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chronicle-receiver nodeos 2.0 compatibility and updated external libs Jan 13, 2020
examples documentation update Feb 25, 2019
external nodeos 2.0 compatibility and updated external libs Jan 13, 2020
systemd systemd unit examples Jun 10, 2019
testing Interactive mode supports a range of blocks May 11, 2019
.gitmodules removed exp_zmq_plugin for now Mar 21, 2019
CREDITS chronicle_sth_decoder: work in progress, stripped-down fill-postgresql Nov 22, 2018
LICENSE.txt Apache 2.0 LICENSE.txt Feb 22, 2019 Release 1.2 Jan 13, 2020
TODO updated TODO Feb 25, 2019 antispam Feb 15, 2019

EOS Chronicle Project

This project is an implementation of work proposal as published at

The goal is to build a scalable and reliable toolset for maintaining EOS blockchain history in a database.

The first stage of the project is to produce a feed of blockchain events that could be consumed by other components for further processing. chronicle-receiver is implementing this as described below.

Git branches

master branch of Chronicle is compatible with releases 1.8 and 2.0 of EOSIO nodeos.

The release on January 13th 2020 is not backward compatible with on-disk data format of Chronicle. If you used Chronicle before, you either need to use chroncile-1.2-backport branch, or start nodeos from snapshot and start Chronicle with --start-block option.

chroncile-1.2-backport branch is compatible with nodeos 1.8 and 2.0, while preserving backward compatibility with on-disk data created by older Chronicle versions. It is recommended to eventually update to release version because it uses newest chainbase library by Block One.

nodeos-1.8rc2 branch of Chronicle is only compatible with the release candidate (nodeos 1.8rc2) because the final release has different output format of state history.

nodeos-1.7 branch of Chronicle is compatible with nodeos releases prior to 1.8rc2 (all revisions of 1.7 and 1.6 releases should work with this version).

The branch nodeos-1.8rc2 is frozen and is not supposed to be updated. Critical updates will be added to master and nodeos-1.7 branches.


The receiver is designed to work with state_history_plugin of nodeos. It connects to the websocket endpoint provided by the state history plugin and starts reading its data from a specific block number.

The receiver can be compiled with a number of exporter plugins, and only one exporter plugin can be enabled in its configuration. Exporter plugins organize the data export to their respective consumers.

Exporters must work in bidirectional mode: the exporter expects that the consumer acknowledges block numbers that it has processed and stored. Should chronicle-receiver stop, it will start from the block number next after acknowledged or last known irreversible, whichever is lower.

The communication between exporter and consumer is performed asynchronously: the receiver starts with a parameter indicating the maximum number of unacknowledged blocks (1000 by default), and it continues retrieving data from nodeos as long as the consumer confirms the blocks within this maximum. Received and decoded data is kept in a queue that is fed to the consumer, allowing it to process the data at its own pace. If the number of unacknowledged blocks reaches the maximum, the reader pauses itself with an increasing timer, varying from 0.1 to 8 seconds. If the pause exceeds 1 second, an informational event is generated.

If nodeos stops or restarts, chronicle-receiver will automatically stop and close its downstream connection. Also if the downstream connection closes, the receiver will stop itself and close the connection to nodeos.

Scanning mode

When mode option is set to scan, chronicle-receiver operates as follows:

  • it reads all available blocks sequentially from state history.

  • it monitors account changes, and as soon as a new ABI is set on a contract, it stores a copy of ABI in its state memory. The state memory keeps all revisions of every contract ABI.

  • upon receiving transaction traces and table deltas, it tries using the ABI and decoding the raw binary data into the ABI-defined structures.

  • all data received from state_history_plugin is converted to JSON format. If there's no valid ABI for decoding raw data, it's presented as a hex string. In this case, an ABI decoder error event is generated.

  • it feeds all JSON data and all error events to the exporter plugin, and the exporter plugin pushes the JSON data to its consumer. As described above, the consumer must send acknowledgements for processed block numbers.

In scan-noexport mode, the receiver requests the blocks from state history sequentially and stores all revisions of contract ABI in its memory. This allows it to be quickly available for interactive mode.

Interactive mode

In interactive mode, chronicle-receiver uses the state database populated by another receiver process that is running in scanning mode. Only one process is allowed to run in scanning mode, and multiple processes can be started in interactive mode.

The exporter plugin, or probably some other plugin, receives a request for particular block number or a range of blocks. This request is passed to the receiver and requested from state_history_plugin. If a range is specified, blocks up to the last before the end block are exported.

During request processing, the decoder retrieves required contract ABI from its ABI history, so that it's the latest copy from a block number that is below the requested block.

Then, the same way as in scanning mode, decoded data is translated into JSON and passed to the exporter plugin.

Receiver does not expect any acknowledgements in interactive mode.

Only irreversible blocks are available for interactive mode.

Note that in case of exp_ws_plugin, you need to specify a different TCP port of the websocket server, so that it does not interfere with the websocket communication in scanning mode when export is enabled.

