# Releases

# v4.4.19

Release Date: 2023-06-27

# Enhancements

Added support for TCP keep-alive in MQTT/TCP and MQTT/SSL listeners #10854 (opens new window).
A new configuration option has been added: zone.<zone-name>.tcp_keepalive = Idle,Interval,Probes. Users can enable the TCP layer's Keep Alive feature and specify time parameters using this configuration. This configuration is only effective on Linux and MacOS systems.

Improved error logs related to Proxy Protocol emqx/esockd#177 (opens new window).

The sample logs before this improvement:

2023-04-20T14:56:51.671735+08:00 [error] supervisor: 'esockd_connection_sup - <0.2537.0>', errorContext: connection_shutdown, reason: {invalid_proxy_info,<<"f\n">>}, offender: [{pid,<0.3192.0>},{name,connection},{mfargs,{...}}]

2023-04-20T14:57:01.348275+08:00 [error] supervisor: 'esockd_connection_sup - <0.2537.0>', errorContext: connection_shutdown, reason: {proxy_proto_timeout,5000}, offender: [{pid,<0.3194.0>},{name,connection},{mfargs,{...}}]

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After the improvement:

2023-04-20T18:07:06.180134+08:00 [error] [esockd_proxy_protocol] The listener 127.0.0.1:8883 is working in proxy protocol mode, but received invalid proxy_protocol header, raw_bytes=<<"f\n">>

2023-04-20T18:10:17.205436+08:00 [error] [esockd_proxy_protocol] The listener 127.0.0.1:8883 is working in proxy protocol mode, but timed out while waiting for proxy_protocol header

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Added a new feature to enable partial certificate chain validation for TLS listeners #10553 (opens new window).
For details please checkout the listener.ssl.external.partial_chain in the emqx.conf config file.
Added a new feature to enable client certificate extended key usage validation for TLS listeners #10669 (opens new window).
For details please checkout the listener.ssl.external.verify_peer_ext_key_usage in the emqx.conf config file.
Added the live_connections field in the HTTP API /api/v4/nodes response #10859 (opens new window).
Previously, this interface had a connections field, which represented the number of active connections on the current node that had not expired. This means that even if the MQTT connection has been disconnected, as long as the client has a persistent session, it would still be counted in the connections field. The newly added live_connections field specifically counts the number of clients with MQTT connections that have not been disconnected.
Added 3 random SQL functions to the rule engine #11113 (opens new window).
- random(): Generates a random number between 0 and 1 (0.0 =< X < 1.0).
- uuid_v4(): Generates a random UUID (version 4) string.
- uuid_v4_no_hyphen(): Generates a random UUID (version 4) string without hyphens.
Added numerical range validation (23-65535) for the mqtt.max_clientid_len configuration parameter #11096 (opens new window).

# Bug fixes

Fixed an issue where the rule engine was unable to access variables exported by FOREACH in the DO clause #10620 (opens new window).
Given a payload: {"date": "2023-05-06", "array": ["a"]}, as well as the following SQL statement:
```
FOREACH payload.date as date, payload.array as elem
DO date, elem
FROM "t/#"
```
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Prior to the fix, the date variable exported by FOREACH could not be accessed in the DO clause of the above SQL, resulting in the following output for the SQL statement: [{"elem": "a","date": "undefined"}]. After the fix, the output of the SQL statement is: [{"elem": "a","date": "2023-05-06"}]
Fixed the issue where the cache of rules failed to update in certain cases #11072 (opens new window).
Prior to the fix, after manually updating the rules, there could be instances where the cache update did not synchronize to certain nodes. This would result in inconsistent rule execution states across different nodes.
Fixed an issue where the WebHook plugin failed to execute the on_client_connack hook #10710 (opens new window).
See https://github.com/emqx/emqx/issues/10628 for more details.

# v4.4.18

Release Date: 2023-04-28

# Enhancements

Improved the placeholder syntax of the rule engine #10470 (opens new window).
The parameters of certain actions support using placeholder syntax to dynamically fill in the content of strings. The format of the placeholder syntax is ${key}.
Prior to the improvement, the key in ${key} could only contain letters, numbers, and underscores. Now the key supports any UTF8 character after the improvement.

