Authoring a Plugin

Processors implement the processor interface defined in .tangent/wit/processor.wit.

Interface

The interface has three methods to implement

Metadata

Name and version of your plugin

Go
Python
Rust

import (
    tangent_sdk "github.com/telophasehq/tangent-sdk-go"
)

var Metadata = tangent_sdk.Metadata{
    Name:    "golang",
    Version: "0.2.0",
}

def metadata(self) -> mapper.Meta:
  return mapper.Meta(name="python-example", version="0.1.0")

use exports::tangent::logs::mapper::Meta;

fn metadata() -> Meta {
    Meta {
        name: "rust".to_string(),
        version: "0.1.0".to_string(),
    }
}

Probe

Used to tell the host which logs to send to the mapper

Go
Python
Rust

import (
    tangent_sdk "github.com/telophasehq/tangent-sdk-go"
)

var selectors = []tangent_sdk.Selector{
    {
        All: []tangent_sdk.Predicate{
            tangent_sdk.EqString("source.name", "myservice"),
        },
    },
}

def probe(self) -> List[mapper.Selector]:
  # Match logs where source.name == "myservice"
  return [
      mapper.Selector(
          any=[],
          all=[
              mapper.Pred_Eq(
                  ("source.name", log.Scalar_Str("myservice"))
              )
          ],
          none=[],
      )
  ]

use exports::tangent::logs::mapper::{Pred, Selector};
use tangent::logs::log::Scalar;

fn probe() -> Vec<Selector> {
    vec![Selector {
        any: Vec::new(),
        all: vec![Pred::Eq((
            "source.name".to_string(),
            Scalar::Str("myservice".to_string()),
        ))],
        none: Vec::new(),
    }]
}

Will send all logs with

{"source.name": "myservice"}

{"source": {"name": "my service"}}

ProcessLogs

This is the business logic of your plugin. It takes in a log.Logview, which allows it to read json data provided by the host. This function can return scalars, lists, or maps. Performance note: Always prefer to fetch scalar values from the log. Scalars do not create heap allocations. Fetching lists and maps allocate on the heap, which hurts performance.

Go
Python
Rust

import (
    tangent_sdk "github.com/telophasehq/tangent-sdk-go"
    "github.com/telophasehq/tangent-sdk-go/helpers"
)

type ExampleOutput struct {
    Msg      string   `json:"message"`
}

func ExampleMapper(lv tangent_sdk.Log) (ExampleOutput, error) {
    var out ExampleOutput
    msg := helpers.GetString(lv, "msg")
    if msg != nil {
        out.Msg = *msg
    }

    return out, nil
}

func init() {
    tangent_sdk.Wire[ExampleOutput](
        Metadata,
        selectors,
        ExampleMapper,
        nil,
    )
}

func main() {}

def process_logs(self, logs: List[log.Logview]) -> bytes:
  buf = bytearray()
  for lv in logs:
      with lv:
          msg = lv.get("msg")
          value = msg.value if msg is not None else ""
          out.extend(json.dumps({"message": value}).encode() + b"\n")
  return bytes(buf)

use exports::tangent::logs::mapper::Guest;
use tangent::logs::log::{Logview, Scalar};

#[derive(Default, Serialize)]
struct ExampleOutput {
    message: String,
}

fn process_logs(input: Vec<Logview>) -> Result<Vec<u8>, String> {
    let mut buf = Vec::new();

    for lv in input {
        let mut out = ExampleOutput::default();

        if let Some(val) = lv.get("msg").and_then(string_from_scalar) {
            out.message = val;
        }

        let json_line = serde_json::to_vec(&out).map_err(|e| e.to_string())?;
        buf.extend(json_line);
        buf.push(b'\n');
    }

    Ok(buf)
}

Enriching logs

Plugins can make network calls to enrich logs. In this example, we batch all unique IPs found in the logs, call a remote API once per IP, and merge the results back into the output. The Go, Python, and Rust examples below show the same enrichment behavior.

