Populate memory ballast size from SPLUNK_BALLAST_SIZE_MIB env variabl…

…e. (open-telemetry#31)

The value of memory ballast can be now provided via SPLUNK_BALLAST_SIZE_MIB
env variable. It will override the value provided via --mem-ballast-size-mib
command line flag.

The SPLUNK_BALLAST_SIZE_MIB env variable can be accessed from the config file.
This is particularly useful for the memorylimiter processor and helps to avoid
specifying the ballast size twice.

README.md

@@ -20,7 +20,7 @@ which requires the following environment variables:
 
 - `${SPLUNK_REALM}`: Which realm to send the data to (for example: `us0`)
 - `${SPLUNK_ACCESS_TOKEN}`: Access token to authenticate requests
-- `${SPLUNK_BALLAST}`: How much memory to allocate to the ballast. This should be set to 1/3 to 1/2 of configured memory.
+- `${SPLUNK_BALLAST_SIZE_MIB}`: How much memory to allocate to the ballast. This should be set to 1/3 to 1/2 of configured memory.
 
 Deploy the collector as outlined in the below. More information
 about deploying and configuring the collector can be found
@@ -32,10 +32,9 @@ Deploy from a Docker container (replace `0.1.0-otel-0.11.0` with the latest
 stable version number if necessary):
 
 ```bash
-$ SPLUNK_REALM=us0 SPLUNK_ACCESS_TOKEN=12345 SPLUNK_BALLAST=683 \
+$ SPLUNK_REALM=us0 SPLUNK_ACCESS_TOKEN=12345 SPLUNK_BALLAST_SIZE_MIB=683 \
   docker run -p 7276:7276 -p 8888:8888 -p 9943:9943 -p 55679:55679 -p 55680:55680 -p 9411:9411 \
-    --name otelcol signalfx/splunk-otel-collector:0.1.0-otel-0.11.0 \
-        --mem-ballast-size-mib=683
+    --name otelcol signalfx/splunk-otel-collector:0.1.0-otel-0.11.0
 ```
 
 ### Kubernetes
@@ -50,8 +49,8 @@ file on GitHub.
 
 ```bash
 $ make otelcol
-$ SPLUNK_REALM=us0 SPLUNK_ACCESS_TOKEN=12345 SPLUNK_BALLAST=683 \
-  ./bin/otelcol --mem-ballast-size-mib=${SPLUNK_BALLAST}
+$ SPLUNK_REALM=us0 SPLUNK_ACCESS_TOKEN=12345 SPLUNK_BALLAST_SIZE_MIB=683 \
+  ./bin/otelcol
 ```
 
 ## Custom Configuration
@@ -62,9 +61,13 @@ be provided.
 For example in Docker:
 
 ```bash
-$ SPLUNK_REALM=us0 SPLUNK_ACCESS_TOKEN=12345 SPLUNK_BALLAST=683 \
+$ SPLUNK_REALM=us0 SPLUNK_ACCESS_TOKEN=12345 SPLUNK_BALLAST_SIZE_MIB=683 \
   docker run -p 7276:7276 -p 8888:8888 -p 9943:9943 -p 55679:55679 -p 55680:55680 -p 9411:9411 \
     -v collector.yaml:/etc/collector.yaml:ro \
     --name otelcol signalfx/splunk-otel-collector:0.1.0-otel-0.11.0 \
-        --config /etc/collector.yaml --mem-ballast-size-mib=683
+        --config /etc/collector.yaml
 ```
+
+Note that if the configuration includes a memorylimiter processor then it must set the
+value of `ballast_size_mib` setting of the processor to the env variable SPLUNK_BALLAST_SIZE_MIB.
+See for example splunk_config.yaml on how to do it.

cmd/otelcol/Dockerfile

@@ -13,5 +13,5 @@ COPY --from=otelcol /otelcol /
 COPY config/collector/splunk_config.yaml /etc/otel/collector/splunk_config.yaml
 COPY config/collector/otlp_config.yaml /etc/otel/collector/otlp_config.yaml
 ENTRYPOINT ["/otelcol"]
-CMD ["--config", "/etc/otel/collector/splunk_config.yaml", "--mem-ballast-size-mib", "${SPLUNK_BALLAST}"]
+CMD ["--config", "/etc/otel/collector/splunk_config.yaml"]
 EXPOSE 13133 14250 14268 55678 55679 55680 7276 9411 9443