# v4.4.17

Release Date: 2023-04-13

# Enhancements

When the listener enabled with Proxy Protocol receives a TCP port probe, no error logs will be printed anymore emqx/esockd#172 (opens new window).
Before the fix, if the listener had enabled the proxy protocol (listener.tcp.external.proxy_protocol=on), but the connection was disconnected after the TCP handshake was completed and before the proxy information was received, the following error log would be printed:
```
[error] supervisor: 'esockd_connection_sup - <0.3265.0>', errorContext: connection_shutdown, reason: {recv_proxy_info_error,tcp_closed}, offender:
```
1
After the fix, no logs will be printed, but you can still view the error reason statistics through the emqx_ctl listeners command.
Improved the error logs of the listener for file descriptor exhaustion emqx/esockd#173 (opens new window).
Before the improvement, the log was:
```
[error] Accept error on 0.0.0.0:1883: emfile
```
1
After the improvement, the log became:
```
[error] Accept error on 0.0.0.0:1883: EMFILE (Too many open files)
```
1
Improved the performance of the rule engine when there are many rules #10283 (opens new window)
Before the improvement, when there were many rules, the rule engine would consume a lot of CPU time on rule queries and matching, becoming a performance bottleneck. In this optimization, by simply adding a cache to the rule list, the rule execution efficiency in this scenario was greatly improved. In our test, we created 700 rules that did not perform any actions (bound to the "do_nothing" debugging action) on a 32-core 32G virtual machine, and sent MQTT messages to EMQX at a rate of 1000 messages per second (that is, the rule trigger frequency was 700 * 1000 times per second). In the above scenario, the CPU usage of the optimized rule engine dropped to 55% ~ 60% of the previous level.

# Fixes

Fixed the issue where Erlang distribution could not use TLS #9981 (opens new window).
For more information on Erlang distribution, see here (opens new window).
Fixed the issue where MQTT bridging could not verify TLS certificates with wildcard domains on the peer side #10094 (opens new window).
Fixed the issue where EMQX could not timely clear the information of disconnected MQTT connections when there were too many messages backlogged in the retainer. #10189 (opens new window).
Before the fix, the emqx_retainer plugin and the EMQX connection information cleanup task shared a process pool. Therefore, if the process pool was blocked by a large number of retain message distribution tasks, many disconnected MQTT connection information would not be cleared in time. See #9409 (opens new window) for details. After the fix, the emqx_retainer plugin uses a separate process pool to avoid this problem.
Fixed the issue where the path of the template file service-monitor.yaml in the Helm Chart was incorrect. #10229 (opens new window)

# v4.4.16

Release Date: 2023-03-10

# Enhancements

Change "EMQ X" to "EMQX" from the outputs of CLIs and names of plugins #10099 (opens new window).

# Bug fixes

Avoid changing the payload of MQTT messages when printing debug logs #10091 . Before this fix, if EMQX receives a message with Payload "e\ne\nc\nc\n2\n\n\n", the log message will be as follows:

2023-03-08T13:28:04.320622+08:00 [debug] mqttx_e34bd582@127.0.0.1:54020 [MQTT] RECV PUBLISH(Q1, R0, D0, Topic=t/1, PacketId=39467, Payload=e, e, c, c, 2, , , )

This is the corresponding log message now:

2023-03-08T14:26:50.935575+08:00 [debug] mqttx_e34bd582@127.0.0.1:54020 [MQTT] RECV PUBLISH(Q1, R0, D0, Topic=t/1, PacketId=39467, Payload=<<"e\ne\nc\nc\n2\n\n\n">>)

# v4.4.15

Release Date: 2023-03-03

This version update includes 8 enhancements and 13 fixes. Among the enhancements, there are new exciting new features worth highlighting:

Upgrade the MongoDB client library of EMQX to support MongoDB 5.1 and above.
Dashboard supports the proxy protocol of HAProxy.
Release the Ubuntu 22.04 installation package.

# Enhancements

The MongoDB library has been upgraded to support MongoDB version 5.1 and greater.
Support proxy protocol of HAProxy for dashboard API 9803 (opens new window).
Added Ubuntu 22.04 package release #9831 (opens new window).
Improve the integration of the banned and the delayed feature #9790 (opens new window). Now when publishing a delayed message will check first if its source client is banned, if true, this publish will be ignored.
Security enhancement for retained messages #9790 (opens new window). The retained messages will not be published if the publisher client is banned.
Now the corresponding session will be kicked when client is banned by clientid #9904 (opens new window).
Add more debug logs for authentication and ACL #9943 (opens new window).
Expose the stats live_connections.count and live_connections.max to Prometheus #9929 (opens new window).