Go
Python
Rust

import (
    "encoding/json"
    "fmt"
    "net/url"

    tangent_sdk "github.com/telophasehq/tangent-sdk-go"
    "github.com/telophasehq/tangent-sdk-go/helpers"
    "github.com/telophasehq/tangent-sdk-go/http"
)

type EnrichedOutput struct {
    IPAddress string `json:"ip_address"`
    Country   string `json:"country"`
    Service   string `json:"service"`
}

func ExampleMapper(lvs []tangent_sdk.Log) ([]EnrichedOutput, error) {
    outs := make([]EnrichedOutput, len(lvs))

    ipToIdx := make(map[string][]int)

    for i, lv := range lvs {
        if svc := helpers.GetString(lv, "service"); svc != nil {
            outs[i].Service = *svc
        }

        ipPtr := helpers.GetString(lv, "ip_address")
        if ipPtr == nil || *ipPtr == "" {
            continue
        }

        ip := *ipPtr
        outs[i].IPAddress = ip
        ipToIdx[ip] = append(ipToIdx[ip], i)
    }

    if len(ipToIdx) == 0 {
        return outs, nil
    }

    reqs := make([]http.RemoteRequest, 0, len(ipToIdx))
    for ip := range ipToIdx {
        u := "https://ipinfo.io/" + url.QueryEscape(ip)

        reqs = append(reqs, http.RemoteRequest{
            ID:     ip,
            Method: http.RemoteMethodGet,
            URL:    u,
        })
    }

    resps, err := http.RemoteCallBatch(reqs)
    if err != nil {
        return nil, fmt.Errorf("remote batch call failed: %w", err)
    }

    type ipinfoPayload struct {
        Country string `json:"country"`
    }

    ipToCountry := make(map[string]string, len(resps))

    for _, resp := range resps {
        if resp.Error != nil && *resp.Error != "" {
            return nil, fmt.Errorf("remote error for ip %s: %s", resp.ID, *resp.Error)
        }

        if resp.Status != 200 {
            return nil, fmt.Errorf("remote returned status %d for ip %s", resp.Status, resp.ID)
        }

        var payload ipinfoPayload
        if err := json.Unmarshal(resp.Body, &payload); err != nil {
            return nil, fmt.Errorf("failed to decode ipinfo response for %s: %w", resp.ID, err)
        }

        ipToCountry[resp.ID] = payload.Country
    }

    for ip, idxs := range ipToIdx {
        country := ipToCountry[ip]
        for _, i := range idxs {
            outs[i].Country = country
        }
    }

    return outs, nil
}

func init() {
    tangent_sdk.Wire[EnrichedOutput](
        Metadata,
        selectors,
        nil,           // per-log handler
        ExampleMapper, // batch handler
    )
}

func main() {}

import json
from typing import List, Dict
from wit_world.exports import mapper
from wit_world.imports import log, http

def process_logs(self, logs: List[log.Logview]) -> bytes:
  outs = []
  ip_to_idxs: Dict[str, List[int]] = {}

  # 1. Extract IPs & service names
  for i, lv in enumerate(logs):
      with lv:
          service = lv.get("service")
          ip = lv.get("ip_address")

          entry = {
              "service": service.value if service else "",
              "ip_address": ip.value if ip else "",
              "country": ""
          }
          outs.append(entry)

          if ip and ip.value:
              ip_to_idxs.setdefault(ip.value, []).append(i)

  if not ip_to_idxs:
      return b"\n".join(json.dumps(o).encode() for o in outs) + b"\n"

  # 2. Build remote requests
  reqs = []
  for ip in ip_to_idxs.keys():
      reqs.append(
          http.RemoteRequest(
              id=ip,
              method=http.RemoteMethod.GET,
              url=f"https://ipinfo.io/{ip}"
          )
      )

  # 3. Make batched remote calls
  resps = http.remote_call_batch(reqs)

  ip_to_country = {}
  for resp in resps:
      if resp.error is not None and resp.error != "":
          raise Exception(f"remote error for ip {resp.id}: {resp.error}")
      if resp.status != 200:
          raise Exception(f"unexpected status {resp.status} for ip {resp.id}")

      payload = json.loads(resp.body.decode())
      ip_to_country[resp.id] = payload.get("country", "")