cmd/otelcol/config/collector/otlp_config.yaml

@@ -41,12 +41,14 @@ processors:
   # The configuration below assumes 2GB of memory. In general, the ballast
   # should be set to 1/3 of the collector's memory, the limit should be 90% of
   # the collector's memory up to 2GB, and the spike should be 25% of the
-  # collector's memory up to 2GB. In addition, the "--mem-ballast-size-mib" CLI
-  # flag must be set to the same value as the "ballast_size_mib". For more
-  # information, see
+  # collector's memory up to 2GB. The simplest way to specify the ballast size is
+  # set the value of SPLUNK_BALLAST_SIZE_MIB env variable. This will overrides
+  # the value of --mem-ballast-size-mib command line flag. If SPLUNK_BALLAST_SIZE_MIB
+  # is not defined then --mem-ballast-size-mib command line flag must be manually specified.
+  # For more information about memory limiter, see
   # https://github.com/open-telemetry/opentelemetry-collector/blob/master/processor/memorylimiter/README.md
   memory_limiter:
-    ballast_size_mib: ${SPLUNK_BALLAST}
+    ballast_size_mib: ${SPLUNK_BALLAST_SIZE_MIB}
     check_interval: 2s
     limit_percentage: 90
     spike_limit_percentage: 25

cmd/otelcol/config/collector/splunk_config.yaml

@@ -41,12 +41,14 @@ processors:
   # The configuration below assumes 2GB of memory. In general, the ballast
   # should be set to 1/3 of the collector's memory, the limit should be 90% of
   # the collector's memory up to 2GB, and the spike should be 25% of the
-  # collector's memory up to 2GB. In addition, the "--mem-ballast-size-mib" CLI
-  # flag must be set to the same value as the "ballast_size_mib". For more
-  # information, see
+  # collector's memory up to 2GB. The simplest way to specify the ballast size is
+  # set the value of SPLUNK_BALLAST_SIZE_MIB env variable. This will overrides
+  # the value of --mem-ballast-size-mib command line flag. If SPLUNK_BALLAST_SIZE_MIB
+  # is not defined then --mem-ballast-size-mib command line flag must be manually specified.
+  # For more information about memory limiter, see
   # https://github.com/open-telemetry/opentelemetry-collector/blob/master/processor/memorylimiter/README.md
   memory_limiter:
-    ballast_size_mib: ${SPLUNK_BALLAST}
+    ballast_size_mib: ${SPLUNK_BALLAST_SIZE_MIB}
     check_interval: 2s
     limit_percentage: 90
     spike_limit_percentage: 25

cmd/otelcol/main.go

@@ -20,6 +20,8 @@ package main
 import (
 	"fmt"
 	"log"
+	"os"
+	"strconv"
 
 	"go.opentelemetry.io/collector/component"
 	"go.opentelemetry.io/collector/service"
@@ -28,6 +30,8 @@ import (
 	"github.com/signalfx/splunk-otel-collector/internal/version"
 )
 
+const ballastEnvVarName = "SPLUNK_BALLAST_SIZE_MIB"
+
 func main() {
 	factories, err := components.Get()
 	if err != nil {
@@ -41,11 +45,29 @@ func main() {
 		GitHash:  version.GitHash,
 	}
 
+	useBallastSizeFromEnvVar()
+
 	if err := run(service.Parameters{ApplicationStartInfo: info, Factories: factories}); err != nil {
 		log.Fatal(err)
 	}
 }
 
+func useBallastSizeFromEnvVar() {
+
+	// Check if the ballast is specified via the env var.
+	ballastSize := os.Getenv(ballastEnvVarName)
+	if ballastSize != "" {
+		// Check if it is a numeric value.
+		_, err := strconv.Atoi(ballastSize)
+		if err != nil {
+			log.Fatalf("Expected a number in %s env variable but got %s", ballastEnvVarName, ballastSize)
+		}
+
+		// Inject the command line flag that controls the ballast size.
+		os.Args = append(os.Args, "--mem-ballast-size-mib="+ballastSize)
+	}
+}
+
 func runInteractive(params service.Parameters) error {
 	app, err := service.New(params)
 	if err != nil {

internal/buildscripts/packaging/fpm/splunk_env.example

@@ -18,4 +18,4 @@ SPLUNK_ACCESS_TOKEN=12345
 SPLUNK_REALM=us0
 
 # How much memory to allocate to the ballast. This should be set to 1/3 to 1/2 of configured memory.
-SPLUNK_BALLAST=683
+SPLUNK_BALLAST_SIZE_MIB=683