# Bug fixes

Fixed an error when forward MQTT messages with User-Property using the republish action #9942 (opens new window).
fix some issues in descriptions of the actions, resources and emqx-modules #9931 (opens new window).
fix there's no error logs when query the JWKS server failed #9931 (opens new window).
The returned client lists of HTTP query GET /api/v4/clients?_page=2&_limit=20 to different nodes might be inconsistent #9926 (opens new window).
Fix the problem that new MQTT TLS connections failed to establish after release hot upgrade #9810 (opens new window). For more detailed information please see: emqx/esockd#170 (opens new window).
Fix a problem in the log message format of MQTT packets #9858 (opens new window). Before this fix, a comma was missing between the flags (DUP) of the fixed header and the fields (ClientId) of the variable header:
```
2023-01-29T13:40:36.567692+08:00 [debug] 127.0.0.1:50393 [MQTT] RECV CONNECT(Q0, R0, D0ClientId=test_client, ... Password=undefined)
```
1
Avoid crash logs in CoAP gateway when receiving liveness checking packets from Load Balancer #9869 (opens new window).
Fix the exclusive topics aren't removed when the session has already been cleaned #9868 (opens new window).
fix the EMQX reports {case_clause,{error,closed}} error log message when websocket connections interrupted emqx/cowboy#8 (opens new window).
fix sometimes the rules cannot be enabled automatically after EMQX is restarted #9911 (opens new window).
fix the {badarg,[{ets,lookup,[gproc,{shared, ... error logs during shutdown #9919 (opens new window).
Delete the files directory when resources were deleted to avoid files leaking #10039 (opens new window).

# v4.4.11

Release Date: 2022-11-26

This release included 18 enhancements and 14 bug fixes. Among the enhancements, therer are new exciting new features worth highlighting.

OCSP (Online Certificate Status Protocol) Stapling.
CRL (Certificate Revocation List) cache.
OTP upgrade from 24.1.5-3 to 24.3.4.2-1.
Customizable client aliases to make it easier to when creating customized authentication and authorization.

It is possible to hot-upgrade from older version v4.4 to this version. Please note though, in order to start making use of the new features such as OCSP Stapling, CRL cache, a node restart (and configuration change) is required.

# Enhancements

OTP upgrade from 24.1.5-3 to 24.3.4.2-1 #9265 (opens new window). Change highlights:
- Erlang/OTP SSL library vulnerability fix (opens new window)
- Added support for OCSP (Online Certificate Status Protocol) Stapling
- Added CRL (Certificate Revocation List) cache auto refresh
Added support for OCSP stapling and CRL caching #9297 (opens new window).
Added support for specifying custom modules for adding clientid and common name aliases #9297 (opens new window). Now you can implement a simple callback to enrich clients with aliases, and then use the aliases in the authentication and authorization (ACL) rules' place holders (%cida for clientid alias and %cna for username alias).
Added support for specifying custom modules for custom authentication #9297 (opens new window). To support simple authentication rules, it is no longer necessary to implement a full-blown plugin.
Added a JWT management for Rule-Engine, for creating and refreshing JWT tokens in rule engine actions #9241 (opens new window). This feature is so far only used in EMQX Enterprise Google PubSub integration. Can be used as webhook integration's JWT authentication against the webhook service endpoint.
Make sure listener's tls_versions config value is one or more of tlsv1, tlsv1.1, tlsv1.2, tlsv1.3 #9260 (opens new window).
Remove useless information from the dashboard listener failure log #9260 (opens new window).
We now trigger the 'message.acked' hook after the CoAP gateway sends a message to the device and receives the ACK from the device #9264 (opens new window). With this change, the CoAP gateway can be combined with the offline message caching function (in the emqx enterprise), so that CoAP devices are able to read the missed messages from the database when it is online again.
Support to use placeholders like ${var} in the HTTP Headers of rule-engine's Webhook actions #9239 (opens new window).
Asynchronously refresh the resources and rules during emqx boot-up #9199 (opens new window). This is to avoid slowing down the boot if some resources spend long time establishing the connection.
Add a warning log if the ACL check failed for subscription #9124 (opens new window). This is to make the ACL deny logging for subscription behave the same as for publish.
JWT ACL claim supports all action to imply the rules applie to both pub and sub #9044 (opens new window).
Added a log censor to avoid logging sensitive data #9189 (opens new window). If the data to be logged is a map or key-value list which contains sensitive key words such as password, the value is obfuscated as ******.
Enhanced log security in ACL modules, sensitive data will be obscured #9242 (opens new window).
Add management.bootstrap_apps_file configuration to bulk import default app/secret when EMQX initializes the database #9273 (opens new window).
Added two new configs for deterministic order of authentication and ACL checks #9283 (opens new window). The two new global config names are auth_order and acl_order. When multiple ACL or auth plugins (or modules) are enabled, without this config, the order (in which each backend is queried) is determined by the start/restart order of the plugin (or module). Meaning, if a plugin (or module) is restarted after initial boot, it may get ordered to the end of the list. With this config, you may set the order with a comma-speapated ACL or auth plugin names (or aliases). For example: acl_order = jwt,http, this will make sure jwt is always checked before http, meaning if JWT is not found (or no acl cliam) for a client, then the ACL check will fallback to use the HTTP backend.
Added configurations to enable more client.disconnected events (and counter bumps) #9267 (opens new window). Prior to this change, the client.disconnected event (and counter bump) is triggered when a client performs a 'normal' disconnect, or is 'kicked' by system admin, but NOT triggered when a stale connection had to be 'discarded' (for clean session) or 'takeovered' (for non-clean session) by new connection. Now it is possible to set configs broker.client_disconnect_discarded and broker.client_disconnect_takeovered to on to enable the event in these scenarios.
For Rule-Engine resource creation failure, delay before the first retry #9313 (opens new window). Prior to this change, the retry delay was added after the retry failure.