State database

chronicle-receiver utilizes chainbase, the same shared-memory database library that is used by nodeos, to store its state. This results in the same behavior as with nodeos:

  • pre-allocated shared memory file is sparse and mostly empty;

  • in case of abnormal termination, the shared memory file becomes dirty and unusable.

The state database keeps track of block numbers being processed, and it stores also ABI for all contracts that it detects from setabi actions. Chainbase is maintaining the history of revisions down to the unacknowledged or irreversible block, in order to be able to roll back in case of a fork or in case of receiver restart.

Websocket exporter plugin

exp_ws_plugin exports the data to a websocket server.

The plugin connects to a specified websocket host and port and opens a binary stream.

The plugin works in one of two possible modes:

In JSON mode (exp-ws-bin-header=false), each outgoing message is a JSON object with two keys: msgtype indicates the type of the message, and data contains the corresponding JSON object, such as transaction trace or table delta.

In binary header mode (exp-ws-bin-header=true), the message format is similar to that used in zmq-plugin for nodeos: each message starts with two native 32-bit unsigned integers indicating message type and options, and the rest of the message is JSON data. Message type values are available in chronicle_msgtypes.h header file. The second integer, options, is currently always zero.

The binary header mode increases the exporter performance by approximately 15%.

In scanning mode, the exporter expects that the server sends back block number acknowledgements in text format, each number in an individual binary message.

In interactive mode, the exporter expects that the server sends each request as a single binary message. The content of each message is either one block number in decimal text notation, or two decimal integers separated by minus sign (-) indicating a range of blocks.


Minimum requirements: Cmake 3.11, Boost 1.67, GCC 8.3.0.

3GB RAM is required for successful compilation. Smaller RAM will cause heavy swapping during the compilation.

Ubuntu 18.10 instructions:

sudo apt update && \
sudo apt install -y git g++ cmake libboost-dev libboost-thread-dev libboost-test-dev \
 libboost-filesystem-dev libboost-date-time-dev libboost-system-dev libboost-iostreams-dev \
 libboost-program-options-dev libboost-locale-dev libssl-dev libgmp-dev

mkdir build
cd build
git clone
cd eos-chronicle
git submodule update --init --recursive
mkdir build
cd build
cmake ..
# use "make -j N" for N CPU cores for faster compiling (may require more RAM)

Ubuntu 18.04 instructions:

wget -O - 2>/dev/null | sudo apt-key add -
sudo apt-add-repository 'deb bionic main'

sudo add-apt-repository ppa:ubuntu-toolchain-r/test

sudo apt update && \
sudo apt install -y git g++-8 cmake libssl-dev libgmp-dev zlib1g-dev
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-8 800 --slave /usr/bin/g++ g++ /usr/bin/g++-8

tar -xvzf boost_1_67_0.tar.gz
cd boost_1_67_0
# use " sudo ./b2 install -j N" for N CPU cores for faster compiling (may require more RAM)
sudo ./b2 install 
cd ..

mkdir build
cd build
git clone
cd eos-chronicle
git submodule update --init --recursive
mkdir build
cd build
cmake ..
# use "make -j N" for N CPU cores for faster compiling (may require more RAM)

examples/exp-dummy-plugin explains how to add and compile your own plugin to chronicle-receiver.

State history

In order for Chronicle to function properly, both trace-history and chain-state-history need to be enabled. Also if contract console output needs to be present in Chronicle output, trace-history-debug-mode needs to be enabled too.

Example config.ini for nodeos version 1.8:

contracts-console = true
validation-mode = light
plugin = eosio::state_history_plugin
trace-history = true
chain-state-history = true
trace-history-debug-mode = true
state-history-endpoint =

Configuring and running

Similarly to nodeos, chronicle-receiver needs a configuration directory with config.ini in it, and a data directory where it stores its internal state.

Further on, we use Linux user eosio for running the receiver, and /home/eosio/chronicle-config as configuration directory, although you may choose other names.

Here's a minimal configuration for the receiver using Websocket exporter. It connects to nodeos process running state_history_plugin at localhost:8080 and exports the data to a websocket server at localhost:8800. In a production environment, hosts may be different machines in the network. The example is using bidirectional mode and default queue sizes.

The receiver would stop immediately if the websocket server is not responding. For further tests, you need a consumer server ready.

The Perl script testing/ can be used as a test websocket server that dumps the input to standard output.

mkdir /home/eosio/chronicle-config
cat >/home/eosio/chronicle-config/config.ini <<'EOT'
# connection to nodeos state_history_plugin
host =
port = 8080
mode = scan
plugin = exp_ws_plugin
exp-ws-host =
exp-ws-port = 8800
exp-ws-bin-header = true

# Start the receiver to check that everything is working as
# expected. Use Ctrl-C to stop it.
/home/eosio/build/eos-chronicle/build/chronicle-receiver \
  --config-dir=/home/eosio/chronicle-config --data-dir=/home/eosio/chronicle-data

# Prepare for long-term run inside a systemd unit

cat >chronicle-config/chronicle-receiver.service <<'EOT'
Description=EOS Chronicle receiver
ExecStart=/home/eosio/build/eos-chronicle/build/chronicle-receiver --config-dir=/home/eosio/chronicle-config --data-dir=/home/eosio/chronicle-data

sudo cp chronicle-config/chronicle-receiver.service /etc/systemd/system/
sudo systemctl daemon-reload
sudo systemctl enable chronicle-receiver
sudo systemctl start chronicle-receiver
# check the status
sudo systemctl status chronicle-receiver

Only one exporter plugin can be activated at a time.

