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[service_discovery] Fix race condition preventing SD initialization #135

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merged 2 commits into from
Apr 18, 2017
Merged

[service_discovery] Fix race condition preventing SD initialization #135

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bd2e154
[service_discovery] Fix race condition preventing SD initialization
olivielpeau Apr 17, 2017
1c5bede
[service_discovery] Avoid calling `available()` twice on pipe
olivielpeau Apr 17, 2017
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37 changes: 24 additions & 13 deletions src/main/java/org/datadog/jmxfetch/App.java
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Original file line number Diff line number Diff line change
Expand Up @@ -3,12 +3,10 @@
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileFilter;
import java.io.FileNotFoundException;
import java.io.InputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.Arrays;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.HashMap;
Expand Down Expand Up @@ -169,6 +167,17 @@ private String getSDName(String config){
return SERVICE_DISCOVERY_PREFIX + splitted[0].substring(2, splitted[0].length());
}

private FileInputStream newSdPipe() {
FileInputStream sdPipe = null;
try {
sdPipe = new FileInputStream(appConfig.getServiceDiscoveryPipe()); //Should we use RandomAccessFile?
LOGGER.info("Named pipe for Service Discovery opened");
} catch (FileNotFoundException e) {
LOGGER.info("Unable to open named pipe for Service Discovery.");
}
return sdPipe;
}

public boolean processServiceDiscovery(byte[] buffer) {
boolean reinit = false;
String[] discovered;
Expand Down Expand Up @@ -210,11 +219,9 @@ void start() {
long delta_s = 0;
FileInputStream sdPipe = null;

try {
sdPipe = new FileInputStream(appConfig.getServiceDiscoveryPipe()); //Should we use RandomAccessFile?
} catch (FileNotFoundException e) {
LOGGER.warn("Unable to open named pipe - Service Discovery disabled.");
sdPipe = null;
if(appConfig.getSDEnabled()) {
LOGGER.info("Service Discovery enabled");
sdPipe = newSdPipe();
}

while (true) {
Expand All @@ -225,13 +232,17 @@ void start() {
}

// any SD configs waiting in pipe?
if(sdPipe == null && appConfig.getSDEnabled()) {
// If SD is enabled and the pipe is not open, retry opening pipe
sdPipe = newSdPipe();
}
try {
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Little nit, but could do
int len = 0
if(sdPipe != null && ((len = sdPipe.available()) > 0)) {
byte[] buffer....

No need to call sdPipe.available twice in succession.

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👍 , addressed in 1c5bede

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@truthbk truthbk Apr 18, 2017 •
edited
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Nice one. My bad.

if(sdPipe != null && sdPipe.available() > 0) {
int len = sdPipe.available();
byte[] buffer = new byte[len];
sdPipe.read(buffer);
setReinit(processServiceDiscovery(buffer));
}
if(sdPipe != null && sdPipe.available() > 0) {
int len = sdPipe.available();
byte[] buffer = new byte[len];
sdPipe.read(buffer);
setReinit(processServiceDiscovery(buffer));
}
} catch(IOException e) {
LOGGER.warn("Unable to read from pipe - Service Discovery configuration may have been skipped.");
}
Expand Down
10 changes: 5 additions & 5 deletions src/main/java/org/datadog/jmxfetch/AppConfig.java
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Expand Up @@ -76,10 +76,10 @@ class AppConfig {
required = false)
private int checkPeriod = 15000;

@Parameter(names = {"--sd_standby", "-w"},
description = "Service Discovery standby.",
@Parameter(names = {"--sd_enabled", "-w"},
description = "Enable Service Discovery.",
required = false)
private boolean sdStandby = false;
private boolean sdEnabled = false;

@Parameter(names = {"--sd_pipe", "-S"},
description = "Service Discovery pipe name.",
Expand Down Expand Up @@ -128,8 +128,8 @@ public int getCheckPeriod() {
return checkPeriod;
}

public boolean getSDStandby() {
return sdStandby;
public boolean getSDEnabled() {
return sdEnabled;
}

public Reporter getReporter() {
Expand Down
1 change: 1 addition & 0 deletions src/test/java/org/datadog/jmxfetch/TestCommon.java
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Expand Up @@ -103,6 +103,7 @@ protected void initApplication(String yamlFileName, String serviceDiscoveryPipeF
if (sdEnabled) {
params.add(4, "--tmp_directory");
params.add(5, "/foo"); //could be anything we're stubbing it out
params.add(6, "--sd_enabled");
}
new JCommander(appConfig, params.toArray(new String[params.size()]));

Expand Down