Skip to main content

Mempool Injector

Often, it's very useful to inject transactions from Fiber into your local mempool.

Fiber offers a Docker image that allows users to do that.


docker run --name fiber-inject \
fiber-inject \
--fiber-api $API_ENDPOINT \
--fiber-key $YOUR_API_KEY \
--enodes $ENODE1,$ENODE2 \
--port 30303

This will subscribe to the Fiber transaction stream and broadcast all the transactions it receives to your local nodes (specified by --enodes, provided they're connected).

Your local enode's IP address should either be the gateway address of your Docker network (usually, or one of the publicly reachable IP addresses of your machine.

The default port number is 30303 (the default p2p port of Ethereum nodes), but you can change it with the --port flag.

We offer a pre-built Docker image for both arm64 and amd64 architectures (under the latest-arm64 and latest-amd64 tags respectively).


It's possible that your local node has reached its maximum amount of peers, and therefore won't accept Fiber inject as another peer.

If the Docker container doesn't print the following (docker logs fiber-inject):

14:51:44.831 INF [DEVP2P] Connected to trusted peer           enode=...

means that your node reached max n. of peers, and you have to add fiber-inject as a trusted peer.

Add Fiber inject as a trusted peer

1. Expose the p2p port of the Docker container


Make sure the mapped port isn't already taken by your local node. You can change the mapped port with the --port flag.

docker run -p 30304:30303 --name fiber-inject \
fiber-inject \
--fiber-api $API_ENDPOINT \
--fiber-key $YOUR_API_KEY \
--enodes $ENODE1,$ENODE2 \
--port 30303

2. Find the enode

Fetch enode from output:

14:51:44.811 INF [DEVP2P] Starting devp2p server               enode=enode://6e45ab02bc08b03da9527ef42e07e12d144eea3365b102b3d7f3b7a3f4ae0aed24a039d346af3a7e0e3c84257458af076e55e8860e262f551dab9d4e472f0fe3@

3. Add enode to your local node's trusted peerset


Make sure you use your mapped port as the enode port.

If you're using geth, you can use the JavaScript console:

geth attach --datadir $DATADIR --exec \

4. Check if the connection was made

Check the output and confirm the connection should have been made.