# Bug fixes

Fix get trace list crash when trace not initialize. #9156 (opens new window)
Fix create trace sometime failed by end_at time has already passed. #9156 (opens new window)
Fix that after uploading a backup file with an non-ASCII filename, HTTP API GET /data/export fails with status code 500 #9224 (opens new window).
Improve the display of rule's 'Maximum Speed' counter to only reserve 2 decimal places #9185 (opens new window). This is to avoid displaying floats like 0.30000000000000004 on the dashboard.
Fix the issue that emqx prints too many error logs when connecting to mongodb but auth failed #9184 (opens new window).
Fix that after receiving publish in idle mode the emqx-sn gateway may panic #9024 (opens new window).
"Pause due to rate limit" log level demoted from warning to notice #9134 (opens new window).
Restore old emqx_auth_jwt module API, so the hook callback functions registered in older version will not be invalidated after hot-upgrade #9144 (opens new window).
Fixed the response status code for the /status endpoint #9210 (opens new window). Before the fix, it always returned 200 even if the EMQX application was not running. Now it returns 503 in that case.
Fix message delivery related event encoding #9226 (opens new window) For rule-engine's input events like $events/message_delivered, and $events/message_dropped, if the message was delivered to a shared-subscription, the encoding (to JSON) of the event will fail. Affected versions: v4.3.21, v4.4.10, e4.3.16 and e4.4.10.
Make sure Rule-Engine API supports Percent-encoding rule_id and resource_id in HTTP request path #9190 (opens new window). Note that the id in POST /api/v4/rules should be literals (not encoded) when creating a rule or resource. See docs Create Rule (opens new window) Create Resource (opens new window).
Calling 'DELETE /alarms/deactivated' now deletes deactived alarms on all nodes, including remote nodes, not just the local node #9280 (opens new window).
When republishing messages or bridge messages to other brokers, check the validity of the topic and make sure it does not have topic wildcards #9291 (opens new window).
Disable authorization for api/v4/emqx_prometheus endpoint on management api listener (default 8081) #9294 (opens new window).

# v4.4.10

Release Date: 2022-10-14

# Enhancements

TLS listener memory usage optimization #9005 (opens new window). New config listener.ssl.$NAME.hibernate_after to hibernate TLS connection process after idling. Hibernation can reduce RAM usage significantly, but may cost more CPU. This configuration is by default disabled. Our preliminary test shows a 50% of RAM usage decline when configured to '5s'.
TLS listener default buffer size to 4KB #9007 (opens new window) Eliminate uncertainty that the buffer size is set by OS default.
Disable authorization for api/v4/emqx_prometheus endpoint #8955 (opens new window).
Added a test to prevent a last will testament message to be published when a client is denied connection #8894 (opens new window).
More rigorous checking of flapping to improve stability of the system #9045 (opens new window). Previsouly only normal disconnects are counted, now the connection rejections (e.g. authentication failure) is also included. Find more about flapping detection in EMQX document (opens new window)
QoS1 and QoS2 messages in session's buffer are re-dispatched to other members in the group when the session terminates #9094 (opens new window). Prior to this enhancement, one would have to set broker.shared_dispatch_ack_enabled to true to prevent sessions from buffering messages, however this acknowledgement costs extra resources.
Fix delayed publish timing inaccuracy caused by OS time change #8908 (opens new window).

