Compress otlp payload with zlib

Dockerfile

@@ -1,9 +1,10 @@
 FROM openresty/openresty:1.21.4.1-0-centos
 
-RUN yum install -y gcc
+RUN yum install -y gcc git zlib-devel
 RUN yum -y --enablerepo=powertools install libyaml-devel libffi-devel
 RUN luarocks install lua-resty-http 0.16.1-0
 RUN luarocks install lua-protobuf 0.3.3
+RUN luarocks install lua-zlib 1.2
 RUN luarocks install busted 2.0.0-1
 RUN luarocks --server=http://rocks.moonscript.org install lyaml
 

docker-compose.yml

@@ -17,20 +17,23 @@ services:
     image: jaegertracing/all-in-one
     ports:
       - 26686:16686
+      - 4319-4320:4317-4318
     networks:
       - opentelemetry-lua
   otel-collector:
     image: otel/opentelemetry-collector-contrib-dev:latest
     command: [ "--config=/etc/otel-collector-config.yaml" ]
+    ports:
+      - 4317:4317
     volumes:
       - ./otel-collector-config.yaml:/etc/otel-collector-config.yaml
-    depends_on:
-      - jaeger
     networks:
       - opentelemetry-lua
   test-server:
     build:
       context: ./examples/server
+    ports:
+      - 10080:80
     depends_on:
       - otel-collector
     networks:

examples/openresty/nginx.conf

@@ -7,7 +7,11 @@ init_worker_by_lua_block {
     local attr = require("opentelemetry.attribute")
 
     -- create exporter
-    local exporter = otlp_exporter_new(exporter_client_new("otel-collector:4317", 3))
+    local use_gzip = true
+    local headers = {}
+    headers["Content-Encoding"] = "gzip"
+    local exporter_timeout = 10000
+    local exporter = otlp_exporter_new(exporter_client_new("otel-collector:4317", 3, headers), exporter_timeout, use_gzip)
     -- create span processor
     local batch_span_processor = batch_span_processor_new(exporter)
     -- create tracer provider

lib/opentelemetry/trace/exporter/http_client.lua

@@ -1,4 +1,8 @@
 local http = require("resty.http")
+local zlib = require("zlib")
+local otel_global = require("opentelemetry.global")
+local exporter_request_compressed_payload_size = "otel.otlp_exporter.request_compressed_payload_size"
+local exporter_request_uncompressed_payload_size = "otel.otlp_exporter.request_uncompressed_payload_size"
 
 local _M = {
 }
@@ -13,9 +17,11 @@ local mt = {
 -- @address             opentelemetry collector: host:port
 -- @timeout             export request timeout second
 -- @headers             export request headers
+-- @httpc               openresty http client instance
+-- @use_gzip            flag to enable gzip compression on request body
 -- @return              http client
 ------------------------------------------------------------------
-function _M.new(address, timeout, headers)
+function _M.new(address, timeout, headers, httpc)
     headers = headers or {}
     headers["Content-Type"] = "application/x-protobuf"
 
@@ -28,29 +34,31 @@ function _M.new(address, timeout, headers)
         uri = uri,
         timeout = timeout,
         headers = headers,
+        httpc = httpc,
     }
+
     return setmetatable(self, mt)
 end
 
 function _M.do_request(self, body)
-    local httpc = http.new()
-    httpc:set_timeout(self.timeout * 1000)
+    self.httpc = self.httpc or http.new()
+    self.httpc:set_timeout(self.timeout * 1000)
 
-    local res, err = httpc:request_uri(self.uri, {
+    local res, err = self.httpc:request_uri(self.uri, {
         method = "POST",
         headers = self.headers,
         body = body,
     })
 
     if not res then
         ngx.log(ngx.ERR, "request failed: ", err)
-        httpc:close()
+        self.httpc:close()
         return nil, err
     end
 
     if res.status ~= 200  then
         ngx.log(ngx.ERR, "request failed: ", res.body)
-        httpc:close()
+        self.httpc:close()
         return nil, "request failed: " .. res.status
     end
 

lib/opentelemetry/trace/exporter/otlp.lua

@@ -14,14 +14,15 @@ local mt = {
     __index = _M
 }
 
-function _M.new(http_client, timeout_ms, circuit_reset_timeout_ms, circuit_open_threshold)
+function _M.new(http_client, timeout_ms, use_gzip, circuit_reset_timeout_ms, circuit_open_threshold)
     local self = {
         client = http_client,
         timeout_ms = timeout_ms or DEFAULT_TIMEOUT_MS,
+        use_gzip = use_gzip or false,
         circuit = circuit.new({
             reset_timeout_ms = circuit_reset_timeout_ms,
             failure_threshold = circuit_open_threshold
-        })
+        }),
     }
     return setmetatable(self, mt)
 end
@@ -35,7 +36,7 @@ end
 -- @return true if call succeeded; false if call failed
 -- @return nil if call succeeded; error message string if call failed
 --------------------------------------------------------------------------------
-local function call_collector(exporter, pb_encoded_body)
+local function call_collector(exporter, pb_encoded_body, use_gzip)
     local start_time_ms = util.gettimeofday_ms()
     local failures = 0
     local res
@@ -54,6 +55,25 @@ local function call_collector(exporter, pb_encoded_body)
             return false, "Circuit breaker is open"
         end
 
