This is the first beta release of version 2.3 series. Changes from version 2.2.5 are as follows.

• [core] forbid empty path string in configuration #1506 (Ichito Nagata)
• [core] use eventfd instead of pipe on linux #1533 (Baodong Chen)
• [core] remove redundancy #1568 #1569 #1584 #1596 (Baodong Chen)
• [core] !env for respecting environment variables from the configuration file #1524 (Yannick Koechlin)
• [core] avoid copying vector when calling writev #1600 (Kazuho Oku)
• [core] alignment-aware allocation from memory pool #1605 (Baodong Chen)
• [core] stash directive for storing arbitrary YAML data #1739 (Ichito Nagata)
• [access-log] log connections that closed prior to sending a response #1235 (Kazuho Oku)
• [compress] update brotli to 1.0.2 #1523 (Kazuho Oku)
• [fastcgi] accept default as a keyword of the extensions attribute #1414 (Ichito Nagata)
• [fastcgi] add verbose mode to fastcgi-cgi gateway #1466 (Kazuho Oku)
• [fastcgi][mruby][proxy] do not delay sending the headers until some chunk of body becomes available #1508 (Ichito Nagata)
• [http1][http2] support for server-timing #1646 #1717 (Ichito Nagata)
• [http1][http2] forward informational responses #1727 (Ichito Nagata)
• [http2] support critical attribute in preload link header #1436 (Kazuho Oku, Frederik Deweerdt)
• [http2] continue to process active streams after sending GOAWAY upon graceful shutdown #1556 (Ichito Nagata)
• [mime] more predefined types #1398 #1632 #1708 #1723 (Jxck, proyb6, OGINO Masanori)
• [mime] mark /+json as compressible #1709 (OGINO Masanori)
• [mruby] Rack middleware support #1217 (Ichito Nagata)
• [mruby] allow running asynchronous operations unbounded to the Rack request being processed #1173 (Ichito Nagata)
• [mruby] add channel class and task method for parallel processing #1336 (Ritta Narita)
• [mruby] implement sleep #1348 (Ichito Nagata)
• [mruby] implement Digest::SHA256 #1387 (Kazuho Oku)
• [mruby] add option to specify mrbgem dependencies out of tree #1446 (Satoshi Tagomori)
• [mruby] on exception, emit filenames and consistent line number of embedded mruby code #1537 (Satoshi Tagomori)
• [mruby] introduce client-warning header for error notification #1562 (Ichito Nagata)
• [mruby] allow fiber switch in constructor #1574 (Kazuho Oku)
• [mruby] fix crash when the rack handler returns a non-number status code #1576 (Kazuho Oku)
• [mruby] add support for redis #1152 (Ichito Nagata)
• [mruby] replace iijson with mattn-json #1684 (Yannick Koechlin, Kazuho Oku)
• [mruby] update mruby and modules #1462 #1685
• [proxy] load balancing support (round-robin, least-conn) #1277 #1361 (Justin Zhu)
• [proxy] cap the amount of request body being buffered #1357 (Frederik Deweerdt)
• [proxy] cap the amount of response body being buffered #1358 (Frederik Deweerdt)
• [proxy] introduce separate timeouts for connection establishment and first-byte #1402 (Frederik Deweerdt)
• [proxy] forward the error to the client when upstream closes the connection abruptly #1490 (Ichito Nagata)
• [proxy] add option to skip supplementation of a Date header #1495 (Frederik Deweerdt)
• [proxy] do not abort when receiving an invalid transfer-encoding header from upstream #1688 (Ichito Nagata)
• [reproxy] connection pooling for reproxy #1434 (Ichito Nagata)
• [ssl] support redis as a data store for session cache / ticket #1087 (Ichito Nagata)
• [ssl] unbundle libressl #1546 (Kazuho Oku)
• [ssl] add support for 425 Too Early status code #1344 (Kazuho Oku)
• [libh2o] enable ECDH in the exmaple server #1602 (Varbin)
• [libh2o] emit less system calls in websocket #1590 (Baodong Chen)
• [libh2o] build examples using evloop #1589 (Baodong Chen)
• [libh2o] add API to release thread-local data #1624 (Baodong Chen)
• [libh2o] h2o_gettimeofday to obtain current time in microsecond order #1726 (Ichito Nagata)
• [misc] include process id in crash backtrace #1254 (Kazuho Oku)
• [misc] backtracing for BSD #1503 (Frederik Deweerdt)
• [misc] fix build issues for Android #1521 (Joel Winarske)
• [misc] switch to Docker-based CI #1551 #1580 (Kazuho Oku)