# Bug fixes

Fix the latency statistics error of the slow subscription module when stats_type is internal or response #8981 (opens new window).
Fix HTTP client library to handle SSL socket passive signal #9145 (opens new window).
Hide redis password in error logs #9071 (opens new window) In this change, it also included more changes in redis client:
- Improve redis connection error logging eredis#19 (opens new window). Also added support for eredis to accept an anonymous function as password instead of passing around plaintext args which may get dumpped to crash logs (hard to predict where). This change also added format_status callback for gen_server states which hold plaintext password so the process termination log and sys:get_status will print '******' instead of the password to console.
- Avoid pool name clashing eredis_cluster#22 (opens new window). Same format_status callback is added here too for gen_servers which hold password in their state.
Fix shared subscription message re-dispatches #9094 (opens new window).
- When discarding QoS 2 inflight messages, there were excessive logs
- For wildcard deliveries, the re-dispatch used the wrong topic (the publishing topic, but not the subscribing topic), caused messages to be lost when dispatching.
Fix shared subscription group member unsubscribe issue when 'sticky' strategy is used. Prior to this fix, if a previously picked member unsubscribes from the group (without reconnect) the message is still dispatched to it. This issue only occurs when unsubscribe with the session kept. Fixed in #9119 (opens new window)
Fix shared subscription 'sticky' strategy when there is no local subscriptions at all. Prior to this change, it may take a few rounds to randomly pick group members until a local subscriber is hit (and then start sticking to it). After this fix, it will start sticking to whichever randomly picked member even when it is a subscriber from another node in the cluster. Fixed in #9122 (opens new window)
Fix rule engine fallback actions metrics reset #9125 (opens new window).

# v4.4.9

Release Date: 2022-09-17

# Enhancements

The exp, nbf and iat claims in JWT authentication support non-integer timestamps

# Bug fixes

Fix rule engine update behaviour which may initialize actions for disabled rules
Fix the issue that the IP address bound to the Dashboard listener did not take effect
Fix the issue that shared subscriptions might get stuck in an infinite loop when shared_dispatch_ack_enabled is set to true
Fix the issue that the rule engine SQL crashes when subject matching null values

# v4.4.8

Release Date: 2022-08-29

# Enhancements

Add GET /trace/:name/detail API to view log trace file information
Improve the log when LwM2M packet parsing fails
Improve the rule engine error log, the log will contain the rule ID when the action execution fails
Improve log when loaded_modules and loaded_plugins files do not exist
Add a guide for changing the default password on Dashboard

# Bug fixes

Fix client.disconnected event not trigger in some cases
Fix the issue that the built-in database authentication did not distinguish the pagination statistics of the authentication data of the client ID and username
Fix Redis driver process leak problem
Fix rule engine MQTT bridge to AWS IOT connection timeout issue
Fix GET /listener request crashing when listener is not ready
Fix the issue that the comparison between any variable and null value in the rule engine SQL always returns false after v4.4.1
Fix incorrectly managing emqx_modules applications as plugins
Fix the issue that when the execution priority of ExHook is higher than that of the rule engine, the topic filtered by the ExHook Message Hook will not trigger the rule engine
Fix the issue that the ExHook management process was forcibly killed due to the supervisor shutdown timeout
Fix the issue that the Client ID parameter in ExProto client.connect hook is not defined
Fix ExProto not triggering disconnect event when client is kicked

# v4.4.7

Release Date: 2022-08-11

# Important Changes

As of version 4.4.7, we will no longer provide packages for macOS 10

# Enhancements

Allows the connection process to be configured to be garbage collected after the TLS handshake is complete to reduce memory footprint, which can reduce memory consumption by about 35% per SSL connection, but increases CPU consumption accordingly
Allows configuring the log level of the TLS handshake log to view the detailed handshake process

# v4.4.6

Release Date: 2022-07-29

# Enhancement

Supports searching and paging of rules in rule engine
Provides CLI ./bin/emqx check_conf to actively check if the configuration is correct
Optimizing Shared Subscription Performance

# Bug fixes

Fix the issue that once the old version of EMQX is uninstalled after hot upgrade, EMQX will not be able to start again
Fix the issue that the keep-alive check for UDP clients in the Multilingual Protocol Extension was incorrect, causing clients not to expire
Fix the issue that the client information in the Multilingual Protocol Extension was not updated in time
Fix the issue that when the client specified Clean Session as false to reconnect, the shared subscription message in the flight window would be re-dispatched to the old session process
Fix the issue that the emqx_lua_hook plugin cannot cancel the message publishing

# v4.4.5

Release Date: 2022-06-30

# Enhancement

QoS and Retain flag in rule engine's message republish actions can now use placeholders
Supports exclusive subscriptions, that is, only one subscriber is allowed for a topic
Dashboard and management API's HTTPS listeners can now use password-protected private key files, providing key_password configuration item
Support for placeholders %u and %c in topic rewrite rules
Support setting MQTT 5.0 properties in the API request for message publishing, such as message expiry interval, response topic, etc.
Optimize the UI when creating rule engine resources, such as folding some uncommon options, etc.
Opened 4 TCP-related configuration items: KeepAlive, TCP_NODELAY, SO_RCVBUF and SO_SNDBUF for the underlying gRPC connection of ExHook