+        if use_gzip then
+            -- Compress (deflate) request body
+            -- the compression should be set to Best Compression and window size
+            -- should be set to 15+16, see reference below:
+            -- https://github.com/brimworks/lua-zlib/issues/4#issuecomment-26383801
+            local deflate_stream = zlib.deflate(zlib.BEST_COMPRESSION, 15+16)
+            local compressed_body, _, _, bytes_out = deflate_stream(pb_encoded_body, "finish")
+
+            otel_global.metrics_reporter:record_value(
+                exporter_request_uncompressed_payload_size, string.len(pb_encoded_body))
+            otel_global.metrics_reporter:record_value(
+                exporter_request_compressed_payload_size, bytes_out)
+
+            pb_encoded_body = compressed_body
+        else
+            otel_global.metrics_reporter:record_value(
+                exporter_request_uncompressed_payload_size, string.len(pb_encoded_body))
+        end
+
         -- Make request
         res, res_error = exporter.client:do_request(pb_encoded_body)
         local after_time = util.gettimeofday_ms()
@@ -101,7 +121,7 @@ function _M.export_spans(self, spans)
             body.resource_spans[1].instrumentation_library_spans[1].spans,
             encoder.for_otlp(span))
     end
-    return call_collector(self, pb.encode(body))
+    return call_collector(self, pb.encode(body), self.use_gzip)
 end
 
 function _M.shutdown(self)

otel-collector-config.yaml

@@ -9,15 +9,10 @@ exporters:
     endpoint: "0.0.0.0:8889"
     const_labels:
       label1: value1
-  logging:
-    loglevel: debug
-
-  #zipkin:
-  #  endpoint: "http://zipkin-all-in-one:9411/api/v2/spans"
-  #  format: proto
-
-  jaeger:
-    endpoint: jaeger:14250
+  debug:
+    verbosity: detailed
+  otlp/jaeger:
+    endpoint: jaeger:4317
     tls:
       insecure: true
 
@@ -37,8 +32,8 @@ service:
     traces:
       receivers: [otlp]
       processors: [batch]
-      exporters: [logging, jaeger]
+      exporters: [debug, otlp/jaeger]
     metrics:
       receivers: [otlp]
       processors: [batch]
-      exporters: [logging, prometheus]
+      exporters: [debug, prometheus]

rockspec/opentelemetry-lua-master-0.rockspec

@@ -14,6 +14,7 @@ description = {
 dependencies = {
     "lua-protobuf = 0.3.3",
     "lua-resty-http = 0.16.1-0",
+    "lua-zlib = 1.2",
 }
 
 build = {

spec/trace/exporter/otlp_spec.lua

@@ -4,6 +4,23 @@ local context = require "opentelemetry.context"
 local tp = Global.get_tracer_provider()
 local tracer = tp:tracer("test")
 
+local function is_gzip(_, _)
+    return function(value)
+        -- check that the value starts with the two magic bytes 0x1f, 0x8b and
+        -- the compression method byte set to 0x08
+        -- reference: https://www.ietf.org/rfc/rfc1952.txt
+        return string.sub(value, 1, 3) == string.from_hex("1F8B08")
+    end
+end
+
+assert:register("matcher", "gzip", is_gzip)
+
+function string.from_hex(str)
+    return (str:gsub('..', function (cc)
+        return string.char(tonumber(cc, 16))
+    end))
+end
+
 describe("export_spans", function()
     it("invokes do_request when there are no failures", function()
         local span
@@ -17,7 +34,28 @@ describe("export_spans", function()
         stub(ngx, "log")
         cb:export_spans({ span })
         ngx.log:revert()
-        assert.spy(c.do_request).was_called_with(c, match.is_string())
+        assert.spy(c.do_request).was_called_with(c, match.is_all_of(match.is_string(), match.is_not_gzip()))
+    end)
+
+    it("invokes do_request with gzip compression when configured", function()
+        local span
+        local ctx = context.new()
+        ctx, span = tracer:start(ctx, "test span")
+        span:finish()
+
+        local headers = {}
+        headers["Content-Encoding"] = "gzip"
+        local c = client.new("http://localhost:8080", 10, headers)
+        spy.on(c, "do_request")
+
+        local cb = exporter.new(c, 10000, true)
+
+        -- Supress log message, since we expect it
+        stub(ngx, "log")
+
+        cb:export_spans({ span })
+        ngx.log:revert()
+        assert.spy(c.do_request).was_called_with(c, match.is_all_of(match.is_string(), match.is_gzip()))
     end)
 
     it("doesn't invoke protected_call when failures is equal to retry limit", function()