cloudwatch-logs (parlel)

A zero-dependency, in-process fake of Amazon CloudWatch Logs. Speaks the AWS JSON 1.1 wire protocol (X-Amz-Target: Logs_20140328.<Operation>). This is the standalone "extend CloudWatch with Logs" deliverable.

Field	Value
Service	`cloudwatch-logs`
Port	`4745`
Protocol	AWS JSON 1.1
Health	`GET /_parlel/health`
Reset	`POST /_parlel/reset`

Default connection

AWS_ENDPOINT_URL=http://127.0.0.1:4745
AWS_REGION=us-east-1
AWS_ACCESS_KEY_ID=parlel
AWS_SECRET_ACCESS_KEY=parlel

Supported operations

Operation	Notes
CreateLogGroup	Rejects duplicates.
DescribeLogGroups	Optional `logGroupNamePrefix`.
DeleteLogGroup
CreateLogStream
DescribeLogStreams	Optional `logStreamNamePrefix`.
DeleteLogStream
PutLogEvents	Returns/validates `nextSequenceToken`.
GetLogEvents	`startTime`/`endTime`/`limit`/`startFromHead`.
FilterLogEvents	Basic substring/term filter pattern.
PutRetentionPolicy	Stores `retentionInDays`.
TagLogGroup / ListTagsLogGroup / UntagLogGroup

Filter patterns

FilterLogEvents supports a simplified CloudWatch Logs pattern:

plain term — message must contain it (AND across terms)
-term — message must not contain it
?term — at least one optional term must match (OR group)
"quoted phrase" — matched as a substring

SDK example

import {
  CloudWatchLogsClient,
  PutLogEventsCommand,
} from "@aws-sdk/client-cloudwatch-logs";

const logs = new CloudWatchLogsClient({
  endpoint: "http://127.0.0.1:4745",
  region: "us-east-1",
  credentials: { accessKeyId: "parlel", secretAccessKey: "parlel" },
});

await logs.send(new PutLogEventsCommand({
  logGroupName: "/app/api",
  logStreamName: "instance-1",
  logEvents: [{ timestamp: Date.now(), message: "started" }],
}));

Access via MCP / preview URL

Under the parlel pool, reach this service through the MCP gateway and the pool's preview URL.

Surface coverage

This emulator faithfully replicates the API surface most application code and agents exercise. Anything below the supported lines is either an intentional design choice for a fast, zero-cost local emulator (✓ By design) or a candidate for a future release (⟳ Roadmap) — never a silent inaccuracy.

Legend: ✅ fully supported · ◐ accepted (stored, not strictly enforced) · ✓ by design · ⟳ on the roadmap.

Area	Limitation
Retention	`retentionInDays` is stored but events are never expired.
Metric filters	Not implemented.
Subscription filters	Not implemented.
Insights queries	`StartQuery`/`GetQueryResults` not implemented.
Filter pattern	Substring/term matching only (no JSON/metric syntax).
Pagination	Tokens are generated but events are returned in full per call.

Configuration — `test.env`

Copy these into your test.env (used by the bridge sidecar flow). Tokens are Parlel's seeded test credentials — any non-empty value is accepted by the emulator, so you rarely need to change them. Swap in real credentials only when pointing at the live service in prod.env.

AWS_ACCESS_KEY_ID=parlel
AWS_SECRET_ACCESS_KEY=parlel
AWS_REGION=us-east-1
AWS_ENDPOINT_URL=http://parlel-bridge:4745