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new 100be4c76 fix(datadog): cap coalesced DogStatsD datagram size, fall
back to per-metric sends (#13665)
100be4c76 is described below
commit 100be4c766b42b84ab1af2876f5cdfc340e253fd
Author: Shreemaan Abhishek <[email protected]>
AuthorDate: Fri Jul 10 11:53:48 2026 +0800
fix(datadog): cap coalesced DogStatsD datagram size, fall back to
per-metric sends (#13665)
---
apisix/plugins/datadog.lua | 31 +++++++++++++++++---
t/plugin/datadog.t | 72 ++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 99 insertions(+), 4 deletions(-)
diff --git a/apisix/plugins/datadog.lua b/apisix/plugins/datadog.lua
index b39f5718c..05c21c6d5 100644
--- a/apisix/plugins/datadog.lua
+++ b/apisix/plugins/datadog.lua
@@ -36,6 +36,10 @@ local defaults = {
constant_tags = {"source:apisix"}
}
+-- DogStatsD agent's default receive buffer (dogstatsd_buffer_size); datagrams
+-- larger than this are silently truncated, so cap coalescing here
+local MAX_DATAGRAM_SIZE = 8192
+
local batch_processor_manager = bp_manager_mod.new(plugin_name)
-- Shared schema for individual tag strings.
@@ -142,7 +146,7 @@ local function generate_tag(entry, const_tags)
end
--- Build all DogStatsD metrics for one entry as a single newline-delimited
packet.
+-- Build the DogStatsD metric lines for one entry.
local function build_metrics(entry, metadata)
-- Generate prefix & suffix according dogstatsd udp data format.
local suffix = generate_tag(entry, metadata.value.constant_tags)
@@ -168,7 +172,7 @@ local function build_metrics(entry, metadata)
core.table.insert(metrics, format("%s:%s|%s%s", prefix .. "egress.size",
entry.response.size, "ms", suffix))
- return concat(metrics, "\n")
+ return metrics
end
@@ -197,8 +201,27 @@ local function push_metrics(entries)
local err_msg, first_fail
for i = 1, #entries do
- -- coalesce the per-request metrics into one datagram
- local send_ok, send_err = sock:send(build_metrics(entries[i],
metadata))
+ local lines = build_metrics(entries[i], metadata)
+ local payload = concat(lines, "\n")
+
+ local send_ok, send_err
+ if #payload <= MAX_DATAGRAM_SIZE then
+ -- coalesce the entry's metrics into one datagram
+ send_ok, send_err = sock:send(payload)
+ else
+ -- too large to coalesce safely: one datagram per metric
+ for j = 1, #lines do
+ if #lines[j] > MAX_DATAGRAM_SIZE then
+ core.log.warn("dogstatsd metric line exceeds ",
MAX_DATAGRAM_SIZE,
+ " bytes, agent may truncate it")
+ end
+ send_ok, send_err = sock:send(lines[j])
+ if not send_ok then
+ break
+ end
+ end
+ end
+
if not send_ok then
err_msg = "failed to send metrics to dogstatsd server: host[" ..
host
.. "] port[" .. tostring(port) .. "] err: " .. send_err
diff --git a/t/plugin/datadog.t b/t/plugin/datadog.t
index a06b030df..2bce63c92 100644
--- a/t/plugin/datadog.t
+++ b/t/plugin/datadog.t
@@ -599,3 +599,75 @@ GET /articles/12345/comments?foo=bar
--- wait: 0.5
--- error_log
property "constant_tags" validation failed
+
+
+
+=== TEST 13: oversized coalesced payload falls back to per-metric datagrams
+--- apisix_yaml
+routes:
+ - uri: /opentracing
+ name: datadog
+ upstream:
+ nodes:
+ "127.0.0.1:1982": 1
+ plugins:
+ datadog:
+ batch_max_size: 1
+ max_retry_count: 0
+ constant_tags:
+ -
"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+ -
"bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb"
+ -
"cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc"
+ -
"dddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd"
+ -
"eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee"
+ -
"ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"
+ -
"gggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg"
+ -
"hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh"
+ -
"iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii"
+ -
"jjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj"
+#END
+--- extra_stream_config
+ server {
+ listen 8125 udp;
+ content_by_lua_block {
+ local core = require("apisix.core")
+ local sock = ngx.req.socket()
+ while true do
+ local data, err = sock:receive()
+ if not data then
+ if err and err ~= "no more data" then
+ core.log.error("socket error: ", err)
+ end
+ return
+ end
+
+ local count = 0
+ for line in data:gmatch("[^\n]+") do
+ count = count + 1
+ core.log.warn("message received: ", line)
+ end
+ core.log.warn("datagram carried ", count, " metric line(s)")
+ end
+ }
+ }
+--- request
+GET /opentracing
+--- response_body
+opentracing
+--- wait: 0.5
+--- grep_error_log eval
+qr/message received: apisix\.[\w.]+?(?=:)|datagram carried \d+ metric line/
+--- grep_error_log_out eval
+qr/message received: apisix\.request\.counter
+datagram carried 1 metric line
+message received: apisix\.request\.latency
+datagram carried 1 metric line
+message received: apisix\.upstream\.latency
+datagram carried 1 metric line
+message received: apisix\.apisix\.latency
+datagram carried 1 metric line
+message received: apisix\.ingress\.size
+datagram carried 1 metric line
+message received: apisix\.egress\.size
+datagram carried 1 metric line
+/