# Bug fixes

Fix the issue of inaccurate memory calculation in Linux OS, and calculate the memory usage of the current OS instead of the memory usage of EMQX
Fix the issue that the old disconnect event of ExHook would be triggered later than the new connect event when the client reconnects
Fix the issue that the execution order of topic rewriting and delayed publish is not fixed, now it is fixed to execute topic rewriting first
Fix the issue that rule engine could not encode MQTT 5.0 user properties
Fix the issue that the count of connack.auth_error is inaccurate when the client uses a protocol version below MQTT v5.0 to access
Fix the issue that the UDP listeners of LwM2M and CoAP gateways could not bind to the specified network interface
Fix Dashboard not starting after removing the default Dashboard user in the configuration file
Fix client.subscribe hook not being able to reject subscriptions
If the placeholder in the ACL rule is not replaced, the client's publish or subscribe operation will be rejected

# v4.4.4

Release Date: 2022-06-01

# Enhancement

Add more time transformation functions to the SQL of rule engine
Add the float2str/2 function to the SQL of rule engine to support specifying the output precision of floating point numbers
Support for using JWT for authorization, now MQTT clients can authorize using specific claims that include a pub-sub whitelist
Improved authentication related metrics to make it easier to understand, now client.authenticate = client.auth.success + client.auth.failure
Support binding the listener of the REST API to a specified network interface
Support multi-condition query and fuzzy query for user data in authentication and authorization using built-in database as data source
Supports querying clients using the length of the message queue and the number of dropped messages as conditions
Support to configure the log time format to be compatible with the time format in older versions
When use_username_as_clientid is configured to true and the client connects without specifying a username, the connection is now rejected with a reason code 0x85
Full randomisation of app secrets (previously partially randomised)
When using CLI for backup and recovery, it is no longer required that the backup file must be located in the backup folder of the EMQX data directory
Hot upgrades between incompatible versions will now be rejected
Allow white spaces in EMQX's installation path
Boot script fail fast on invalid node name (improve error message readability)

# Bug fixes

Fix the issue that rule engine's SQL function hexstr_to_bin/1 could not handle half-byte
Fix the issue that the alarm was not cleared when the rule engine resource was deleted
Fix Dashboard HTTPS listener's verify option not taking effect
Fix the issue that messages were lost when the peer session was terminated during the delivery of QoS 1 messages through shared subscriptions
Fix the issue that when the log tracer encounters large packets, the heap size grows too fast and triggers the policy of forcibly closeing the connection process
Fix the issue that the MQTT-SN client would be disconnected when retransmitting QoS 2 messages
Fix the issue that the subscriber's connection was disconnected due to the wrong user properties type in the message publishing API api/v4/mqtt/publish
Fix the issue that some authentication algorithms were unavailable due to the PostgreSQL driver not adapting to OTP 24
Fix the issue that the returned results did not match the query conditions when querying subscriptions with multiple conditions
Fix rule engine resource connection test not working
Fix multiple Dashboard display issues

# v4.4.3

Release Date: 2022-04-18

# Enhancement

Rule engine supports resetting metrics of the specified rule
Add connection confirmation and authorization completion events to the rule engine
Rule engine supports copying rule for fast reuse
SQL in rule engine supports zip, gzip and other compression and decompression functions
Improve the error message when rule engine fails to parse payload
Improve the connection test for some resources in rule engine
Support setting execution priority for ExHook
ExHook callback interface adds a Protobuf field RequestMeta meta to return the EMQX cluster name
Support local policy for shared subscriptions, which will preferentially send messages to shared subscribers under the node where messages flow in. In some scenarios, the efficiency of shared message scheduling will be improved, especially when the MQTT bridge is configured as a shared subscription
RSA-PSK-AES256-GCM-SHA384, RSA-PSK-AES256-CBC-SHA384, RSA-PSK-AES128-GCM-SHA256 and RSA-PSK-AES128-CBC- SHA256 four new TLS PSK cipher suites are supported, removing two insecure cipher suites PSK-3DES-EDE-CBC-SHA and PSK-RC4-SHA from the default configuration
Diagnostic logging for wait_for_table of mnesia
- Prints check points of mnesia internal stats
- Prints check points of per table loading stats, help to locate the problem of long table loading time.
Subscribing to an empty topic is prohibited in strict mode
Generate default files when loaded_modules and loaded_plugins files do not exist

