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Antelope Chronicle Project

Chronicle is a software component designed to process the history of an Antelope (formely EOSIO) blockchain.


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.

At the moment only one exporter plugin is implemented in the core Chronicle package: exp_ws_plugin. Also, a new project called "chronos" implments an exporter plugin that writes the blockchain updates directly in its database.

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 limit. Received and decoded data is kept in a queue that is fed to the consumer, allowing the consumer 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 0.05 to 0.5 seconds. If the pause exceeds 500 milliseconds, an informational message is printed on console output.

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. The package includes a systemd unit file which would restart the receiver automatically in this case.

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 the ABI in its state memory. The state memory keeps all revisions of every contract ABI.

  • upon receiving transaction traces or table deltas, it tries to decode the raw data using the available contract ABI.

  • 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 database. This allows the ABIs to be quickly available for the 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 the 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.

The 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. This mode is deprecated and will be removed from future releases, as the binary mode is about 15% faster.

In binary header mode (exp-ws-bin-header=true), each message consists of a binary 64-bit header and JSON data: the header consists of two 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 set to zero.

In scanning mode, the exporter expects that the server sends back block number acknowledgements as decimal numbers 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.

The pinned build script will produce a Debian package and a binary archive.

mkdir -p /opt/src/
cd /opt/src/
git clone --recursive
cd eos-chronicle
./pinned_build/ && mkdir build && \
 nice ./pinned_build/ /opt/src/chronicle-deps /opt/src/eos-chronicle/build $(nproc)

State history plugin in nodeos

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. The state history endpoint address and port needs to be reachable from the host where Chronicle receiver is running.

Example config.ini for nodeos:

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.

See the Chronicle tutorial for a more detailed and complete example.

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 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 -p /srv/memento_wax1/chronicle-config
cat >/srv/memento_wax1/chronicle-config/config.ini <<'EOT'
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.
/usr/local/sbin/chronicle-receiver \
  --config-dir=/srv/memento_wax1/chronicle-config --data-dir=/srv/memento_wax1/chronicle-data

# install systemd unit file
cp /usr/local/share/chronicle_receiver\@.service /etc/systemd/system/
systemctl daemon-reload

# You may need to initialize the Chronicle database from the first block
# in the state history archive. See the Chronicle Tutorial for more
# details. You may point it to some other state history source during
# the initialization. Here we launch it in scan-noexport mode for faster initialization.
/usr/local/sbin/chronicle-receiver --config-dir=/srv/memento_wax1/chronicle-config \
 --data-dir=/srv/memento_wax1/chronicle-data \ --port=8080 \
 --start-block=186332760 --mode=scan-noexport --end-block=186332800

# Once it stops at the end block, launch the service
systemctl enable chronicle_receiver@memento_wax1
systemctl start chronicle_receiver@memento_wax1

# watch the log
journalctl -u memento_dbwriter@wax1 -f

Alternatively, Chronicle data can be downloaded from an archive at EOS Amsterdam snapshots server:

An example of initializing Chronicle data from a snapshot:

cd /srv/memento_wax1
curl | tar xzSvf -
systemctl enable chronicle_receiver@memento_wax1
systemctl start chronicle_receiver@memento_wax1

Only one exporter plugin can be activated at a time (as of now, only one is implemented, but it can be changed in the future).

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.

  • skip-account-info = true|false (=false) Disable account permissions and metainformation 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.

  • enable-receiver-filter = true|false (=false) if enabled, activates output filtering on traces matching the include-receiver filters.

  • include-receiver = NAME If enable-receivers-filter is enabled, one or multiple include-receiver options specify the EOSIO account names that need to be matched in traces. The receiver looks for these names in receipt receivers of every action in trace, and outputs the trace only if at least one name matches. The smart contract executing an action is always receiving a receipt, so you can easily filter by contracts. Also in token transfers, normally payer and payee are receiving receipts.

  • enable-auth-filter = true|false (=false) if enabled, activates output filtering on traces matching include-auth filters.

  • include-auth = NAME If enable-auth-filter is enabled, one or multiple include-auth options specify the account names that are looked up in action authorizations. Only the traces matching at least one authorization will be included in the output.

  • blacklist-action = CONTRACT:ACTION This option defines action names for specific contracts that are blocking the output of corresponding traces. Multiple (contract:action) tuples can be specified. By default, only eosio:onblock is blacklisted.

  • enable-tables-filter = true|false (=false) if enabled, activates output filtering on table deltas for contracts matching include-tables-contract filters.

  • include-tables-contract = NAME If enable-tables-filter is enabled, one or multiple include-tables-contract options specufy the contract names for which table deltas would be included in the output.

  • blacklist-tables-contract = NAME This option allows excluding contract names from table deltas. Multiple options can be specified, and those contracts will be blacklisted from table deltas export.

If both enable-receiver-filter and enable-auth-filter are enabled, the output will include traces matching any of the filters. The blacklist has absolute precedence: regardless of filters configuration, if a transaction matches the blacklist, it is dropped from output.

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.

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.

Release 1.3

  • New options for filtering: enable-receiver-filter, include-receiver, enable-auth-filter, include-auth, blacklist-action

Release 1.5

  • changed default value for receiver-state-db-size from 1024 to 16384

  • new option: blacklist-tables-contract

  • Debian package builder and packages published on Github

Release 1.6

  • Replaced external dependencies from B1 repo to our own repo

  • Debian package includes /usr/local/share/chronicle_receiver@.service

Release 2.0

  • Added compatibility with Leap 3.1

  • Added pinned_build scripts, fixating on Boost 1.80.0 and Clang 11.0.1

  • The state database is not compatible with 1.6 state, so Chronicle needs to be reinitialized.

Release 2.1

  • Bugfix: primary_key resolved as boolean in decoder_plugin.cpp

Release 2.2

  • Bugfix: ack for a block lower than the previously aknowledged was crashing chronicle

Release 2.3

  • Bugfix: if action arguments or a table row contained trailing garbage, Chronicle failed to decode it.

Release 2.4

  • Bugfix: consumer sending websocket close message causes a crash

Release 2.5

  • Updated external dependencies to match Leap 4.0

Release 3.0

  • Chronicle 3.0 database is not compatible with that of 2.x, so a rescan or restart from a snapshot is required.

  • CMake files optimized for customized builds, like the Chronos project.

  • Enabled compiler optimization for faster performance.

  • Bugfix in Chronicle database: it had an entry for every account even if ABI was empty.

  • Improvements in socket error handling.

  • New event type: BLOCK_STARTED (1014).

  • New attributes in BLOCK_COMPLETED (1010) event: producer, previous, transaction_mroot, action_mroot, trx_count.

  • More frequent pause events; slower pause timer ramp-up.

  • default value for receiver-state-db-size set to 1024

  • The package is renamed from eosio-chronicle to antelope-chronicle.

Ecosystem links

Source code, license and copyright

Source code repository:

Copyright 2018-2023

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.