If you need to move or copy the state data, flush the system cache first:

sync; echo 3 > /proc/sys/vm/drop_caches

Command-line and configuration options

The following options are available from command-line only:

  • --data-dir=DIR (mandatory): Directory containing program runtime data;

  • --config-dir=DIR Directory containing configuration files such as config.ini. Defaults to ${HOME}/config-dir;

  • -h [ --help ]: Print help message and exit;

  • -v [ --version ]: Print version information;

  • --print-default-config: Print default configuration template. The output will have empty plugin option, so you will need to add an exporter plugin to it.

  • --config=FILE (=config.ini): Configuration file name relative to config-dir;

  • --logconf=FILE (=logging.json): Logging configuration file name/path for library users. An example file that is only printing error messages is located in examples/ folder.

The following options are available from command line and config.ini:

  • host = HOST (=localhost): Host to connect to (nodeos with state_history_plugin);

  • port = PORT (=8080): Port to connect to (nodeos with state-history plugin);

  • receiver-state-db-size = N (=1024): State database size in MB;

  • mode = MODE: mandatory receiver mode. Possible values:

    • scan: read state history blocks sequentially and export via export plugin.

    • scan-noexport: read state history blocks sequentially and skip any export. This is the fastest mode to collect ABI revisions so that interactive access can fetch required blocks.

    • interactive: interactive mode allows the consumer request random blocks. Irreversible-only mode is automatically set in this mode.

  • report-every = N (=10000) Print informational messages every so many blocks;

  • max-queue-size = N (=10000) If the asynchronous processing queue reaches this limit, the receiver will pause.

  • skip-block-events = true|false (=false) Disable BLOCK events in export. This saves CPU time if you don't need block attributes, such as BP signatures and block ID.

  • skip-table-deltas = true|false (=false) Disable table delta events in the export.

  • skip-traces = true|false (=false) Disable transaction trace events in the export.

  • irreversible-only = true|false (=false) fetch irreversible blocks only

  • start-block = N (=0) Initialize Chronicle state from given block. This is intended for starting Chronicle off a node that started from a portable snapshot. The snapshot has all table contents in the beginning, so Chronicle will process them all before continuing with the blocks. It may take some significant time. This option is only allowed when Chronicle data directory is empty.

  • end-block = N (=4294967295) Stop receiver before this block number

  • stale-deadline = N (=10000) If there were no new blocks from state history socket within this time (in milliseconds), chronicle-receiver will stop and exit. The deadline timer is not used if the receiver is paused by a slow consumer.

Options for exp_ws_plugin:

  • exp-ws-host = HOST (mandatory): Websocket server host to connect to;

  • exp-ws-port = PORT (mandatory): Websocket server port to connect to;

  • exp-ws-path = PATH (/): Websocket server URL path;

  • exp-ws-bin-header = true|false (=false) Enable binary header mode (message type and options as binary integers, followed by JSON);

  • exp-ws-max-unack = N (=1000): Receiver will pause at so many unacknowledged blocks;

  • exp-ws-max-queue = N (=10000): Receiver will pause if outbound queue exceeds this limit.

Sample output

At you can download about 31MB of gzipped JSON output. The raw output of exp_ws_plugin is prettyfied and separated by double newline characters.

Release notes

Release 1.0

This release is based on libraries of particular older versions. It uses abieos library from November 13th, with an additional patch. Newer versions of those libraries are introducing some incompatible changes, and the work is in progress to adapt Chronicle to those changes.

Release 1.1

  • Unidirectional mode is no longer supported.

  • skip-to option is removed.

  • exp_zmq_plugin is removed because of instable work with Boost ASIO.

  • Newest libraries from repositories are used, and the most dramatic change is that channels are processed asynchronously. Also all asynchronous tasks must be wrapped in appbase priority queue.

  • In addition to latest copy of ABI for each contract, the internal state database stores a history of all ABI revisions for all contracts. This is used in interactive mode.

  • New configuration option: mode and 3 modes: scan, scan-noexport, and interactive. Interactive mode allows requesting individual blocks and block ranges.

  • New options: irreversible-only, end-block.

Release 1.2

This release supports nodeos versions 1.8 ans 2.0, and not compatible with nodeos-1.7.

  • New message types: 1011, 1012, 1013 (PERMISSION, PERMISSION_LINK, ACC_METADATA).

  • New field block_id in BLOCK and BLOCK_COMPLETED messages.

  • New options: stale-deadline, exp-ws-path, start-block, skip-traces.

  • Bugfixes and improvements.

Third-party software

Source code, license and copyright

Source code repository:

Copyright 2018-2020

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

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