Pub/Sub walkthrough

Send a message through Pub/Sub on the emulator: create a topic and a subscription, publish hello, pull it back and acknowledge it, then delete what you made. Each step shows the output to expect. The steps were run against Vera 1.2.3 on 9 November 2026. The outputs shown were captured in an earlier run, and their IDs and times differ on every run.

Before you start

• A running emulator. Start Vera as described in Get started. Pub/Sub is included in the Free plan.
• gcloud or curl. The gcloud steps were run with gcloud 585.0.0. The REST steps use curl, plus python3 to copy an ID from one response into the next request. Pub/Sub on the emulator is REST only, so client libraries that use gRPC by default won’t connect.
• No Google Cloud account. The emulator doesn’t check credentials, and no real project is needed. This walkthrough uses example-project.

Point your client at the emulator

Run these in a terminal of their own, so this setup doesn’t mix with your real Google Cloud work. They use Google Cloud’s address on your machine, as published in Get started: if you published another host port, use that one.

gcloud

Turn off credentials, pick the project and send Pub/Sub requests to the emulator. The Service Usage and Resource Manager lines keep the helper calls some gcloud commands make on the emulator too.

export VERA_ENDPOINT="http://localhost:8081"
export CLOUDSDK_AUTH_DISABLE_CREDENTIALS=true
export CLOUDSDK_CORE_PROJECT=example-project
export CLOUDSDK_API_ENDPOINT_OVERRIDES_SERVICEUSAGE="$VERA_ENDPOINT/_gcp/serviceusage/"
export CLOUDSDK_API_ENDPOINT_OVERRIDES_CLOUDRESOURCEMANAGER="$VERA_ENDPOINT/_gcp/cloudresourcemanager/"
export CLOUDSDK_API_ENDPOINT_OVERRIDES_PUBSUB="$VERA_ENDPOINT/_gcp/pubsub/"

REST

Every request goes to the project’s Pub/Sub path, with no Authorization header:

export VERA_ENDPOINT="http://localhost:8081"
BASE="$VERA_ENDPOINT/_gcp/pubsub/v1/projects/example-project"

Create a topic and a subscription

A subscription receives the messages published to its topic, so create the topic first.

gcloud

gcloud pubsub topics create example-topic --quiet
gcloud pubsub subscriptions create example-subscription --topic=example-topic --quiet

Output

Created topic [projects/example-project/topics/example-topic].
Created subscription [projects/example-project/subscriptions/example-subscription].

REST

curl -X PUT "$BASE/topics/example-topic" \
  -H "Content-Type: application/json" -d '{}'

Response

{
  "name": "projects/example-project/topics/example-topic"
}

curl -X PUT "$BASE/subscriptions/example-subscription" \
  -H "Content-Type: application/json" \
  -d '{"topic":"projects/example-project/topics/example-topic"}'

The subscription comes back with its defaults:

Response

{
  "ackDeadlineSeconds": 10,
  "expirationPolicy": {
    "ttl": "2678400s"
  },
  "messageRetentionDuration": "604800s",
  "name": "projects/example-project/subscriptions/example-subscription",
  "pushConfig": {},
  "state": "ACTIVE",
  "topic": "projects/example-project/topics/example-topic"
}

Publish a message

gcloud

gcloud pubsub topics publish example-topic --message=hello

The message ID differs on every run.

Output

messageIds:
- '14108660267742776'

REST

Message data is base64: aGVsbG8= is hello.

curl -X POST "$BASE/topics/example-topic:publish" \
  -H "Content-Type: application/json" \
  -d '{"messages":[{"data":"aGVsbG8="}]}'

The message ID differs on every run.

Response

{
  "messageIds": ["14108660267742776"]
}

Pull the message

gcloud

--auto-ack acknowledges the message as it’s pulled, so it isn’t delivered again.

gcloud pubsub subscriptions pull example-subscription \
  --auto-ack --limit=1 --format=json

aGVsbG8= is hello in base64. The ackId and publishTime differ on every run.

Output

[
  {
    "ackId": "YWNrLWNmYWNmNDFhZjRjODRjMTJiLTE2ZDBhM2Nm",
    "ackStatus": "SUCCESS",
    "message": {
      "data": "aGVsbG8=",
      "messageId": "14108660267742776",
      "publishTime": "2026-11-02T23:10:54.812Z"
    }
  }
]

REST

Pull the message and save the response to pull.json:

curl -X POST "$BASE/subscriptions/example-subscription:pull" \
  -H "Content-Type: application/json" -d '{"maxMessages":1}' -o pull.json
cat pull.json

The ackId and publishTime differ on every run.

Response

{
  "receivedMessages": [
    {
      "ackId": "YWNrLTEyYTA2NTdmNmZiYTQzODdhLTE2ZDBhM2Nm",
      "message": {
        "data": "aGVsbG8=",
        "messageId": "14108660267742776",
        "publishTime": "2026-11-02T23:10:56.202Z"
      }
    }
  ]
}

Then acknowledge it, so it isn’t delivered again. Do it within the subscription’s 10-second acknowledgment deadline: in testing of Vera 1.2.0 preview, a message left unacknowledged past its deadline was returned by a later pull, with a new ackId. The first line copies the ackId from pull.json into ack.json. The emulator answers {}.

python3 -c 'import json; p=json.load(open("pull.json")); json.dump({"ackIds":[x["ackId"] for x in p["receivedMessages"]]},open("ack.json","w"))'
curl -X POST "$BASE/subscriptions/example-subscription:acknowledge" \
  -H "Content-Type: application/json" -d @ack.json

Clean up

Delete the subscription first, then the topic.

gcloud

gcloud pubsub subscriptions delete example-subscription --quiet
gcloud pubsub topics delete example-topic --quiet

Output

Deleted subscription [projects/example-project/subscriptions/example-subscription].
Deleted topic [projects/example-project/topics/example-topic].

REST

Each request answers {}. Then remove the two files the pull and the acknowledgment used.

curl -X DELETE "$BASE/subscriptions/example-subscription"
curl -X DELETE "$BASE/topics/example-topic"
rm pull.json ack.json

Next steps

• Pub/Sub: what else the emulator supports there, such as push subscriptions, and where it stops. There’s no gRPC, and push endpoints on the public internet aren’t called.
• Using the emulator: the setup every service shares, and the limits that apply to all of them.
• All services: what you can test on each Google Cloud service.