# Bug fixes

Fix the issue that the TLS configuration item server_name_indication is set to disable and does not take effect
Fix potential process leak issue in MongoDB driver
Fix the issue that the password of the default Dashboard user modified via the CLI command would be reset after the node leaves the cluster
Silence grep and sed warnings in docker-entrypoint.sh
Fix the backup file cannot be deleted and downloaded when the API path contains ISO8859-1 escape characters
Fix the issue that the Redis driver would crash when DNS resolution failed, etc
Fix the issue that the headers field configuration in the Data to Web Server action of the rule engine did not take effect
Fix the issue that the MQTT Bridge plugin cannot be started when only the subscription topic is configured but QoS is not configured
When creating a rule, if a rule with the same ID already exists, the rules engine will now report an error instead of replacing the existing rule
Fix the issue that the HTTP driver process pool may not be deleted

# v4.4.2

Release Date: 2022-04-01

# Important changes

For Docker images, the configuration directory /opt/emqx/etc has been removed from the VOLUME list, making it easier for users to rebuild images with changed configurations.
CentOS 7 Erlang runtime rebuilt on OpenSSL-1.1.1n (previously 1.0), prior to v4.3.13, EMQX will fail to handshake and trigger malformed_handshake_data exception when clients use certain cipher suites.
CentOS 8 Erlang runtime system rebuilt on RockyLinux 8. centos8 will remain in the package name for backward compatibility.

# Enhancement

Windows package support for building on Erlang/OTP 24.
Add command line interface emqx_ctl pem_cache clean to allow forcibly clear x509 certificate cache to reload immediately after certificate file update.
Refactored ExProto so that anonymous clients can also be displayed on Dashboard.
Topic configuration items in bridges can now use ${node} placeholders.
Add validation of UTF-8 strings in MQTT packets in strict mode. When set to true, invalid UTF-8 strings will cause the client to disconnect.
MQTT-SN gateway supports initiative to synchronize registered topics after session resumed.
Improve the writing precision of rule engine floating point data from 10 decimal places to 17 decimal places.
EMQX will prompt how to modify the initial password of Dashboard at startup.

# Bug fixes

Fix the issue that the el8 installation package cannot be started on Amazon Linux 2022, the error content is errno=13 Permission denied.
Fix an issue where the client could not reconnect if the connection process was blocked in some cases. Now waiting for more than 15 seconds without a response will force the old connection process to be closed.
Fix the issue of query resource request timeout when rule engine resource is unavailable.
Fix the issue of {error, eexist} error when re-run after hot upgrade failed.
Fix an issue where publishing to a non-existing topic alias would crash the connection.
Fix 500 error when querying lwm2m client list on another node via HTTP API.
Fix HTTP API for subscribing topics crashes when invalid QoS are passed in.
Fix the issue that the connection count was not updated because the related resources were not released when the connection process accessed through the ExProto exited abnormally.
Fix an issue where the value of server_keepalive configuration item would be incorrectly applied to MQTT v3.1.1 clients.
Fix Stomp client not firing $event/client_connection event messages.
Fix the issue that the system memory alarm was incorrectly activated when EMQX was started.
Fixed an issue where messages that failed to be delivered due to unregistered topics were not retransmitted when topics were successfully registered with the MQTT-SN client.
Fix EMQX startup output error log when duplicate plugins are configured in loaded_plugins file.
Fix MongoDB related features outputting excessive error logs when configured incorrectly.
Add format check for Dashboard User and AppID, special characters such as / are not allowed.
Corrected the reason code in the DISCONNECT packet returned when kicking the client to 0x98.
Auto subscriptions will ignore empty topics.

# v4.4.1

Release Date: 2022-02-21

This patch release only includes a CI change for the Windows package.

# v4.4.0

Release Date: 2022-02-18

NOTE:

4.4.0 is in sync with: 4.3.12.
The build of Windows package has some issues in the current version, we will fix it in the next version

