write Samples. List Metrics adds none.