  # 4. Assign country back to outputs
  for ip, idxs in ip_to_idxs.items():
      for i in idxs:
          outs[i]["country"] = ip_to_country.get(ip, "")

  # 5. Return JSON
  buf = bytearray()
  for o in outs:
      buf.extend(json.dumps(o).encode() + b"\n")
  return bytes(buf)

use serde::{Deserialize, Serialize};
use tangent::logs::log::Logview;
use exports::tangent::logs::mapper::http::{RemoteMethod, RemoteRequest, remote_call_batch};

#[derive(Default, Serialize)]
struct EnrichedOutput {
    ip_address: String,
    country: String,
    service: String,
}

fn process_logs(input: Vec<Logview>) -> Result<Vec<u8>, String> {
    let mut outs = Vec::<EnrichedOutput>::with_capacity(input.len());
    let mut ip_to_idxs: std::collections::HashMap<String, Vec<usize>> = std::collections::HashMap::new();

    // 1. Extract IPs & services
    for (i, lv) in input.iter().enumerate() {
        let mut out = EnrichedOutput::default();

        if let Some(svc) = lv.get("service").and_then(string_from_scalar) {
            out.service = svc;
        }

        if let Some(ip) = lv.get("ip_address").and_then(string_from_scalar) {
            if !ip.is_empty() {
                ip_to_idxs.entry(ip.clone()).or_default().push(i);
            }
            out.ip_address = ip;
        }

        outs.push(out);
    }

    // If no IPs, return quickly
    if ip_to_idxs.is_empty() {
        let mut buf = Vec::new();
        for o in outs {
            let line = serde_json::to_vec(&o).map_err(|e| e.to_string())?;
            buf.extend(line);
            buf.push(b'\n');
        }
        return Ok(buf);
    }

    // 2. Build remote requests
    let reqs: Vec<RemoteRequest> = ip_to_idxs
        .keys()
        .map(|ip| RemoteRequest {
            id: ip.clone(),
            method: RemoteMethod::Get,
            url: format!("https://ipinfo.io/{}", ip),
        })
        .collect();

    // 3. Make batched calls
    let responses = remote_call_batch(&reqs).map_err(|e| e.to_string())?;
    let mut ip_to_country = std::collections::HashMap::new();

    #[derive(Deserialize)]
    struct IpInfoPayload {
        country: Option<String>,
    }

    // 4. Validate & parse responses
    for resp in responses {
        if let Some(err) = resp.error {
            if !err.is_empty() {
                return Err(format!("remote error for {}: {}", resp.id, err));
            }
        }
        if resp.status != 200 {
            return Err(format!(
                "unexpected status {} for ip {}",
                resp.status, resp.id
            ));
        }

        let payload: IpInfoPayload =
            serde_json::from_slice(&resp.body).map_err(|e| e.to_string())?;

        ip_to_country.insert(resp.id, payload.country.unwrap_or_default());
    }

    // 5. Attach countries to outputs
    for (ip, idxs) in ip_to_idxs {
        let country = ip_to_country.get(&ip).cloned().unwrap_or_default();
        for idx in idxs {
            outs[idx].country = country.clone();
        }
    }

    // 6. Return JSONL
    let mut buf = Vec::new();
    for o in outs {
        let line = serde_json::to_vec(&o).map_err(|e| e.to_string())?;
        buf.extend(line);
        buf.push(b'\n');
    }

    Ok(buf)
}

Local dev loop

tangent plugin compile --config tangent.yaml --wit ./.tangent/wit
tangent plugin test --config tangent.yaml
tangent run --config tangent.yaml

# In a separate window
tangent bench --config tangent.yaml --seconds 30 --payload tests/input.json

​Interface

​Metadata

​Probe

​ProcessLogs

​Enriching logs

​Local dev loop