The compare base of this change set is 4.3.12

# Important changes

For Debian/Ubuntu users, Debian/Ubuntu package (deb) installed EMQX is now started from systemd. This is to use systemd's supervision functionality to ensure that EMQX service restarts after a crash. The package installation service upgrade from init.d to systemd has been verified, it is still recommended that you verify and confirm again before deploying to the production environment, at least to ensure that systemd is available in your system
Package name scheme changed comparing to 4.3. 4.3 format: emqx-centos8-4.3.8-amd64.zip 4.4 format: emqx-4.4.0-rc.1-otp24.1.5-3-el8-amd64.zip
- Erlang/OTP version is included in the package name, providing the possibility to release EMQX on multiple Erlang/OTP versions
- centos is renamed to el. This is mainly due to centos8 being dead (replaced with rockylinux8)
MongoDB authentication supports DNS SRV and TXT Records resolution, which can seamlessly connect with MongoDB Altas
Support dynamic modification of MQTT Keep Alive to adapt to different energy consumption strategies.
Support 4.3 to 4.4 rolling upgrade of clustered nodes. See upgrade document for more dtails.
TLS for cluster backplane (RPC) connections. See clustering document for more details.
Add new feature for slow subscription to count the time spent in the process of message transmission, and record and display the time-consuming clients and topics.
Add new feature for online log tracing to support real-time tracing of client events and viewing on the dashboard.

# Minor changes

Bumped default boot wait time from 15 seconds to 150 seconds because in some simulated environments it may take up to 70 seconds to boot in build CI
Dashboard supports relative paths and custom access paths
Supports configuring whether to forward retained messages with empty payload to suit users who are still using MQTT v3.1. The relevant configurable item is retainer.stop_publish_clear_msg
Multi-language hook extension (ExHook) supports dynamic cancellation of subsequent forwarding of client messages
Rule engine SQL supports the use of single quotes in FROM clauses, for example: SELECT * FROM 't/#'
Change the default value of the max_topic_levels configurable item to 128. Previously, it had no limit (configured to 0), which may be a potential DoS threat
Improve the error log content when the Proxy Protocol message is received without proxy_protocol configured.
Add additional message attributes to the message reported by the gateway. Messages from gateways such as CoAP, LwM2M, Stomp, ExProto, etc., when converted to EMQX messages, add fields such as protocol name, protocol version, user name, client IP, etc., which can be used for multi-language hook extension (ExHook)
HTTP client performance improvement
Add openssl-1.1 to RPM dependency

# v4.4-beta.1

Release Date: 2021-12-21

EMQX 4.4-beta.1 is released now, it mainly includes the following changes:

Important changes:

Starting from 4.4, EMQX releases are named with Erlang/OTP release in the package name. e.g. emqx-4.4.0-otp24.1.5-3-centos7-arm64.rpm
For Debian/Ubuntu users, Debian/Ubuntu package (deb) installed EMQX now now run on systemd. This is to use systemd's supervision functionality to ensure that EMQX service restarts after a crash. The package installation service upgrade from init.d to systemd has been verified, but it is still recommended that you verify and confirm again before deploying to the production environment, at least to ensure that systemd is available in your system
MongoDB authentication supports DNS SRV and TXT Records resolution, which can seamlessly connect with MongoDB Altas
Support dynamic modification of MQTT Keep Alive to adapt to different energy consumption strategies
Support 4.3 to 4.4 rolling upgrade of clustered nodes. See upgrade document for more dtails.
TLS for cluster backplane (RPC) connections. See clustering document for details.

Minor changes:

Dashboard supports relative paths and custom access paths
Supports configuring whether to forward retained messages with empty payload to suit users who are still using MQTT v3.1. The relevant configurable item is retainer.stop_publish_clear_msg
Multi-language hook extension (ExHook) supports dynamic cancellation of subsequent forwarding of client messages
Rule engine SQL supports the use of single quotes in FROM clause, for example: SELECT * FROM't/#'
Change the default value of the max_topic_levels configurable item to 128. Previously, it had no limit (configured to 0), which may be a potential DoS threat
Improve the error log content when the Proxy Protocol message is received but the proxy_protocol configuration is not turned on
Add additional message attributes to the message reported by the gateway. Messages from gateways such as CoAP, LwM2M, Stomp, ExProto, etc., when converted to EMQX messages, add fields such as protocol name, protocol version, user name, client IP, etc., which can be used for multi-language hook extension (ExHook)
HTTP client performance improvement
Add openssl-1.1 to RPM dependency

Bug fixes:

Various RPC timeouts or even indefinite hangs, e.g. client becomes unresponsive due to the a bug in Erlang/OTP which is triggered under high load
Fix the issue that the lock management process ekka_locker crashes after killing the suspended lock owner
Fix the issue that the Path parameter of WebHook action in rule engine cannot use the rule engine variable
Fix MongoDB authentication module cannot use Replica Set mode and other issues
Fix the issue of out-of-sequence message forwarding between clusters. The relevant configurable item is rpc.tcp_client_num
Fix the issue of incorrect calculation of memory usage
Fix MQTT bridge malfunction when remote host is unreachable (hangs the connection)
Fix the issue that HTTP headers may be duplicated

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